An astonishing three quarters of Americans are deficient in vitamin D, according to a study published last year in the Archives of Internal Medicine. Are you one of them? Low levels of vitamin D have been associated with cancer risk, osteoporosis (brittle bones), depression, weak and fatty muscles, and more. Let’s take a look at what vitamin D is, what it does for you, and how to make sure you’re getting enough of it.
What is vitamin D?
Vitamin D is one of the essential nutrients, meaning your body cannot function without it. According to the Mayo Clinic, there are several forms of vitamin D, two of which are important for humans; D2 (ergocalciferol) which is made by plants, and D3 (cholecalciferol) which our bodies make in our own skin using UVB rays from the sun. Vitamin D is a fat soluble vitamin, which means that our bodies can only store and use vitamin D with fat. Unlike many of the other essential vitamins, vitamin D is found naturally in relatively few foods. Also unlike other vitamins, D is converted into a hormone by our liver, and it’s this hormone that is so essential to our bodies and well-being.
What does Vitamin D do?
The main function of Vitamin D is to keep the calcium and phosphorus we need in our blood. It also aids in the absorption of calcium, which is why it often accompanies calcium in supplements and fortified foods. It’s considered essential to bone health, and recommended for the treatment and prevention of osteoporosis and soft bones; reason enough to make sure you’re not lacking.
But vitamin D is vitally important in other, lesser-known ways. Vitamin D has long been established as vital to muscle strength and function, and a study published this year in the Journal of Clinical Endocrinology and Metabolism showed a clear link between inadequate levels of vitamin D and excess levels of fat in the muscles. Fatty muscles have been associated with diabetes, and also with decreased strength, power, and muscle function, according to Marie Spano, Vice President of the International Society of Sports Nutrition (ISSN) writing for Bodybuilding.com.
Spano also writes that Vitamin D is essential for our immune function and helps us fight several auto-immune diseases (Wikipedia goes on to say that lower levels of vitamin D in Winter due to less sun exposure may be why we see an upswing in cold and flu cases, citing the journal Epidemiology and Infection).
Vitamin D has also been strongly associated with the prevention of hypertension and cancer, according to The Mayo Clinic, both of which are huge threats to the life expectancy of Americans today.
How do you get enough vitamin D?
Now comes the tricky part. The United States Food and Drug Administration recommends that all people ages four and over get 400 international units (IUs) or 10mcg of Vitamin D every day.
To give you an idea, one cup of vitamin D fortified milk contains about 115-124 IUs, and there are about 100 IUs in one cup of fortified orange juice. Not many of us have four cups of milk and/or orange juice everyday, and these are two of the richest dietary sources of vitamin D. However, salmon, a nutritional super-food, contains about 794 IUs of vitamin D in a three ounce serving. Mackerel is also high in vitamin D (399 IUs per serving), as are sardines (46 IUs), liver (36 IUs), and eggs (25 IUs). Looking at which foods are good sources, it’s easy to see why so many Americans aren’t getting enough vitamin D. With perhaps the exception of eggs, few of us eat many of these foods weekly, let alone daily. Bad news for vegetarians; very few plant-based foods are good sources of vitamin D. Your best bets are fortified cereals (40 IUs) and hard-to-find UVB exposed mushrooms (400 IUs).
What about getting vitamin D via sun exposure? The National Institute of Health says that about 5 – 30 minutes in the sun between 10am and 3pm to any part of the body not covered by clothing or coated with sunscreen, twice per week, should be enough to help your body make all the vitamin D it needs. However, they also say that a lot of factors reduce the power of the sun’s UV rays, many so much that there just isn’t enough to help you create much vitamin D at all. Clouds are an obvious problem, as is location. Above 42 degrees north latitude (think the top of California) UV energy is too weak to make vitamin D from November all the way to February.
Supplements are a good option for making sure you get enough vitamin D. Most multi-vitamins will contain vitamin D, as well as most calcium supplements. Vitamin D stand-alone supplements are also readily available. The U.S. Institute of Medicine of the National Academy of Sciences recommends we supplement with 200 IUs of vitamin D daily, however, the Mayo Clinic points out that many physicians and organizations recommend we supplement with 400-800 IUs daily for the treatment and prevention of osteoporosis and soft bones. With the upper level of safe daily doses of vitamin D at 2,000 IUs, there’s no reason not to err on the safe side and take 400-800 IUs of vitamin D every day. The best strategy, is to make sure you’re getting a little sun exposure, some vitamin D rich foods, and supplementing.
Dietary Supplement Fact Sheet: Vitamin D, The Office of Dietary Supplements for the National Institutes of Health
Vitamin D – Mayoclinic.com, The Mayo Clinic
Bodybuilding.com – Vitamin D – Why It’s Essential For Muscle Health! – Marie Spano, Marie Spano, MS, RD
Low levels of vitamin D linked to muscle fat, decreased strength in young people, ScienceDaily
Vitamin D deficiency soars in the US, study says: Scientific American, Jordan Lite
Vitamin D – Wikipedia, the free encyclopedia, Wikipedia