Vitamin D: Are You D-Pleted?

Photo Illustration by Michael Northrup

Update Aug. 26, 2010: In a recent study published in Genome Research, a team of British and Canadian scientists found that the “sunshine vitamin,” vitamin D, interacts with and may even regulate genes related to colorectal cancer, type 1 diabetes and other diseases. More research is needed, but this study lends further evidence to the importance of getting enough vitamin D.

Unless you live in the tropics, you probably need more D, a vitamin produced in the skin by ultraviolet (UV) rays from sunlight. Grey skies, weak winter sun, sunscreen use and an indoor lifestyle mean that most of us are lacking in this essential vitamin.

“Most blood tests we order for vitamin D show that levels are low or moderately low,” says Jessica Strasburg, MD, a family practitioner at Cleveland Clinic Solon Family Health Center. “Many adults are at risk for vitamin D deficiency, since the ability to produce and utilize the vitamin decreases with age.” 

A key role in your health

Too little vitamin D may result in serious health problems. “Vitamin D is important to bone health. It is vital for normal calcium absorption and critical in treating osteoporosis. In children, lack of vitamin D causes rickets,” says Bruce Long, MD, a Cleveland Clinic rheumatologist with a special interest in the vitamin. 

Vitamin D is also thought to play a role in preventing cancer, heart attacks, strokes and diabetes, and may help preserve thinking and memory. The vitamin also appears to prevent hypertension during pregnancy, calm the pain of arthritis, and increase muscle strength and coordination. It may even help prevent and treat multiple sclerosis.

How to get your D

Fifteen minutes of afternoon summer sun daily on unprotected arms and legs will give you what you need. “You need strong, direct sunlight,” says Dr. Strasburg. So most of us should leave off the sunscreen for 15 minutes — and then apply it to prevent skin cancer. 

However, if you are at risk for skin cancer or have a history of skin cancer, you’ll need alternative sources of vitamin D. You can get some vitamin D by taking multivitamins or calcium supplements with D. The vitamin is found in fatty fish, egg yolks and beef liver, and is added to yogurt and other calcium-fortified products. These include milk, cereal, bread and some brands of orange juice.

Most of us need supplementation

Even with these measures it’s hard to ingest enough vitamin D to meet the recommended daily allowance, which will soon increase to 800 international units per day. “That’s why most doctors in northern Ohio recommend vitamin D supplements,” says Dr. Strasburg.

A simple blood test will let you know if your vitamin D levels are normal. If your levels are low, your doctor will prescribe vitamin D and recheck levels in about three months. If they are still low, your dose will be increased; if they’re too high, it will be lowered.

1,000-5,000 units a day typical

“Generally, our patients take 1,000 to 5,000 units of vitamin D3 (available over the counter in 400, 800, 1,000 and 2,000 units) once a day. Some who require high doses may choose to take 50,000 units of vitamin D2 (a prescription drug) once or twice a week,” says Dr. Long. “D2 and D3 are both effective, but those bothered by taking too many capsules often choose vitamin D2.”

Having bariatric surgery or untreated celiac disease usually means you need higher doses of D because less of the vitamin is reabsorbed through the digestive tract. Also, with aging, we make less vitamin D3 in our skin and may need higher doses.

Once vitamin D levels are normal, doses are adjusted to avoid potential toxicity.  “One study found toxic levels of vitamin D among individuals taking 40,000 units daily for five months. However, no toxicity was found among those taking 10,000 units daily for five months, and taking 1,000 units daily is safe,” says Dr. Long.