The Rumor: We’ve underestimated how much vitamin D we really need — and most people don’t get enough.
Recent studies blame everything from poor memory to cancer on having a low amount of vitamin D in the bloodstream. The official guideline for vitamin D supplementation is set at 600 IU per day, but some say that amount is too low and claim we need much as 20,000 IU each week to beat vitamin D deficiency. So who’s right?
The Verdict: We could probably all use more vitamin D – but no one dose fits all.
Back in the 1930s in the U.S., fortifying milk with vitamin D all but eradicated rickets, a bone-deforming condition that once affected millions of American children. Once scientists identified vitamin D deficiency as the cause of the disease, adding the vitamin to the leading beverage for toddlers was a no-brainer.
But today, understanding how much vitamin D we need isn’t as cut and dry. The official Institute of Medicine (IOM) recommendation is 600 IU a day; this amount helps with bone growth and calcium absorption. Regular exposure to sunlight (which causes the body to produce vitamin D) or daily intake of foods high in vitamin D — such as cheese, fatty fish and fortified orange juice and milk — was thought to provide enough vitamin D for most people.
However, a growing number of experts have found that the casual consumption of vitamin D isn’t enough to keep a healthy level of the nutrient circulating in the blood.
“Just about everyone is deficient in vitamin D today,” says Michael F. Holick, Ph.D., MD, professor of medicine, physiology and biophysics at the Boston University School of Medicine. Dr. Holick, who consumes 20,000 IU of vitamin D a week, says that trying to get that same dose from sunlight alone would mean lying in the sun in a bathing suit for at least a half hour every single day of the year. Obviously, that kind of Baywatch-like lifestyle is unrealistic (and not ideal for those with skin-cancer issues).
The National Institutes of Health’s (NIH) Office of Dietary Supplements recognizes that plenty of people aren’t getting enough vitamin D; they’ve identified risk groups who may need supplements. If you have dark skin, are of Asian, African or Middle-Eastern descent, live in a region that receives less sunlight, regularly wear sunscreen SPF 8 or higher, are a breastfeeding mother, have celiac or Crohn’s disease or live above the 37-degree latitude line (that’s roughly from Philadelphia to San Francisco), you may fit the NIH’s criteria for a supplement.
To further complicate matters, experts can’t agree on what, exactly, vitamin D helps protect us from. The IOM concluded that vitamin D is definitely needed for bone strength. Studies show it also may protect us from certain cancers, autoimmune disorders and Alzheimer’s.
“Vitamin D receptors are in every cell of our body and we’ve already identified over 80 metabolic processes that are dependent on it,” says Dr. Holick. The NIH points out that a “growing body of research suggests that vitamin D might play a role in the prevention and treatment of type 1 and type 2 diabetes, hypertension, glucose intolerance, multiple sclerosis and other medical conditions.”
That said, too much vitamin D comes with its own risks. High consumptions have been associated with kidney damage and even an increased risk of pancreatic cancer.
So: Do you need more vitamin D — and if so, how much? “Everyone is different, with a different weight, sun exposure and eating habits,” says Perry Holman, executive director of the Vitamin D Society in Canada. “[Everyone’s] bodies use the vitamin D differently. So you cannot give one dosage recommendation for everyone.” You may want to consider a dose that falls somewhere between the IOM’s recommended 600 IU per day and the NIH’s recommended maximum of 4,000 IU. Ask your doctor what’s healthiest for you.
