Nutritional advice

Objectives:
With an aging population and no cure for dementia on the horizon, risk factor modification prior to disease onset is an urgent health priority. Therefore, this meta-analysis (review article) has been conducted.

What is the effect of low vitamin D status or vitamin D supplementation on cognition in midlife and older adults without a diagnosis of dementia?

Study design:
This review article included 26 observational (cross-sectional and longitudinal cohort) studies and 3 intervention studies (n = 19-9,556).

Results and conclusions:
The investigators found in 26 observational studies that low vitamin D status was associated with worse cognitive performance [OR = 1.24, CI = 1.14-1.35] and cognitive decline [OR = 1.26, CI = 1.09-1.23] in midlife and older adults without a diagnosis of dementia; with cross-sectional yielding a stronger effect compared to longitudinal studies.

However, the investigators found in 3 intervention studies that vitamin D supplementation showed no significant benefit on cognition compared with control [SMD = 0.21, CI = -0.05 to 0.46].

The investigators concluded that observational evidence demonstrates low vitamin D is related to poorer cognition in midlife and older adults without a diagnosis of dementia; however, interventional studies are yet to show a clear benefit from vitamin D supplementation. From the evidence to date, there is likely a therapeutic age window relevant to the development of disease and therefore vitamin D therapy. Longitudinal lifespan studies are necessary to depict the optimal timing and duration in which repletion of vitamin D may protect against cognitive decline and dementia in aging, to better inform trials and practice towards a successful therapy.

Original title:
A Systematic Review and Meta-Analysis of The Effect of Low Vitamin D on Cognition by Goodwill AM and Szoeke C.

Link:
https://www.ncbi.nlm.nih.gov/pubmed/28758188

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Objectives:
Many publications have investigated the association between metal ions and the risk of Alzheimer's disease (AD), but the results were ambiguous. Therefore, this meta-analysis (review article) has been conducted.

What is the association between serum copper/zinc/iron levels and Alzheimer's disease risk?

Study design:
This review article included 44 case-control studies.

Results and conclusions:
The investigators found in 35 case-control studies (2,128 Alzheimer's disease patients and 2,889 healthy controls. The mean age of the patient groups was >54), that serum copper levels were significant higher in Alzheimer's disease patients [MD = 9.13, 95% CI = 6.17 to 12.09, p 0.00001].

The investigators found in 22 case-control studies (1,027 Alzheimer's disease patients and 1,949 healthy controls. The mean age of the patient groups was >54), that serum zinc levels were significant lower in Alzheimer's disease patients [MD = -7.80, 95% CI = -11.61 to -3.99, p 0.0001].

The investigators found in 25 case-control studies (1,379 Alzheimer's disease patients and 1,664 healthy controls. The mean age of the patient groups was >62.74), that serum iron levels were significant lower in Alzheimer's disease patients [MD = -13.01, 95% CI = -20.75 to -5.27, p = 0.001].

The investigators concluded that serum copper levels are significantly increased, while serum zinc/iron levels are significantly decreased in Alzheimer's disease patients.

Original title:
Serum Copper, Zinc, and Iron Levels in Patients with Alzheimer's Disease: A Meta-Analysis of Case-Control Studies by Li DD, Zhang W, [...], Zhao P.

Link:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5605551/

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Objectives:
The potential glucose-lowering effects of pomegranate have been reported in animal and observational studies, but intervention studies in humans have generated mixed results. Therefore, this review article (meta-analysis) has been conducted.

What are the effects of pomegranate supplementation on measures of glucose control, insulin levels and insulin sensitivity in humans?

Study design:
This review article included 16 RCTs with 538 subjects. 14 trials adopted parallel study designs and the 2 remaining trials used crossover designs.
The total number of subjects included in each study ranged from 14 to 74 subjects.
The mean age of participants in each trial ranged from 30 to 70 years, with differing age ranges in most studies.
11 studies used pomegranate juice as a supplement (the dosage ranged from 120 to 500 ml/day).
2 studies used pomegranate seed oil as treatments (the dosage ranged from 400 to 2000 mg/day).
3 studies utilized pomegranate extract as the intervention (the dosage ranged from 710 to 1420 mg/day).  
The duration of the pomegranate intervention varied from 1 to 12 weeks (median: 5.5 weeks).

Overall, significant heterogeneity was detected for FBI and HOMA-IR, but subgroup analysis could not identify factors significantly influencing these parameters.
No significant publication bias was found.

Results and conclusions:
The investigators found that pomegranate did not significantly affect the measures of:
-FBG (fasting blood glucose) [WMD = -0.6 mg/dL, 95% CI = -2.79 to 1.58, p = 0.59, I2 = 0%];
-FBI (fasting blood insulin) [WMD = 0.29 μIU/mL, 95% CI = -1.16 to 1.75, p = 0.70, I2 = 60.4%];
-HOMA-IR (homeostatic model assessment of insulin resistance) [WMD = -0.04, 95% CI = -0.53 to 0.46, p = 0.88, I2 = 59.8%] or;
-HbA1c (glycated haemoglobin) [WMD = -0.11%, 95% CI = -0.39 to 0.18, p = 0.46, I2 = 0%].
These results were robust in sensitivity analysis.

The investigators found meta-regression analysis showed that the factor (dose of pomegranate juice supplementation) was not associated with the treatment effects on FBG level [coefficient = -0.006, 95% CI = -0.023 to 0.011, p = 0.46].

The investigators found no significant difference in the FBG-lowering effect between trials that were conducted in subjects with cardiovascular disease risk [WMD = 0.30 mg/dL, 95% CI = -2.36 to 2.97, p = 0.82] and those that were conducted in healthy individuals [WMD = -2.53 mg/dL, 95% CI = -6.36 to 1.30, p = 0.19].

The investigators found no statistically significant differences in the pooled effects of pomegranate on FBG in the subgroups stratified by study designs, intervention durations, types of intervention, baseline BMI and baseline FBG levels (FBG levels at the beginning of the studie).

The investigators concluded pomegranate supplements have no favourable effect on improvements in glucose and insulin metabolism. The current evidence suggests that daily pomegranate supplementation is not recommended as a potential therapeutic strategy in glycemic management. Further large-scale RCTs with longer duration are required to confirm these results.

Original title:
Lack of efficacy of pomegranate supplementation for glucose management, insulin levels and sensitivity: evidence from a systematic review and meta-analysis by Huang H, Liao D, […], Zhu Y.

Link:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5629805/

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Objectives:
Do patients with type 2 diabetes benefit from a low carbohydrate diet?

Study design:
This review article included a total of 9 RCTs with 734 patients with type 2 diabetes.

Results and conclusions:
The investigators found that low carbohydrate diet significantly reduced HbA1c level [WMD = -0.44, 95% CI = -0.61 to -0.26, p= 0.00] of patients with type 2 diabetes.

The investigators found that low carbohydrate diet significantly reduced triglycerides concentration [WMD = -0.33, 95% CI = -0.45 to -0.21, p = 0.00] of patients with type 2 diabetes.

The investigators found that low carbohydrate diet significantly increased HDL cholesterol concentration (WMD = 0.07, 95% CI = 0.03 to 0.11, p = 0.00] of patients with type 2 diabetes.

The investigators found that low carbohydrate diet was not associated with decreased level of total cholesterol and LDL cholesterol.

The investigators found subgroup analyses showed that short term intervention of low carbohydrate diet was effective for weight loss [WMD = -1.18, 95% CI = -2.32 to -0.04, p = 0.04] in patients with type 2 diabetes.

The investigators concluded there is a beneficial effect of low carbohydrate diet intervention on glucose control in patients with type 2 diabetes. The low carbohydrate diet intervention also has a positive effect on triglycerides and HDL cholesterol concentrations, but without significant effect on long term weight loss.

Original title:
Efficacy of low carbohydrate diet for type 2 diabetes mellitus management: A systematic review and meta-analysis of randomized controlled trials by Meng Y, Bai H, […], Chen L.

Link:
https://www.ncbi.nlm.nih.gov/pubmed/28750216

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A low carbohydrate diet is a diet that is largely made up of meals/products with 20-40 En% carbohydrate. Practically, this means that all meals/products that you eat on a daily basis should on average contain 20-40 En% carbohydrate.
20-40 En% carbohydrate means that the total amounts of carbohydrate make up for a 20-40% of the total kcal of the diet. Check here which products contain 20-40 En% carbohydrate.

Objectives:
Polyunsaturated fats (PUFAs) have been shown to reduce type 2 diabetes (T2DM) risk and improve insulin responsiveness in T2DM subjects, but whether the plant sources of omega-3 PUFA (alpha-linolenic acid [ALA]) have an effect on glycemic control requires further investigation. Therefore, this review article (meta-analysis) has been conducted.

Does alpha-linolenic acid dietary intake reduce diabetes risk?

Study design:
This review article included a total of 8 RCTs involving 212 participants with type 2 diabetes.
5 trials (62.5%) were parallel designs and 3 (37.5%) were crossover designs.
Participants were generally middle-aged (median age  =  54 years, range  =  47-64 years) and overweight or obese (median BMI  =  30.7, range  =  28.0-33.2).
Overall, participants had controlled diabetes (median HbA1c = 6.8%, median FBG = 7.95 mmol/L) and the majority of studies indicated the use of hypoglycemic drugs or other medications, although all studies excluded the use of insulin therapy.
The dose of ALA ranged from 1.5 to 7.4 g/day with a median assigned dose of 4.4, 5.4 and 5.4 g/day of ALA for trials that reported HbA1c, FBG and FBI, respectively.
The median duration of the treatment was 3 months, ranging from 2 to 12 months.
7 studies (87.5%) were considered high quality (MQS ≥8).

Results and conclusions:
The investigators found compared to a control diet, a median dose of 4.4 g/day of alpha-linolenic acid intake for a median duration of 3 months did not affect HbA1c (%) of patients with type 2 diabetes [MD =  -0.01, 95% = -0.32 to 0.31, p  =  0.96].

The investigators found compared to a control diet, a median alpha-linolenic acid dose of 5.4 g/day did not lower fasting blood glucose (FBG) of patients with type 2 diabetes [MD  = 0 .07, 95% CI = -0.61 to 0.76, p  = 0 .84] or fasting blood insulin (FBI) of patients with type 2 diabetes [MD  =  7.03, 95% CI = -5.84 to 19.89, p  = 0 .28].

The investigators found summary effect estimates were generally compromised by considerable and unexplained heterogeneity [I2 ≥ 75%].

The investigators found in the subgroup analysis of continuous predictors, a reduction in HbA1c (%) and FBG (mmol/L) was significantly associated with an increased intake of ALA.

The investigators found further adjustment for publication bias using Duval and Tweedie's trim-and-fill analysis provided an adjusted, significant MD of 0.25 [95% CI = -0.38 to -0.12, 0.001) for HbA1c (%).

The investigators concluded alpha-linolenic acid-enriched diet with a median alpha-linolenic acid dose of 4.4 g/day during 3 months has no effects on HbA1c, FBG or FBI in patients with type 2 diabetes. The scarce number of existing RCTs and the presence of heterogeneity in the meta-analysis limit the ability to make firm conclusions about alpha-linolenic acid in type 2 diabetes management. The potential for alpha-linolenic acid to have dose-dependent effects warrants further research in this area.

Original title:
The effect of alpha-linolenic acid on glycemic control in individuals with type 2 diabetes: A systematic review and meta-analysis of randomized controlled clinical trials by Jovanovski E1, Li D, […], Vuksan V.

Link:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5457843/

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4.4 g/day alpha-linolenic acid can be achieved by taking 1 to 2 tablespoons of flax or salba-chia seeds or about 12 whole walnuts per day.

 

Objectives:
Available studies in the literature on the selenium levels in Alzheimer's disease (AD) are inconsistent with some studies reporting its decrease in the circulation, while others reported an increase or no change as compared to controls. Therefore, this meta-analysis (review article) has been conducted.

Do lower circulatory (plasma/serum and blood), erythrocyte and cerebrospinal fluid (CSF) selenium levels increase Alzheimer's disease risk?

Study design:
This review article included 12 case-control/observational studies reporting selenium concentrations in Alzheimer's disease and controls.

Results and conclusions:
The investigators found random-effects meta-analysis indicated a decrease in circulatory [SMD = -0.44], erythrocellular [SMD = -0.52] and cerebrospinal fluid [SMD = -0.14] selenium levels in Alzheimer's disease patients compared to controls

The investigators found stratified meta-analysis demonstrated that the selenium levels were decreased in both the subgroups with [SMD = -0.55] and without [SMD = -0.37] age matching between Alzheimer's disease and controls.

The investigators also found a direct association between decreased selenium levels and glutathione peroxidase (GPx) in Alzheimer's disease.

The investigators concluded that circulatory selenium concentration is significantly lower in Alzheimer's disease patients compared to controls and this decrease in selenium is directly correlated with an important antioxidant enzyme, the glutathione peroxidase, in Alzheimer's disease.

Original title:
A systematic review and meta-analysis of the circulatory, erythrocellular and CSF selenium levels in Alzheimer's disease: A metal meta-analysis (AMMA study-I) by Reddya VS, Bukkeb S, […], Pandeye AK.

Link:
http://www.sciencedirect.com/science/article/pii/S0946672X1630205X%20

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Objectives:
Does higher protein intake increase bone mineral density?

Study design:
This review article included 6 RCTs and 20 prospective cohort studies.
There were no adverse effects of higher protein intakes.
Studies were heterogeneous and confounding could not be excluded.

Results and conclusions:
The investigators found moderate evidence suggested that higher protein intake may have a protective effect on lumbar spine bone mineral density compared with lower protein intake [net percentage change = 0.52%, 95% CI = 0.06%-0.97%, I2 = 0%, n = 5] but had no effect on total hip, femoral neck, or total body bone mineral density or bone biomarkers.

The investigators concluded that higher protein intake may have a protective effect on lumbar spine bone mineral density. May have because studies were heterogeneous and confounding could not be excluded. Therefore, high-quality, long-term studies are needed to clarify dietary protein's role in bone health.

Original title:
Dietary protein and bone health: a systematic review and meta-analysis from the National Osteoporosis Foundation by Shams-White MM, Chung M, […], Weaver CM.

Link:
https://www.ncbi.nlm.nih.gov/pubmed/28404575

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A higher protein diet is a diet with 20-35 En% protein. The easiest way to meet a diet with 20-35 En% protein is to choose food items/meals with also 20-35 En% protein. Check here which products contain 20-35 En% protein.
 

Objectives:
Current studies evaluating the association of tea consumption and bone mineral density (BMD) have yielded inconsistent findings. Therefore, this meta-analysis (review article) has been conducted.

Does tea consumption increase bone mineral density?

Study design:
This review article included 4 cohort, 1 case-control and 8 cross-sectional studies including a total of 12,635 cases (6,059 in the tea consumption group and 6,576 individuals in non-tea consumption group).

Results and conclusions:
The investigators found tea consumption significantly reduced the occurrence of low bone mass with 34% [OR  =  0.66, 95% CI  =  0.47-0.94, p =  0.02].

The investigators found tea consumption significantly yielded higher mineral densities in several bones, including:
-the lumbar spine [standardized mean difference (SMD) = 0.19, 95% CI = 0.08-0.31, p  =  0.001];
-hip [SMD = 0.19, 95% CI = 0.05-0.34, p  =  0.01];
-femoral neck [mean difference (MD) = 0.01, 95% CI = 0.00-0.02, p  =  0.04];
-Ward triangle [MD = 0.02, 95% CI = 0.01-0.04, p  =  0.001] and;
-greater trochanter [MD = 0.03, 95% CI = 0.02-0.04, p  0.00001]
than the non-tea consumption group.

The investigators concluded that tea consumption increases bone mineral density, especially in the lumbar spine, hip, femoral neck, Ward triangle and greater trochanter, which can prevent bone loss.

Original title:
Updated association of tea consumption and bone mineral density: A meta-analysis by Zhang ZF, Yang JL, [...], Liu ZX.

Link:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5371490/

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Objectives:
It has been unclear whether supplemental probiotics therapy improves clinical outcomes in type 2 diabetic patients. Therefore, this meta-analysis (systematic review) has been conducted.

Do probiotics supplements improve clinical outcomes in type 2 diabetic patients?

Study design:
This review article included 12 RCTs involving 684 type 2 diabetic patients.

Results and conclusions:
The investigators found a significant decreased glucose level in the probiotics group [pooled standardized mean difference = -0.18 mg/dL, 95% CI = -0.35 to -0.01, p = 0.04, I2 = 64%, p = 0.004] compared to the control group.

The investigators found a significant reduction in HbA1c in the probiotics group [pooled standardized mean difference = -0.38%, 95% CI = -0.62 to -0.14, p = 0.002, I2 = 0%, p = 0.72] compared to the control group.

The investigators found a significant reduction in fasting insulin level in the probiotics group [pooled standardized mean difference = -0.38, 95% CI = -0.59 to -0.18, p = 0.003, I2 = 0%, p = 0.81] compared to the control group.

The investigators found a significant reduced HOMA-IR level in the probiotics group [pooled standardized mean difference = -0.99, 95% CI = -1.52 to -0.4, p = 0.0002, I2 = 86%, p 0.00001] compared to the control group.

The investigators found a significant reduced CRP level in the probiotics group [pooled standardized mean difference = -1.34 mg/L, 95% CI = -1.76 to -0.92, p 0.00001, I2 = 90%, p 0.00001] compared to the control group.

The investigators found a non-significant reduction in both triglyceride levels [SMD = -0.23, 95% CI = -0.48 to 0.02, p = 0.07, I2 = 52%, p = 0.03] and cholesterol levels [total cholesterol: SMD = -0.18, 95% CI = -0.42 to 0.06, p = 0.14, I2 = 47%, p = 0.05 and LDL-cholesterol: SMD = -0.03, 95% CI = -0.20 to 0.14, p = 0.73, I2 = 3%, p = 0.41] in the probiotics group compared to the control group.

The investigators concluded that probiotics supplementation is associated with significant improvement in HbA1c and fasting insulin in type 2 diabetes patients. These results may provide evidence for encouraging use of probiotics in patients with type 2 diabetes mellitus. However, more randomized placebo-controlled trials with larger sample sizes are warranted to confirm these findings.

Original title:
Effect of Probiotics on Glucose and Lipid Metabolism in Type 2 Diabetes Mellitus: A Meta-Analysis of 12 Randomized Controlled Trials by Yao K, Zeng L, [...], Zou X.

Link:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5491138/

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Objectives:
Is there a relationship between serum 25(OH)D (vitamin D blood level) and mortality risk in the general population?

Study design:
This review article included 14 prospective cohort studies that involved 5562 deaths out of 62548 individuals.
In the parametric model, which is based on 11 studies and 59231 individuals, the lowest quantile as the reference category has been used.

Evidence of heterogeneity for the RR was apparent when highest were compared with lowest categories [p = 0.008, I2 = 58%].

There was no evidence of publication bias.

Results and conclusions:
The investigators found for “highest compared with lowest” categories of 25(OH)D, a significant reduced risk of 29% for mortality [RR = 0.71, 95% CI = 0.50-0.91].

The investigators found in the parametric model, the estimated summary RRs of mortality were 0.86 [95% CI = 0.82-0.91], 0.77 [95% CI = 0.70-0.84] and 0.69 [95% CI = 0.60-0.78] for individuals with an increase of 12.5, 25 and 50 nmol 25(OH)D serum values/L, respectively, from a median reference category of ∼27.5 nmol/L.
However, no significant decrease in mortality was found above ∼87.5 nmol/L.

The investigators concluded there is a nonlinear decrease in mortality risk as circulating 25(OH)D increases, with optimal concentrations ∼75-87.5 nmol/L. Because many adults do not achieve these 25(OH)D values, large prospective randomized trials are urgently needed to investigate whether vitamin D supplementation is able to reduce mortality risk in the general population.

Original title:
Vitamin D deficiency and mortality risk in the general population: a meta-analysis of prospective cohort studies by Zittermann A, Iodice S, [...], Gandini S.

Link:
http://ajcn.nutrition.org/content/95/1/91.full

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Objectives:
Does soy isoflavone reduce the frequency and severity of hot flashes?

Study design:
This review article included 19 trials (13 included hot flash frequency, of which 10 for severity and 3 for composite scores).
17 trials were selected for meta-analyses to clarify the effect of soybean isoflavones on hot flash frequency (13 trials) and severity (9 trials).

Results and conclusions:
The investigators found intake of soy isoflavones (median = 54 mg aglycone equivalents) for 6 weeks to 12 months significantly reduced the frequency (combined fixed-effect and random effects model) of hot flashes by 20.6% [95% CI = -28.38 to -12.86, p 0.00001] compared with placebo [p heterogeneity = 0.0003, I2 = 67% for random effects model].

The investigators also found isoflavones significantly reduced hot flash severity by 26.2% [95% CI = -42.23 to -10.15, p = 0.001] compared with placebo [p heterogeneity 0.00001, I2 = 86% for random effects model].

The investigators found isoflavone supplements providing more than 18.8 mg of genistein (the median for all studies) were more than twice as potent at reducing hot flash frequency than lower genistein supplements.

The investigators concluded soy isoflavone supplements (54 mg per day for 6 weeks to 12 months), derived by extraction or chemical synthesis, are significantly more effective than placebo in reducing the frequency and severity of hot flashes. Additional studies are needed to further address the complex array of factors that may affect efficacy, such as dose, isoflavone form, baseline hot flash frequency and treatment duration.

Original title:
Extracted or synthesized soybean isoflavones reduce menopausal hot flash frequency and severity: systematic review and meta-analysis of randomized controlled trials by Taku K, Melby MK, […], Messina M.

Link:
http://journals.lww.com/menopausejournal/Abstract/2012/07000/Extracted_or_synthesized_soybean_isoflavones.11.aspx

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Objectives:
There is an ongoing debate on the involvement of systemic copper (Cu) dysfunctions in Alzheimer's disease (AD) and clinical studies comparing Cu levels in serum, plasma and cerebrospinal fluid (CSF) of AD patients with those of healthy controls have delivered non-univocal and often conflicting results. Therefore, this review article has been conducted.

Does blood level of copper increase in Alzheimer’s disease?

Study design:
This review article included 26 studies including a pooled total of 761 AD subjects and 664 controls for serum Cu studies, 205 AD subjects and 167 controls for plasma Cu and of 116 AD subjects and 129 controls for CSF Cu.

Results and conclusions:
The investigators found Alzheimer's disease patients have higher levels of serum copper than healthy controls. Plasma data did not allow conclusions, due to their high heterogeneity, but the meta-analysis of the combined serum and plasma studies confirmed higher copper levels in Alzheimer's disease patients. 

The investigators found the analysis of CSF data revealed no difference between Alzheimer's disease patients and controls.

The investigators concluded Alzheimer's disease patients have higher levels of serum and plasma copper than healthy controls.

Original title:
Copper in Alzheimer's disease: a meta-analysis of serum, plasma, and cerebrospinal fluid studies by Bucossi S, Ventriglia M, […], Squitti R.

Link:
http://www.ncbi.nlm.nih.gov/pubmed/21187586

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Objectives:
The association between dietary vitamin K intake and the risk of fractures is controversial. Therefore, this meta-analysis (review article) has been conducted.

Does dietary vitamin K intake reduce risk of fractures?

Study design:
This review article included 4 cohort studies and 1 nested case-control study, including 80,982 total subjects and 1114 fracture cases.

The fractures were assessed using confirmed self-reported, medical and radiological report. Dietary vitamin K intake was assessed with a food-frequency questionnaire (FFQ) in 4 studies, only 1 study used 4-day or 7-day food record.
Vitamin K intake in all included studies refers exclusively to the intake of phylloquinone (vitamin K1), which is the predominant form of vitamin K in foods.
All subjects were more than 30 years old.
Duration of follow-up for the included studies ranged from 6.9 to 10 years.
Most studies provided RRs that were adjusted for age, BMI, BMD, physical activity, vitamin D and calcium intake, smoking and alcohol consumption.

The Begg and Egger tests did not show any substantial asymmetry (p  =  0.50 for Begg test and p  =  0.32 for Egger tests). Further trim and filled meta-analysis showed that there were no trimming data added.

Results and conclusions:
The investigators found for highest vs. the lowest dietary vitamin K intake a significant reduced risk of 22% [RR = 0.78, 95% CI = 0.56-0.99, I2  =  59.2%, p  = 0 .04] for fractures.

The investigators found for every increment of 50μg dietary vitamin K intake per day a significant reduced risk of 3% [RR  = 0.97, 95% CI = 0.95-0.99, I2  =  25.9%, p  = 0 .25] for fractures.

The investigators found a significant reduced risk of 24% [RR = 0.76, 95% CI = 0.58-0.93, I2  =  59.2%, p  = 0 .04] for fractures in studies with more than 10 years of follow-up.

The investigators concluded that higher dietary vitamin K intake; at least 50μg dietary vitamin K intake per day decreases the risk of fractures. This review article offers additional evidence on the relationship between dietary vitamin K intake and risk of fractures. The benefit of vitamin K should be confirmed in future well-designed prospective cohort studies and clinical trials.

Original title:
Vitamin K intake and the risk of fractures: A meta-analysis by Hao G, Zhang B, [...], Cao X.

Link:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5413254/

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Objectives:
In view of the vital role of oxidative stress in the pathogenesis of Alzheimer's disease (AD), the potential of antioxidant supplements to prevent AD have gained much interest, while there are conflicting results on this topic in recent years. Therefore, this review article has been conducted.

Does dietary intake of vitamin C and E and β-carotene decrease risk of Alzheimer's disease?

Study design:
This review article included 7 articles (dietary intake, but no supplements).

Results and conclusions:
The investigators found a significant decreased risk for Alzheimer disease of 24% [pooled relative risk = 0.76 95% CI = 0.67-0.84] for dietary intake of vitamin E and of 17% [pooled relative risk = 0.83, 95% CI = 0.72-0.94] for dietary intake of vitamin C.

However, the investigators found a non-significant decreased risk of 12% [pooled relative risk = 0.88, 95% CI = 0.73-1.03] for dietary intake of β-carotene.

The investigators concluded dietary intakes of vitamin C and E lower the risk of Alzheimer's disease, with vitamin E exhibiting the most pronounced protective effects. The findings will be of significance to the prevention and interventional treatment of Alzheimer's disease.

Original title:
Dietary intakes of vitamin E, vitamin C, and β-carotene and risk of Alzheimer's disease: a meta-analysis by Li FJ, Shen L and Ji HF.

Link:
http://www.ncbi.nlm.nih.gov/pubmed/22543848

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Objectives:
Does diabetes increase risk of incident dementia and mild cognitive impairment?

Study design:
This review article included 19 prospective longitudinal studies including 6184 subjects with diabetes and 38530 subjects without diabetes. All subjects were without dementia or mild cognitive impairment at baseline (=at the beginning of the study).

There was no publication bias.

Results and conclusions:
The investigators found persons with diabetes had a significant increased risk of 46% for Alzheimer's disease [RR = 1.46, 95% CI = 1.20-1.77]. Significant means that there is an association with a 95% confidence.

The investigators found persons with diabetes had a significant increased risk of 148% for vascular dementia [RR = 2.48, 95% CI = 2.08-2.96].

The investigators found persons with diabetes had a significant increased risk of 51% for any dementia [RR = 1.51, 95% CI = 1.31-1.74]. Significant because RR of 1 was not found in the 95% CI of 1.31 to 1.74. RR of 1 means no risk/association.

The investigators found persons with diabetes had a significant increased risk of 21% for mild cognitive impairment [RR = 1.21, 95% CI = 1.02-1.45].

The investigators concluded diabetes is a risk factor for incident dementia (including Alzheimer's disease, vascular dementia and any dementia) and mild cognitive impairment.

Original title:
Diabetes as a risk factor for dementia and mild cognitive impairment: a meta-analysis of longitudinal studies by Cheng G, Huang G, [...], Wang H.

Link:
http://onlinelibrary.wiley.com/doi/10.1111/j.1445-5994.2012.02758.x/epdf

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Objectives:
Manganese (Mn) is one of the most studied environmental heavy metals linked to Alzheimer’s disease (AD). However, it remains unclear whether serum manganese levels are associated with Alzheimer’s disease and mild cognition impairment (MCI, a prodromal stage of AD). Therefore, this meta-analysis (review article) has been conducted.

Does a lower serum manganese level increase risk of cognitive decline?

Study design:
This review article included 17 studies, involving 836 cases and 1254 health controls (HC).

The sample size of the included studies ranged from 8 to 758. The average age of the patient groups ranged from 66.2 to 87.0 years. The proportion of female patients ranged from 33% to 80%.

Strong heterogeneity existed among the studies. Heterogeneity was not due to methods for measuring manganese levels, geographic locations, age and gender of patients.

There was no publication bias in the present meta-analysis evaluated by the Egger’s test (p = 0.258) and Begg’s test (p = 0.107).

Results and conclusions:
The investigators found random-effects meta-analysis showed that patients with Alzheimer’s disease had significantly reduced serum manganese levels compared with health control subjects [SMD = -0.39, 95% CI = -0.71 to -0.08, p = 0.015].

The investigators found mild cognition impairment individuals had a tendency toward reduced serum manganese levels compared with health control subjects [SMD = -0.31, 95% CI = -0.70 to 0.08, p = 0.117].

The investigators found a significant decrease in serum manganese levels in patients with cognitive impairment (including both AD patients and MCI patients) [SMD = -0.37, 95% CI = -0.60 to -0.13, p = 0.002].

The investigators found no significant differences between Alzheimer’s disease and mild cognition impairment patients in serum levels [SMD = 0.24, 95% CI = -0.23 to 0.72, p = 0.310].

The investigators concluded that the serum manganese levels are lower in Alzheimer’s disease patients and manganese deficiency may be a risk factor for Alzheimer’s disease. However, the results should be interpreted with caution due to the high heterogeneity of the studies.

Original title:
Association of Serum Manganese Levels with Alzheimer’s Disease and Mild Cognitive Impairment: A Systematic Review and Meta-Analysis by Du K, Liu M, [...], Wei M.

Link:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5372894/

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Objectives:
Previous meta-analyses identified an inverse association of coffee consumption with the risk of type 2 diabetes. However, an updated meta-analysis is needed because new studies comparing the trends of association for caffeinated and decaffeinated coffee have since been published. Therefore, this review article has been conducted.

Does coffee intake reduce type 2 diabetes risk in a dose-response manner?

Study design:
This review article included 28 prospective cohort studies with 1109272 study participants and 45335 cases of type 2 diabetes. The follow-up duration ranged from 10 months to 20 years.

Results and conclusions:
The investigators found for compared with no or rare coffee consumption, a significant reduced risk of type 2 diabetes of:
8% [RR = 0.92, 95% CI = 0.90-0.94] for 1 cup/day;
15% [RR= 0.85, 95% CI = 0.82-0.88] for 2 cups/day;
21% [RR = 0.79, 95% CI = 0.75-0.83] for 3 cups/day;
25% [RR = 0.75, 95% CI = 0.71-0.80] for 4 cups/day;
29% [RR = 0.71, 95% CI = 0.65-0.76] for 5 cups/day and;
33% [RR = 0.67, 95% CI = 0.61-0.74] for 6 cups/day.

The investigators found a significant decreased risk of type 2 diabetes of 9% [RR = 0.91, 95% CI = 0.89-0.94] for an increasement of 1 cup/day caffeinated coffee and 6% [RR = 0.94, 95% CI = 0.91-0.98] for an increasement of 1 cup/day decaffeinated coffee [p for difference = 0.17].

The investigators concluded coffee consumption is inversely associated with the risk of type 2 diabetes in a dose-response manner. Both caffeinated and decaffeinated coffee is associated with reduced diabetes risk.

Original title:
Caffeinated and decaffeinated coffee consumption and risk of type 2 diabetes: a systematic review and a dose-response meta-analysis by Ding M, Bhupathiraju SN, […], Hu FB.

Link:
http://www.ncbi.nlm.nih.gov/pubmed/24459154

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Objectives:
The prevalence of obesity and diabetes is increasing among children, adolescents and adults. Although estimates of the efficacy of exercise training on fasting insulin and insulin resistance have been provided for adults, similar estimates have not been provided for youth. Therefore, this review article has been conducted.

Study design:
This review article included 24 trials.

Results and conclusions:
The investigators found a small to moderate effect for exercise training on fasting insulin and improving insulin resistance in youth [Hedges’ d effect size = 0.48, 95% CI = 0.22-0.74, p 0.001 and 0.31, 95% CI = 0.06-0.56, p 0.05, respectively].

The investigators concluded there is evidence to support the use of exercise training in the prevention and treatment of type 2 diabetes in youth.

Original title:
Exercise and Insulin Resistance in Youth: A Meta-Analysis by Fedewa MV, Gist NH, […], Dishman RK.

Link:
http://www.pediatricsdigest.mobi/content/133/1/e163.abstract

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Objectives:
Reported associations between protein intake from different sources and type 2 diabetes (T2D) have been inconsistent.Therefore, this review article has been conducted.

Study design:
This review article included 11 prospective cohort studies with 505,624 participants and 37,918 type 2 diabetes cases (follow-up range: 5-24 years).

Results and conclusions:
The investigators found for the comparison of the highest with lowest categories of total protein intakes a significant higher risk of 9% for type 2 diabetes [RR = 1.09, 95% CI = 1.06 to 1.13]. Significant means that there is an association with a 95% confidence.

The investigators found for the comparison of the highest with lowest categories of animal protein intakes a significant higher risk of 19% for type 2 diabetes [RR = 1.19, 95% CI = 1.11 to 1.28].

The investigators found for the comparison of the highest with lowest categories of plant protein intakes a non-significant reduced risk of 5% for type 2 diabetes [RR = 0.95, 95% CI = 0.89 to 1.02]. Non-significant means it cannot be said with a 95% confidence that a daily higher intake of plant protein really reduced risk of type 2 diabetes with 5%.

The investigators found for the comparison of the highest with lowest categories of plant protein intakes a significant reduced risk of 7% for type 2 diabetes among women [RR = 0.93, 95% CI = 0.85 to 1.00].

The investigators found for the comparison of the highest with lowest categories of plant protein intakes a significant reduced risk of 9% for type 2 diabetes among US populations [RR = 0.91, 95% CI = 0.84 to 0.97].

The investigators concluded that a higher intake of total and animal protein are both associated with an increased risk of of type 2 diabetes. However, a higher intake of plant protein decreases risk of type 2 diabetes among women and US populations.

Original title:
Dietary protein intake and risk of type 2 diabetes: results from the Melbourne Collaborative Cohort Study and a meta-analysis of prospective studies by Shang X, Scott D, […], Sanders KM.

Link:
https://www.ncbi.nlm.nih.gov/pubmed/27629053

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Objectives:
Garlic is a common spicy flavouring agent also used for certain therapeutic purposes. Garlic's effects on blood glucose have been the subject of many clinical and animal studies. However, studies reporting hypoglycemic effects of garlic in humans are conflicting. Therefore, this review article (meta-analysis) has been conducted.

Has garlic supplementation lowering effects on glycemic control measurements such as fasting blood glucose (FBG), postprandial glucose (PPG) and glycated haemoglobin (HbA1c)?

Study design:
This review article included a total of 7 RCTs (parallel design) that involved 9 comparisons with 513 subjects. The trials varied in size from 33 to 180 subjects. The study duration varied from 4 to 24 week (median: 12 week). The trials enrolled male and female subjects, both healthy and with diabetes.

Doses of garlic in the treatment group ranged from 600 to 1500 mg/d.

Results and conclusions:
The investigators found pooled analyses showed that garlic supplementation resulted in a statistically significant lowering in fasting blood glucose [SMD = -1.67, 95% CI = -2.80 to -0.55, p = 0.004].

The investigators could not perform a pooled analyse for postprandial glucose (PPG) control and glycosylated haemoglobin (HbA1c) outcomes, because only 1 study included in the meta-analysis reported PPG variables and only 2 studies reported HbA1c variables.

The investigators concluded that garlic supplementation (600 to 1500 mg/d) during 12 weeks results in a lowering in fasting blood glucose. More trials are needed to investigate the effectiveness of garlic on HbA1c and PPG.

Original title:
Garlic intake lowers fasting blood glucose: meta-analysis of randomized controlled trials by Hou LQ, Liu YH and Zhang YY.

Link:
http://apjcn.nhri.org.tw/server/APJCN/24/4/575.pdf

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Objectives:
Lutein and zeaxanthin are thought to have beneficial effects on protecting the lens against cataract formation, but findings from epidemiologic studies have been inconsistent. Therefore, this review article has been conducted.

Does dietary lutein and zeaxanthin intake reduce age-related cataract risk?

Study design:
This review article included 6 prospective cohort studies, involving 4416 cases and 41999 participants.

Results and conclusions:
The investigators found for comparing the highest with the lowest categories of dietary lutein and zeaxanthin intake, a significant reduced risk for nuclear cataract of 25% [RR = 0.75, 95% CI = 0.65-0.85], but the reduced risk was not significant for cortical cataract [RR = 0.85, 95% CI = 0.53-1.17] and for posterior subcapsular cataract [RR = 0.77, 95% CI = 0.40-1.13]. Significant means, there is an association with a 95% confidence.

The investigators found in dose-response analysis that every 300 μg/d increment in dietary lutein and zeaxanthin intake was significantly associated with a 3% [RR = 0.97, 95% CI = 0.94-0.99] reduction in the risk of nuclear cataract.

The investigators found in dose-response analysis that every 300 μg/d increment in dietary lutein and zeaxanthin intake was non-significantly associated with a 1% [RR = 0.99, 95% CI = 0.95-1.02] reduction in the risk of cortical cataract. Non-significantly means, there is no association with a 95% confidence.

The investigators found in dose-response analysis that every 300 μg/d increment in dietary lutein and zeaxanthin intake was non-significantly associated with a 3% [RR = 0.97, 95% CI = 0.93-1.01] reduction in the risk of posterior subcapsular cataract. Non-significantly because RR of 1 was found in 95% CI of 0.93 to 1.01. RR of 1 means no risk.

The investigators concluded dietary lutein and zeaxanthin intake (at least 300 μg/d) is associated with a reduced risk of age-related cataract, especially nuclear cataract in a dose-response manner, indicating a beneficial effect of lutein and zeaxanthin in age-related cataract prevention.

Original title:
A dose–response meta-analysis of dietary lutein and zeaxanthin intake in relation to risk of age-related cataract by Ma L, Hao ZX, [...], Pan JP.

Link:
http://link.springer.com/article/10.1007/s00417-013-2492-3

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Objectives:
Hormonal effects of soy and isoflavones have been investigated in numerous trials with equivocal findings. Therefore, this review article has been conducted.

What are hormonal effects of soy and isoflavones in both pre- and postmenopausal women?

Study design:
This review article included 47 (11 of pre-, 35 of post- and 1 of perimenopausal women) randomized or residential crossover trials of soy or isoflavones for 4 or more weeks on estrogens, SHBG, FSH, LH, progesterone and thyroid hormones in women was assessed independently in duplicate.

The studies ranged from 4 to 104 weeks long: 29 were 4-12 weeks in duration, 9 were 13-26 weeks, 7 were 27-52 weeks and 2 were >1 year.

Results and conclusions:
The investigators found in premenopausal women, soy or isoflavone consumption did not affect primary outcomes estradiol, estrone or SHBG concentrations, but significantly reduced secondary outcomes FSH and LH [by approximately 20% using standardized mean difference (SMD), p = 0.01 and p = 0.05, respectively].

The investigators found in 10 studies that soy or isoflavone consumption increased menstrual cycle length by 1.05 days [95% CI = 0.13-1.97].

The investigators found in post-menopausal women, soy or isoflavone consumption had no statistically significant effects on estradiol, estrone, SHBG, FSH or LH, although there was a small statistically non-significant increase in total estradiol with soy or isoflavones [by approximately 14% using standardized mean difference (SMD), p = 0.07, 21 studies].

The investigators concluded isoflavone-rich soy products decrease FSH and LH in premenopausal women and may increase estradiol in post-menopausal women. The clinical implications of these modest hormonal changes remain to be determined.

Original title:
Effects of soy protein and isoflavones on circulating hormone concentrations in pre- and post-menopausal women: a systematic review and meta-analysis by Hooper L, Ryder JJ, […], Cassidy A.

Link:
http://humupd.oxfordjournals.org/content/15/4/423.full

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Objectives:
What is the relationship between intake of 12 major food groups and risk of type 2 diabetes (T2D)?

Study design:
This review article included prospective cohort studies.
The 12 major food groups are whole grains, refined grains, vegetables, fruits, nuts, legumes, eggs, dairy, fish, red meat, processed meat and sugar-sweetened beverages (SSB).

The meta-evidence was graded "low" for legumes and nuts; "moderate" for refined grains, vegetables, fruit, eggs, dairy and fish; and "high" for processed meat, red meat, whole grains and sugar-sweetened beverages.

Results and conclusions:
The investigators found 6 out of the 12 food-groups showed a significant relation with risk of type 2 diabetes; 3 of them a decrease of risk with increasing consumption (whole grains, fruits and dairy) and 3 an increase of risk with increasing consumption (red meat, processed meat and sugar-sweetened beverages) in the linear dose-response meta-analysis.

The investigators found evidence of a non-linear relationship between fruits, vegetables, processed meat, whole grains and sugar-sweetened beverages and type 2 diabetes risk.

The investigators found optimal consumption of risk-decreasing foods resulted in a 42% reduction and consumption of risk-increasing foods was associated with a threefold type 2 diabetes risk, compared to non-consumption.

The meta-evidence was graded "low" for legumes and nuts; "moderate" for refined grains, vegetables, fruit, eggs, dairy and fish; and "high" for processed meat, red meat, whole grains, and sugar-sweetened beverages. Among the investigated food groups, selecting specific optimal intakes can lead to a considerable change in risk of type 2 diabetes.

The investigators concluded that a higher consumption of whole grains, fruits and dairy products reduces type 2 diabetes risk, while a higher consumption of red meat, processed meat and sugar-sweetened beverages increases type 2 diabetes risk.

Original title:
Food groups and risk of type 2 diabetes mellitus: a systematic review and meta-analysis of prospective studies by Schwingshackl L, Hoffmann G, […], Boeing H.

Link:
https://www.ncbi.nlm.nih.gov/pubmed/28397016

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Objectives:
Olive oil (OO) as food is composed mainly of fatty acids and bioactive compounds depending from the extraction method. Both had been discussed as health promoting with still open questions. Therefore, this meta-analysis (systematic review) has been conducted.

Does olive oil intake reduce risk of type 2 diabetes?

Study design:
This review article included 4 cohort studies including 15,784 type 2 diabetes cases and 29 intervention trials.

Results and conclusions:
The investigators found the highest olive oil intake category showed a 16% reduced risk of type 2 diabetes [RR = 0.84, 95% CI = 0.77, 0.92) compared with the lowest. The reduced risk was significant.

The investigators found evidence for a nonlinear relationship between olive oil intake and the reduced risk of type 2 diabetes.

The investigators found in patients with type 2 diabetes that olive oil supplementation resulted in a significantly more pronounced reduction in HbA1c [MD = -0.27%, 95% CI = -0.37 to -0.17] and fasting plasma glucose [MD = -0.44 mmol/L, 95% CI = -0.66 to -0.22] as compared with the control groups.

The investigators concluded that the intake of olive oil is beneficial for the prevention and management of type 2 diabetes. This conclusion regards olive oil as food and might not been valid for single components comprising this food.

Original title:
Olive oil in the prevention and management of type 2 diabetes mellitus: a systematic review and meta-analysis of cohort studies and intervention trials by Schwingshackl L, Lampousi AM, […], Boeing H1.

Link:
https://www.ncbi.nlm.nih.gov/pubmed/28394365

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Objectives:
Nutrition therapy is an integral part of self-management education in patients with type 2 diabetes. Carbohydrates with a low glycemic index are recommended, but the ideal amount of carbohydrate in the diet is unclear. Therefore, this meta-analysis (systematic review) has been conducted.

Has carbohydrate restriction (below 45 En% carbohydrate) beneficial effects on glycemic control in type 2 diabetes?

Study design:
This review article included 10 RCTs. In total, 1,376 subjects with type 2 diabetes were included in this analysis. Forty-nine percent were male and the average age was 58 years. The majority were obese; mean BMI ranged from 26 kg/m² in an Asian population to 37 kg/m² in an American population.

The duration of the intervention varied from 3 to 24 months.

The average predefined targets for the assigned carbohydrate restriction were 25 En% (range 14-40 En%). The average reported intake was 30 En% (range 14-45 En%) after 3 or 6 months of intervention and 38 En% (range 27-45 En%) at 1 year (5 trials).

Results and conclusions:
The investigators found following a carbohydrate diet of 30 En% (range 14-45 En%) during 3 to 6 months significantly reduced HbA1c level of patients with type 2 diabetes with 0.34% [95% CI = 0.06 to 0.63] compared with a diet of 45-60 En% carbohydrate (high-carbohydrate diet).
Owing to heterogeneity, however, the quality of the evidence for this is only moderate. However, at 1 year or later, HbA1c level (seven trials included) was similar in the two groups.

The investigators found the greater the carbohydrate restriction, the greater the glucose-lowering effect [R = -0.85, p 0.01].

The investigators found the effect of the 2 types of diet on BMI/body weight, LDL cholesterol, QoL and attrition rate was similar throughout interventions.

The investigators concluded that carbohydrate restriction (below 45 En% carbohydrate) has a greater effect on glycemic control in type 2 diabetes than an high-carbohydrate diet in the short term. The magnitude of the effect was correlated to the carbohydrate intake, the greater the restriction, the greater glucose lowering, a relationship that has not been demonstrated earlier. However, in the long term, the glucose-lowering effect of high-carbohydrate diet (HCD) and low-carbohydrate diets (LCD) was similar.

Original title:
Systematic review and meta-analysis of dietary carbohydrate restriction in patients with type 2 diabetes by Snorgaard O, Poulsen GM, [...], Astrup A.

Link:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5337734/

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