Nutritional advice

Objectives:
Although exercise can improve insulin sensitivity, no adequate synthesis exists of exercise intervention studies with regard to their effect on insulin sensitivity. Therefore, this review article (meta-analysis) has beeen conducted.

Does exercise improve insuline sensitivity?

Study design:
This review article included data found across 2509 subjects (115 samples, 78 reports).
The median of mean age was 43 years.
The median of mean preintervention fasting insulin was 8 mU/L.

Results and conclusions:
The investigators found the overall mean effect size for 2-group postintervention comparisons was 0.38 [95% CI = 0.25-0.51, I2 = 0%] and for 2-group pre-post comparisons was 0.43 [95% CI = 0.30-0.56, I2 = 52%].

The investigators found higher mean insulin sensitivity for treatment than control subjects.

The investigators found the postintervention mean of 0.38 was consistent with treatment subjects ending studies with a mean fasting insulin of 6.8 mU/L if control participants’ mean fasting insulin were 7.9 mU/L.
Exploratory moderator analyses did not document different insulin sensitivity effect sizes across intervention characteristics or sample attributes.

The investigators concluded exercise is a valuable primary care and community health strategy for healthy adults to improve insulin sensitivity and lower the risk for diabetes conferred by insulin resistance.

Original title:
Insulin Sensitivity Following Exercise Interventions: Systematic Review and Meta-Analysis of Outcomes Among Healthy Adults by Conn VS, Koopman RJ, […], Hafdahl AR.

Link:
http://journals.sagepub.com/doi/pdf/10.1177/2150131913520328

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Objectives:
Although several epidemiological studies have investigated the association between dietary calcium intake and the risk of esophageal cancer, the results are inconsistent. Therefore, this review article (meta-analysis) has been conducted.

Does dietary calcium intake reduce risk of esophageal cancer?

Study design:
This review article included 3 cohort studies and 14 case-control studies, including 3,396 cases (subjects with esophageal cancer) and 346,815 controls (subjects without esophageal cancer).

Egger’s test showed no evidence of significant publication bias.

The sample size was large enough to evaluate the effect of calcium intake on esophageal cancer.

A dose-response effect analysis could not be performed due to the incomplete data of dietary calcium intake.

The average of highest dietary calcium intake in Asian populations was 621 mg/day.

Results and conclusions:
The investigators found for highest vs. lowest dietary calcium intake a significant reduced risk of 20% for esophageal cancer [pooled OR = 0.80, 95% CI = 0.71-0.91, I2 = 33.6%].
This significant reduced risk was also found in studies conducted in Asia [OR = 0.67, 95% CI = 0.52-0.86, I2 = 0.0%], studies published after 2000 [OR = 0.64, 95% CI = 0.53-0.77, I2 = 0.0%), studies adjusted for dietary energy intake [OR = 0.83, 95% CI = 0.70-0.98, I2 = 3.6%], studies of esophageal squamous cell carcinoma [OR = 0.76, 95% CI = 0.60-0.96, I2 = 28.3%], cohort studies [OR = 0.67, 95% CI = 0.54-0.84, I2 = 23.6%] and studies with high quality score [OR = 0.76, 95% CI = 0.66-0.87, I2 = 12.7%].

The investigators found in sensitivity analysis (conducted by leaving one study out in turn and pooling the ORs of the remaining studies) the summary ORs did not substantially change, which indicated that the results were statistically robust.

The investigators concluded that a higher intake (621 mg/day) of dietary calcium has protective effect against esophageal cancer - especially esophageal squamous cell cancer - in Asian populations. To further solidify the association of dietary calcium intake with the risk of esophageal cancer, well-designed studies - especially prospective cohort studies with validated FFQ and adjusted for dietary energy intake - should be conducted.

Original title:
Protective Effect of Dietary Calcium Intake on Esophageal Cancer Risk: A Meta-Analysis of Observational Studies by Li Q, Cui, L, […], Wang L.

Link:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5452240/

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Objectives:
Although pre-exercise consumption of a low-glycemic-index (LGI) carbohydrate meal is generally recommended, the findings regarding subsequent exercise performance are inconsistent. Therefore, this review article (meta-analysis) has been conducted.

Does a pre-exercise low-glycemic-index carbohydrate meal lead to greater endurance performance than a pre-exercise high-glycemic-index (HGI) meal?

Study design:
This review article included 15 trials (randomized controlled or crossover trials).
All included studies were of low research quality.

Results and conclusions:
The investigators found the synthesized effect size [d  = 0.42, z  = 3.40, p  = 0.001] indicated that the endurance performance following a low-glycemic-index carbohydrate meal was superior to that following a high-glycemic-index meal.

The investigators found subgroup analyses demonstrated that the treatment effect did not vary across outcome measures (exercise to exhaustion, time trial and work output) or athletic status (trained or recreational participants).

The investigators concluded weak evidence supports the claim that endurance performance following pre-exercise consumption of a low-glycemic-index (LGI) carbohydrate meal is superior to that following pre-exercise consumption of a high-glycemic-index (HGI) meal. Further high-quality research in this area is warranted.

Original title:
Effect of pre-exercise carbohydrate diets with high vs low glycemic index on exercise performance: a meta-analysis by Heung-Sang Wong S, Sun FH, […], Ya-Jun Huang W.

Link:
https://www.ncbi.nlm.nih.gov/pubmed/28383695

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A low-glycemic-index (LGI) carbohydrate diet is a diet with a lot of products with GI lower than 55. Products with GI lower than 55 are called low-glycemic-index carbohydrate products. These products are low-glycemic-index carbohydrate products.
 

Objectives:
Evidence shows cruciferous vegetables exhibit chemoprotective properties, commonly attributed to their rich source of isothiocyanates. However, epidemiological data examining the association between cruciferous vegetable intake and colorectal neoplasms have been inconclusive. Therefore, this review article (meta-analysis) has been conducted.

Does cruciferous vegetable intake decrease colon cancer risk?

Study design:
This review article included 33 articles.
Subgroup analysis for individual cruciferae types (n = 8 studies) and GST polymorphism (n = 8 studies) were performed. Pooled adjusted odds ratios (ORs) comparing highest and lowest categories of dietary pattern scores were calculated.

Results and conclusions:
The investigators found when comparing highest with lowest categorie, cruciferous vegetable intake significantly reduced risk of colon cancer with 16% [OR = 0.84, 95% CI = 0.72-0.98, p value heterogeneity 0.001].

The investigators found when comparing highest with lowest categorie, broccoli intake significantly reduced risk of colorectal neoplasms with 20% [OR = 0.80, 95% CI = 0.65-0.99, p value heterogeneity = 0.02].

The investigators found stratification by GST genotype showed that the GSTT1 null genotype confered a reduction in colorectal neoplasms risk of 22% [OR = 0.78, 95% CI = 0.64-0.95, p value heterogeneity = 0.32].

The investigators concluded this meta-analysis provides support to the hypothesis that cruciferous vegetable intake protects against cancer of the colon. This meta-analysis also demonstrates the significance of gene-diet interactions and the importance of assessing individual cruciferous vegetables.

Original title:
Cruciferous vegetables and risk of colorectal neoplasms: a systematic review and meta-analysis by Tse G and Eslick GD.

Link:
http://www.ncbi.nlm.nih.gov/pubmed/24341734

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Objectives:
Does physical activity reduce gastric cancer risk?

Study design:
This review article included 7 cohort studies (with mean reported follow-up ranging from 6 to 18.8 years) and 9 case control studies reporting 11,111 cases of gastric cancer among 1,606,760 patients.

There was no evidence of publication bias, both quantitatively [Begg and Mazumdar rank correlation test, p = 0.62] and qualitatively, on visual inspection of the funnel plot.

Results and conclusions:
The investigators found the risk of gastric cancer was 21% [OR = 0.79, 95% CI = 0.71-0.87, I2 = 55%]  lower among the most physically active people as compared with the least physically active people, after adjustment for important confounders, including age, obesity, and other risk factors for gastric cancer (smoking, alcohol, dietary patterns and socioeconomic status).
This protective effect was seen for gastric cancers in the cardia [OR = 0.80, 95% CI = 0.63-1.00, 4 studies] and distal stomach [OR = 0.63, 95% CI = 0.52-0.76, 5 studies].

The investigators found increasing physical activity was associated with a reduced risk of gastric cancer in both men [OR = 0.86, 95% CI = 0.75-0.99, 10 studies] and women [OR = 0.72, 95% CI = 0.55-0.94, 3 studies].

The investigators found in 12 studies that increased recreational physical activity showed an 18% reduction in gastric cancer risk [OR = 0.82, 95% CI = 0.72-0.94].

The investigators found the effect size was significantly smaller in high-quality studies [OR = 0.86, 95% CI = 0.75-0.99, 6 studies] as compared with low-quality studies [OR = 0.74, 95% CI = 0.69-0.81, 10 studies]. The results were consistent across sex, study quality, study design and geographic location.

The investigators concluded physical activity - especially recreational physical activity - is associated with reduced risk of gastric cancer. Lifestyle interventions focusing on increasing physical activity may decrease the global burden of gastric cancer, in addition to a myriad of other health benefits with being physically active, which include cardiovascular, metabolic and psychologic wellbeing.

Original title:
Physical Activity Is Associated with Reduced Risk of Gastric Cancer: A Systematic Review and Meta-analysis by Singh S, Varayil JE, […], Iyer PG.

Link:
http://cancerprevention.aacrjournals.org/content/7/1/12.abstract

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Objectives:
There have been inconsistent results about the association between consumption of fruits and vegetables and renal cell carcinoma (RCC) risk. Therefore, this review article (meta-analysis) has been conducted.

Does consumption of fruits and vegetables reduce renal cell carcinoma risk?

Study design:
This review article included 19 observational studies (4 cohort, 1 pooled and 14 case-control studies), involving 10,215 subjects with renal cell carcinoma.

Only 4 studies adjusted for all the 3 main risk factors for renal cell carcinoma (16 studies adjusted for tobacco smoking, 15 for BMI and 4 for hypertension).
The majority of included studies (16/19) were of high quality (NOS score ≥ 7).

Results and conclusions:
The investigators found for highest vs. lowest vegetables intake a significant reduced risk of 27% for renal cell carcinoma [SRR = 0.73, 95% CI = 0.63-0.85, I2 = 53.5%, p = 0.004]. Significant means that there is an association with a 95% confidence.

The investigators found for highest vs. lowest vegetables intake a non-significant reduced risk of 13% for renal cell carcinoma in cohort studies [SRR = 0.87, 95% CI = 0.72-1.06].

The investigators found in dose-response analysis a significant reduced risk of 10% for renal cell carcinoma per 1 serving/day vegetables intake [SRR = 0.90, 95% CI = 0.84-0.96, I2 = 69.0%, p 0.001].

The investigators found a non-linear association between vegetable intake and renal cell carcinoma risk [p = 0.001 for non-linearity] with a significant reduction in renal cell carcinoma risk when increasing the intake up to about 3 servings/d intake of vegetables. Higher intake was associated with a further, but more modest decrease in risk.

The investigators found for highest vs. lowest fruits intake a significant reduced risk of 14% for renal cell carcinoma [SRR = 0.86, 95% CI = 0.75-0.98, I2 = 47.4%, p = 0.012].

The investigators found for highest vs. lowest fruits intake a significant reduced risk of 28% for renal cell carcinoma among European [SRR = 0.72, 95% CI = 0.56-0.93]. However, this reduced risk was not significant among North Americans [SRR = 0.97, 95% CI = 0.81-1.16].

The investigators found for highest vs. lowest fruits intake a significant reduced risk of 22% for renal cell carcinoma in population-based case-control studies [SRR = 0.78, 95% CI = 0.63-0.97]. However, this reduced risk was not significant in cohort studies [SRR = 0.90, 95% CI = 0.73-1.10] and in hospital-based case-control studies [SRR = 0.96, 95% CI = 0.69-1.33].

The investigators found in dose-response analysis no associaition between 1 serving/day increment of fruits and renal cell carcinoma risk [SRR = 0.97, 95% CI = 0.93-1.01, I2 = 57.8%, p = 0.011].

The investigators found a linear association between fruits intake and renal cell carcinoma risk [p = 0.221 for non-linearity].

The investigators concluded that consumption of 1-3 servings/d vegetables and high fruits may lower the risk of renal cell carcinoma development. May lower, because significant associations for vegetables and fruits were only observed in case-control, but not in cohort studies. Because of the measurement errors of exposure assessment, the high heterogeneity across studies and unmeasured confounding factors, further investigation with good designs are needed.

Original title:
Consumption of fruits and vegetables and risk of renal cell carcinoma: a meta-analysis of observational studies by Zhang S, Jia Z, [...], Yang J.

Link:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5438616/

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Objectives:
The association of red meat consumption with the risk of stomach cancer has been reported by many studies, with inconclusive results. Therefore, this review article has been conducted.

Does a high red meat consumption increase stomach cancer risk?

Study design:
This review article included a total of 18 studies (cohort and case-control studies) involving 1,228,327 subjects.

Results and conclusions:
The investigators found for the highest versus lowest categories of red meat intake a significant increased risk of 37% for gastric cancer [pooled RR = 1.37, 95% CI = 1.18-1.59, I2 = 67.6%, p 0.001].

The investigators found in population-based case-control studies, a significant increased risk of 58% for gastric cancer [pooled RR = 1.58, 95% CI = 1.22-2.06, I2 = 73.0%, p 0.001].

The investigators found in hospital-based case-control studies, a significant increased risk of 63% for gastric cancer [pooled RR = 1.63, 95% CI = 1.38-1.92, I2 = 19.1%, p = 0.284].

The investigators found, however, no association among cohort studies [RR = 1.00, 95% CI = 0.83-1.20, I2 = 33.9%, p = 0.158].

The investigators found the significant association was also presented in the subgroup analysis by geographic area (Asia, Europe), publication year (≥2000), sample size (1,000, ≥1,000) and quality score (7 stars, ≥7 stars).

The investigators found in dose-response analysis that every 100 g/day increment in red meat intake significant increased gastric cancer risk with 17% [RR = 1.17, 95% CI = 1.05-1.32].

The investigators found in linear regression model that the risk of gastric cancer increased with increasing level of red meat consumption.

The investigators concluded that a increased intake of red meat might be a risk factor for stomach cancer. Might be because the risk was not significant among cohort studies. Therefore, further larger prospective cohort studies are warranted to verify this association.

Original title:
Red meat consumption and stomach cancer risk: a meta-analysis by Song P, Lu M, […], Zhao Q.

Link:
https://link.springer.com/article/10.1007/s00432-014-1637-z

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Objectives:
Does allium vegetable consumption reduce gastric cancer risk?

Study design:
This review article included 22 case-control and 4 cohort studies with more than 10,000 cases.

Results and conclusions:
The investigators found in 10 case-control and 4 cohort studies for the highest versus lowest allium vegetables intake category a significant reduced risk of 22% for gastric cancer [OR = 0.78, 95% CI = 0.67-0.91].

The investigators found in 12 case-control studies for the highest versus lowest garlic intake category a significant reduced risk of 40% for gastric cancer [OR = 0.60, 95% CI = 0.47-0.76].

The investigators found in 13 case-control studies for the highest versus lowest onion intake category a significant reduced risk of 45% for gastric cancer [OR = 0.55, 95% CI = 0.41-0.73].

The investigators found in 4 cohort studies for the highest versus lowest allium vegetables intake category a non-significant increased risk of 2% for gastric cancer [RR = 1.02, 95% CI = 0.88-1.18]. Non-significant means no association with 95% confidence.

The investigators concluded high allium vegetable consumption, like garlic and onion is likely to reduce gastric cancer risk. Likely because this evidence is derived mainly from case-control studies. Therefore, further data from large cohorts are desirable for conclusive confirmation.

Original title:
Allium vegetable intake and gastric cancer: a case-control study and meta-analysis by Turati F, Pelucchi C, […], Galeone C.

Link:
https://www.ncbi.nlm.nih.gov/pubmed/25215621

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Objectives:
Previous studies regarding the relationship between legume intake and risk of prostate cancer have reported inconsistent results. Therefore, this review article (meta-analysis) has been conducted.

Does legume intake reduce prostate cancer risk?

Study design:
This review article included 8 prospective cohort studies reporting 281,034 individuals and 10,234 incident prostate cancer cases.

Results and conclusions:
The investigators found when comparing high consumption of legumes with low consumption a significant reduced risk of 15% [RR = 0.85, 95% CI = 0.75-0.96, p = 0.010, I2 = 45.8%] for prostate cancer.

The investigators found dose-response meta-analysis indicated that the risk of prostate cancer reduced by 3.7% [95% CI = 1.5%-5.8%] for each 20 grams per day increment of legume intake.

The investigators concluded that a high dietary intake of legumes, at least 20 grams per day is associated with a low incidence of prostate cancer.

Original title:
Legume intake and risk of prostate cancer: a meta-analysis of prospective cohort studies by Li J and Mao QQ.

Link:
https://www.ncbi.nlm.nih.gov/pubmed/28423366

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Objectives:
It has been suggested that prenatal exposure to n-3 long-chain fatty acids protects against asthma and other allergy-related diseases later in childhood. The extent to which fish intake in pregnancy protects against child asthma and rhinitis symptoms remains unclear. Therefore, this review article (meta-analysis) has been conducted.

Does fish consumption during pregnancy reduce risk of asthma and other allergy-related diseases later in childhood?

Study design:
This review article included data from 60,774 mother-child pairs participating in 18 European and US birth cohort studies.
Information on wheeze, asthma and allergic rhinitis prevalence was collected using validated questionnaires.
The time periods of interest were: infancy (0-2 years), preschool age (3-4 years) and school age (5-8 years).
The median fish consumption during pregnancy ranged from 0.44 times/week in The Netherlands to 4.46 times/week in Spain.

Results and conclusions:
The investigators found maternal fish intake during pregnancy was not associated with offspring wheeze symptoms in any age group nor with the risk of child asthma [adjusted meta-analysis relative risk per 1-time/week = 1.01, 95% CI = 0.97-1.05] and allergic rhinitis at school age [RR = 1.01, 95% CI = 0.99-1.03].

These results were consistently found in further analyses by type of fish and seafood consumption and in sensitivity analyses.

The investigators concluded maternal fish intake during pregnancy is not associated with offspring wheeze symptoms in any age group (0-2 years, 3-4 years and 5-8 years) or with the risk of child asthma and allergic rhinitis at school age (5-8 years).

Original title:
Fish and seafood consumption during pregnancy and the risk of asthma and allergic rhinitis in childhood: a pooled analysis of 18 European and US birth cohorts by Stratakis N, Roumeliotaki T, […], Chatzi L.

Link:
https://www.ncbi.nlm.nih.gov/pubmed/28338907

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Objectives:
Thyroid cancer (TC) is the most common malignancy of the endocrine system. The relationship between iodine intake and thyroid cancer risk is controversial always. Therefore, this review article (meta-analysis) has been conducted.

Does dietary intake of iodine reduce thyroid cancer risk?

Study design:
This review article included 8 case-control studies with in total 2213 subjects with thyroid cancer and 2761 subjects without thyroid cancer.

With regard to publication bias, owing to the limited number (below 10) of studies included in the saltwater fish, shellfish and iodine intake analyses, publication bias was not assessed.

Results and conclusions:
The investigators found adequate or excess iodine dietary intake (>300 μg/d) significantly decreased the risk of thyroid cancer with 26% [OR = 0.74, 95% CI = 0.60-0.92].

The investigators found high consumption of saltwater fish (≥3 times/wk or ≥12 times/mo) significantly decreased the risk of thyroid cancer with 28% [OR = 0.72, 95% CI = 0.55-0.95, p = 0.02].

The investigators found high consumption of shellfish (≥3 times/wk or ≥12 times/mo) significantly decreased the risk of thyroid cancer with 30% [OR = 0.70, 95% CI = 0.52-0.96, p = 0.03].

The investigators concluded a higher intake of dietary iodine (>300 μg/d) may decrease the risk of thyroid cancer in populations mainly based in coastal cities or on islands. May decrease, because this review article did not include cohort  studies.

Original title:
The relationship between iodine intake and the risk of thyroid cancer: A meta-analysis by Cao LZ, Peng XD, [...], Li S.

Link:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5440127/

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Objectives:
Prostate cancer (PCa) is the fifth leading cause of cancer-related deaths worldwide. Many epidemiological studies have investigated the association between prostate cancer and lycopene, however, results have been inconsistent. Therefore, this review article (meta-analysis) has been conducted.

Does lycopene reduce prostate cancer risk?

Study design:
This review article included 42 studies including 43,851 cases of prostate cancer reported from 692,012 participants.

Results and conclusions:
The investigators found dietary intake of lycopene was significantly associated with a reduced prostate cancer risk of 12% [RR = 0.88, 95% CI = 0.78-0.98, p = 0.017].

The investigators found circulating concentrations of lycopene were significantly associated with a reduced prostate cancer risk of 12% [RR = 0.88, 95% CI = 0.79-0.98, p = 0.019].

The investigators found sensitivity analyses within the dose-response analysis further revealed a significant linear dose-response for dietary lycopene and prostate cancer risk such that prostate cancer decreased by 1% for every additional 2 mg of lycopene consumed [p = 0.026].

The investigators found prostate cancer risk decreased by 3.5 to 3.6% for each additional 10 μg/dL of circulating lycopene in the linear and nonlinear models, respectively [p-linear = 0.004, p-non linear = 0.006].

The investigators found no association between lycopene and advanced prostate cancer. However, there was a trend for protection against prostate cancer aggressiveness [RR = 0.74, 95% CI = 0.55-1.00, p = 0.052].

The investigators concluded that higher dietary and circulating lycopene concentrations reduce prostate cancer risk. This was accompanied by dose-response relationships for dietary and circulating lycopene. Further studies are required to determine the mechanisms underlying these associations.

Original title:
Increased dietary and circulating lycopene are associated with reduced prostate cancer risk: a systematic review and meta-analysis by Rowles JL, Ranard KM, […], Erdman JW Jr.

Link:
https://www.ncbi.nlm.nih.gov/pubmed/28440323

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Objectives:
There are conflicting reports on the correlation between manganese (Mn) levels and breast cancer. Therefore, this review article (meta-analysis) has been conducted.

Does manganese deficiency increase risk of breast cancer?

Study design:
This review article included 11 case-control studies involving 1302 subjects.

There was no evidence of publication bias. Sensitivity analysis showed that excluding any one study from the pooled analysis did not vary the results substantially.

Results and conclusions:
The investigators found the random-effects meta-analysis results indicated that subjects with breast cancer had lower manganese levels in serum and hair than healthy controls [SMD = -1.51, 95% CI = -2.47 to -0.56, I2 = 97.8%, p 0.001].

The investigators found in subgroup analysis that subjects with breast cancer had lower manganese levels than healthy controls in China [SMD = -1.32, 95% CI = -2.33 to -0.32] and Korea [SMD = -4.08, 95% CI = -4.63 to -3.54], but not in Turkey [SMD = -0.96, 95% CI = -3.19 to 1.27].

The investigators found in subgroup analysis that the differences of manganese levels between patients with breast cancer and healthy controls were similar in different sample specimens:
serum [SMD = -1.24, 95% CI = -2.31 to -0.16];
hair [SMD = -1.99, 95% CI = -3.91 to -0.06] and;
different types of manganese measurement:

ICP-AAS [SMD = -1.14, 95% CI = -2.24 to -0.04];
GFAAS [SMD = -1.94, 95% CI = -2.38 to -1.49];
ICP-AES [SMD = -3.77, 95% CI = -4.70 to -2.85]. These findings can well explain that  the between-study variability was the main source of heterogeneity.

The investigators concluded there is an association between deficient manganese concentration and breast cancer. However, the subgroup analysis found that there was contradiction regarding races and geography, like China and Turkey. Thus this finding needs further confirmation by trans-regional multicenter, long-term observation in a cohort design to obtain better understanding of causal relationships between manganese levels and breast cancer, through measuring manganese at baseline to investigate whether the highest manganese category versus lowest was associated with breast cancer risk.

Original title:
The association between deficient manganese levels and breast cancer: a meta-analysis by Shen F, Cai WS, [...],Xu B.

Link:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4443096/

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Objectives:
Does polyphenol supplementation increase sport performance?

Study design:
This review article included 14 studies. Of these, the studied populations were predominately-trained males with an average intervention dose of 688 ± 478mg polyphenols per day.

Results and conclusions:
The investigators found pooled results demonstrated polyphenol supplementation for at least 7 days significantly increased performance by 1.90% [95% CI = 0.40-3.39].

The investigators found sub-analysis of 7 studies using quercetin significantly increased performance by 2.82% [95% CI = 2.05-3.58].

The investigators found no adverse effects reporting in studies in relation to the intervention.

The investigators concluded daily 688mg polyphenol supplementation, preferably quercetin supplementation for at least 7 days increases performance in healthy individuals.

Original title:
Polyphenols and Performance: A Systematic Review and Meta-Analysis by Somerville V, Bringans C and Braakhuis A.

Link:
https://www.ncbi.nlm.nih.gov/pubmed/28097488

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Objectives:
Quantification of the association between the intake of fruit and vegetables and risk of esophageal squamous cell carcinoma (ESCC) is controversial even though several studies have explored this association. Therefore, this review article (meta-analysis) has been conducted.

Does a high intake of vegetables and fruit decrease risk of esophageal squamous cell carcinoma?

Study design:
This review article included a total of 32 observational studies involving 10037 cases of esophageal squamous cell carcinoma.

There was no evidence of publication bias.

Results and conclusions:
The investigators found highest vs. lowest vegetable intake, significantly reduced risk of esophageal squamous cell carcinoma with 44% [SRR = 0.56, 95% CI = 0.45-0.69, p-heterogeneity 0.001]. Significant means there is an association with a 95% confidence.

The investigators found highest vs. lowest fruit intake, significantly reduced risk of esophageal squamous cell carcinoma with 47% [SRR = 0.53, 95% CI = 0.44-0.64, p-heterogeneity 0.001].

The investigators found similar results in a linear dose-response analysis and there was evidence of non-linear associations for intakes of fruit [p non-linearity 0.001] and vegetables [p non-linearity = 0.041].

The investigators concluded that intakes of vegetables and fruit reduce risk of esophageal squamous cell carcinoma. Further investigation with prospective designs, validated questionnaires and good control of important confounders is warranted.

Original title:
Intake of fruit and vegetables and risk of esophageal squamous cell carcinoma: A meta-analysis of observational studies by Liu J, Wang J, […], Lv C.

Link:
http://www.ncbi.nlm.nih.gov/pubmed/23319052

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Objectives:
Prostate cancer (PCa) now remains the 2nd most frequently diagnosed cancer. In recent years, chemoprevention for prostate cancer becomes a possible concept. Especially, many phytochemicals rich foods are suggested to lower the risk of cancer. Among these foods, green tea is considered as effective prevention for various cancers. However, clinical trials and previous meta-analyses on the relationship between green tea consumption and the risk of prostate cancer have produced inconsistent outcomes. Therefore, this review article (meta-analysis) has been conducted.

Does green tea intake reduce prostate cancer risk?

Study design:
This review article included 4 cohort studies, 3 case-control studies and 3 RCTs. The cohort studies and case-control studies which investigated the association between green tea intake and prostate cancer risk included 1435 cases among 96,332 individuals and the 3 RCTs studied the relationship between EGCG and prostate cancer incidence included 87 volunteers in EGCG arms of 179 individuals.

No publication bias was found.

Results and conclusions:
The investigators found in observational studies (4 cohort studies and 3 case-control studies) for the highest versus lowest category of green tea intake a non-significant reduced prostate cancer risk of 8% [RR = 0.92, 95% CI = 0.77-1.11, I2 = 0%, p = 0.46] for all studies;

a non-significant reduced prostate cancer risk of 2.3% [RR = 0.977, 95% CI = 0.80-1.19] for cohort studies and;
a non-significant reduced prostate cancer risk of 27.7% [RR = 0.623, 95% CI = 0,368-1.056, I2  = 0%, p =  0.46] for case-control studies.

The investigators found no association between 1-5 cups of green tea per day and prostate cancer risk.

However, the investigators found 7 cups of green tea per day significantly reduced prostate cancer risk with 19% [RR = 0.81, 95% CI = 0.67-0.97]. The significant reduced prostate cancer risk increased to 26% [RR = 0.74, 95% CI = 0.59-0.93] for 9 cups and to 44% [RR = 0.56, 95% CI = 0.35-0.92) for 15 cups.

The investigators found in 3 RCTs when compared to placebo green tea catechins significantly reduced prostate cancer risk  with 62% [RR = 0.38, 95% CI = 0.16-0.86, p  =  0.02].

The investigators concluded that at least 7 cups/day green tea intake reduces prostate cancer. This is further confirmed by the potential protective effect of green tea catechins on prostate cancer. Further prospective study with accurate measurement of green tea intake is required to substantiate these conclusions.

Original title:
Green tea and the risk of prostate cancer: A systematic review and meta-analysis by Guo Y, Zhi F, […], Zhang X.

Link:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5380255/

Additional information of El Mondo:
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Objectives:
The association between meat consumption and the risk of hepatocellular carcinoma (HCC) is still inconclusive. Therefore, this review article has been conducted.

Does meat consumption increase risk of hepatocellular carcinoma?

Study design:
This review article included 7 cohort studies and 10 case-control studies.

Results and conclusions:
The investigators found for the highest vs. lowest consumption levels a non-significant increased risk for hepatocellular carcinoma of 10% [RR = 1.10, 95% CI = 0.85-1.42] for red meat, a non-significant increased risk of 1% [RR = 1.01, 95% CI = 0.79-1.28] for processed meat and a non-significant decreased risk of 3% [RR = 0.97, 95% CI = 0.85-1.11] for total meat. Non-significant means, there is no association with a 95% confidence.

The investigators found for the highest vs. lowest consumption levels a significant decreased risk for hepatocellular carcinoma of 31% [RR = 0.69, 95% CI = 0.58-0.81] for white meat and a significant decreased risk of 22% [RR = 0.78, 95% CI = 0.67-0.90] for fish. The results remained quite stable after stratification by the confounding factors.
Significant means, there is an association with a 95% confidence.

The investigators concluded a high level of white meat or fish consumption reduces the risk of hepatocellular carcinoma, while intake of red meat, processed meat or total meat is not associated with hepatocellular carcinoma risk. These results suggest that dietary intervention may be a promising approach for prevention of hepatocellular carcinoma, which still need to be confirmed by further well-designed prospective studies and experimental research.

Original title:
Systematic review with meta-analysis: meat consumption and the risk of hepatocellular carcinoma by Luo J, Yang Y, [...], Zhu Y.

Link:
http://www.ncbi.nlm.nih.gov/pubmed/24588342

Additional information of El Mondo:
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A review article of cohort studies or case-control studies will answer the following question:
"Should I change my diet?".

Objectives:
Is there an association between meat intake and risk of esophageal cancer?

Study design:
This review article included 7 cohort studies and 28 case-control studies.

Results and conclusions:
The investigators found for the highest versus lowest total meat consumption categories a non-significant increased risk of 19% [95% CI = 0.98-1.46] for esophageal cancer.

The investigators found for the highest versus lowest red meat consumption categories a significant increased risk of 55% [95% CI = 1.22-1.96] for esophageal cancer.

The investigators found for the highest versus lowest processed meat consumption categories a significant increased risk of 33% [95% CI = 1.04-1.69] for esophageal cancer.

The investigators found for the highest versus lowest white meat consumption categories a significant decreased risk of 28% [95% CI = 0.60-0.86] for esophageal cancer.

The investigators found for the highest versus lowest poultry consumption categories a significant decreased risk of 17% [95% CI = 0.72-0.96] for esophageal cancer.

The investigators found for the highest versus lowest fish consumption categories a non-significant decreased risk of 5% [95% CI = 0.76-1.19] for esophageal cancer.

The investigators found when stratified by histological subtype, positive associations among esophageal squamous cell carcinoma and red meat, white meat and poultry and esophageal adenocarcinoma with total meat and processed meat.

The investigators concluded red meat and processed meat consumption increase risk of esophageal cancer, while white meat and poultry decrease risk of esophageal cancer. Fish consumption is not associated with incidence of esophageal cancer.

Original title:
Meat consumption is associated with esophageal cancer risk in a meat- and cancer-histological-type dependent manner by Zhu HC, Yang X, […], Sun XC.

Link:
http://www.ncbi.nlm.nih.gov/pubmed/24395380

Additional information of El Mondo:
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Objectives:
Epidemiological studies assessing the relationship between dietary vitamin B2 and the risk of breast cancer have produced inconsistent results. Therefore, this review article (meta-analysis) has been conducted.

Does dietary vitamin B2 intake reduce breast cancer risk?

Study design:
This review article included 10 epidemiologic studies (cohort or patient-controle studies) comprising totally 12,268 breast cancer patients.

No publication bias was found.

Results and conclusions:
The investigators found comparing the highest to the lowest dietary vitamin B2 intake a significant reduced risk of 15% for breast cancer [pooled relative risk = 0.85, 95% CI = 0.76-0.95, I2 = 40.7%].

The investigators found dose-response analysis showed that an increment of 1 mg/day dietary vitamin B2 intake significantly reduced risk of breast cancer with 6% [relative risk = 0.94, 95% CI = 0.90-0.99].

The investigators concluded that dietary vitamin B2 intake, at least 1 mg/day, is related to the reduced risk of breast cancer. However, additional research is also necessary to further explore this association.

Original title:
Dietary vitamin B2 intake and breast cancer risk: a systematic review and meta-analysis by Yu L, Tan Y and Zhu L.

Link:
https://www.ncbi.nlm.nih.gov/pubmed/28035488

Additional information of El Mondo:
Find more information/studies on vitamin B2 and breast cancer right here.
 

Objectives:
Is there an association of intake of different vitamins and multiple-vitamin supplements and the incidence of colorectal cancer?

Study design:
This review article included 47 articles (cohort studies).

There was unacceptable heterogeneity for studies of multiple-vitamin supplements, so findings were inconclusive.

Results and conclusions:
The investigators found a significant reduced risk of 12% [multivariable-adjusted RR = 0.88, 95% CI = 0.81-0.95] for colorectal cancer when comparing the highest versus lowest dietary vitamin B9 (folate) intake. Significant means that there is an association with a 95% confidence.

The investigators found a significant reduced risk of 13% [multivariable-adjusted RR = 0.87, 95% CI = 0.77-0.99] for colorectal cancer when comparing the highest versus lowest dietary vitamin D intake. Significant because RR of 1 was not found in the 95% CI of 0.77 to 0.99. RR of 1 means no risk/association.

The investigators found a significant reduced risk of 12% [multivariable-adjusted RR = 0.88, 95% CI = 0.79-0.99] for colorectal cancer when comparing the highest versus lowest dietary vitamin B6 intake.

The investigators found a significant reduced risk of 14% [multivariable-adjusted RR = 0.86, 95% CI = 0.76-0.97] for colorectal cancer when comparing the highest versus lowest dietary vitamin B2 intake.

The investigators found, however, no association between both dietary vitamine A, C, E, B3 and B12 and the risk of colorectal cancer.

The investigators concluded high dietary vitamin B9 (folate), D, B6 and B2 intake reduces risk of colorectal cancer, but further study is needed.

Original title:
Vitamin and multiple-vitamin supplement intake and incidence of colorectal cancer: a meta-analysis of cohort studies by Liu Y, Yu Q, […], Li K.

Link:
https://www.ncbi.nlm.nih.gov/pubmed/25491145

Additional information of El Mondo:
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Objectives:
Red meat intake has been associated with risk of colorectal cancer, potentially mediated through heterocyclic amines. The metabolic efficiency of N-acetyltransferase 2 (NAT2) required for the metabolic activation of such amines is influenced by genetic variation. The interaction between red meat intake, NAT2 genotype and colorectal cancer has been inconsistently reported. Therefore, this review article has been conducted.

Is there an interaction between red meat intake, NAT2 genotype and colorectal cancer?

Study design:
This review article included 11 retrospective case-control studies with 8,290 colorectal cancer cases and 9,115 controls (subjects without colorectal cancer).

Results and conclusions:
The investigators found the highest quartile of red meat intake was associated with a 41% increased risk of colorectal cancer compared with the lowest quartile [OR = 1.41, 95% CI = 1.29-1.55].
However, a significant association was observed only for studies with retrospective diet data, not for studies with diet prospectively assessed before cancer diagnosis.

The investigators found when combining all studies, high red meat intake was similarly associated with colorectal cancer in those with a rapid/intermediate NAT2 genotype [OR = 1.38, 95% CI = 1.20-1.59] as with a slow genotype [OR = 1.43, 95% CI = 1.28-1.61, p interaction = 0.9].

The investigators concluded high red meat intake was associated with increased risk of colorectal cancer only from retrospective case-control studies and not modified by NAT2 enzyme activity.

Original title:
Red Meat Intake, NAT2, and Risk of Colorectal Cancer: A Pooled Analysis of 11 Studies by Ananthakrishnan AN, Du M, […], Chan AT.

Link:
http://cebp.aacrjournals.org/content/cebp/24/1/198.full.pdf

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Objectives:
The association between dietary carbohydrate intake and colorectal cancer risk remains controversial. Therefore, this review article (meta-analysis) has been conducted.

Does higher dietary carbohydrate intake increase colorectal cancer risk?

Study design:
This review article included 8 case-controle studies en 9 prospective cohort studies involving 14,402 colorectal cancer patients among 846004 participants; 17 studies with 9,235 cases were to assess the association on colon cancer and 13  studies with 3,272 cases were to  assess the association on rectum cancer. 

No publication bias was found.

Results and conclusions:
The investigators found no association between dietary carbohydrate intake and colorectal cancer risk [pooled RR = 1.08, 95% CI = 0.93-1.23, I2 = 68.3%, p-heterogeneity 0.001]. No association because RR of 1 was found in the 95% CI of 0.93 to 1.23. RR of 1 means no risk/association.

The investigators found no association between dietary carbohydrate intake and colon cancer risk [pooled RR = 1.09, 95% CI = 0.95-1.25, I2 = 48.3%].

The investigators found no association between dietary carbohydrate intake and rectum cancer risk [pooled RR = 1.17, 95% CI = 0.98-1.39, I2 = 17.8%].

The investigators found in subgroup analyses for study design, a non-significant association for both case-control studies [summary RR = 1.40, 95% CI = 0.93-2.09] and cohort studies [summary RR = 0.99, 95% CI = 0.85-1.15].  

The investigators found in stratified analysis by geographic locations, higher dietary   carbohydrate intake had no significant association on colorectal cancer risk among American populations [summary RR = 1.08, 95% CI = 0.89-1.30], European populations [summary RR = 1.23, 95% CI = 0.91-1.64] or Asian population [summary RR = 0.98, 95% CI = 0.65-1.46].

The investigators found higher dietary carbohydrate intake significantly increased risk of colorectal cancer with 23% in men populations [summary RR = 1.23, 95% CI = 1.01-1.57], but not in women populations.

The investigators concluded that higher dietary carbohydrate intake increases colorectal cancer risk in men populations. Further studies are wanted to confirm this relationship.

Original title:
A meta-analysis between dietary carbohydrate intake and colorectal cancer risk: Evidence from 17 observational studies by Huang J, Pan G, [...], Zhu Z.

Link:
http://www.bioscirep.org/content/ppbioscirep/early/2017/03/15/BSR20160553.full.pdf

Additional information of El Mondo:
Find more information/studies on carbohydrates and colorectal cancer right here.
 

Objectives:
Previous observational studies regarding the existence of an association between folate intake and the risk of breast cancer have been inconsistent. Therefore, this review article has been conducted.

Does a higher dietary folate intake reduce breast cancer risk?

Study design:
This review article included 14 prospective cohort studies that reported data on 677,858 individuals.
The participant follow-up period ranged 4.7-17.4 years and the number of individuals per study ranged 11,699-88,818.
There was no publication bias.

Results and conclusions:
The investigators found no association between dietary folate intake and breast cancer risk for highest versus lowest category  [RR =  0.97, 95% CI = 0.90-1.05, p  = 0.451, I2 =  57.5%, p = 0.004].

The investigators found dose-response meta-analysis findings showed no association between the risk of breast cancer and a 100 µg/day increase in dietary folate intake [RR = 0.99, 95% CI = 0.98-1.01, p = 0.361, I2 = 66.2%, p 0.001].

The investigators found evidence of a nonlinear relationship between dietary folate intake and the risk of breast cancer.

A daily dietary folate intake of 200-320 µg was associated with a reduced risk of breast cancer. However, daily folate intake levels >400 µg was associated with a increased risk of breast cancer.

The investigators found overall folate intake level was associated with a reduced breast cancer risk of 36% if the patients had a daily alcohol intake >10 g [RR for highest versus lowest category = 0.64, 95% CI = 0.43-0.97].

The investigators concluded there are no effects of increased dietary folate intake on the incidence of breast cancer. But, a daily dietary folate intake of 200-320 µg was associated with a reduced risk of breast cancer. However, daily folate intake levels >400 µg was associated with a increased risk of breast cancer. Future studies should focus on specific populations in order to analyze primary breast cancer prevention.

Original title:
Folate Intake and the Risk of Breast Cancer: A Dose-Response Meta-Analysis of Prospective Studies by Zhang YF, Shi WW, […], Zhou YH.

Link:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4059748/

Additional information of El Mondo:
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Objectives:
There is no published systematic review and meta-analysis regarding the effect of olive oil consumption on cancer occurrence. Therefore, this review article has been conducted.

Does olive oil consumption reduce cancer risk?

Study design:
This review article included 19 case-control studies (13800 cancer patients and 23340 controls).

Random effects meta-analysis was applied in order to evaluate the research hypothesis.
Heterogeneity of the effect-size measures was observed in studies performed in the Mediterranean region (n = 15, p = 0.0002), whereas no heterogeneity was observed in non-Mediterranean studies (n = 4, p = 0.12).

Results and conclusions:
The investigators found when comparing with the lowest, the highest category of olive oil consumption was significantly associated with lower odds of having any type of cancer [log odds ratio = -0.41, 95% CI = -0.53 to -0.29, Cohran's Q = 47.52, p = 0.0002, I2 = 62%].

The investigators found both Mediterranean and non-Mediterranean people reported olive oil intake were less likely to have developed any type of cancer.

The investigators found olive oil consumption was significantly associated with lower odds of developing breast cancer [logOR = -0.4,  95% CI = -0.78 to -0.12] and a cancer of the digestive system [logOR = -0.36, 95% CI = -0.50 to -0.21] compared with the lowest intake.

The investigators concluded olive oil consumption probably reduces risk of any type of cancer, especially breast cancer and cancer of the digestive system. Probably, because this review article only included case-control studies and there was heterogeneity.
The reduced risk is similar to studies performed in Mediterranean as well as non-Mediterranean countries. However, it is still unclear whether olive oil's monounsaturated fatty acid content or its antioxidant components are responsible for its beneficial effects.

Original title:
Olive oil intake is inversely related to cancer prevalence: a systematic review and a meta-analysis of 13800 patients and 23340 controls in 19 observational studies by Psaltopoulou T, Kosti RI, […], Panagiotakos DB.

Link:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3199852/

Additional information of El Mondo:
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Objectives:
Many studies suggest that high-fat diets are linked to the etiology of non-Hodgkin's lymphoma (NHL). However, the findings are inconsistent and therefore the association between fat and non-Hodgkin's lymphoma remains unclear. Therefore, this review article (meta-analysis) has been conducted.

Does a high fat dietary intake increase non-Hodgkin's lymphoma risk?

Study design:
This review article included two cohort studies and eight case-control studies.

The funnel plot revealed no evidence for publication bias.

Results and conclusions:
The investigators found a significant higher risk of 26% for non-Hodgkin's lymphoma for total fat consumption [RR = 1.26, 95% CI = 1.12-1.42]. Significant because RR of 1 was not found in the 95% CI of 1.12 to 1.42. RR of 1 means no risk/association.

The investigators found subgroup analysis showed a significant higher risk of 41% for diffuse large B-cell lymphoma for total fat consumption [RR = 1.41, 95% CI = 1.08-1.84]. However, there was no significant association between total fat consumption and increase risk of follicular lymphoma [RR = 1.21, 95% CI = 0.97-1.52], small lymphocytic lymphoma/chronic lymphocytic leukemia [RR = 0.91, 95% CI = 0.68-1.23] nor with T cell lymphoma [RR = 1.12, 95% CI = 0.60-2.09].
No significant because RR of 1 was found in the 95% CI of 0.60 to 2.09. RR of 1 means no risk/association.

The investigators concluded that total fat consumption increases non-Hodgkin's lymphoma; especially diffuse large B-cell lymphoma.

Original title:
Dietary Fat Consumption and Non-Hodgkin's Lymphoma Risk: A Meta-analysis by Han TJ, Li JS, [...], Xu HZ.

Link:

https://www.ncbi.nlm.nih.gov/pubmed/28094569

Additional information of El Mondo:
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Lymphoma is the most common blood cancer. The two main forms of lymphoma are Hodgkin lymphoma and non-Hodgkin lymphoma (NHL). The human body has two main types of lymphocytes that can develop into lymphomas:

1. B lymphocytes (B cells) and;
2. T lymphocytes (T cells).

B-cell lymphomas are much more common than T-cell lymphomas and account for approximately 85 percent of all non-Hodgkin lymphomas. Diffuse large B cell lymphomas (DLBCLs) are the commonest subtype of non-Hodgkin's lymphoma. They constitute about 30 to 40% of adult non-Hodgkin's lymphoma.

A high total fat consumption corresponds to a diet with >35 En% fat and/or >10 En% saturated fat. A diet with >35 En% fat is a diet with a lot of products/meals providing >35 En% fat.