Vitamin D has a key role in calcium metabolism in humans and therefore vital for healthy bone development and maintenance in humans. Very low serum calcium levels (less than 50nmol/L) are often found in populations who live in countries with limited sunlight, but a new study by Narchi et al. show that similar problems can also exist in sun-rich countries such as the United Arab Emirates.
This study focused on adolescent females who are particularly at risk of vitamin D deficiency. Such low levels both increase the risk of osteoporosis to the teenage girls when they are older and may cause a number of serious problems in any future offspring they may have including cardiomyopathy, hypocalcaemic seizures and rickets.
Narchi et al. determined the serum vitamin D levels of 293 girls aged between 11 and 18 years in the UAE of Emarati descent. They also ask detailed questions about their exposure to sun and the type of dress they usually wore. They classified vitamin D insufficiency, deficiency and severe deficiency as 50-75 nmol/L, 27.5-50nmol/L and <27.5 nmol/L respectively. The results for each category were 1%, 19.8% and 78.8% respectively i.e., over three quarters of the girls had severe deficiency which is likely to lead to problems for them and their offspring in later life.
The authors commented that these levels were lower than results from pregnant women and young mothers with the same demographics. They also noted that the youngest girls aged between 11 and 13 had the highest serum vitamin D levels but then the levels decline with advancing age. In common with local traditional values, most of the girls kept at least their arms covered when outside the home, however when the sun exposure values were calculated (1.75 hours per day), this degree of coverage did not explain the extremely low vitamin serum values. It is hypothesized that the skin pigmentation of this population could be a partial explanation, as a far higher dose of ultraviolet B is required to maximize cutaneous vitamin D production compared with people with lighter or unpigmented skins.
Some vitamin D supplementation took place, but there was poor compliance of tablet/capsule consumption. The most successful vector was vitamin D supplemented milk. It is clear that urgent further work on supplementation is required in these populations to raise their serum vitamin D levels to sufficiency.