Valuable Insights Into the Importance of Vitamin D and Sun

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April 03, 2004 | 60,007 views

Vitamin D deficiency is a major problem in the United States but many Americans are not aware that they may be lacking this important nutrient. Although word is beginning to leak out even among the traditional medical community, testing for vitamin D will not skyrocket like cholesterol or other testing because there is no expensive drug to push, thus making the public more aware.

It is essential to understand that in order to know how much vitamin D you should be taking, you should get your blood level checked.Unfortunately, very few doctors do the blood test for vitamin D. You can't rely on the media to expose the issue. If and when they do, it will be too late for most of you and you will have suffered decreased bone density and an increased risk of many cancers. But you don't have to wait for the media.

You can read my article on vitamin D testing and get up-to-date on this important topic before it is too late. Unless you are getting significant sun exposure on large amounts of your skin, in fact, I would advise reading the article right now.

Vitamin D is such an important topic that we recently conducted an exclusive interview with one of the top vitamin D researchers in the world, William B. Grant, Ph.D. Here you will get the insights of someone who is on the cutting edge of vitamin D research and knowledgeable about the importance of sun exposure for health. Taking a few minutes to read through the information below will broaden your understanding of this important issue to help you reach higher levels of health.

GRANT: Let me preface this interview by qualifying my background and the information I present. I have a Ph.D. in physics and have worked for 30 years in remote sensing of the atmosphere and studying aerosols and ozone. For the past seven years, I have applied the ecologic approach for the study of dietary and environmental links to chronic diseases and have read the health literature extensively.

Thus, the information presented is based on my best understanding of the situation and may not be fully in accord with views held by others. It appears that the health care community is beginning to awaken to the great importance of vitamin D for optimal health so that better answers to these questions should be available in the next few years.

Also, a few words about "vitamin D." When produced in the skin or ingested, it is a "vitamin" or "prehormone"and essential for life. Just as cholesterol is metabolized in to testosterone, precholesterol is turned into cholecalciferol (vitamin D), which is metabolized into what now is looking more and more like a hormone [25(OH)D]. In turn, this is metabolized in the kidneys or other organs into an even more potent hormone [1,25(OH)2D].

<>Vitamin D is an essential part of the endocrine system [1] as it controls several of the adrenal hormones, growth of cells, production of enzymes and has other direct genomic functions. The key difference in definition is that hormones have DNA receptor sites, and vitamin A is in that family as well as vitamin D, and vitamins are parts of coenzyme systems (not genomic). In a way, vitamins A and D are both vitamins and hormones. Vitamin D is also produced in plants such as algae, as well as mushrooms (which are neither animals nor plants) exposed to ultraviolet-B (UVB) radiation [2, 2a]. Fish obtain their vitamin D from zoo plankton and, likely, phytoplankton.


1. In your estimation, how many Americans are likely to be lacking in vitamin D right now?

Based on my study of the Atlas of Cancer Mortality for the United States [3] and the geographic variation of multiple scleros is among U.S. veterans of WWII, and a reading of the literature,I think that 80 percent to 90 percent of Americans are vitamin D deficient.

Those with the best vitamin D status live in Hawaii and rural regions of the southwest, which have the highest UVB radiation in July [4]. Those with the worst vitamin D status are those with darker skins and those who live in Alaska and urban regions of the northeast. Nearly all Americans are vitamin D deficient in winter/spring when there is not enough UVB reaching the surface.

2. What is the optimal level of vitamin D?

The current understanding is that serum 25(OH)D levels should be in the 30 to 40 ng/ml (75-100 nmol/L) range for cancer prevention and optimal health. The only way to determine one’s 25(OH)D levels is though blood tests, which can be ordered through a physician or nutritionist. However, care should be exercised in choice of a laboratory since the testing methods and quality of the tests may vary. In addition, since 25(OH)D and parathyroid hormone (PTH)are inversely correlated and have opposite effects on calcium in bones, one could also have PTH levels measured.

Vitamin D Dose Recommendations
Age Dosage
Below 5 35 units per pound per day
Age 5 - 10 2500 units
Adults 5000 units
Pregnant Women 5000 units
There is no way to know if the above recommendations are correct. The ONLY way to know is to test your blood. You might need 4-5 times the amount recommended above. Ideally your blood level of 25 OH D should be 60ng/ml.
I believe that Dr. Grant is a bit conservative in his recommendation here and I believe that an optimal level of vitamin D is between 45 and 50. I also highly recommend testing though as it is relatively dangerous if one exceeds a vitamin D level of 60.


3. What are some of the diseases that can result if a person’s vitamin D levels are less than optimal?

There is a large and growing list of diseases related to vitamin D deficiency. The bone diseases, rickets, osteopenia, osteoporosis and osteomalacia, are well known. The role of vitamin D here is to facilitate the absorption of dietary vitamin D and help with calcium metabolism [5].

Muscle pain and weakness is another [6]. There are about 16 types of internal cancers for which vitamin D is a risk reduction factor [7]. Other diseases include multiple sclerosis [8], type 1 diabetes mellitus [9], rheumatoid arthritis [10] and heart disease [11].

4. In your article you mention "the time required in the sun [for optimal vitamin D] is probably 15 to 30 minutes per day with at least hands and face exposed in the mid-latitudes during summer." What do you recommend for people who cannot get outside to achieve this exposure, or who live in areas that make it difficult to make vitamin D from the sun?

First, note that the 15 to 30 minutes per day generally applies to fair-skinned, thin, younger individuals, with the more of the body exposed, the better. Darker-skinned individuals may require several hours per day. For those unable to derive sufficient vitamin D from solar UVB, artificial UVB lamps are a viable option, as are vitamin D supplements.

5. Do you think that overdosing on vitamin D is a serious concern for people taking vitamin D supplements, or is it relatively difficult to reach dangerous levels?

I do--too much can lead to bone loss [12]. In addition, a new study from Finland has shown that those with average values of serum 25(OH)D have lower risks of prostate cancer than those with lower or higher values [13].

My recent ecologic study indicates that high summertime UVB levels are a risk factor for prostate cancer, while low wintertime UVB levels are also a risk factor [14].

6. Is there an alternative to sun exposure that you feel would give the same benefits in terms of vitamin D?

The two viable options are artificial UVB and supplements. If visiting an indoor tanning salon, be sure to ask for the booth with the highest UVB (280-315 nm) to UVA (315-400 nm) ratio since only UVB produces vitamin D. UVA is useful in producing a browner tan.

Dietary sources of vitamin D are generally insufficient to produce optimal serum 25-hydroxyvitamin D (25(OH)D) since milk contains only 400 I.U. of vitamin D3 and 800 to 1000 I.U. per day are probably required. Fish oil with vitamin D can be consumed, but one should see whether and how much vitamin A is included. Vitamins A and D interact and one does not want too much vitamin A [15].

Dr. Mercola's Comment: While sun tanning booths can clearly increase one’s UVB exposure it does come with some risks. There are X-rays emitted from the ends of the bulbs so ideally lead tape should be wrapped around the bulb ends. Additionally the magnetic ballast that provides the current to the fluorescent bulbs emits high levels of EMF radiation that is likely linked to certain cancers. Because of these conditions I would strongly advise against nearly all commercial sun tanning booths. However, if the above criteria are met then they should be fine, because the actual light and UV exposure from the bulbs is relatively safe if applied with wisdom and caution.

7. Are there symptoms of inadequate vitamin D levels before a person reaches extreme deficiency or becomes sick with a related illness? In other words, would someone be able to tell if they were lacking vitamin D without receiving a blood test?

Not really, although there are several symptoms of disease onset that one can look for. One is muscle pain, especially in winter [16]. Another is easily fractured bones. However, even these symptoms are evidence of serious vitamin D deficiency and illness.

8. What is your opinion of sunscreens and sunblocks? Should they be used or do they block the beneficial effects of the sun?

The use of sunscreens is good at the beginning of the sunny season if one spends much time out of doors and also for those with fair skin in very sunny climates. The tan that develops with sun exposure is nature’s way of protecting against too much UV radiation.

However, constant application of sunscreens reduces the photoproduction of vitamin D [17]. It should be noted that skin pigmentation adapts over periods of millennia to local solar UV radiation (UVR) [18]. The problem in the United States, Australia and New Zealand is that most of the inhabitants have their ancestry in northern Europe, where pale skin is required for optimal vitamin D production.

The optimal skin pigmentation for solar UVR levels typical of the latitudes for the United States would be closer to that of those from Southeast Asia and the Middle East, i.e., more olive in complexion.

Dr. Mercola's Comment: I believe Dr. Grant is not aware of some of the other concerns about sunscreens that I presented in an earlier article.I normally advise against them

9. What food sources of vitamin D do you feel are best in terms of the quality and absorption availability of the vitamin D?

Fish--but not all types. Best are probably cold-water ocean fish such as salmon, sardines, herring, and mackerel; milk and now orange juice are now being fortified [19]. To get much D from fish requires consumption of the skin and fat under the skin, around the fins and at the tail. But while these are tidbits for grizzlies, Inuit, Eskimo and Northwest Pacific Indians and other traditional peoples they are not for most in the United States.

However, one has to consider the environmental and health consequences of drinking milk and orange juice. Fish bioaccumulate mercury and other toxins, and the world’s fish supply is rapidly being depleted. Not all people are lactose tolerant; milk fat is associated with various diseases such as breast cancer [20]. Orange juice has lots of sucrose and can give rise to reactive hypoglycemia when consumed on an empty stomach. See Fuller and Casparian [2000] for a chart showing the vitamin D content of various foods.

10. Is it possible for the body to store enough vitamin D from summer sun exposure to last through several months of winter?

Vitamin D is stored in the blood for a few weeks and in the fat for a few months. Serum 25(OH)D levels generally drop by 20 percent to 30 percent during winter in midlatitudes [21] and the prevalence of hypovitaminosis D increases markedly [22]. Low winter/springtime serum 25(OH)D levels are associated with the development of a number of autoimmune diseases (e.g., autism [23] and type 1 diabetes mellitus [24]) and schizophrenia [25]; cancer detection increases in winter/spring as well [26]).

Concluding statement

Much has been learned about the role of vitamin D in maintaining optimal health and preventing disease. Unfortunately, the health community has not given enough attention to vitamin D because for years the focus has been on its 'nutritional' role in bone, not its other genomic functions, which were basically unknown, and because when adding 'vitamin' D to foods in the early years to prevent bone problems (in the UK and later in the U.S.) there were many problems of excess, so much so that deaths occurred.

Another reason seems to be that vitamin D can be produced by solar UVB, and solar UVR is associated with skin cancer, premature skin aging and cataract formation. I plan to devote much of my efforts in the next few years to furthering the understanding of the role of vitamin D in maintaining optimal health and educating the general public and the health community. You are welcome to follow my progress at my Web site,

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