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Vitamin D Deficiency


Updated May 20, 2014

Vitamin D Deficiency

Exercise is Fun

Photo: Noel Hendrickson / Getty Images

Researchers Robert Scragg and Carlos Camargo took that same database compiled by the U.S. government used in the study above (the Third NHANES) and looked for a link between vitamin D levels and outdoor activity in adults. They found that, indeed, vitamin D levels decreased with age. They also found that participating in outdoor physical activity decreased with age. People aged 60 or more, however, that did some daily outdoor activity had the vitamin D levels of a young adult. So the conclusion is that vitamin D levels in the body don’t decrease with age, but people’s amount of time outdoors does. This is good news. You can keep your vitamin D levels up simply by spending a bit of time outdoors every day.

Vitamin D Deficiency and Arthritis

There even might be a link between vitamin D deficiency and rheumatic diseases like arthritis. A doctor at a rheumatology clinic has all new patients tested for vitamin D deficiency. After testing 231 patients, he found that 162 (70%) had low levels of vitamin D and 26% had severe vitamin D deficiency. Unfortunately, this is just an observation. We don’t know what the average for that town is or is rheumatic diseases may impact vitamin D levels (for example, people with rheumatic diseases may stay indoors more because they don’t feel good). It was also not mentioned if giving vitamin D supplements and increasing the vitamin D levels impacted their symptoms. That said, this is yet another area that is interesting for more study about the impact of Vitamin D on health.

Alright Already, Where Do I Get Some?

Get some from three places: food, sunlight and supplements. Most foods do not contain vitamin D. Some fatty fish have it (like salmon) and fish liver oils are a good source (Yuck!). Beef liver, cheese and egg yolks also have some amount of vitamin D. Cereals and milk are often fortified with vitamin D. In fact, two glasses of vitamin D fortified milk a day gives enough vitamin D for people up to the age 50. Supplements are a bit harder to figure out. There is a lot of controversy about whether the body can really use supplements of vitamin D (especially without added calcium). The jury is still out on whether taking supplements is an effective way to counter vitamin D deficiency. Don’t go all vitamin D crazy either. High levels of vitamin D are unhealthy. The sun is your best bet. Simply make sure you spend a little bit of time (around 15 minutes) outside each day. Just having your hands and face exposed during that time is enough. Don’t overdo it though. Be careful of skin cancer, and be sure that you are not getting overexposed to the sun either.

How Do I Get Outside?

It may seem like a dumb question, but figuring out how to get outside is a challenge for many people. If you work in an office building and live in a neighborhood where you drive everywhere, finding time during the week to be outside is a real challenge. The most obvious way to do it is to go for a short walk at lunch. You get the health benefits of walking combined with the benefits of vitamin D. If you can’t do that, you’ll have to be creative. You can get your vitamin D exposure in parking lots (just park further away or walk around a bit). You can also just find a nice outdoor spot to make a few phone calls during the day. I like to make all those calls when you know you’ll be on hold outside. Brainstorm a few ways to get yourself outside during your day.

The Problems with Vitamin D Deficiency Research

After reading all that, it seems like a great idea for everyone to focus on getting more vitamin D. Not so fast. It gets complicated. Here are some factors, pointed out in an National Institutes of Health (NIH) review of vitamin D, that make the “Should I take vitamin D supplements?” question difficult:
  • Many vitamins need to have other chemicals or vitamins present to be of any good. For example, taking vitamin D supplements without any added calcium may be a waste. Most studies haven’t measured both calcium and vitamin D together.
  • Vitamin levels can vary widely in a rats and probably do in people too. In other words, a person’s vitamin D levels could shift over time and that shift hasn’t been factored in studies either.
  • Complex factors could impact vitamin D deficiency including the time of year (less sunlight exposure in winter), the latitude (in higher latitudes, the sunlight is weaker and produces less vitamin D), physical activity levels, diet, etc.
  • The current tests for vitamin D levels have a lot of variation in them.
  • We don’t have any real evidence that keeping vitamin D levels in the normal range actually prevents illness or disease.
  • We don’t know what target vitamin D levels should be in people with various conditions.
  • People with illnesses probably go outside less. Lower vitamin D levels might be a result of a chronic illness, not a cause.
  • Illness (and medications) might interact with how the body produces vitamin D, causing a vitamin D deficiency.

The Bottom Line

If you get outside daily and have some exposure to sunlight, your vitamin D levels are probably okay. If you are inside a lot, it isn’t a bad idea to focus on spending a few extra minutes outside each day. If you have an illness or just can’t get out, consider asking your doctor to check your vitamin D levels. After all, 40% of men and 50% adults are thought to be vitamin D deficient. Of course, the solution is the same –- just spend a little bit of time outside each day.


Robert Scragg and Carlos A. Camargo, Jr. Frequency of Leisure-Time Physical Activity and Serum 25-Hydroxyvitamin D Levels in the US Population: Results from the Third National Health and Nutrition Examination Survey. American Journal of Epidemiology 2008 168(6):577-586;

Muhammad Haroon, South Infirmary-Victoria University Hospital, Cork, Ireland. Presented at European Union League Against Rheumatism. 2008. Paris.

Michal L. Melamed, MD, MHS; Erin D. Michos, MD, MHS; Wendy Post, MD, MS; Brad Astor, PhD. 25-Hydroxyvitamin D Levels and the Risk of Mortality in the General Population. Arch Intern Med. 2008;168(15):1629-1637.

National Institutes of Health. Office of Dietary Supplements. Dietary Supplement Fact Sheet: Vitamin D.

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