Vitamin D insufficiency is increasingly being shown to lead to a raft of detrimental metabolic changes. In particular to date, insulin resistance and immune dysfunction have been identified as arising from an insufficient plasma level of vitamin D. The wide ranging metabolic problems that are associated with poor vitamin D status are not surprising given that vitamin D is a hormone that can regulate gene expression through interaction with the nuclear vitamin D receptor. While the metabolic effects of vitamin D insufficiency can lead to chronic ill health, they are particularly problematic during pregnancy because evidence suggests that many of these metabolic changes are associated with a poor pregnancy outcome. Further, many of these detrimental metabolic changes may affect the long-term health of the offspring. In this regard the benefits of an optimal vitamin D intake during pregnancy are of interest. Recent research suggests that supplementing pregnant women with vitamin D provides health benefits and improves pregnancy outcomes.
For example, in a recent study, the benefits of vitamin D supplementation were tested in healthy pregnant women using a randomised-placebo controlled clinical trial (the most robust sort of study)1. The women in the study were supplemented with either 400 IU per day of vitamin D (as the vitamin D3 cholecalciferol form of the vitamin) or a placebo tablet for 8 weeks beginning at week 25 of gestation. As expected the vitamin D supplements caused a significant increase in the plasma 25-hydroxyvitamin D (the biological marker of vitamin D status) concentrations of the subjects compared to the placebo. In addition, those taking the vitamin D supplements experienced a significant decrease in plasma levels of C-reactive protein, fasting plasma glucose, systolic blood pressure, diastolic blood pressure and insulin concentrations. At the same time increases in the total plasma antioxidant capacity of blood, plasma glutathione concentrations, and measures of insulin sensitivity improved in those taking the vitamin D supplements.
Therefore vitamin D has metabolic benefits in pregnant women which mirror those benefits seen in non-pregnant individuals. These changes centre on improvements to the insulin system and also improvements in the levels of oxidation and inflammation. The rise in plasma glutathione concentrations and the improvements in the total antioxidant capacity likely reflect reductions in the levels of oxidative stress seen with vitamin D supplementation. As oxidation levels fall, the rate of antioxidants depletion declines, thus increasing plasma antioxidant levels. These result also highlight the association between insulin resistance and systemic inflammation. This further supports the view that insulin resistance and its associated metabolic changes (termed the metabolic syndrome), are a driving factor in the inflammation that may be a cause of cardiovascular disease. The vitamin D dose in this study was modest, and higher intake have been recommended in the nutritional literature, suggesting that even modest intakes of vitamin D may be beneficial.
Dr Robert Barrington’s Nutritional Recommendation: Vitamin D insufficiency is an unnecessary cause of disease because it is so easily reversed. Exposure to sunlight is the best way to maintain adequate vitamin D status. However, in those areas where year round sunlight is not available, vitamin D must be obtained from the diet. Because dietary sources of vitamin D are limited, supplements are usually necessary. Around 2000 IU per day in healthy adults has been suggested as necessary to maintain vitamin D levels at optimal concentrations during the winter months in high latitude regions.
RdB
