Nutrition and health

Objectives:
Does iron supplementation during pregnancy improve maternal haematological status and birth weight?

Study design:
This review article included 48 RCTs (17,793 women) and 44 cohort studies (1,851,682 women).

The dose of iron in RCTs ranged from 10 mg to 240 mg daily. Duration of supplementation varied from 7 to 8 weeks up to 30 weeks during pregnancy.

Significant heterogeneity existed for several outcomes that could not be explained substantially by pre-specified subgroups.

Results and conclusions:
The investigators found iron supplementation during pregnancy increased maternal mean haemoglobin concentration by 4.59 g/L [95% CI = 3.72 to 5.46] compared with controls.

The investigators found iron with folic acid was associated with a significant increase in mean haemoglobin concentration of 10.41 g/L [95% CI = 5.36 to 15.46, I2 = 0%, 9 trials] and reduction in risk of anaemia in the third trimester or at delivery of 56% [95% CI = 0.37 to 0.53, I2 = 44%, 5 trials]. Significant means there is an association with a 95% confidence.

The investigators found iron supplementation during pregnancy significantly reduced the risk of anaemia with 50% [95% CI = 0.42 to 0.59] compared with controls.

The investigators found iron supplementation during pregnancy significantly reduced the risk of iron deficiency (of the mother) with 41% [95% CI = 0.46 to 0.79] compared with controls.

The investigators found iron supplementation during pregnancy significantly reduced the risk of iron deficiency anaemia with 60% [95% CI = 0.26 to 0.60] compared with controls.

The investigators found iron supplementation during pregnancy significantly reduced the risk of low birth weight (2500 g) with 19% [95% CI = 0.71 to 0.93] compared with controls.

However, the investigators found iron supplementation during pregnancy non-significantly reduced the risk of preterm birth with 16% [95% CI = 0.68 to 1.03] compared with controls. Non-significant means there is no association with a 95% confidence.

The investigators found in cohort studies that anaemia in the first or second trimester was significantly associated with a higher risk for low birth weight of 29% [adjusted odds ratio 1.29, 95% CI = 1.09 to 1.53] and preterm birth with 21% [adjusted odds ratio = 1.21, 95% CI = 1.13 to 1.30].

The investigators found in exposure-response analysis that for every 10 mg increase in iron dose/day, up to 66 mg/day, the relative risk of maternal anaemia was significantly 0.88 [95% CI = 0.84 to 0.92, p for linear trend 0.001].

The investigators found in exposure-response analysis that birth weight increased by 15.1 g [95% CI = 6.0 to 24.2, p for linear trend = 0.005] and risk of low birth weight significantly decreased by 3% [relative risk = 0.97, 95% CI = 0.95 to 0.98, p for linear trend 0.001] every 10 mg increase in dose/day.

Furthermore, the investigators found for each 1 g/L increase in mean haemoglobin, birth weight increased by 14.0 g [95% CI = 6.8 to 21.8, p for linear trend = 0.002]. However, mean haemoglobin was not associated with the risk of low birth weight and preterm birth.

The investigators found no evidence of a significant effect on duration of gestation, small for gestational age births and birth length and duration of iron use was not significantly associated with the outcomes after adjustment for dose.

The investigators concluded daily prenatal use of iron substantially improved birth weight in a linear dose-response fashion, probably leading to a reduction in risk of low birth weight. An improvement in prenatal mean haemoglobin concentration linearly increased birth weight and a linear decrease in maternal anaemia with higher doses of iron, up to 66 mg/day.

Original title:
Anaemia, prenatal iron use, and risk of adverse pregnancy outcomes: systematic review and meta-analysis by Haider BA, Olofin I, […], Fawzi WW.

Link:
http://www.bmj.com/content/346/bmj.f3443

Additional information of El Mondo:
Find more information/studies on iron and pregnancy right here.

Iron deficiency anaemia occurs when there isn't enough iron in the body. Anaemia is a condition where the amount of haemoglobin in the blood is below the normal level.
Iron deficiency anaemia has been defined as haemoglobin 110 g/L and serum ferritin 12 µg/L.

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/

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

Objectives:
Randomised controlled trials (RCTs) have observed contrasting results on the effects of vitamin C on circulating biomarkers of glycaemic and insulin regulation. Therefore, this meta-analysis (systematic review) has been conducted.

Has vitamin C supplementation a favorable effect on circulating biomarkers of glycaemic and insulin regulation?

Study design:
This review article included 22 RCTs with 937 participants.

Results and conclusions:
The investigators found overall, vitamin C supplementation did not modify glucose, HbA1c and insulin concentrations.

The investigators found, however, subgroup analyses showed that vitamin C supplementation significantly reduced glucose concentrations with 0.44 mmol/L [95% CI = -0.81 to -0.07, p =0.01] in patients with type 2 diabetes and in interventions with a duration greater than 30 days [-0.53%, 95% CI = -0.79 to -0.10, p = 0.02].

The investigators found vitamin C administration had greater effects on fasting [-13.63 pmol/L, 95% CI = -22.73 to -4.54, p 0.01] compared to postprandial insulin concentration. However, meta-regression analyses showed that age was a modifier of the effect of vitamin C on insulin concentration.

The investigators found the effect size of vitamin C supplementation was associated with baseline BMI and plasma glucose levels and with the duration of the intervention.

The investigators concluded vitamin C supplementation has greater reduction in glucose concentrations in patients with type 2 diabetes, older individuals and with more prolonged supplementation (greater than 30 days). Personalized interventions with vitamin C may represent a feasible future strategy to enhance benefits and efficacy of interventions. Nevertheless, results need to be interpreted cautiously due to limitations in the primary studies.

Original title:
Effects of vitamin C supplementation on glycaemic control: a systematic review and meta-analysis of randomised controlled trials by Ashor AW, Werner AD, […], Siervo M.

Link:
https://www.ncbi.nlm.nih.gov/pubmed/28294172

Additional information of El Mondo:
Find more information/studies on vitamin C and diabetes right here.

Objectives:
Is supplementation of formula milk with LCPUFA (long-chain polyunsaturated fatty acids) both safe and beneficial for full-term infants, while focusing on effects on visual function, neurodevelopment and physical growth?

Study design:
This review article included 15 RCTs (n = 1889).
9 studies assessed visual acuity, 6 of which used visual evoked potentials (VEP), 2 Teller cards and 1 both. 4 studies reported beneficial effects and the remaining 5 did not.
GRADE analysis of the outcomes indicated that the overall quality of evidence was low.

Results and conclusions:
The investigators found a meta-analysis of 3 RCTs (n = 244) showed significant benefit for sweep VEP acuity at 12 months (log of the minimum angle of resolution) [MD = -0.15, 95% CI = -0.17 to -0.13, I2 = 0%, low-quality of evidence].
However, the meta-analysis of 3 other RCTs (n = 256) showed no benefit for visual acuity measured with Teller cards at 12 months (cycles/degree) [MD = -0.01, 95% CI = -0.12 to 0.11, I2 = 0%, low-quality of evidence].

The investigators found meta-analysis of 4 RCTs (n = 661) revealed no significant differences between LCPUFA and placebo groups in BSID Mental Developmental Index scores at 18 months [MD = 0.06, 95% CI = -2.01 to 2.14, I2 = 75%, low-quality of evidence] and no significant differences in BSID Psychomotor Development Index scores at 18 months [MD = 0.69, 95% CI = -0.78 to 2.16, I2 = 61%, low-quality of evidence].

There were also no significant differences between the two groups in BSID-II scores at one year and two years of age.

The investigators found meta-analysis of 5 RCTs (n = 521) showed that the supplemented group had lower weight (z scores) at one year of age [MD = -0.23, 95% CI = -0.40 to -0.06, I2 = 83%, low-quality of evidence] and that the two groups showed no significant differences with respect to length and head circumference (z scores).

The investigators found meta-analysis at 18 months and at two years revealed no significant differences between the two groups with respect to weight (kg), length (cm) and head circumference (cm).

The investigators concluded there are no beneficial effects or harms of LCPUFA supplementation on neurodevelopmental outcomes of formula-fed full-term infants and no consistent beneficial effects on visual acuity. Therefore, routine supplementation of full-term infant milk formula with LCPUFA cannot be recommended at this time.

Original title:
Long chain polyunsaturated fatty acid supplementation in infants born at term by Jasani B, Simmer K, […], Rao SC.

Link:
https://www.ncbi.nlm.nih.gov/pubmed/28281303

Additional information of El Mondo:
Find more information/studies on pregnancy and LCPUFA right here.
 

Objectives:
Does magnesium supplementation reduce risk of cardiovascular disease among diabetic subjects?

Study design:
This review article included RCTs.

Results and conclusions:
The investigators found magnesium supplementation significantly improved fasting plasma glucose with 4.641 mg/dL [WMD = -4.641 mg/dL, 95% CI = -7.602 to -1.680, p = 0.002]. A more beneficial effect of magnesium supplementation was observed in diabetic subjects with hypomagnesaemia.

The investigators found magnesium supplementation significantly improved high-density lipoprotein (HDL or good cholesterol) with 3.197 mg/dL [WMD = 3.197 mg/dL, 95% CI = 1.455 to 4.938, p 0.001]. A more beneficial effect of magnesium supplementation was observed in diabetic subjects with hypomagnesaemia.

The investigators found magnesium supplementation significantly improved low-density lipoprotein (LDL or bad cholesterol) with 10.668 mg/dL [WMD = -10.668 mg/dL, 95% CI = -19.108 to -2.228, p = 0.013]. A more beneficial effect of magnesium supplementation was observed in diabetic subjects with hypomagnesaemia.

The investigators found magnesium supplementation significantly improved plasma triglycerides with 15.323 mg/dL [WMD = -15.323 mg/dL, 95% CI = -28.821 to -1.826, p = 0.026]. A more beneficial effect of magnesium supplementation was observed in diabetic subjects with hypomagnesaemia.

The investigators found magnesium supplementation significantly improved systolic blood pressure with 3.056 mmHg [WMD = 3.056 mmHg, 95% CI = -5.509 to -0.603, p = 0.015]. A more beneficial effect of magnesium supplementation was observed in diabetic subjects with hypomagnesaemia.

The investigators concluded magnesium supplementation has a favourable effect on risk factors of cardiovascular diseases. Although future large RCTs are needed for making robust guidelines for clinical practice.

Original title:
Effect of magnesium supplementation on type 2 diabetes associated cardiovascular risk factors: a systematic review and meta-analysis by Verma H and Garg R.

Link:
https://www.ncbi.nlm.nih.gov/pubmed/28150351

Additional information of El Mondo:
Find more information/studies on cardiovascular diseases, cholesterol and magnesium right here.

Objectives:
Is a low maternal circulating 25 hydroxyvitamin D (25-OHD) associated with an increased risk of preterm birth or spontaneous preterm birth and can vitamin D supplementation alone during pregnancy reduce risk of preterm birth?

Study design:
This review article included 6 RCTs and 18 observational studies.

Results and conclusions:
The investigators found maternal circulating 25-OHD deficiency significantly increased risk of preterm birth with 25% [pooled OR = 1.25, 95% CI = 1.13-1.38]. However, maternal circulating 25-OHD insufficiency was not associated with an increased risk of preterm birth [pooled OR = 1.09, 95% CI = 0.89-1.35]. Not associated because OR of 1 was found in 95% CI of 0.89 to 1.35. OR of 1 means no risk/association.

The investigators found vitamin D supplementation alone during pregnancy significantly reduced risk of preterm birth with 43% [pooled RR = 0.57, 95% CI = 0.36-0.91]. Significantly because RR of 1 was not found in 95% CI of 0.36 to 0.91. RR of 1 means no risk/association.

The investigators found maternal circulating 25-OHD 50 nmol/L significantly increased risk of spontaneous preterm birth with 45% [pooled OR = 1.45, 95% CI = 1.20-1.75]. 

The investigators concluded a maternal circulating 25-OHD 50 nmol/L increases risk of spontaneous preterm birth and vitamin D supplementation alone during pregnancy reduces risk of preterm birth. However, extrapolation of the results must be done with caution and there is urgent need for larger, better-designed RCT to confirm this effect.

Original title:
Vitamin D and risk of preterm birth: Up-to-date meta-analysis of randomized controlled trials and observational studies by Zhou SS, Tao YH, […], Tao FB.

Link:
https://www.ncbi.nlm.nih.gov/pubmed/28150405

Additional information of El Mondo:
Find more information/studies about vitamin D, pregnancy, review article, significant and 95% CI right here.

Objectives:
The conclusions from epidemiological studies are controversial between apple and pear consumption and type 2 diabetes mellitus (T2DM) risk. Therefore, this meta-analysis (systematic review) has been conducted.

Study design:
This review article included a total of 5 independent prospective cohort studies with 14,120 T2DM incident cases among 228,315 participants.

Results and conclusions:
The investigators found consumption of apples and pears was associated with 18% reduction in type 2 diabetes mellitus risk [multivariate-adjusted relative risk = 0.82, 95% CI = 0.75-0.88, I2 = 0.00%] when comparing the highest versus lowest category.

The investigators found dose-response analysis showed that one serving per week increment of apple and pear consumption was associated with a 3% [95% CI = 0.96-0.98, p for trend 0.001] reduction in type 2 diabetes mellitus risk.

The investigators concluded a higher consumption of apples and pears; at least one serving per week reduces type 2 diabetes mellitus risk.

Original title:
Apple and pear consumption and type 2 diabetes mellitus risk: a meta-analysis of prospective cohort studies by Guo XF, Yang B, […], Li D.

Link:
https://www.ncbi.nlm.nih.gov/pubmed/28186516

Additional information of El Mondo:
Find more information/studies on fruit consumption and diabetes right here.

The standard serving size is a 1/2 cup of sliced fruit. A medium pear produces approximately 1 cup of fruit; so an average medium pear equals two fruit servings.
1 small apple = 1 serving.
 

Objectives:
Does niacine supplementation reduce blood lipids levels in patients with type 2 diabetes mellitus?

Study design:
This review article included randomized controlled trials.

The meta-analysis showed the absence of publication bias and any dose-response relations between niacin and effect size.

There was a significant heterogeneity for the impact of niacin on LDL cholesterol and fasting plasma glucose.

Results and conclusions:
The investigators found niacin supplementation significantly increased HDL cholesterol with 0.27 mmol/L [95% CI = 0.24 to 0.30, p 0.001] in patients with type 2 diabetes mellitus.

The investigators found niacin supplementation significantly reduced LDL cholesterol with 0.250 mmol/L [95% CI = -0.47 to -0.03, p 0.05] in patients with type 2 diabetes mellitus.

The investigators found niacin supplementation significantly reduced triglycerides with 0.39 mmol/L [95% CI = -0.43 to -0.34, p 0.001] in patients with type 2 diabetes mellitus.

The investigators found niacin supplementation significantly increased fasting plasma glucose with 0.085 mmol/L [95% CI = 0.029 to 0.141, p 0.05] compared with controls in patients with long term treatment.

The investigators concluded niacin alone or in combination improves lipid abnormalities in patients with type 2 diabetes mellitus, but requires monitoring of glucose in long term treatment.

Original title:
Effect of niacin on lipids and glucose in patients with type 2 diabetes: A meta-analysis of randomized, controlled clinical trials by Ding Y, Li Y and Wen A.

Link:
http://www.ncbi.nlm.nih.gov/pubmed/25306426

Additional information of El Mondo:
Find more information on niacin (vitamin B3) and diabetes.

Objectives:
Observational studies suggest an association between dietary fiber intake and risk of type 2 diabetes, but the results are inconclusive. Therefore, this review article (meta-analysis) has been conducted.

Does dietary fiber intake reduce risk of type 2 diabetes?

Study design:
This review article included 17 prospective cohort studies of dietary fiber intake and risk of type 2 diabetes involving 19,033 cases and 488,293 participants.

Results and conclusions:
The investigators found total dietary fiber intake significantly reduced risk of type 2 diabetes with 19% [combined RR = 0.81, 95% CI = 0.73-0.90].

The investigators found dietary cereal fiber intake significantly reduced risk of type 2 diabetes with 23% [combined RR = 0.77, 95% CI = 0.69-0.85].

The investigators found dietary fruit fiber intake significantly reduced risk of type 2 diabetes with 6% [combined RR = 0.94, 95% CI = 0.88-0.99].

The investigators found dietary insoluble fiber intake significantly reduced risk of type 2 diabetes with 25% [combined RR = 0.75, 95% CI = 0.63-0.89].

The investigators found a nonlinear relationship of total dietary fiber intake with risk of type 2 diabetes [p for nonlinearity 0.01].

The investigators found dietary fiber intake of 15g per day non-significantly reduced risk of type 2 diabetes with 2% [combined RR = 0.98, 95% CI = 0.90-1.06].

The investigators found dietary fiber intake of 20g per day non-significantly reduced risk of type 2 diabetes with 3% [combined RR = 0.97, 95% CI = 0.87-1.07].

The investigators found dietary fiber intake of 25g per day significantly reduced risk of type 2 diabetes with 11% [combined RR = 0.89, 95% CI = 0.80-0.99].

The investigators found dietary fiber intake of 30g per day significantly reduced risk of type 2 diabetes with 24% [combined RR = 0.76, 95% CI = 0.65-0.88].

The investigators found dietary fiber intake of 35g per day significantly reduced risk of type 2 diabetes with 34% [combined RR = 0.66, 95% CI = 0.53-0.82].

The investigators found that the risk of type 2 diabetes decreased by 6% [combined RR = 0.94, 95% CI = 0.93-0.96] for 2 g/day increment in cereal fiber intake.

The investigators concluded that the intakes of dietary fiber, at least 25g total dietary fiber intake per day reduce risk of type 2 diabetes.

Original title:
Dietary fiber intake and risk of type 2 diabetes: a dose–response analysis of prospective studies by Yao B, Fang H, […], Zhao Y.

Link:
http://link.springer.com/article/10.1007/s10654-013-9876-x

Additional information of El Mondo:
Find more information on fiber and type 2 diabetes right here.

Objectives:
The association between serum folate and vitamin B12 levels and the risk of diabetic peripheral neuropathy (DPN) remains unclear. Therefore, this review article (meta-analysis) has been conducted.

Do reduced serum levels of folate and vitamin B12 increase peripheral neuropathy risk among patients with type 2 diabetes?

Study design:
This review article included 16 studies of serum folate levels (1190 patients with diabetic peripheral neuropathy and 1501 patients without diabetic peripheral neuropathy) and 18 studies of serum vitamin B12 levels (1239 patients with diabetic peripheral neuropathy and 1562 patients without diabetic peripheral neuropathy) in patients with type 2 diabetes mellitus (T2DM).

Results and conclusions:
The investigators found reduced serum levels of folate in patients with type 2 diabetes and diabetic peripheral neuropathy compared with patients with type 2 diabetes but without diabetic peripheral neuropathy [WMD = -1.64, 95% CI = -2.46 to -0.81].
A subgroup analysis confirmed this association in the Chinese population, but not in the Caucasian and mixed populations.

The investigators found reduced serum levels of vitamin B12 in patients with type 2 diabetes and diabetic peripheral neuropathy compared with patients with type 2 diabetes but without diabetic peripheral neuropathy [WMD = -70.86, 95% CI = -101.55 to -40.17].
A subgroup analysis confirmed this association in the Chinese population, but not in the Caucasian and mixed populations.

The investigators concluded reduced serum levels of folate and vitamin B12 increase peripheral neuropathy risk among patients with type 2 diabetes. These findings support the need for further controlled studies in defined patient populations and the importance of monitoring serum folate and vitamin B12 levels in patients with type 2 diabetes.

Original title:
Serum folate, vitamin B12 levels and diabetic peripheral neuropathy in type 2 diabetes: A meta-analysis by Wang D, Zhai JX and Liu DW.

Link:
https://www.ncbi.nlm.nih.gov/pubmed/28081987

Additional information of El Mondo:
Find more information/studies on diabetes, folate and vitamin B12 right here.

Diabetic peripheral neuropathy is a long-term complication of diabetes. Exposure to high blood glucose levels over an extended period of time causes damage to the peripheral nerves; the nerves that go to the arms, hands, legs and feet. It is one of many complications associated with diabetes, with nearly 60 percent of diabetics having some form of nerve damage.

Objectives:
Is there an association between individual micronutrients and blood pressure in patients with type 2 diabetes?

Study design:
This review article included 11 RCTs (13 interventions, 723 patients with type 2 diabetes and ages ranging from 50.7 to 66.8 years and 54% of them were males. The duration of diabetes varied from 4.6 to 8.6 years) with 3 to 52 weeks of follow-up were classified according to the type of micronutrient intervention: sodium (n = 1), vitamin C (n = 2), vitamin D (n = 7) and magnesium (n = 1).
Only a meta-analysis of vitamin C and D was able to perform with the available data.

Results and conclusions:
The investigators found vitamin C significantly reduced diastolic blood pressure of patients with type 2 diabetes with 2.88mmHg [WMD = -2.88 mmHg, 95% CI = -5.31 to -0.46, p = 0.020].
However, vitamin C not significantly reduced systolic blood pressure [WMD = -3.93mmHg, 95% CI = -14.78 to 6.92, p = 0.478].
Significant means that there is an association with a 95% confidence.

The investigators found vitamin D significantly reduced diastolic blood pressure of patients with type 2 diabetes with 2.44mmHg [WMD = -2.44 mmHg, 95% CI = -3.49 to -1.39, p  0.001].

The investigators found vitamin D significantly reduced systolic blood pressure of patients with type 2 diabetes with 4.56mmHg [WMD = -4.56 mmHg, 95% CI = -7.65 to -1.47, p = 0.004].

The investigators concluded vitamin D and possibly vitamin C have beneficial effects on blood pressure in patients with type 2 diabetes. Therefore, these interventions might represent a novel approach to the treatment of hypertension in patients with type 2 diabetes.

Original title:
Effects of individual micronutrients on blood pressure in patients with type 2 diabetes: a systematic review and meta-analysis of randomized clinical trials by de Paula TP, Kramer CK, [...], Azevedo MJ.

Link:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5233957/

Additional information of El Mondo:
Find more information/studies on diabetes and vitamin C and D right here.