You May Not Need That Vitamin D Supplement After All

Vitamin D is essential for healthy bones, but can it really prevent cancer or improve heart health? Many confusing claims have been made about the vitamin so we spoke to three doctors to find out the truth.


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Vitamin D is crucial, but not a cure-all supplement.

vitamin d pills

Photo by Jacob Fox

Photo by Jacob Fox

Vitamin D helps promote calcium absorption, making it necessary for strong bones. It behaves as a hormone in our body and affects our overall health, but doctors aren’t sure of its exact benefits beyond the skeleton. “There is increasing interest in how it may impact other aspects of health,” says Douglas K. Owens, MD, MS, general internist, vice chair of the U.S. Preventive Services Task Force and professor at Stanford University. “However, the truth is that more research needs to be done. It could play a role in preventing cardiovascular disease and certain cancers. We just don’t have enough evidence at this time to say definitively if vitamin D should be used for those purposes.”


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You may not notice you’re deficient.

neck pain heart attack

Photo by Getty Images

Photo by Getty Images

The signs of vitamin D deficiency are extremely subtle, hard to detect and not always present. “Most people have no symptoms until they have a severe deficiency,” says Kim Pfotenhauer, DO, assistant professor of medicine in the primary care department at Touro University California College of Osteopathic Medicine. “At that point, some may experience bone pain or fracture, or muscle pain or weakness.” And unless your levels are very low, you probably won’t notice health improvements if you start taking a vitamin D supplement—so don’t toss the bottle aside when you don’t immediately feel like a million bucks.


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Most people don’t need their vitamin D level checked.

girl sipping her drink

Photo by Lauren Naefe/Stocksy

Photo by Lauren Naefe/Stocksy

Many primary care docs automatically check the amount of vitamin D circulating in your blood when you get routine blood work done at your physical. “However, we don’t have sufficient evidence to recommend for or against screening for vitamin D deficiency in people who are generally healthy and aren’t at increased risk for the condition,” says Owens. “Anyone who is wondering if they should take any vitamin or is concerned about their vitamin D levels should talk to their doctor.” Those with the highest risk for vitamin D deficiency include breastfed infants, older adults, people with darker skin, malabsorption issues (like IBS) or anorexia nervosa, people who are obese or have had gastric bypass surgery and folks with limited sun exposure (including those who constantly wear sunscreen, cover their skin or live farther away from the equator).

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Doctors don’t all agree on the definition of vitamin D deficiency.

female doctor talking with female patient

Photo by Getty Images

Photo by Getty Images

If your physician tells you you’re low on vitamin D, ask what definition they’re using and discuss your risk level for true deficiency because there’s no official consensus about what the ideal vitamin D level is. Less than 12 ng/mL of vitamin D circulating in the blood is generally considered to be true deficiency, but some doctors put the cutoff as high as 33 ng/mL. “The Institute of Medicine has looked at research and said probably achieving 20 ng/mL is the best indicator for maximum bone health,” says Larry Johnson, MD, author of the vitamin chapters for the Merck Manuals and associate professor of geriatrics for the Reynolds Institute on Aging at UAMS College of Medicine.


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Even if you’re low, you don’t need a large supplement.

eggs and salmon for vitamin d

Photo by Andy Lyons Cameraworks, LTD/Andy Lyons

Photo by Andy Lyons Cameraworks, LTD/Andy Lyons

The Recommended Dietary Allowance for people between 1 and 70 years old is 600 International Units (IU) per day. Adults over 70 should aim to consume 800 IU. Johnson suggests trying to figure out how much of the vitamin you’re getting from your diet and sunlight (UV rays trigger our bodies to synthesize the vitamin), then taking a very low-dose supplement to get you close to that 600 benchmark. Vitamin D isn’t readily available in many foods, but some foods rich in it are swordfish, salmon, tuna, eggs and fortified milk, yogurt and orange juice. If you’re not sure how much you’re already taking in, talk to your doctor because large doses over time can be unhealthy.