Vitamin D is suggested to have protective effects against type 1 diabetes. However, the results from observational studies have been inconsistent. We aimed to examine their association by conducting a meta-analysis of observational studies. Multiple databases were searched in June 2013 to identify relevant studies including both case-control and cohort studies. Either a fixed- or random-effects model was used to calculate the pooled risk estimate. We identified eight studies (two cohort studies and six case-control studies) on vitamin D intake during early life and three studies (two cohort studies and one case-control study) on maternal vitamin D intake during pregnancy. The pooled odds ratio for type 1 diabetes comparing vitamin D supplementation with non-supplementation during early life was 0.71 (95% confidence interval [CI], 0.51–0.98). Similar results were observed in the case-control subgroup analysis but not in the cohort subgroup analysis. The pooled odds ratio with maternal intake of vitamin D during pregnancy was 0.95 (95% CI, 0.66–1.36). In conclusion, vitamin D intake during early life may be associated with a reduced risk of type 1 diabetes. However, there was not enough evidence for an association between maternal intake of vitamin D and risk of type 1 diabetes in the offspring.

Vitamin D might elicit protective effects against cardiovascular disease by decreasing the level of circulating high-sensitivity C-reactive protein (hs-CRP), an inflammatory marker. Thus, we conducted a meta-analysis of randomized controlled trials to evaluate the association of vitamin D supplementation with circulating hs-CRP level. A systematic literature search was conducted in September 2013 (updated in February 2014) via PubMed, Web of Science, and Cochrane library to identify eligible studies. Either a fixed-effects or a random-effects model was used to calculate pooled effects. The results of the meta-analysis of 10 trials involving a total of 924 participants showed that vitamin D supplementation significantly decreased the circulating hs-CRP level by 1.08 mg/L (95% CI, −2.13, −0.03), with the evidence of heterogeneity. Subgroup analysis suggested a higher reduction of 2.21 mg/L (95% CI, −3.50, −0.92) among participants with baseline hs-CRP level ≥5 mg/L. Meta-regression analysis further revealed that baseline hs-CRP level, supplemental dose of vitamin D and intervention duration together may be attributed to the heterogeneity across studies. In summary, vitamin D supplementation is beneficial for the reduction of circulating hs-CRP. However, the result should be interpreted with caution because of the evidence of heterogeneity.

Adequate intake of dietary fibers has proven metabolic and cardiovascular benefits, molecular mechanisms remain still limited. This study was aimed to investigate the effects of cereal dietary fiber on obesity-related liver lipotoxicity in C57BL/6J mice fed a high-fat/cholesterol (HFC) diet and underlying mechanism. Forty-eight adult male C57BL/6J mice were randomly given a reference chow diet, or a high fat/choleserol (HFC) diet supplemented with or without oat fiber or wheat bran fiber for 24 weeks. Our results showed mice fed oat or wheat bran fiber exhibtied lower weight gain, lipid profiles and insulin resistance, compared with HFC diet. The two cereal dietary fibers potently decreased protein expressions of sterol regulatory element binding protein-1 and key factors involved in lipogenesis, including fatty acid synthase and acetyl-CoA carboxylase in target tissues. At molecular level, the two cereal dietary fibers augmented protein expressions of peroxisome proliferator-activated receptor alpha and gamma, liver X receptor alpha and ATP-binding cassette transporter A1 in target tissues. Our findings indicated that cereal dietary fiber supplementation abrogated obesity-related liver lipotoxicity and dyslipidemia in C57BL/6J mice fed a HFC diet. In addition, the efficacy of oat fiber is greater than wheat bran fiber in normalizing these metabolic disorders and pathological profiles.

Whey supplementation is beneficial for human health, possibly by reducing the circulating C-reactive protein (CRP) level, a sensitive marker of inflammation. Thus, a meta-analysis of randomized controlled trials was conducted to evaluate their relationship. A systematic literature search was conducted in July, 2014, to identify eligible studies. Either a fixed-effects model or a random-effects model was used to calculate pooled effects. The meta-analysis results of nine trials showed a slight, but no significant, reduction of 0.42 mg/L (95% CI −0.96, 0.13) in CRP level with the supplementation of whey protein and its derivates. Relatively high heterogeneity across studies was observed. Subgroup analyses showed that whey significantly lowered CRP by 0.72 mg/L (95% CI −0.97, −0.47) among trials with a daily whey dose ≥20 g/day and by 0.67 mg/L (95% CI −1.21, −0.14) among trials with baseline CRP ≥3 mg/L. Meta-regression analysis revealed that the baseline CRP level was a potential effect modifier of whey supplementation in reducing CRP. In conclusion, our meta-analysis did not find sufficient evidence that whey and its derivates elicited a beneficial effect in reducing circulating CRP. However, they may significantly reduce CRP among participants with highly supplemental doses or increased baseline CRP levels.