Men's Osteoporosis Support Group

Vitamin D: How much, where to get it, sunscreens, safety and benefits?

Update 9-26-10. See the Update posted on the Men's Osteoporosis site regarding research showing more than two-fold increased risk of pancreatic cancer in individuals with serum vitamin D levels equal to or greater than 100 nmol/L (40 ng/mL). This is not conclusive research showing a definite causal relationship to high serum vitamin D and pancreatic cancer risk. But it is suggestive, and thus something to discuss with your care provider. And might be reason to try to maintain serum vitamin D levels between 30-40 ng/mL (75-100 nmol/L).

Update 10/10/10. See the Update regarding two more studies showing potential problems with high and/or low levels of serum vitamin D. One study found overall higher mortality in older men with high or low concentrations of serum vitamin D. The other found more aggressive forms of prostate cancer when there was higher circulating serum vitamin D.

Update 1/2/11. See this Update dated today with additional vitamin D information. Particularly the November 30, 2010 Institutes of Medicine online vitamin D report, which presents controversial recommendations to not take calcium or vitamin D supplements.

Update 3/13/11. See the Update dated today for a link to a website with the D-Estimator spreadsheet to help estimate serum vitamin D production from the sun, and for other information on the topic of vitamin D.


Getting adequate vitamin D, either through UV B radiation or food and/or supplements, is reported to be important for bone health and overall health. I see only one advantage to solar UV B radiation as your source of vitamin D--it is free. Its disadvantages include that it increases your risk of skin cancer. It is also much more complex to have to monitor the daily UV Index, know your skin type, sun yourself for just the right amount of time the right number of times per week on the right amount of exposed skin and with the weather cooperating with your schedule. And, for those with dark, pigmented skin, UV B is a very poor source of vitamin D in non-tropical latitudes. The alternative is to take a proper dosage of vitamin D supplement that your annual or semi-annual serum vitamin D results confirm is keeping you in the normal range. This is suggested to be greater than 30 ng/mL and probably no higher than 90 ng/mL. All of this depends upon knowing your serum vitamin D level. That means you need to have it tested, then retested if it was low and you need to adjust it with added UV B radiation or vitamin D supplements. Thereafter you should have testing done on at least an annual basis to confirm nothing has changed. If you don't have testing done, it appears there is no risk of overdose from taking 1-2,000 IU day of vitamin D2 or D3 per day. That will likely keep you in the normal range, but would best be tested to be sure it is sufficient. NOTE: Consult your physician on this issue, I am not a physician and am not giving individual medical advice. You have to do what you and your care provider determine is best for your health.


Here are some references for the information that I will discuss in this article. I highly recommend you read both full text articles to get a wealth of information on vitamin D, a very important hormone/vitamin and/or watch the YouTube video to get Dr. Holick's side of the issue. There are several other YouTube videos from the conference where Dr. Holick spoke that discuss vitamin D, so check them out while there.

Am J Clin Nutr. 2008 Aug;88(2):570S-577S. Sun exposure and vitamin D sufficiency. Gilchrest BA. PMID: 18689404. Free full text available online.

Am J Clin Nutr. 2004 Dec;80(6 Suppl):1678S-88S. Sunlight and vitamin D for bone health and prevention of autoimmune diseases, cancers, and cardiovascular disease. Holick MF. PMID: 15585788. Free full text available online.

Ann Epidemiol. 2009 Jul;19(7):468-83. Vitamin D for cancer prevention: global perspective. Garland CF and others. PMID: 19523595.

Dr. Holick YouTube video on vitamin D.

Dr. Robert P. Heaney YouTube video on vitamin D deficiency.

Some general information on vitamin D.

From my readings, the normal serum vitamin D should be at least 30 ng/mL (75 nmol/L). I have seen several figures for the normal range extending up to at least 70 ng/mL (175 nmol/L), or higher. You will see in the Garland study above that 40-60 ng/mL is the suggested range. The 30 ng/mL point is where studies show that intestinal absorption of calcium is maximized--a main function of vitamin D. It is also where serum PTH (parathyroid hormone) is no longer suppressible by vitamin D as it is when less than 20 ng/mL and up to about 30 ng/mL. It is also the point where the epidemiological studies find decreased rates of the various cancers compared to participants with lower vitamin D levels. See this study, Am J Prev Med. 2007 Mar;32(3):210-6. Optimal vitamin D status for colorectal cancer prevention: a quantitative meta analysis. Gorham ED and others. PMID: 17296473. Note the correlation was linear--exactly what you would expect--as each group, divided into quintiles, was measured. That is, as every quintile's vitamin D level went up, their cancer rate went down just as you would expect if vitamin D were the cause of the decreased cancer rates. So, although not a controlled clinical trial, this is the best type result for an epidemiological study. It is not adequate to prove cause, but it highly suggestive.

100 IU of vitamin D elevates serum levels by about 1 ng/mL. Knowing this should allow you to titrate your serum vitamin D by upping the dose of vitamin D supplement according to this equation: 100 IU=1 ng/mL. if your vitamin D is 10 ng/mL lower than it should be, you would then need to supplement with 1,000 IU vitamin D, or an equal amount of solar UV B radiation. Note from viewing Dr. Heaney's video that there is great variability among people given the same dose of vitamin D. Thus the need to recheck your serum levels at regular intervals to be sure you have responded as expected, with levels not too low nor too high. Also note the great range of safety before reaching an overdose, which would be more than ten times the suggested normal serum vitamin D level.

Vitamin D from solar UV radiation is also variable based upon the time of year, the time of day, air pollution, skin pigmentation, etc. Both the free full-text articles I refer to have information to help people interested in obtaining vitamin D from solar (or UV light) radiation. African-Americans, and others with darker skins due to melanin pigmentation, who don't benefit from solar UV radiation elevating vitamin D as much as lighter-skinned individuals, may be forced to take supplements, especially if they live in northern latitudes.

Sunshine or vitamin D supplements?

I want to try to summarize the "battle" regarding vitamin D and sunshine vs. supplements. The two researchers with differing viewpoints that I will discuss are Dr. Barbara A. Gilchrest, Dermatologist, and Dr. Michael F. Holick, Professor of Medicine, Physiology and Biophysics. Their free full text articles are referenced above.

There is general agreement that most Americans are not maintaining serum vitamin D levels at what are considered to be normal levels. The question is how best to get those serum levels back to normal. Additionally there is disagreement as to whether there is strong enough evidence that vitamin D is responsible for reducing the risk of several cancers and other medical conditions such as M.S., diabetes, autoimmune diseases, etc. It is known that UV radiation increases the risk of skin cancer, but it also apparently reduces the risk of other cancers, including, colon, breast, prostate and several other types. Dr. Gilchrest says this cancer-lowering evidence is based upon epidemiological studies which don't have the same weight as randomized, placebo-controlled clinical trials. Dr. Holick says the evidence is overwhelming that proper levels of serum vitamin D correlate with reductions in several cancers.

Both investigators agree that sunshine can effectively produce vitamin D. Dr. Gilchrest, however, says there is no safe level of UV radiation, it all damages DNA. Therefore she says we should always use sunscreen when we are out in the sun. Since sunscreen can block up to 99% of UV B radiation, the wavelength that produces vitamin D, Gilchrest says we should thus take vitamin D supplements to maintain proper serum vitamin D levels. Dr. Holick says there is a safe UV radiation level and that we can get short amounts of sunshine safely to most effectively increase serum vitamin D levels.

Dr. Holick agrees that there is a burden of skin cancer from UV radiation. He says that the burden from other types of cancer that affect people from low serum vitamin D levels far outweighs the money, time and health issues of skin cancer. Dr. Gilchrest says that, no matter why you want to raise serum vitamin D levels, there is no reason to risk increased skin cancer by doing that. Instead just up the intake of vitamin D supplements. This can accomplish the goal of increased serum vitamin D, with whatever benefits that entails, and without any increased risk of skin cancer.

How to get adequate vitamin D

There are basically two ways these researchers recommend to get vitamin D. Dr. Gilchrest: Always use sunscreen, which will allow a small amount of solar UV B to form vitamin D. Then add an adequate amount of vitamin D via supplements. "Adequate" would have to be determined by, most likely, twice yearly serum vitamin D tests, one at the end of summer and one at the end of winter. Dr. Holick would suggest some time in the sun from 10:00 AM to 3:00 PM without sunscreen a day or more per week. You would likely pick the amount of time based upon your skin type and the daily UV score. If you were to then continue to be in the sun you would apply adequate sunscreen to block further UV radiation as much as possible.

What I will do. (See my disclaimer note above) With my history of facial skin cancer, and with my desire to most easily and effectively maintain proper serum vitamin D levels, I will chose to place sunscreen on when I'm outside and to take adequate amounts of vitamin D3 supplements as indicated by twice-yearly serum vitamin D tests. Currently I'm taking 2,000 IU/day and will adjust that as indicated by future serum vitamin D test results.

Some additional discussion

This October, after spending about five months in Wyoming, much of that time out in the sun hiking, biking, golfing, etc., but always with sunscreen, my serum vitamin D was 28 ng/mL, which is slightly below normal. Additionally I was taking 2,000 IU of vitamin D three times a week. I wasn't taking it daily since I was confident that my time in the sun was keeping my vitamin D levels normal, or higher, and that the supplement was probably overkill.

I'm 66 years old, the age when the body no longer produces the same amount of vitamin D from UV as it did when we were young adults. I've seen figures that suggest people older than 70 only produce 25% of the amount of vitamin D from UV radiation they did when young.

So there appears to be a quite complex issue here as regards maintaining serum vitamin D at adequate levels. I see all these factors potentially involved: age, time in the sun, time with or without sunscreen, time of year with its effect on UV B radiation doses, time of day, amount and type of clothing you are wearing, dose and type of vitamin D supplement you are taking, air pollution, skin type, whether you eat any foods that contain vitamin D, and there are probably some others.

I see no way to assure you are not deficient for serum vitamin D without annual or semi-annual testing. To correct a deficiency, if found, will then require some guess work as to what will best do the job. Your age, daily time in the sun, use of sunscreens, etc., will all have to be figured into your thinking. Then add in the amount of sunshine or supplements that you think will correct, and retest some months later to see if it worked. Readjust, if needed, and maintain what you were doing until further tests indicate the need to change.

How important is it to maintain adequate levels? I've read at least one study regarding prostate cancer that found a U-shaped result regarding serum vitamin D levels. That is, adequate amounts reduced prostate cancer, excess amounts were equally as bad as inadequate amounts. There appears to be little research--especially good, solid research--to indicate the need for super high vitamin D levels. But there is a lot of research to show that it is wise to maintain your vitamin D at, or somewhat above, 30 ng/ML (75 nmol/L). True this might not all be randomized, controlled clinical trials. But if you are my age you can't wait for those to happen. You have to accept the best data available. And that pretty strongly suggests that we will reduce our risk of multiple cancers, and other medical conditions, by maintaining adequate vitamin D levels.

Bottom Line: Get your serum vitamin D level tested, then adjust by either UV radiation or supplements to keep it at or above 30 ng/ML.

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