Hardly a day goes by without some media covering vitamin D, but its popularity isn’t translating to adequate use among the public, as many are still deficient in this nutrient. An article by Jane Brody in the New York Times noted those who lack vitamin D are more likely to face health problems, such as poor bone development as well as decreased brain, heart, muscle and immune system function. Low vitamin D levels have been linked to colon, breast and prostate cancers; high blood pressure and cardiovascular disease (CVD); arthritis; multiple sclerosis; and diabetes.
The modern lifestyle of indoor living contributes to the low vitamin D levels, Brody wrote, because humans source this nutrient from the sun’s ultraviolet-B rays. Early humans evolved close to the equator, and spent most of their time in the sun. Today, we are more likely to spend our days in offices, and use sunscreen when we venture outside.
While the article noted more foods are fortified with vitamin D, consumers still have trouble obtaining it by eating. Along with fortified milk, cereal and orange juice, vitamin D is also in wild-caught oily fish (salmon, mackerel, bluefish and canned tuna).
Those who are most likely to be low in vitamin D are people who live in colder regions, people who avoid the sun, babies who are exclusively breast-fed and the elderly who live in nursing homes.
Dr. Michael Holick of Boston University, a leading expert on vitamin D and author of “The Vitamin D Solution" was quoted in the article as saying the ideal levels of vitamin D, as measured in the blood as 25-hydroxyvitamin D, are above 30 nanograms per milliliter, but U.S. levels are around 18 to 22 nanograms for Caucasians and 13 to 15 nanograms for African Americans.
The Institutes of Medicine (IOM) puts the recommended daily intake of vitamin D at 200 I.U. a day from birth to age 50 (including pregnant women), 400 for adults aged 50 to 70 and 600 for those older than 70. The article said the IOM is reviewing these recommendations, but many experts recommend daily supplementation of 1,000 to 2,000 IU a day for adults and 400 IU for children. Dr. Holick also suggested going outside in summer unprotected by sunscreen (except for the face) wearing minimal clothing from 10 a.m. to 3 p.m. two or three times a week for 5 to 10 minutes. Getting enough vitamin D in the summer will produce adequate year-long levels, he said.
Brody noted getting too much vitamin D isn’t an issue if acquired through the sun because the body will stop producing it after a certain point. However, toxicity can occur with supplementation. Symptoms of vitamin D toxicity include nausea, vomiting, poor appetite, constipation, weakness and weight loss, as well as dangerous amounts of calcium that can result in kidney stones, confusion and abnormal heart rhythms. However, experts said it’s difficult to reach toxicity levels, as studies have shown adult who took 10,000 I.U. a day for six months or longer experienced no adverse effects.