Vitamin D: Researchers continue to explore wide range of benefits

Liz Meszaros, MDLinx | January 31, 2019

Of all the vitamins, it is perhaps vitamin D that garners the most attention and claims about its ability to prevent or improve a wide range of chronic conditions. Indeed, vitamin D has been touted to benefit everything from autoimmunity and bone mineral disease to several cancers, diabetes, cardiovascular disease, and multiple sclerosis.

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Researchers have devoted a lot of time and effort to assess a long list of chronic diseases vitamin D may prevent or improve.

Here are some of the latest findings on the effects of vitamin D, which were chosen from literally hundreds of studies published this year alone:

  • May lower oxidative stress parameters. In a systematic review and meta-analysis of 13 clinical trials, researchers found that vitamin D supplementation increased serum levels of total antioxidant capacity (P=0.001) and glutathione (an important antioxidant; P=0.003), and decreased malondialdehyde (a marker for oxidative stress) concentrations (P < 0.001).
  • May improve left ventricular function in patients with heart failure (HF) aged ≥ 50 years. Researchers conducted a post hoc analysis of the Effect of Vitamin D on Mortality in Heart Failure (EVITA) study to determine the effects of 3 years of daily vitamin D supplementation (4,000 IU/d) on echocardiography parameters in 400 patients with HF. They found no effects at 12 or 36 months in any left ventricular echocardiographic parameters. They did find, however, that vitamin D supplementation was associated with a 2.73% increase in left ventricular ejection fraction at 12 months in patients aged ≥ 50 years, which was still significant at 36 months (2.60%).

  • May improve symptoms of autism spectrum disorder (ASD) in children. In a placebo-controlled trial, researchers assessed the effects of vitamin D (2,000 IU/d), docosahexaenoic acid (722 mg/d), or a combination of both in 73 children aged 2.5 to 8 years with ASD. They found significant improvements in scores of social awareness with both docosahexaenoic acid alone and combined with vitamin D (P=0.03). They also observed a trend towards greater improvements with the combination of these two supplements in measures of social communicative functions and taste and smell.
  • May protect against acute respiratory infections. In a meta-analysis, researchers evaluated 25 randomized controlled trials of vitamin D3 or vitamin D2 supplementation that assessed the incidence of acute respiratory infection as an outcome of efficacy. They found that vitamin D supplementation significantly reduced the risk of acute respiratory infections in all 10,933 subjects included in the final analysis (adjusted OR: 0.88; 95% CI: 0.81-0.96; heterogeneity P < 0.001). Further, they found that the protective effects of vitamin D were more pronounced in those with a lower baseline concentration of 25-hydroxyvitamin D (25[OH]D; < 25 nmol/L) than in those with a higher concentration (≥ 25 nmol/L; adjusted OR: 0.30 vs 0.75; P=0.006).

  • May improve health-related quality of life (HRQOL) in patients with breast cancer in early survivorship. In 553 breast cancer patients/survivors enrolled in a matched cohort study of breast cancer outcomes, researchers found that over 50% used vitamin D supplements, and that those who used a naturopathic oncology provider in early survivorship were more likely to use them (P < 0.05). Baseline use of vitamin D supplements was associated with higher levels of self-reported HRQOL at enrollment (P < 0.05) and predictive of better HRQOL at 6-month follow-up (P < 0.05). Researchers also found that sufficient serum levels of vitamin D at baseline and follow-up were associated with better HRQOL at follow-up (P < 0.05).
  • Higher serum vitamin D levels may be associated with lower blood glucose levels. In a cross-sectional study, researchers included 680 women aged 35-74 years, in whom they measured serum 25[OH]D and glucose levels via fasting blood samples. Serum vitamin D levels less than 30 ng/mL (65.4% of subjects) were associated with blood glucose levels of 100 mg/dL or more (OR: 1.29; 95% CI: 1.05-1.57), as were levels of less than 20 ng/mL (OR: 1.25; 95% CI: 1.04-1.50).

In all of these studies, researchers stressed the need for further investigation and clinical trials to validate their results.

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