Most Common Vitamin Deficiency in the US
And why you might want to supplement

Over 41% of Americans are vitamin D deficient. SHOULD YOU SUPPLEMENT VITAMIN D?
We need vitamin D to assist in the absorption of calcium, keep bones strong and prevent osteoporosis and fractures, and prevent autoimmune diseases. Some studies have shown it may even help prevent cancer. Vitamin D, the “sunshine vitamin”, is synthesized by our skin from sunlight. With winter just around the corner, most of us are not getting enough sun. Luckily, vitamin D is stored in fat, so it can last you weeks once you’ve got it. Still, if you aren’t getting enough of this vitamin in your diet, winter sun exposure may not cut it.
So where do we get vitamin D in our diet? It is mostly found in the oils of fatty fish and animal livers, and is added to some dairy products and cereals. The best source is cod liver oil but... let’s be honest, how many of us have this hanging out in our pantry? There are all sorts of supplements for vitamin D: pills full of fish oils, isolated vitamin D2 and D3 (hint: D3 is much more effective at increasing blood vitamin D levels), but do you really need to take these?
The RDA (recommended daily allowance) for vitamin D is 600 IU for healthy children and adults, and 800 IU for the elderly and pregnant/lactating women. A tablespoon of cod liver oil provides 227% of your RDA, 3 oz of salmon provides 75%, a cup of fortified milk provides 16%, and a single egg (yolk included) provides 7%. But what if you’re vegan, vegetarian, lactose intolerant? Not to worry, mushrooms that are exposed to ultraviolet light while growing have increased amounts of vitamin D, and can provide around 60% of your RDA per serving! Many non-dairy mills are also vitamin D fortified as well, just check the packaging on the brand you prefer.
BOTTOM LINE: you do not need to take vitamin D supplements with a well-rounded nutritious diet of whole foods. If you cannot eat any of these foods for whatever reason, it is worth looking into supplementation. Vitamin D supplementation is fairly safe; the UL (upper limit) for vitamin D is 4,000 IU/day for everyone aged 9+. But, of course, it’s wise to consult your doctor before starting any supplements.