Nutritional advice

Objectives:
The role of zinc in the etiology of type 2 diabetes has been widely reported in recent decades. However, much remains uncertain concerning the effect of zinc on the risk of developing type 2 diabetes. Therefore, this review article has been conducted.

Does zinc reduce risk of type 2 diabetes?

Study design:
This review article included 16 studies.
There was no publication bias.

Results and conclusions:
The investigators found in 7 prospective cohort studies and 1 cross-sectional study (146,027 participants aged between 18 and 84 years and of both genders, belonging to different ethnic groups. Of which, 11,511 type 2 diabetes cases) when comparing the highest versus lowest dietary zinc intakes, a significantly reduced risk of 13% [OR = 0.87, 95% CI = 0.78-0.98, I2 = 64.5%, p = 0.003] for type 2 diabetes.
This relationship was stronger and more evident in rural compared to urban areas [rural areas: OR = 0.59, 95% CI = 0.48-0.73, I2 = 0.0%, p = 0.843 versus urban areas: OR = 0.94, 95% CI = 0.86-1.02, I2 = 43.9%, p = 0.113].

The investigators found no association between supplementary [OR = 0.94, 95% CI = 0.75-1.19, I2 = 85.4%, p = 0.009] or total zinc intake from both diet and supplementation [OR = 0.95, 95% CI = 0.82-1.11, I2 = 56.5%, p = 0.129] and type 2 diabetes risk.

The investigators found in population-based studies that high serum/plasma zinc levels significantly increased risk of type 2 diabetes with 64% [OR = 1.64, 95% CI = 1.25-2.14, I2 > 22.5%, p = 0.275].

The investigators concluded high dietary zinc intake reduces risk of type 2 diabetes. This relationship is stronger and more evident in rural compared to urban areas. However, an elevated serum/plasma zinc concentration is associated with an increased risk of type 2 diabetes in the general population.

Link:
Zinc Intake and Status and Risk of Type 2 Diabetes Mellitus: A Systematic Review and Meta-Analysis by Fernández-Cao JC, Warthon-Medina M, […], Lowe NM.

Link:
https://www.mdpi.com/2072-6643/11/5/1027/htm

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

Serum/plasma zinc levels can be increased by eating products that contain a lot of zinc and/or taking zinc supplements.
 

Objectives:
Does magnesium reduce risk of type 2 diabetes?

Study design:
This review article included 35 cohort studies and 26 RCTs (1,168 participants).

Results and conclusions:
The investigators found compared to the lowest magnesium dietary intake, the highest level was associated with a 22% lower risk for type 2 diabetes.

The investigators found the risk for type 2 diabetes was reduced by 6% for each 100mg increment in daily magnesium dietary intake.

The investigators found in 26 RCTs (1,168 participants) that magnesium supplementation significantly reduced:
-the fasting plasma glucose (FPG) level [SMD = -0.32, 95% CI = -0.59 to -0.05];
-2-h oral glucose tolerance test (2-h OGTT) result [SMD = -0.30, 95% CI = -0.58 to -0.02];
-fasting insulin level [SMD = -0.17, 95% CI = -0.30 to -0.04];
-homeostatic model assessment-insulin resistance (HOMA-IR) score [SMD = -0.41, 95% CI = -0.71 to -0.11];
-triglyceride (TG) level;
-systolic blood pressure (SBP) and;
-diastolic blood pressure (DBP).

The investigators found trial sequential analysis (TSA) showed an inverse association, with most benefits of magnesium supplementation on glucose metabolism being stable.

The investigators concluded magnesium dietary intake has an inverse dose-response association with type 2 diabetes incidence and supplementation appears to be advisable in terms of glucose parameters in type 2 diabetes/high-risk individuals.

Original title:
Association of Magnesium Consumption with Type 2 Diabetes and Glucose Metabolism: a Systematic Literature Review and Pooled Study with Trial Sequential Analysis by Zhao B, Deng H, [...], Zhang W.

Link:
https://www.ncbi.nlm.nih.gov/pubmed/31758631

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

Objectives:
Observational evidence suggests higher nut consumption is associated with better glycemic control. However, it is unclear if this association is causal. Therefore, this review article has been conducted.

Is there a causal relationship between consumption of tree nuts or peanuts and reduced risk of type 2 diabetes?

Study design:
This review article included a total of 40 RCTs with 2,832 unique participants, with a median duration of 3 months (range: 1-12 months).

Results and conclusions:
The investigators found overall consumption of tree nuts or peanuts had a favourable effect on HOMA-IR values [WMD = -0.23, 95% CI = -0.40 to -0.06, I2 = 51.7%] and fasting insulin levels [WMD = -0.40 μIU/mL, 95% CI = -0.73 to -0.07 μIU/mL, I2 = 49.4%].

The investigators found, however, there was no significant effect of nut consumption on fasting blood glucose levels [WMD = -0.52 mg/dL, 95% CI = -1.43 to 0.38 mg/dL, I2 = 53.4%] or HbA1c [WMD = 0.02%, 95% CI = -0.01% to 0.04%, I2 = 51.0%].

The investigators concluded consumption of peanuts or tree nuts decreases HOMA-IR and fasting insulin levels. These findings suggest that nut consumption may improve insulin sensitivity. In the future, well-designed clinical trials are required to elucidate the mechanisms that account for these observed effects.

Original title:
The effect of nuts on markers of glycemic control: a systematic review and meta-analysis of randomized controlled trials by Tindall AM, Johnston EA, […], Petersen KS.

Link:
https://www.ncbi.nlm.nih.gov/pubmed/30722007

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

Objectives:
The incidence of type 2 diabetes mellitus (DM) has increased in the US over the last several years. The consumption of low-fat dairy foods has been linked with decreasing the risk of diabetes mellitus but studies have yet to show a clear correlation. Therefore, this review article has been conducted.

Is there a causal relationship between consumption of low-fat dairy foods and reduced risk of type 2 diabetes?

Study design:
This review article included 30 RCTs.
The total sample size was 2,900 with >50% female participants, but the distribution varied greatly across different studies.
The mean age of subjects ranged from 18-63 years.
The funnel plots for all 3 outcomes (HOMA-IR, waist circumference and body weight) did not suggest significant publication bias.

Results and conclusions:
The investigators found (794 individuals) comparing high intake to the control group, consumption of low-fat dairy foods significantly reduced the HOMA-IR values [MD = -1.21, 95% CI = -1.74 to -0.67, p 0.00001, I2 = 92%].

The investigators found (1,348 individuals) comparing high intake to the control group, consumption of low-fat dairy foods significantly reduced waist circumference [MD = -1.09 cm, 95% CI = -1.68 to -0.58, p 0.00001, I2 = 94%].

The investigators found for body weight (2,362 individuals), the low-fat dairy foods intervention group weighed 0.42 kg less than the control group [p 0.00001, I2 = 92%].

The investigators found limiting to studies that were assessed to have low risk of bias did not significantly change the point estimates or heterogeneity statistics (Q or I2) for all 3 outcomes.
Similarly excluding studies with a physical activity component did not significantly alter point estimates or heterogeneity statistics for all 3 outcomes.

The investigators concluded low-fat dairy products have a beneficial effect on HOMA-IR, waist circumference and body weight. This could impact dietary recommendations to reduce type 2 diabetes risk.

Original title:
The Effects of Dairy Intake on Insulin Resistance: A Systematic Review and Meta-Analysis of Randomized Clinical Trials by Sochol KM, Johns TS, […], Melamed ML.

Link:
https://www.mdpi.com/2072-6643/11/9/2237/htm

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

Objectives:
In recent years, cardiovascular diseases (CVDs) have become a focus topic and global concern. There have been mixed reports on the relationship between whole grain or cereal fiber intake and the risk of type 2 diabetes. Therefore, this review article has been conducted.

Does grain or cereal fiber dietary intake reduce risk of type 2 diabetes?

Study design:
This review article included 7 cohort studies and 1 case-control study with a total of 434,903 participants and 14,728 cases of type 2 diabetes.
The average follow-up was 12.6 years.
There was no publication bias.

Results and conclusions:
The investigators found whole grain or cereal fiber dietary intake was associated with a reduced risk of 26% [combined RR = 0.74, 95% CI = 0.67 to 0.82, I2 = 56.8%, p = 0.06] for type 2 diabetes.
This reduced risk was 38% [pooled RR = 0.68, 95% CI = 0.64-0.73, I2 = 0.0%, p = 0.452] in sensitivity analysis.

The investigators found whole grain or cereal fiber dietary intake was associated with a reduced risk of 32% [combined RR = 0.68, 95% CI = 0.49 to 0.88] for type 2 diabetes among males.

The investigators found whole grain or cereal fiber dietary intake was associated with a reduced risk of 26% [combined RR = 0.74, 95% CI = 0.64 to 0.77] for type 2 diabetes among females.

The investigators concluded that increased whole grain and cereal fiber dietary intake reduce risk of type 2 diabetes.

Original title:
Whole grain and cereal fiber intake and the risk of type 2 diabetes: a meta-analysis by Wang Y, Duan Y, […], Jin Y.

Link:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6627783/

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

Objectives:
Although many studies have shown that low zinc status is associated with diabetes, the putative effects of zinc supplementation on glycemic control are inconclusive. Therefore, this review article (meta-analysis) has been conducted.

Does zinc supplementation reduce risk of diabetes mellitus?

Study design:
This review article included 32 RCTs, involving a total of 1,700 participants in 14 countries.

Results and conclusions:
The investigators found overall, compared with their respective control groups, the subjects in the zinc supplementation group had a statistically significant reduction in concentrations of :
-fasting glucose [WMD = -14.15 mg/dL, 95% CI = -17.36 to -10.93 mg/dL];
-2-h postprandial glucose [WMD = -36.85 mg/dL, 95% CI = -62.05 to -11.65 mg/dL];
-fasting insulin [WMD = -1.82 mU/L, 95% CI = -3.10 to -0.54 mU/L];
-homeostasis model assessment for insulin resistance [WMD = -0.73, 95% CI = -1.22 to -0.24]:
-glycated hemoglobin [WMD = -0.55%, 95% CI = -0.84 to -0.27%] and;
-high-sensitivity C-reactive protein [WMD = -1.31 mg/L, 95% CI = -2.05 to -0.56 mg/L].

The investigators found, moreover, subgroup analyses revealed that the effects of zinc supplementation on fasting glucose were significantly influenced by diabetic status and the formulation of the zinc supplement.

The investigators concluded several key glycemic indicators are significantly reduced by zinc supplementation, particularly the fasting glucose in subjects with diabetes and in subjects who received an inorganic zinc supplement. Together, these findings support the notion that zinc supplementation may have clinical potential as an adjunct therapy for preventing or managing diabetes.

Original title:
Zinc supplementation improves glycemic control for diabetes prevention and management: a systematic review and meta-analysis of randomized controlled trials by Wang X, Wu W, [...], Wang F.

Link:
https://www.ncbi.nlm.nih.gov/pubmed/31161192

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

Objectives:
Dietary proteins, including those obtained from animal and plant sources, have inconsistently been correlated with type 2 diabetes mellitus (T2DM) risk. Therefore, this review article (meta-analysis) has been conducted.

Does dietary protein intake increase risk of type 2 diabetes mellitus?

Study design:
This review article included 21 cohort studies with a total of 487,956 individuals and 38,350 T2DM cases (persons with type 2 diabetes mellitus).

Results and conclusions:
The investigators found high total dietary protein intake was associated with an increased risk of 10% for type 2 diabetes mellitus [RR = 1.10, p = 0.006] whereas moderate total dietary protein intake was not significantly associated with type 2 diabetes mellitus risk [RR = 1.00,  p = 0.917].  
Not significantly because the calculated p-value of 0.917 was larger than the p-value of 0.05.

The investigators found, moreover, an increased risk of 13% [RR = 1.13, p = 0.013] for type 2 diabetes mellitus was observed with high  dietary animal protein intake whereas moderate animal protein intake had little or no effect on type 2 diabetes mellitus risk [RR = 1.06, p = 0.058].

The investigators found, high dietary intake of plant protein did not affect type 2 diabetes mellitus risk [RR = 0.93, p = 0.074], whereas moderate intake was associated with a reduced risk of 6% for type 2 diabetes mellitus [RR = 0.94, p  0.001].

The investigators concluded high dietary total protein and dietary animal protein intakes are associated with an increased risk of type 2 diabetes mellitus, whereas moderate plant protein intake is associated with a decreased risk of type 2 diabetes mellitus.

Original title:
Dietary protein intake and subsequent risk of type 2 diabetes: a dose-response meta-analysis of prospective cohort studies by Ye J, Yu Q, [...], Wang Y.

Link:
https://www.ncbi.nlm.nih.gov/pubmed/30929078

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

A diet with high protein intake is a diet with a minimum of 35 En% protein (En% = energy percentage). These products from the supermarket contain at least 35 En% protein.
35 En% protein means that the amounts of protein contribute 35% to the total calories (kcal) of the diet.
If the diet contains 2000 kcal, 175 grams of protein contribute 35% to this 2000 kcal.
1 gram of protein gives 4 kcal. Thus, 175 grams of protein provide 700 kcal and 700 kcal is 35% of 2000 kcal.

A diet with moderate protein consumption is a diet with 20-25 En% protein. The easiest way to follow a diet with moderate protein consumption is to choose only products/meals that also contain 20-25 En% protein. These products from the supermarket contain 20-25 En% protein.

 

Objectives:
The role of gut microbiota in the management of diabetes has been shown. Several current trials are investigating the effect of probiotics and prebiotics, which are widely used to modulate intestinal microbiota, on inflammatory factors and biomarkers of oxidative stress in diabetic patient. However, their findings are controversial. Therefore, this review article (meta-analysis) has been conducted.

Do probiotic and synbiotic supplementation improve biomarkers of inflammation and oxidative stress in diabetic patients?

Study design:
This review article included 16 RCTs (n = 1,060).

Randomized controlled trials (RCTs) reported the effect of probiotics or synbiotics on circulating (serum and plasma) inflammatory marker (hs-CRP) and oxidative stress indicators (malondialdehyde [MDA], glutathione [GSH], nitric oxide [NO] and total antioxidant capacity [TAC]) among patients with diabetes.

The methodological quality varied across these trials.

Results and conclusions:
The investigators found probiotic and synbiotic supplementation significantly decreased hs-CRP level [SMD = -0.38, 95% CI = -0.51 to -0.24, p = 0.000] and the oxidative stress indicator malondialdehyde [SMD = -0.61, 95% CI = -0.89 to -0.32, p = 0.000] in diabetic patients compared to those in subjects receiving placebos.

The investigators found, in addition, probiotic and synbiotic supplementation significantly increased total antioxidant capacity [SMD = 0.31, 95% CI = 0.09 to 0.52, p = 0.006], nitric oxide [SMD = 0.62, 95% CI = 0.25 to 0.99, p = 0.001] and glutathione [SMD = 0.41, 95% CI = 0.26, 0.55, p = 0.000] levels.

The investigators concluded that probiotic and synbiotic supplementation improve biomarkers of inflammation and oxidative stress in diabetic patients. Further studies are needed to develop clinical practice guidelines for the management of inflammation and oxidative stress in these patients.

Original title:
The effect of probiotic and synbiotic supplementation on biomarkers of inflammation and oxidative stress in diabetic patients: A systematic review and meta-analysis of randomized controlled trials by Zheng HJ, Guo J, [...], Wang Y.

Link:
https://www.ncbi.nlm.nih.gov/pubmed/30794924

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

Oxidative stress is an imbalance between free radicals and antioxidants in your body. Antioxidants can reduce oxidative stress.
 

Objectives:
Various mechanisms link higher total homocysteine to higher insulin resistance and risk of type 2 diabetes (T2D). Folate supplementation is recognized as a way to lower homocysteine. However, randomized controlled trials (RCTs) show inconsistent results on insulin resistance and type 2 diabetes outcomes. Therefore, this review article (meta-analysis) has been conducted.

Does folate supplementation improve insulin resistance and type 2 diabetes outcomes?

Study design:
This review article included 29 RCTs (22,250 participants) that assessed the effect of placebo-controlled folate supplementation alone or in combination with other B vitamins on fasting glucose, insulin, homeostasis model assessment for insulin resistance (HOMA-IR), glycated hemoglobin (HbA1c) or risk of type 2 diabetes.

The meta-analysis was conducted using both random- and fixed-effects models to calculate weighted mean differences (WMDs) or risk ratios with 95% CIs.
Heterogeneity was low in all meta-analyses.

Results and conclusions:
The investigators found when compared with placebo, folate supplementation significantly lowered fasting insulin [WMD = -13.47 pmol/L, 95% CI = -21.41 to -5.53 pmol/L, p 0.001] and HOMA-IR [WMD = -0.57 units, 95% CI = -0.76 to -0.37 units, p 0.0001], but no overall effects were observed for fasting glucose or HbA1c.

The investigators found subgroup analysis showed no signs of effect modification except for change in homocysteine, with the most pronounced effects in trials with a change of >2.5 µmol/L.
Changes in homocysteine after folate supplementation correlated with changes in fasting glucose [β = 0.07, 95% CI = 0.01 to 0.14, p = 0.025] and HbA1c [β = 0.46, 95% CI = 0.06 to 0.85, p = 0.02].

The investigators found only 2 studies examined folate supplementation on risk of type 2 diabetes and they found no change in RR [pooled RR = 0.91, 95% CI = 0.80 to 1.04, p = 0.16].

The investigators concluded that folate supplementation lowers fasting insulin and HOMA-IR. However, folate supplementation does not reduce risk of type 2 diabetes.

Original title:
Effect of folate supplementation on insulin sensitivity and type 2 diabetes: a meta-analysis of randomized controlled trials by Lind MV, Lauritzen L, [...], Eriksen JN.

Link:
https://www.ncbi.nlm.nih.gov/pubmed/30615110

Additional information of El Mondo:
Find more information/studies on diabetes and folate (also called folic acid) right here.
 

Objectives:
Evidence from randomized controlled trials (RCTs) suggests that viscous dietary fiber may offer beneficial effects on glycemic control and, thus, an improved cardiovascular disease risk profile. Therefore, this review article (meta-analysis) has been conducted.

Does viscous dietary fiber supplementation improve glycemic control in type 2 diabetes?

Study design:
This review article included 28 RCTs of ≥3 weeks in duration that assessed the effects of viscous fiber on markers of glycemic control in type 2 diabetes with a total of 1,394 participants.

Results and conclusions:
The investigators found that viscous fiber at a median dose of ∼13.1 g/day significantly reduced HbA1c in type 2 diabetes [MD = -0.58%, 95% CI = -0.88 to -0.28, p = 0.0002] compared with control and in addition to standard of care.

The investigators found that viscous fiber at a median dose of ∼13.1 g/day significantly reduced fasting blood glucose in type 2 diabetes [MD = -0.82 mmol/L, 95% CI = -1.32 to -0.31, p = 0.001] compared with control and in addition to standard of care. 

The investigators found that viscous fiber at a median dose of ∼13.1 g/day significantly reduced HOMA-insulin resistance in type 2 diabetes [MD = -1.89, 95% CI = -3.45 to -0.33, p = 0.02] compared with control and in addition to standard of care.

The investigators found the certainty of evidence was graded moderate for HbA1c, fasting glucose, fasting insulin and HOMA-IR and low for fructosamine.

The investigators concluded that 13.1 g/day viscous fiber supplements improve conventional markers of glycemic control beyond usual care and should be considered in the management of type 2 diabetes.

Original title:
Should Viscous Fiber Supplements Be Considered in Diabetes Control? Results From a Systematic Review and Meta-analysis of Randomized Controlled Trials by Jovanovski E, Khayyat R, […], Vuksan V.

Link:
https://www.ncbi.nlm.nih.gov/pubmed/30617143

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