Philip J. Goscienski, M.D.
Nearly a century ago physicians recognized that something in fish fats (does anyone remember taking cod liver oil as a kid?) prevented rickets in children. Rickets is a softening of the bone that leads to bowlegs and other skeletal abnormalities and poor tooth formation. It virtually disappeared in industrialized countries when dairy products and other foods were fortified with vitamin D — and moms began pushing cod liver oil.
Stone Age kids never drank cow's milk but their bodies made all the vitamin D that they needed. Humans originated in sunny Africa where hunter-gatherer kids still don't wear clothes. Since the body only needs a few minutes a day of sun exposure at that latitude to convert cholesterol in the skin into vitamin D it's not likely that those toddlers grew up bowlegged. And now we know that they avoided some even worse problems.
Under ideal conditions we make all the vitamin D we need but migration and lifestyle factors can lead to a deficiency. North Americans who live above a line joined by Los Angeles and Atlanta get inadequate D-producing sun exposure for half the year because of the angle of the sun's rays during the winter. Especially among seniors, who spend little time outdoors and cover up with clothing and sunscreen in an effort to lower their risk of skin cancer, low levels of vitamin D are the rule.
Rickets is making a resurgence among dark-skinned ethnic groups whose clothing styles allow little skin exposure. The infants of pregnant women with low levels of vitamin D are especially at risk.
Low levels of vitamin D are so consistently associated with cancer of the breast, ovary, colon and pancreas and some immune-related diseases that the old recommendation of 400 International Units (IU) has been revised upward. The emerging recommendation is 1,000 units per day and some researchers would double it. The risk of toxicity using oral preparations is minimal; it would take months at a daily intake several times that large to cause illness.
Ten or 15 minutes of summer sun exposure with arms and head uncovered and un-sun-screened several times a week would be adequate but only supplements, especially in the winter, can give us what we need. Cod liver oil has too much vitamin A and most adults don't drink milk.
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.