Vitamin D PDF Print E-mail

Vitamin D is one of the star nutrients today, not only because a deficiency of this nutrient is common, but especially because new research has shown the extensive role it plays in the prevention of a range of chronic diseases.
MF Holick, Professor of medicine, physiology and biophysics at Boston University School of Medicine, has the following to say: ‘Today we face what is in fact a “medically significant” epidemic of vitamin D deficient people. Forty to sixty per cent of Americans are seasonally or chronically vitamin D deficient. Many who practice dermatology and their supporters in the sunscreen industry have scared the public right out of the sun, the best way to produce the vitamin D the body needs. These “naysayers” have ignored the mountain of peer-reviewed science demonstrating that moderate exposure to natural or artificial sunlight has powerful beneficial impact on health. Simply put, the American Academy of Dermatology and the sunscreen industry have their heads buried in the sand.’1

Forty to sixty per cent of the elderly are at risk for a deficiency, but even among young white girls in the USA, 48% are deficient towards the end of winter and 17% remain deficient towards the end of summer because of skin blocks.
Even individuals taking vitamin D supplements usually combined with a multivitamin tablet or together with a calcium/magnesium supplement may be getting insufficient vitamin D because the amount in most combinations is less than 200 units and there is a growing consensus that 1 000 international units (IU) may be the minimum dose required.


Vitamin D is made in the skin when it is exposed to sunlight. However in this form it is inactive. It then goes through a number of steps in order to become active. From the skin it goes to the liver where it becomes 25-hydroxy vitamin D and then to the kidney where it gets modified into its active form, namely 125-dihydroxy vitamin D. This route is interesting because it gives us a picture of how and why vitamin D can become deficient .

As indicated above, lack of sun exposure is probably the major cause of vitamin D deficiency. Because the medical establishment has constantly warned against sun exposure, people either avoid the sun or apply sunblock on the skin. A good sunblock can prevent 95% of the sun’s rays from making contact with the skin, shutting down vitamin D production. People living in long-winter areas and those with dark skins often don’t get enough sunlight to manufacture sufficient vitamin D.

People with diseases of the liver and/or kidney, and those with fat malabsorption may all have vitamin D deficiency (vitamin D is fat-soluble).


Vitamin D functions more like a hormone than a vitamin. It circulates around the body and can activate processes like a hormone rather than just being a building block like most vitamins. Think of the skin as an organ producing a hormone, which is vitamin D
According to Dr Cannell, vitamin D may be crucial in reducing the risk for many illnesses including 17 types of cancer, heart disease, types 1 and 2 diabetes mellitus, hypertension, osteoporosis, osteoarthritis, chronic pain, multiple sclerosis, and other auto-immune diseases.2

One of the major properties of vitamin D is that it is a major inhibitor of skin cell growth. This property led to the early development of vitamin D analogs used in the treatment of psoriasis which has major skin proliferation. It also regulates cell growth in general, which is why it is thought to play a role in suppressing cancer growth. According to Dr Holick, studies have shown that vitamin D can decrease the risk of getting colon and prostate cancer by 50%, and decrease the incidence of ovarian and breast cancer substantially. Is the warning to decrease sun exposure partially responsible for the increasing incidence of these cancers? This is a question all of us should be asking. With sunlight freely available this would constitute a huge saving in terms of medical treatments, doctors’ visits and hospital care.3

Vitamin D is a major nutrient for bone health. Without sufficient vitamin D, calcium absorption cannot be maximised, leading to deficient calcium and osteoporosis. Severe vitamin D deficiency leads to rickets in children and osteomalacia in adults but more marginal deficiencies will certainly also contribute to osteoporosis.

In its active form vitamin D has been found to modulate T-cell responsiveness such that the auto-immune responses are diminished. Studies have already shown that supplementation with vitamin D may decrease the risk of developing auto-immune disease.

While most dermatologists seem to be concerned about sun exposure and warn people to use sunscreens and cover up to avoid skin cancer, the evidence for this is not as clear as is made out. For example, there is evidence of melanoma occurring more among desk workers than sailors who work outdoors.4 It was also found to occur more commonly on non-exposed areas than on the head and arms. Other studies have also shown that using sunscreen offers no protection against skin cancer.5

There also appears to be an association between vitamin D level in the blood and overall cancer risk. In a randomised double-blind controlled trial over 4 years using calcium or calcium plus vitamin D, the group taking the vitamin D had a 60% decrease in the relative risk of cancer.6

Vitamin D may not be easily obtainable from the diet alone as very few foods contain this vitamin. Perhaps many adults remember taking cod liver oil when they were children. This is a very good source of vitamin D. Oily fish like salmon and mackerel are also a good source. Milk and orange juice may be fortified with vitamin D but in very small amounts.

Sun exposure is the best and most efficient way of obtaining enough vitamin D. The amount of exposure time varies according to the sun latitude and pigmentation of the skin. Dr Horlick, an expert on vitamin D, suggests 30 - 60 minutes of exposure to the face, arms and legs 2 - 3 times per week for an individual living in the UK, but this may be only 5 - 10 minutes for a Caucasian. The rule is to go for a light pinkness which will be equivalent to about 20 000 units of vitamin D orally. The body is able to store vitamin D and so can store sufficient vitamin D for the winter months provided winter is not much longer than a few months and individuals get back into the sun as soon as possible. Once your exposure time is complete apply the sun block to avoid getting burnt.

Holick believes that vitamin D evolved early in evolution to modulate cell growth and decrease cancer risk and also to modulate the kidneys to produce the hormone rennin which has a regulating effect on blood pressure.

Healthy adults who have some sun exposure should take at least 1 000 IU/day or 25 micrograms/day, but this may be increased to 3 000 IU/day or 75 micrograms in sick individuals if indicated. Vitamin D is fat-soluble and can accumulate in the body fat in excess amounts if too much is taken. High doses, i.e. above 1 000 IU/day should only be taken under supervision of a specialist.

With regard to sun exposure, maximum intake of vitamin D is reached before the skin turns pink. Further exposure will not increase the levels of vitamin D. The most natural form of vitamin D is ‘cholecalciferol’. The synthetic analog is called ergocalciferol but may not be as safe to use. The only vitamin D product available in South Africa is called calciferol and is made by Aspen Pharmaceuticals.7 There are also other more expensive analogs used by medical doctors. Vitamin D is also available in cod Liver oil.

Pregnant women should take 2 000 IU/day, and even up to 4 000 IU may be not enough for breast-feeding women. This recommendation is in opposition to the conventional medical recommendation that 200 IU is enough, which is not supported by modern scientific evidence.8 Babies need 400 IU after they are born if on formula, 600 IU if breast-fed, and 1 000 IU after the age of one year (Vitamin D Council Newsletter: ).

The evidence that moderate and reasonable sun exposure is dangerous to our health needs to be re-assessed. By warning people against sun exposure we may be adding to an epidemic of cancer and other chronic diseases. Sun exposure is free and the benefits of some exposure far exceeds the risks involved.

Vitamin D is not easily obtained from food. The skin has evolved to produce vitamin D from sunlight. Vitamin D is essential to our health and today we are seeing millions of people deficient in this vitamin partly because of the fear of sunlight and also because the majority of people spend so much time indoors.

As parents cover up their children and dermatologists continue to warn parents about sun exposure, the incidence of asthma, diabetes and autism continues to rise. Clearly the issues are complex and not due to a single factor but how many more factors do we need to keep adding to the soup together with pollution, electromagnetic smog, drugs and other nutrient deficiencies? At the very least doctors who warn people about exposure to sunshine should also recommend and prescribe vitamin D supplementation.9

The amount of vitamin D present in most vitamin/mineral products is far too low to keep levels of this nutrient in the safe range without good doses of sunshine. I am not recommending uncontrolled and unlimited sun exposure. Sunburn can damage the skin. Start slowly for perhaps 10 minutes per day and gradually increase exposure over a few weeks. Use clothing and natural sun blocks made from natural ingrediants  only as required to prevent over exposure and sunburn once  exposure is sufficient.
Enjoy the sun!

1.    Holick MF. The UV Advantage. I Books, 2004.
2.    Cannell J, Vasquez DC. Measuring your vitamin D levels: Your most important blood test?
3.    Holick MA. Vitamin D: Importance in the prevention of cancers, type 1 diabetes, heart disease and osteoporosis. Am J Clin Nutr 2004; 79: 362-371.
4.    Garland FC. Occupational sunlight exposure and melanoma in the US Navy. Arch Environ Health 1990; 45: 261-267.
5.    Dennis LK, Beane Freeman LE. Sunscreen use and the risk for melanoma: a quantitative review. Ann Intern Med 2003; 139: 966-978.
6.    Lappe JM, et al. Vitamin D and calcium supplementation reduces cancer risk: results of a randomized trial. Am J Clin Nutr 2007; 85: 15861591.
7.    Vieth R, Chan PC. Efficacy and safety of vitamin D3 intake exceeding the lowest observed adverse effect level. Am J Clin Nutr 2001; 73: 288-294.
8.    Basile LA, et al. The effect of high-dose vitamin D supplementation on serum vitamin D levels and milk calcium concentration in lactating women and their infants. Breastfeed Med 2006; 1: 27-35.
9.    Cashman KD. Vitamin D in childhood and adolescence. Postgrad Med J 2007; 83: 230-235.