Health Problems Linked to Vitamin D Deficiency

Man framing sun with hands.
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Vitamin D deficiency has been linked to a host of age-related health conditions such as high blood pressure, osteoporosis and even overall mortality. Vitamin D is fast on its way to becoming the “number one vitamin.”

Is It Really a Vitamin?

Technically, no. Vitamins are micronutrients that the body uses in various processes. Vitamin D is a prohormone, a substance that the body converts into a hormone. But that’s a technicality. The thing you need to remember about vitamin D is that your body can make it from sunlight.

Making Vitamin D

What happens is that sunlight (specifically UV-B radiation) hits your skin it reacts with some chemicals (7-dehydrocholesterol) to start making vitamin D. The process is complex and not very interesting. What you need to remember is that around 15 minutes of exposure to sunlight on your hands and face every day is plenty for your body to make enough vitamin D under normal circumstances. If you live up north (or way down south), the atmosphere filters out a lot of the UV-B during winter and you may need more exposure.

What Good Does It Do?

Lots of good, we just don’t really know exactly how it works. Vitamin D seems to keep your blood pressure low, reduce inflammation and give the immune system a boost -- all beneficial for keeping your heart health and (maybe) even fighting off cancer. We do know that vitamin D is essential for good bone health -– it helps your bones absorb calcium (and calcium is what bones are made of). Kids without exposure to vitamin D can develop rickets (a disease where their legs become extremely bow-legged) and older adults with vitamin D deficiencies may develop bone diseases.

Research on vitamin D deficiency and depression, vitamin D deficiency and back pain and vitamin D deficiency and heart attacks all show that vitamin D has a larger role to play than just bone health. Vitamin D has been implicated in autoimmune disease too. Diseases like multiple sclerosis may be caused by vitamin D deficiency.


Two major forms of vitamin D are vitamin D2 and vitamin D3. Vitamin D2 is also called ergocalciferol and vitamin D3’s other name is cholecalciferol. When you look at supplements, most seem to focus on vitamin D3 (cholecalciferol) and you’ll see that listed as the ingredient. Read below for more on vitamin D supplementation.

Who Is Deficient?

Vitamin D deficiency seems to be common in the U.S. Maybe we are all just spending too much time inside. It is estimated the 25% of U.S. adults have less than 18 nanograms per milliliter of vitamin D (severe vitamin D deficiency). Overall, 40% of men and 50% of women are thought to be lower than the healthy level of vitamin D (28 nanograms per milliliter). The people most at risk are anyone who spends a lot of time indoors (the elderly and the homebound, for example) and people with dark skin (dark skin absorbs less sunlight).

What Happens in Your Body?

When vitamin D levels are low, your body just doesn’t seem to work as well. Vitamin D deficiency has been linked to high blood pressure, insulin problems, those with HIV, diabetes risk, obesity, thyroid disorders, and more. Receptors for vitamin D have been found in pancreatic cells that make insulin (leading to a theoretical connection between vitamin D and diabetes). We know that more heart attacks happen in the winter (when people go outside less and therefore have lower vitamin D levels) and that people survive cancer better in the summer (when their vitamin D levels are higher). But we don’t fully understand why these things are happening or what exactly vitamin D is doing in the body.

Risk of Death

In a study, records from 13,331 adults from a national survey database compiled by the U.S. government were examined to determine a link between death and vitamin D deficiency (defined as lower than 25-hydroxyvitamin D (25(OH)D). Vitamin D levels were tested from 1988 to 1994 and the people were followed until 2000 for information about the cause of death. On average, people in the study were followed for 8.7 years.

Researchers found that vitamin D deficiency was linked to all-cause mortality. People in with the lowest levels (bottom 25%) of vitamin D had a 26% increase in the risk of death during the study period compared to people with the highest levels of vitamin D. This accounted for 3.1% of the mortality risk of the total population.​

Because the sample was representative of the total U.S. population, we can generalize from this study to say that 3.1% of deaths in the U.S. are linked to vitamin D deficiency. Researchers believe that vitamin D deficiency is an independent risk factor for heart disease and should be considered with other risk factors like family history, high blood pressure or being overweight. Vitamin D deficiency may also be a factor in cancer deaths as well.


We know that many older adults have vitamin D deficiencies. The real question is whether the deficiency has something to do with the aging body (for example, the body can’t produce sufficient levels of vitamin D anymore) or whether older people’s behavior is different (for example, they don’t get exposed to much sunlight). This is an important question because it will answer the question of “what do we do about vitamin D deficiency in older adults?”

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.


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.

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 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 a 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 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 between them.
  • We don’t have any real evidence that keeping vitamin D levels in the normal range actually prevent 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% ​of 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.

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Article Sources

  • 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.
  • Muhammad Haroon, South Infirmary-Victoria University Hospital, Cork, Ireland. Presented at European Union League Against Rheumatism. 2008. Paris.
  • National Institutes of Health. Office of Dietary Supplements. Dietary Supplement Fact Sheet: Vitamin D.
  • 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;