Philip J. Goscienski, M.D.
When humans migrated from sunny climates to northern latitudes and then had to suffer through several ice ages as well, they upset nature's plan for vitamin D. As early peoples expanded farther north they became lighter-complexioned, the better to gather in UVB rays. Insufficient vitamin D lowers fertility, so that those that retained dark skin didn't reproduce as fast. That explains why fair skin and blond hair predominate in northern Europe.
Recent lifestyle changes make it even more difficult to keep up with our need for vitamin D. Long sleeves, hats and sunscreens are very effective in reducing the risk of skin cancer. Unfortunately they also prevent us from making enough vitamin D even in the summer. And those who live in the upper reaches of North America couldn't make enough vitamin D during winter months if they wandered around stark naked!
Nature has found a way to protect northerners, provided that they get enough sun exposure during the summer. Vitamin D is fat soluble. We can store it in our fat deposits and release it during the winter months when UVB rays are unable to penetrate the ozone layer. Persons who fail to build up stores of vitamin D during the months of plentiful UVB rays will enter the slack months with low levels and no reserves. Moreover, the elderly are likely to avoid the summer sun by staying indoors and to cover up with clothing or to use sunscreen when they do go outdoors.
Stone Age babies never became deficient in vitamin D, partly because their mothers produced breastmilk that had adequate amounts. Prehistoric moms carried their babies with them wherever they went in their hunt for food, so their nurslings got some sun exposure every day, plenty for the needs of their growing bones. Today's infants aren't so lucky. Mothers in northern latitudes, especially those with darker skin pigmentation, produce breastmilk that has virtually no vitamin D. The little sunlight that brightens the room of a modern infant passes through windows that filter out UVB rays.
Sunlight is the best source of vitamin D. It only requires about 10 or 15 minutes of exposure to the face and arms, 2 or 3 times a week, an amount that does not significantly increase the risk of melanoma or other forms of skin cancer.
Most experts on vitamin D agree that the current recommendation of 400 International Units (IU) per day is not enough, especially for the elderly and pregnant or nursing women. An intake of 1,000 IU per day is safe, and will probably become the recommended standard for most older persons.
Milk is fortified with 100 IU in 8 ounces but dark-skinned individuals, who need it the most, usually cannot tolerate dairy products. Cod liver oil is an old remedy, but its awful taste is almost impossible to disguise. Other choices include oily fish, and fruit juices and cereals to which vitamin D has been added. A supplement that contains calcium and magnesium in addition to vitamin D is another choice. Very few multivitamin/multimineral supplements supply adequate amounts of all three without also providing too much vitamin A, so shop carefully.
Philip J. Goscienski, M.D. is the author of Health Secrets of the Stone Age, Better Life Publishers 2005. Contact him at firstname.lastname@example.org.