The Many Benefits of Vitamin D

You probably know that vitamin D is necessary for strong bones. But did you know that it's also important for the proper functioning of your immune system, muscles, and nerves? And in the right amounts, vitamin D may even help prevent or delay some of the health conditions we fear most: cancer and heart failure.

The Many Benefits of Vitamin D

An analysis of studies of women aged 55 and older found that women with higher levels (40 ng per milliliter of blood) of vitamin D were 60-70% less likely to develop cancer than those with lower (20 ng per milliliter of blood) levels.

Similar studies found that higher vitamin D levels are also associated with better outlooks for prostate, colorectal, pancreatic, and lung cancers.

And cancer isn't the only condition that may be prevented by vitamin D. Research also indicates that vitamin D supplements may reduce the risk of the following:

  • Heart disease
  • Acute respiratory infections
  • Falls
  • Fractures

In addition, investigators are looking into the role of vitamin D deficiency in age-related declines in thinking, as well as memory loss and dementia.

Getting Enough Vitamin D

However, many people may not be getting enough vitamin D to receive its benefits. The current daily recommendation for vitamin D, established by the Institute of Medicine of the National Academies, is 600 IU (international units) for healthy men and women aged 19 to 70. This amount correlates with levels of 20 ng/ml (nanograms per milliliter of blood).

But 20 ng/ml of vitamin D is significantly lower than the amount researchers think may protect against cancer. Furthermore, researchers currently investigating vitamin D's role in preventing or delaying heart disease and other health problems are using supplements that provide 100,000 IU a month (approximately 3,300 IU a day—far more than the amounts recommended by the Institute of Medicine).

Even if you only want to obtain 600 IU a day, it can be difficult. Vitamin D, long known as the "sunshine vitamin," can be produced in the body when the skin is exposed to sunlight—but most people don’t synthesize enough. Add in the fact that vitamin D is not commonly found in many of the foods we eat, and the result is an epidemic of deficiency.

Good Food Sources of Vitamin D

Fortunately, there are a few foods (some D-fortified) that provide significant amounts of the nutrient. Here are a few options:

  • Fatty fish such as salmon, swordfish and mackerel: 450 IUs of vitamin D in a 3-oz. serving.
  • Tuna, canned in water: 154 IUs in a 3-oz. serving.
  • Fortified milk: 120 IUs in an 8-oz. (1 cup) serving.
  • Fortified yogurt: 80 IUs in a 6-oz. serving.
  • Sardines packed in oil: 46 IUs in two sardines.
  • Egg yolk: 41 IUs in 1 yolk.

If you're struggling to get enough vitamin D from your diet, you may want to speak to your doctor about supplements. But be aware that adverse health effects are possible with extremely high doses, and the National Institutes of Health Office of Dietary Supplements has established a tolerable upper intake level of 4,000 IU a day.

"It’s best if your vitamin D dose is individualized," recommends dietitian Alison Massey, MS, RD, Director of Diabetes Education at Mercy Medical Center in Baltimore. "The general daily recommendation of 600 IUs isn’t necessarily appropriate for everyone, especially those who currently have low blood levels or are at higher-than normal-risk of developing a deficiency."

Alison Massey, MS, RD, LDN, CDE, reviewed this article.


Massey, Alison, MS, RD, LDN, CDE. Email to author May 13, 2016.

"Vitamin D: Fact Sheet for Consumers." National Institutes of Health Office of Dietary Supplements. Page updated April 15, 2016.

McDonnell SL, Baggerly C, French CB, et al. "Serum 25-Hydroxyvitamin D Concentrations >40 ng/ml Are Associated With >65% Lower Cancer Risk: Pooled Analysis of Randomized Trial and Prospective Cohort Study." PLOS ONE April 6, 2016.

Mohr SB, Gorham ED, Kim J, Hofflich H, Cuomo RE, Garland CF. "Could Vitamin D Sufficiency Improve the Survival of Colorectal Cancer Patients?" The Journal of Steroid Biochemistry and Molecular Biology April 2015; 148:239-244.

Weinstein SJ, Purdue MP, Warner SA, et al. "Serum 25-Hydroxyvitamin D, Vitamin D Binding Protein and Risk of Colorectal Cancer in the Prostate, Lung Colorectal and Ovarian Cancer Screening Trial." International Journal of Cancer 15 March 2015; 136(6):E654-E664.

Scragg R, Waayer D, Stewart AW, et al. "The Vitamin D Assessment (VIDA) Study: Design of a Randomized Controlled Trial of Vitamin D Supplementation for the Prevention of Cardiovascular Disease, Acute Respiratory Infection, Falls and Non-Vertebral Fractures." Journal of Steroid Biochemistry and Molecular Biology. Online 10 September 2015. doi: 10.1016/j.jsbmb.2015.09.010

Kuzma E, Soni M, Littlejohns TJ, et al. "Vitamin D and Memory Decline: Two Population-Based Prospective Studies." Journal of Alzheimer’s Disease. 22 Februrary 2016; 50(4):1099-1108.

"Vitamin D: Fact Sheet for Health Professionals." National Institutes of Health Office of Dietary Supplements. Accessed May 10, 2016.