Are You Getting Enough Vitamin D?

An expert breaks down what you need to know

It’s February — a time of year when many of us aren’t getting the amount of sunlight we’d prefer. Instead, we’re stuck with gloomy clouds, rain and snow. And you know what? That lack of sun can turn into a lack of vitamin D… which could have major health implications. To find out more, we turned to Food Fix author Dr. Mark Hyman, who explained why vitamin D is so vital to our health — and how we can make sure we’re getting enough.


Katie Couric: I recently got a physical and my internist checked my vitamin D levels… Is this something everyone should do?

Dr. Mark Hyman: Absolutely, vitamin D has a huge impact on the health and function of your whole system, and regulates hundreds of genes. About 80% of our population is deficient or insufficient.

Vitamin D deficiency is often missed and has been linked to many cancers, high blood pressure, heart disease, diabetes, depression, fibromyalgia, chronic muscle pain, bone loss, and autoimmune diseases like multiple sclerosis.

It acts on a cellular docking station, called a receptor, that then sends messages to our genes. That’s how vitamin D controls so many different functions — from preventing cancer to reducing inflammation, boosting mood, easing muscle aches and fibromyalgia, and building bones. When we don’t get enough, it impacts every area of our biology — because it affects the way our cells and genes function.

These are just a few examples of the power of vitamin D. It’s an essential nutrient for optimal health, and without checking our levels, a hidden deficiency could put us at risk for many imbalances.

There’s been a great deal of research on Vitamin D. Why is it so important? Why is it helpful?

Optimal vitamin D intake reduces cellular growth (which promotes cancer) and improves cell differentiation (which puts cells into an anti-cancer state). That makes vitamin D one of the most potent cancer inhibitors — and explains why vitamin D deficiency has been linked to colon, prostate, breast, and ovarian cancer and why optimal levels could reduce the risk of those types of cancer. Another review of 10 randomized controlled trials (the gold standard in research) with 79,055 total patients has found that taking vitamin D improved cancer-related mortality after diagnosis.

What is considered low or the healthy range?

It’s important to understand that the Dietary Reference Intakes, or DRIs, are intended as general population-based guidelines and are often based on the minimum level required to prevent deficiency diseases like rickets, not on what’s needed for optimal health. They do not differentiate or take into account a person’s unique medical history, genetics, ethnicity, dietary intake, symptoms, or environmental conditions — including sunlight exposure.

The best way to test for vitamin D is to have your doctor measure 25-hydroxyvitamin D, shortened to 25(OH)D. The recommendation from the Institute of Medicine is that between 30 and 50 ng/ml (nanograms per deciliter) is the general level for adequate bone and overall health needed in healthy individuals. However, the optimal level is over 45 ng/ml. Normal is defined as the average of a population. If everyone has a low level, that doesn’t make it normal — much less optimal.

Something else to think about: Attaining those “optimal” blood levels levels typically requires often about 3,000–4,000 IU a day of vitamin D3, which is about 6 times current daily recommendations for supplementation put out by the IOM.

Research by vitamin D pioneer Dr. Michael Holick, Professor of Medicine, Physiology, and Dermatology at Boston University School of Medicine, recommends intakes of up to 2,000 IU a day — or enough to keep blood levels of 25(OH)D between 50 to 125 ng/ml. That may sound high, but it’s still safe: Lifeguards have levels of 250 ng/ml without toxicity. I look for optimal levels between 50 to 85 ng/ml; in my experience as well as that of my colleagues at The UltraWellness Center we’ve found this is the most effective range for our patients.

Can you get Vitamin D from certain foods? I was given a once-a-month pill to get my levels up.

Vitamin D is one of those nutrients that is harder to acquire from food, though not impossible. Since it’s fat-soluble, the body can store it, which is why you can take one mega-dose a month to balance your levels (though I recommend daily dose). The best food sources are fish liver oils, such as cod liver oil, wild salmon, mackerel, herring, sardines in oil, and whole eggs. Mushrooms, especially porcini, are a good plant source of vitamin D. But most of us don’t eat enough of these or get outside in the sunshine enough to optimize our levels. Sunlight is the most effective way to get vitamin D up naturally — and depending on your skin tone, you may not need much at all. Just 15 minutes or so of exposed skin in the midday sun will get you what you need, though living in northern latitudes or having darker skin may require more. Just be careful not to let yourself get pink. Vitamin D production is already maximized before you get to that point.

What about calcium? What’s the latest research on how vitamin D needs to be added to calcium, to make sure it works? My doctor recommends I get calcium from foods like dark leafy vegetables, yogurt, etc.

Vitamin D is essential for helping you use calcium. It increases intestinal calcium absorption from foods and helps our bones properly mineralize. I always recommend using food first so I agree with getting calcium as much as possible from your diet. Many Americans take too many calcium supplements and, especially in the absence of enough vitamin D, this can lead to increased kidney stones, mineral deposits, and imbalances in other minerals like iron and zinc.

We also have calcium added to so many of our foods. Countries with low calcium intake, a plant-based, low-acid diet, and plenty of sun exposure have very low rates of osteoporosis. I support the intake of adequate calcium from food, especially dark green leafy vegetables, tahini, and nuts and making sure vitamin D levels are optimal. One recent analysis of 33 RCTs found no correlation between calcium and vitamin D supplementation to reduce hip fractures and the total amount of fractures in older adults, but we do know that we need optimal levels of both calcium and vitamin D in the blood to prevent the risk of fracture. That’s why food and sunlight are some of the best ways to get these nutrients, though I do use supplementation for patients who need it to achieve optimal levels.


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