The One Nutrient You Absolutely Must Supplement
By Suzanne W. Dixon, MPH, MS, RD

What is the Something You’re Supplementing?

I don’t push or promote a lot of dietary supplements. I’m certainly not against supplements. But in my mind, supplements should be exactly what the name suggests: they are to supplement something, not replace it.

The “something” is a healthy, varied, plant-based diet. Without the baseline of the right diet, supplements are a wasted effort.

The Vitamin D Exception

As the saying goes, there’s an exception to every rule. Dietary supplements are no different. I have rarely said, “Everybody needs X dietary supplement…” until now.

Other than people who have a medical reason not to take vitamin D, everybody needs a vitamin D supplement. Yep, you heard me correctly. Everyone needs a vitamin D supplement.

Evidence of the benefits of getting adequate vitamin D is impressive. The research continues to accumulate at a rapid pace.


Higher blood levels of vitamin D reduce the risk of numerous diseases and conditions, but none more so than cancer. Public health experts estimate that if every adult in the United States (US) got a minimum of 1,000 international units (IU) of vitamin D per day, cancer rates would go down.

1,000 IU per day is two and a half times the current recommended dietary allowance (RDA). A large proportion of people in the US don’t come close to this level of intake with food alone.

The research most strongly supports a role for vitamin D in reducing colon cancer risk. But plenty of studies suggest that getting more vitamin D will reduce risk of many cancers, including those of the breast, prostate, and lung. These four cancers – colon, breast, prostate, and lung – account for the majority of cancer deaths in the US.

Heart Disease

Vitamin D may lower risk of heart disease through a number of actions in the body. Vitamin D appears to prevent hypertension (high blood pressure), a leading cause of heart disease.

Vitamin D seems to improve the function of blood vessels and to prevent hardening of the arteries. It promotes more healthful levels of hormones that regulate heart function. Finally, it seems to have good anti-inflammatory effects.

Flu (Influenza)

The vitamin D–chronic disease connection gets all the press. It shouldn’t. Vitamin D may play an important role in preventing infectious diseases too. Vitamin D levels tend to be lower in winter, because people get less sun exposure. In much of the country, the sun isn’t strong enough for the body to make vitamin D anyway.

Health experts have speculated that lower levels of vitamin D in the winter encourage the spread of flu. This speculation has come full-circle. Just this month, results of a randomized, double-blind, placebo-controlled trial validated that vitamin D may indeed play a role in flu epidemics and pandemics.

School children in the study who had not previously taken vitamin D supplements, and who were randomized to receive vitamin D, had 64% lower risk of getting flu than the kids who didn’t get a vitamin D supplement.


Vitamin D has a double role in diabetes. Not getting enough vitamin D during early childhood, and possibly during pregnancy, may increase the likelihood of developing type-1 diabetes.

Lower levels of vitamin D also may increase the risk of type-2 diabetes in people with other risk factors for the disease, such as obesity. Vitamin D plays a role in how the body makes and uses insulin. Without enough vitamin D, insulin resistance – a hallmark of type-2 diabetes – worsens.

Bone Health

The role of vitamin D in bone health is clear. The body must have plenty of vitamin D to absorb calcium. Calcium, of course, is a key building block of bones.

Beyond the calcium connection, vitamin D has other roles to play in keeping bones strong. The nutrient helps the body properly produce and regulate the hormones needed to make new bone.

Finally, vitamin D may play an indirect role by preventing falls among the elderly. Falling is one of the leading causes of bone fractures and disability in older adult populations. Vitamin D improves neuromuscular – nerve and muscle – function. This improves strength and coordination. Better strength and coordination leads to fewer falls.

Even More Benefits

Beyond cancer, heart disease, flu, types-1 and 2 diabetes, and bone health, vitamin D can do more.

Vitamin D plays a critical role in immune function. Numerous studies demonstrate that low levels of vitamin D may contribute to the development and severity of autoimmune conditions. This includes rheumatoid arthritis, lupus, inflammatory bowel disease (Crohn’s disease and ulcerative colitis), and multiple sclerosis.

Low vitamin D levels seem to worsen chronic pain too. A Mayo Clinic study found that chronic pain patients with low levels of vitamin D required nearly twice as much narcotic pain medication as those with higher blood vitamin D levels. They had significantly worse physical function and felt worse about their own health too.

And from the weekend warrior to the serious athlete, people should take notice of vitamin D. This critical nutrient improves muscle and nerve function. Low blood levels of vitamin D seem to worsen athletic performance. When levels are returned to normal, performance is likely to improve.

How Much Is Enough?

As with all supplements, talk to your doctor before adding in vitamin D. Once you get the go-ahead, consider supplementing 1,000 to 2,000 IU of vitamin D per day. This is the range that many vitamin D experts feel is appropriate for most people.

But the best way to know how much D you need? Get your blood levels checked. It’s a simple test and will help guide your decision as to how much D you should be taking.

For more information or article references, visit

Author's Bio: 

Suzanne Dixon, MPH, MS, RD, is an internationally recognized expert in nutrition, chronic disease, cancer, health and wellness as well as the Executive Editor of Nutrition Intelligence Report, a free natural health and nutrition newsletter. For more information, past issues or to sign up for a free subscription, visit