Vitamin D supplementation is imperative for most people to maintain healthy vitamin D levels. However, current recommendations do not differentiate between ethnic groups. Melanin competes with with the vitamin D in our skin for UVB absorption. As a result, those with more melanin in their skin produce less vitamin D through sun exposure than during a given period of time than those with a lighter skin type. Therefore, researchers theorize vitamin D supplement requirements may differ between skin types.
African American and dark-skinned ethnic subgroups are at an increased risk of vitamin D deficiency than caucasians. In fact, it is estimated that vitamin D deficiency is over 20% more prevalent among African Americans compared to Caucasians. It has been also shown that populations in northern latitudes have a higher prevalence of vitamin D deficiency.
In a new study, researchers evaluated data from a recent randomized controlled trial. The trial studied 125 women of Somali (East African) and Caucasian (Finnish) ethnicities, and serum 25(OH)D response to vitamin D supplementation was the main outcome assessed. For baseline measurements, both groups of women were randomized into three supplementation groups, either placebo, 400 or 800 IU vitamin D3 per day.
- At baseline the, Somali group were older (by 12 years; p < 0.001), had a greater BMI (by 2 kg/m2; p < 0.001) and a greater body weight (by 12.5 kg; p < 0.001).
- Average vitamin D levels were 3.32 ng/ml lower among Somali women compared to Caucasian women (p = 0.006).
- Somali women required a 1.3 – 1.5 times higher dose compared to Caucasian women to maintain vitamin D levels greater than 20 ng/ml (50 nmol/l).
- They found that 8 mcg/day (320 IU) vitamin D intake was necessary for Caucasian women to maintain serum 25(OH)D levels > 12 ng/ml (30 nmol/L), whereas 18 mcg/day (720 IU) vitamin D was necessary for the Somali women to maintain level > 12 ng/ml (30 nmol/L).
This study demonstrates the different vitamin D requirements for different ethnicities. More research is required to better understand dose-response vitamin D interventions for specific ethnicities.