Despite the ease with which an adequate vitamin D intake can be achieved, recent reports indicate its serious deficiency among particular demographic groups in this country. Vitamin D is important in its own right for healthy bones and teeth, but it also facilitates the absorption of many other essential nutrients including magnesium, vitamin B12, phosphorous, and iron. Vitamin D also helps to maintain a balance of the right elements required for healthy blood and bones and when it is present in sufficient amounts, it can also boost immunity.
The sun is the most available source of the vitamin and people who spend long hours working indoors, avoiding the hot weather, or avoiding the sun for fear of skin cancer or wrinkles can invite other health problems. Exposure to sunshine indoors won't help since the UVB rays necessary for vitamin D production do not penetrate glass. Anything that inhibits the transmission of the sun's ultraviolet B (UVB) rays to the earth's surface or anything that blocks the penetration of the UVB radiation into the skin will interfere with the body's ability to produce vitamin D. Sunscreens are often used to reduce risk of skin cancer but unfortunately, those with a sun protection factor (SPF) greater than eight can also prevent the skin from making the essential vitamin.
The dangers of this deficiency cannot be taken lightly. Production of the protein that binds calcium in the intestinal cells slows down when vitamin D is lacking, leaving the bones with less than enough of that nutrient, raising the risk for osteomalacia in adults and rickets in children. Calcium deficiency can increase the risk of several other chronic diseases, with recent research linking it to colon cancer and a higher risk of suffering a heart attacks and developing breast cancer.
A vitamin D deficiency can occur when dietary intake is lower than recommended levels over time, when exposure to sunlight is limited, when the kidneys cannot convert vitamin D to its active form or when absorption of vitamin D from the digestive tract is inadequate due to other diseases. To counteract these problems it is often necessary to apply sunscreen only after one is exposed to to the sun for a long enough time for vitamin D synthesis to elapse. For most individuals, sun exposure for five to 10 minutes two or three times a week on the arms, hands and face is enough.
Darker skinned individuals, including many of those of Middle Eastern decent, often require longer sunshine exposure than light-skinned people because the high melanin level on darker skin reduces the ability to synthesise vitamin D. One US study reported that 42 per cent of African-American women aged between 15 and 49 were vitamin D deficient, against 4 per cent of white women. Women in the UAE may be at particular risk. Those who cover all of their skin whenever they are outside for cultural or religious reasons are more susceptible to the deficiency and living in crowded urban environments creates an additional risk. Tall buildings and smog from heavy motor vehicle traffic can block UVB rays and prevent vitamin D production.
A poor diet may also compound the risks presented by the deficiency because, once it is made by an obese individual, it is stored in fatty tissue, where it is far less bio-available. Fat stores under the skin serve to impede the vitamin's release into the blood stream. While people in the UAE can easily maintain adequate vitamin D nutrition through sun exposure this is not the only way to do so. Those unable to get out into the sunshine can consume vitamin D fortified foods. While only a few contain good sources of vitamin D naturally - fatty fish such as salmon, mackerel and tuna among them - fortified milk and cod liver oil can serve as vitamin D supplements. Dietary supplements may in some cases be useful sources of needed nutrients but scientists agree that nutrient needs should be met primarily through consuming foods, or in the case of vitamin D, though natural exposure to sunlight.
The UAE is not the first country to face public health problems associated with vitamin D deficiencies. In the 1930s rickets became a major public health problem in the United States and led to a milk fortification programme that almost eliminated this problem. Now, nearly 98 per cent of the milk supply in the United States is fortified with vitamin D. Just two cups of vitamin D-fortified milk is usually enough to fortify the body against the risks of a slew of diseases.
Serah Theuri is assistant professor of clinical nutrition in the department of Natural Science and Public Health at Zayed University in Abu Dhabi