Research reveals how UV exposure and ethnicity affect vitamin D levels, calls for customized supplement guidelines

Recent research published in journals clinical nutrition discuss the need to adjust UV exposure and other factors that alter desirable vitamin D levels depending on an individual's ethnicity.

study: Ambient ultraviolet B rays, supplements, and other factors interact to differentially impact vitamin D status according to ethnicity: a cross-sectional study. Image credit: Anna Martyanova / Shutterstock.com

vitamin D

Vitamin D deficiency occurs in 13-40% of Europeans. However, it is up to 70 times more prevalent among whites.

Vitamin D is produced in the skin after exposure to ultraviolet B (UVB) light. However, the amount of vitamin D produced during this process varies depending on the individual's skin color and age, as well as the intensity of incoming solar radiation. Supplementing with vitamin D and eating fortified foods can also increase circulating vitamin D levels in the body.

Skin synthesis from UVB can meet 80-100% of vitamin D requirements, making sunlight the most important natural source of vitamin D for many people.”

Once vitamin D enters the blood, it is metabolized to its active form, 25-hydroxyvitamin D (25(OH)D), which is the most accurate measure of vitamin D status in the body.

About research

The UK Biobank cohort, which included approximately 440,000 white, black and Asian people, was included in the study. The median age of the study cohort was 58 years.

UVB exposure was estimated by linking data from the Tropospheric Emission Monitoring Internet Service to participants' addresses. We calculated cumulative exposure to UVB over a 135-day period prior to blood sample collection. These values ​​were analyzed for association with circulating vitamin D levels, body mass index (BMI), and other variables in different combinations of different ethnic groups.

Median UVB exposure was 90 kJ/m²Meanwhile, more than 40% of the study cohort reported taking vitamin D supplements. More than 66% of study participants were overweight or obese.

What did the research show?

Median vitamin D levels for Asians were approximately 25 ng/mL, compared to 31 ng/mL and 48 ng/mL for black and white participants, respectively.

Regardless of ethnicity, UVB exposure was strongly associated with vitamin D levels. This increase was most significant among whites, at 35%, compared to 20% and 15% for black and Asian participants, respectively. Men, younger people, people who spend more time outdoors, and people with low weight or normal BMI were more likely to have high vitamin D levels.

In Caucasians, UVB exposure accounted for 14% of the variation in vitamin D levels, increasing by 1 nmol/L for every 10 kJ/m.² Increased exposure. These findings highlight the importance of encouraging healthy amounts of sun exposure, especially for Caucasians.

Black and Asian study participants had a two to four times smaller increase in vitamin D with UVB exposure than whites, likely due to increased skin pigmentation that prevents UVB utilization. . This observation may explain why vitamin D supplementation was the most important predictor of vitamin D levels among Asian participants.

Other factors predicting elevated vitamin D levels in non-whites included age. Conversely, as BMI increased and cholesterol levels increased, vitamin D levels were often lower in white people. An inverse association with BMI was observed in all groups, especially those using vitamin D supplements.

Interactions between factors

Caucasians had lower increases in vitamin D levels with age, even as UVB exposure increased. Among all groups, men showed a more pronounced increase in UVB exposure, with black men showing twice as much increase in vitamin D levels as black women.

For whites, taking no supplements had a greater increase in UVB exposure than taking supplements, which was in stark contrast to the pattern observed in blacks. The reason for this association is still unclear. However, it may suggest a feedback pathway that limits the increase in vitamin D levels according to baseline levels, possibly through hepatic synthesis.

conclusion

Vitamin D deficiency was prevalent in the UK Biobank population, particularly among non-whites. More specifically, about 50% of Asians, 33% of blacks, and 12% of whites were vitamin D deficient.

The body's ability to produce vitamin D appears to decrease with age. Therefore, older adults require higher doses of vitamin D. Nevertheless, it is also important to prescribe the appropriate dose for people under 60 years of age. Perhaps because vitamin D is stored in fatty tissue, doses may need to be adjusted among people who are heavier or have higher cholesterol levels.

The findings of this study are practical, as improved prediction will enable a more nuanced approach to vitamin D supplementation and deficiency prevention in diverse populations.”