The ABCs of Vitamin D

Vitamin D deficiency is most commonly associated with decreased bone density, which can increase the risk of osteoporosis and fractures. According to Dr. David Arvold of St. Luke's Internal Medicine Associates, many studies have shown an association between low vitamin D levels and heart disease, hypertension (high blood pressure), diabetes, cancer, several autoimmune diseases, premenstrual syndrome, anxiety, and depression. However, he cautions that while vitamin D supplements may decrease the risk of these conditions, there isn't enough proof at this time.

Our bodies naturally produce vitamin D when exposed to direct sunlight; however, factors like time of day, cloud cover, angle of the sun, smog and sunscreen can affect how much vitamin D we produce. Although most diets provide some amount of vitamin D, even vitamin D-fortified foods can't compensate for limited sun exposure and the impact of aging.

How much is enough?

The amount of vitamin D we need depends on factors like gender, age, skin color, and pregnancy. According to the National Institutes of Health, infants and children should receive 400 international units (IU) of vitamin D per day, while older adults and people with limited sun exposure or darker skin tones require higher amounts. In addition, certain medications prescribed to reduce inflammation, lower cholesterol, support weight loss or control epileptic seizures can interfere with vitamin D metabolism, increasing the need for higher doses for patients taking these drugs.

"Many doctors believe that daily supplementation of 800 to 1,000 IU is desirable for all adults, a point of considerable discussion and debate," Dr. Arvold says. "In general, unless an individual has low levels of vitamin D or a condition that causes deficiency, intakes of more than 1,000 IU daily just aren't necessary."

This chart reflects the general daily recommendations for vitamin D intake:

Sunshine, salmon, and supplements

For younger adults, 10 to 15 minutes of summer sun three times a week without sunscreen usually produces enough vitamin D. At the same time, sun exposure also increases the risk of skin cancer, so it's important to apply sunscreen for longer periods. When it comes to food sources, most of the vitamin D in the American diet comes from fortified cereal, margarine, orange juice, and milk, with fish being one of the few foods naturally high in vitamin D. But as the IU tally below indicates, most adults will need a supplement in order to get enough vitamin D:

• Salmon, 3.5 ounces, 360 IU
• Margarine (fortified), 1 tablespoon, 250 IU
• Tuna (canned in oil), 3 ounces, 200 IU
• Milk (fortified), 8 ounces, 100 IU
• Orange juice (fortified), 8 ounces, 100 IU
• Egg, 20 IU
• Swiss cheese, 1 ounce, 12 IU

To learn more about vitamin D allowances, talk to your doctor or contact a St. Luke's Family Medicine clinic. To find out about vitamin D requirements for infants and children, talk to your pediatrician or contact St. Luke's Pediatric Associates at 218.249.7870.