Vitamin D - Let the Sunshine In


I’ve been seeing a lot of headlines lately about vitamin D. I recently read that one of the largest labs in the country reports vitamin D blood testing has risen for the last four years and is already up 90% so far this year. So does vitamin D really prevent disease and death or is it just a lot of hype? I reviewed the literature to learn more about vitamin D – and here is what I learned.

What is Vitamin D?

Vitamin D is a fat-soluble vitamin obtained from sunlight, certain food and dietary supplements. It seems it really does prevent disease and protects overall health.

Exposure to sunlight is what stimulates vitamin D production in the body. When sunlight strikes the skin it triggers the production of vitamin D – first in the liver [25(OH)D] and then the kidney [1,25(OH)2D]. Vitamin D is present naturally in only a few foods but it’s added to others (most milk, orange juice and cereal products are vitamin D “fortified”). Vitamin D is also available as a dietary supplement.

What does Vitamin D do?

  1. Vitamin D works in the intestines to help absorb calcium and keep calcium blood levels normal. Vitamin D deficiency can cause calcium levels to go too low. This can result in a life threatening condition called “tetany” that causes severe muscle cramps and spasms. Toxicity (or too high levels) of vitamin D can cause calcium levels to go too high and that, too, can be life-threatening.
  2. Vitamin D works along with calcium to keep bones strong. Vitamin D and calcium together protect against osteoporosis. Ricketts is a bone disease in growing children that causes bone deformities because of vitamin D deficiency . Osteomalacia is bone disease in adults caused by vitamin D deficiency. It makes bones soft and can cause muscle weakness and bone pain.
  3. Vitamin D prevents cancers. Many studies are showing that there seems to be a relationship between low vitamin D levels and all types of cancers. It is believed that vitamin D somehow helps cells stay “normal” and so makes them less likely to grow abnormally or out of control as they do in cancer.
  4. Vitamin D prevents death. Studies have shown low vitamin D levels are linked to heart disease, peripheral arterial disease, diabetes, hypertension – in addition to all types of cancers. One recent study in the Archives of Internal Medicine found that there was a 26% higher risk of death in those with the lowest vitamin D levels.

Who is at greatest risk for having low vitamin D levels?

  • Adults over age 50.
  • People with little sun exposure – those who live in northern regions (New England, Alaska), the homebound, people with indoor occupations or who spend little time in the sun.
  • People with dark skin, particularly African Americans (darker skin reduces the body’s ability to produce vitamin D from sun exposure).
  • People with a BMI greater than 30 (increased body fat interferes with this fat soluble vitamin’s ability to move from the fatty tissue into the blood stream).
  • People unable to absorb fat normally because of medical conditions such as pancreatic enzyme deficiency, Crohn’s disease, cystic fibrosis, celiac disease, surgical removal of part of the stomach or intestines, and some forms of liver disease.
  • People on certain medications such as prednisone, the weight loss drug orlistat (Alli and Xenical), the cholesterol lowering drug cholestyramine (Questran, LoCholest, and Prevalite), phenobarbital and Dilantin.

How do I find out if I have enough vitamin D?

With a blood test called 25-OH vitamin D. This test is the most accurate measurement of the amount of vitamin D in the body.

What should my 25-OH vitamin D level be?

There is currently no universal agreement or guidelines on the right level of vitamin D. Most sources agree on the following:

  • 40 nmol/L or less is a deficiency.
  • 75 nmol/L is high enough to award health protection and disease prevention.
  • 500 nmol/L or higher is considered toxic and could cause nausea, vomiting, poor appetite, constipation, weakness, and weight loss or even lead to dangerously high calcium and phosphorus levels.

How much vitamin D should I take?

This, too, is under discussion and study. Current guidelines recommend between 200 and 600 IU of vitamin D a day for adults. Many believe that these should be revised upward to at least 800 IU per day or more.

The Food and Nutrition Board of the Institute of Medicine recommends an intake of 1,000 IU for infants up to 12 months of age and 2,000 IU for children, adults, pregnant, and lactating women as the tolerable upper limit. Daily intake above these levels is not recommended. Doses of up to 10,000 IU/day have been given without apparent harmful effects in healthy adults but more study is needed.

How can I increase my vitamin D levels?

There are three ways:

  1. Sunlight
  2. Food
  3. Dietary supplements.


How much sun you need to boost your vitamin D level depends on where you live (north or south), the time of year (winter or summer), the amount of cloud cover, your skin color (dark or light), and the time of day (strength or weakness of the suns rays).

Of course, you still should remain aware of the skin cancer risks, but “safe sun” for the purpose of increasing vitamin D production and disease prevention has been proposed as:

5 to 30 minutes of sun exposure without sunscreen between 10 AM and 3 PM at least twice a week to the face, arms, legs, or back.

Many dermatologists oppose any unprotected sun exposure because of the skin cancer risks. Others argue that because higher levels of vitamin D protect against other more deadly types of cancer and other diseases, too, a limited amount of unprotected sun exposure may do more good than harm. It is best to discuss the right amount of “safe sun” exposure in your particular case with your health professional.


Here are the foods highest in vitamin D (including the number of IU each contains):

  • Cod Liver Oil, 1 Tbs: 1,360 IU
  • Salmon, cooked, 3 1/2 oz: 360 IU
  • Mackerel, cooked, 3 1/2 oz: 345 IU
  • Sardines, canned in oil, drained, 3 1/2 oz: 270 IU
  • Milk, nonfat, reduced fat, and whole, vitamin D fortified, 1 c: 98 IU
  • Margarine, fortified, 1 Tbs: 60 IU
  • Pudding, 1/2 c prepared from mix and made with vitamin D fortified milk: 50 IU
  • Dry cereal, Vitamin D fortified w/10% of the recommended daily value, 3/4 c: 40-50 IU (other cereals may be fortified with more or less vitamin D)
  • Liver, beef, cooked, 3 1/2 oz: 30 IU
  • Egg, 1 whole (vitamin D is present in the yolk): 25 IU

Dietary Supplements

Vitamin D supplements can be purchased in health food stores at a relatively modest price. You want to buy Vitamin D3 (not D2) because D3 is more potent. It can be purchased over the counter in doses of 400 IU, 1000 IU, 2000 IU and 4000 IU. It is available by prescription in doses of 50,000 IU which is taken once a week.

It is not yet known if dietary supplements offer the same benefits as vitamin D that is naturally produced by the body. This is another area of interest with this vitamin that is still under study.

Smart Health Choices for Vitamin D

  • Consider your risks – do you live in a northern region and have limited sun exposure? Are you dark skinned, homebound, or always indoors?
  • Get your vitamin D level checked. The next time you have blood work done request that a 25-OH vitamin D be included.
  • If your level is less than 40 nmol/L:
    1. Try to get the recommended amount of “safe sun” exposure
    2. Increase vitamin D containing foods in your diet
    3. Consider adding supplements in doses from 800 IU to 2000 IU daily depending on how low your level is.
    4. Meet with your health provider to discuss your overall risk profile and how vitamin D might fit into your risk reduction strategies.

Links to More Info

This information is offered for educational purposes only and is not intended to diagnose, prescribe or treat. For that please seek direct care from a health professional.

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3 comments so far. (Post your own)

#1 | On April 11, 2009, Michelle McLeod said:

Hi Carla,

Interesting information on vitamin D.  Thanks for directing me to this blog.  In fact, I really like this web site.  Lots of interesting topics.  I hope to visit the site from time to time.


#2 | On April 12, 2009, Carla Mills said:

Thanks for your nice comment, Michelle - and for stopping by. I hope you’ll come back to visit again!


#3 | On April 27, 2009, Coleen Dooley said:

Your article on Vitamin D is very informative as is your entire web page! I,too,have found a low vitamin D level more prevalent in my clients. As a psychiatric nurse practitioner in private practice in the Fl Keys, I recommend you as a great resource for my clients.

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