Are You Part of the 10 Percent Who Needs More Riboflavin for Healthy Blood Pressure? 25 Jan 2012
At TalkingNutritionDSM, we often write about the importance of getting enough folic acid, vitamin B6 and vitamin B12, especially when it comes to their roles in amino acid metabolism. In fact, these metabolic processes, needed for DNA synthesis and the interconversion of amino, also require riboflavin. An emerging area of nutrition research at the moment involves the interplay between micronutrients and different genes and how they affect health outcomes. Wilson et al. write today about the effects of riboflavin supplementation on hypertension in people with a common variant of a gene involved in amino acid metabolism, with clinically important results.
The gene in question has been studied widely. It is called methylenetetrahydrofolate reductase and codes for an enzyme of the same name. A common genetic variant of this gene is when cytosine is replaced with thymine at position 677, which leads to the amino acid valine being incorporated into the enzyme instead of alanine. This produces an enzyme that is more sensitive to heat and has a lower activity. For people with the normal genetic polymorphism (CC) or who have one copy of the ineffective enzyme (CT), there are no significant health effects. In people with two copies of the ineffective enzyme (TT), homocysteine levels accumulate in the blood because the enzyme can no longer efficiently convert it to methionine. Around 10% of the population has the TT genetic variant, according to Schneider, Rees, Liu and Clegg.
In the study by Wilson, subjects who had previously participated in a riboflavin study by the same group and had the defective enzyme were invited back for the second part of a cross-over study after four years. The subjects initially selected all had cardiovascular disease and most had high blood pressure that was being treated. When subjects’ blood pressure was compared in relation to gene polymorphism, people with the TT genotype had significantly higher blood pressure. During the follow-up intervention, the TT participants were provided with 1.6 mg riboflavin a day or placebo for 16 weeks, and the treatment was the opposite of what they had been given in the first part of the study. The riboflavin dose was equivalent to the Recommended Dietary Allowance for adult men in Ireland where the study was conducted.
After 16 weeks, systolic blood pressure had declined by 9 mm Hg and diastolic by 6 mm Hg in subjects supplemented with riboflavin, whereas there was no change in the placebo group. Interestingly, although functional riboflavin status improved in the treated group, the average test results after supplementation still indicated borderline deficiency. The authors note that an improvement in blood pressure like this could be achieved by weight-loss of around 10 kg or daily vigorous exercise. Since there are no toxic effects known from excess riboflavin consumption, widespread increases in riboflavin intakes or fortification could have meaningful effects on blood pressure for people with the TT genotype with no risk to the general population.
Main reference:
Wilson CP, Ward M, McNulty H, et al. Riboflavin offers a targeted strategy for managing hypertension in patients with the MTHFR 677TT genotype: a 4-y follow-up. The American Journal of Clinical Nutrition 2012. http://www.ajcn.org/content/early/2012/01/24/ajcn.111.026245.abstract
