Why Is Vitamin D So Important for Your Health?

Internal Medicine World ReportAugust 2007
Volume 0
Issue 0

Vitamin D is one of the most important vitamins for our overall health, but many people in the United States, as well as worldwide, are not getting enough of this vitamin. And the only way to know if you're getting enough of this vitamin is by doing an expensive test. And everyday it seems, new studies show new reasons why this vitamin is so important to our health.

Although vitamin D can be stored in your body fat until it is needed, the problem is that it's not so easy to get enough vitamin D into your body.

The main job of vitamin D is to keep the right amount of calcium and phosphorus in your blood?these are the 2 nutrients that work together to make your bones strong. If you don't have vitamin D in your body, only a small amount of the calcium from your diet can be absorbed by your body, and only a little more than half of phosphorus is absorbed. Without enough calcium and phosphorus being absorbed in your body, your bones would become brittle and break easily.

Until recently, experts believed that the main role of vitamin D was to keep our bones healthy and prevent them from breaking up. But new research has shown many other reasons why this vitamin is so important for our health.

The Reasons Why Vitamin D Is So Important

It helps to:

  • Prevent bone fractures
  • Prevent falls in older people and osteoporosis
  • Reduce the risk of cancer, especially colon cancer, prostate cancer, and breast cancer
  • Reduce the risk of diabetes, especially in young people and in those living in high altitude
  • Protect against heart disease, including high blood pressure and heart failure
  • Reduce your risk for multiple sclerosis
  • Improve you mood
  • Improve your lung function.

If You Don't Get Enough Vitamin D

  • Your bones can become weak and can break
  • Children can get "rickets," a disease that prevents their bones from growing properly, delays their growth, and causes problems with their immune system
  • Adults can develop "osteomalacia," a disease that weakens the bones and makes them hurt, and also causes fractures
  • Older adults can get osteoporosis, which doesn't cause pain, but makes the bones thin and easy to fracture

The best way to know if you are getting enough vitamin D is to have a specific blood test. Otherwise, you may not know that you're not getting enough vitamin D until you start having symptoms associated with vitamin D deficiency. The vitamin D test is very expensive, so it's not routinely done.

How Much Vitamin D Do You Need?

The amounts of vitamin D the US government now recommends for the different age-groups are too small. Most experts say that people should take much more of this vitamin every day than is now recommended. They believe that if you don't get enough exposure to sunlight, all children and adults need about 800 to 1000 units (marked as "800 IU") of vitamin D every day.

People who are older than 65 probably need even more than 1000 IU, because they usually don't spend much time in the sun and their bodies don't absorb vitamins the way it used to. And people who are at risk for vitamin D deficiency, and those who are already vitamin D deficient, need even higher levels of the vitamin.

People have been taking as much as 2000 IU units of the vitamin without any problems. But just like you can get too much of any good thing, you can also get too much vitamin D if you take much greater amounts, although this rarely happens. Vitamin D overdose will cause you to become sick with nausea and vomiting. It can also make you feel weak and confused, and make your heartbeat irregular.

What Are the Best Sources?

The best source for vitamin D is sunlight. Only few foods supply vitamin D in significant amounts. The best source for this vitamin for humans is the sun, not supplements. The problem is that too much exposure to the sun can cause skin cancer, but too little sun exposure is the reason that many people today don't get enough vitamin D.

Because it's difficult to get all the vitamin D you need from food, and since you don't want to be exposed to too much sunlight, most people need short-time sun exposures and daily vitamin D supplements. Spending a short time in the sun each day, without sun block, may not be a bad idea, unless you have a special sensitivity to sun exposure. Check with your doctor if you're not sure.

You can get vitamin D supplements over the counter at the supermarket, a drugstore, or any health food store. Some vitamin D supplements are available only by prescription and are given to people who are vitamin D deficient.

If your skin is exposed to summer sunlight for about 10 to 15 minutes at least twice a day, you're probably getting enough vitamin D. But when you use sunscreen, it prevents the skin from soaking up enough vitamin D.

And in the winter, the sun isn't strong enough to give us sufficient amounts of vitamin D. People who live in northern regions might not get enough vitamin D from sunshine, even in the summer. People who live in big cities might not get enough vitamin D, because pollution can block the sun's rays.

Foods that Provide Vitamin D

Only a few foods naturally contain vitamin D, but some foods are fortified with this vitamin. These are some of the best sources:




Cod liver oil

1 Tablespoon


Salmon, cooked

3 1/2 ounces


Mackerel, cooked

3 1/2 ounces


Sardines, canned in oil and drained

1 3/4 ounces


Tuna fish, canned in oil

3 ounces


Milk (skim, low fat, whole), vitamin D fortified

1 cup


Margarine, fortified

1 Tablespoon


Pudding (from mix, with vitamin D-fortified milk)

1/2 cup


Cereal, vitamin D fortified

3/4 to 1 cup



1 whole


Liver or beef, cooked

3 1/2 ounces


Cheese, Swiss

1 ounce


Who Is at Risk for Vitamin Deficiency?

If you belong to any of the following groups, you may be at risk of vitamin D deficiency, in which case you should ask your doctor to for the vitamin D test:

  • Infants who are only breast-fed or who get less than 2 cups each day of vitamin D?fortified formula or milk
  • People with dark skin (which doesn't absorb the sunlight as well as light skin)
  • People who don't get a lot of exposure to sunlight
  • People who use sunscreen often
  • Older people are at very high risk, in part because aging skin doesn't absorb sunlight as well as younger skin
  • People who are obese
  • People who have medical conditions that interfere with their body's ability to absorb fat, such as cystic fibrosis, celiac disease, or pancreatitis
  • People who have liver or kidney problems
  • People who live in the northern hemisphere in the winter months
  • People who take certain medicines, like anti-seizure drugs or steroids.
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