Tuesday, October 14, 2008
There are thirteen vitamins humans need for growth and development and to maintain good health. The human body cannot make these essential bio-molecules. They must be supplied in the diet or by bacteria in the intestine, except for vitamin D. Skin makes vitamin D when exposed to ultraviolet B (UVB) radiation from the sun. A light-skinned person will synthesize 20,000 IU (international units) of vitamin D in 20 minutes sunbathing on a Caribbean beach.
Vitamin D is also unique in another way. It is the only vitamin that is a hormone, a type of steroid hormone known as a secosteroid, with three carbon rings.
....The vitamin D hormone system controls the expression of more than 200 genes and the proteins they produce. In addition to its well-known role in calcium metabolism, vitamin D activates genes that control cell growth and programmed cell death (apoptosis), express mediators that regulate the immune system, and release neurotransmitters (e.g., serotonin) that influence one’s mental state.
.....Rickets, a softening and bending of bones in children, first described in 1651, is another nutritionally-specific disease ....An autopsy study done in Boston in the late 1800s showed that more than 80 percent of children had rickets.
Early in the 20th century an investigator found that cod liver oil could prevent rickets in puppies. The nutritional factor in the oil that promotes skeletal calcium deposition was named "vitamin D," alphabetically after already-named vitamins A, B, and C. Rickets was thought to be another vitamin-deficiency disease, and the curative agent, a steroid hormone, was mislabeled a "vitamin."
Now, a century later, a wealth of evidence suggests that rickets, its most florid manifestation, is the tip of a vitamin D insufficiency/deficiency iceberg. A lack of Vitamin D can also trigger infections (influenza and tuberculosis), autoimmune diseases (multiple sclerosis, Type 1 diabetes, rheumatoid arthritis, and inflammatory bowel disease), cardiovascular disease, and cancer. Practitioners of conventional medicine (i.e., most MDs) are just beginning to appreciate the true impact of vitamin D deficiency. In 1990, medical journals published less than 20 reviews and editorials on vitamin D. Last year they published more than 300 reviews and editorials on this vitamin/hormone. This year, on July 19, 2007, even the New England Journal of Medicine, the bellwether of pharmaceutically-oriented conventional medicine in the U.S., published a review on vitamin D that addresses its role in autoimmune diseases, infections, cardiovascular disease, and cancer (N Engl J Med 2007;357:266–281).
.... A growing body of evidence indicates .... that vitamin D can prevent a whole host of cancers – colon, breast, lung, pancreatic, ovarian, and prostate cancer among them. Colon cancer rates are 4 to 6 times higher in North America and Europe, where solar radiation is less intense, particularly during the winter months, compared to the incidence of colon cancer near the equator.
.....There is now strong scientific evidence that vitamin D does indeed reduce the risk of cancer. Evidence from a well-conducted, randomized, placebo-controlled, double-blind trial proves beyond a reasonable doubt that this is the case, at least with regard to breast cancer. A Creighton University study has shown that women over the age of 55 who took a 1,100 IU/day vitamin D supplement, with calcium, and were followed for 4 years had a highly statistically significant (P <0.005) 75% reduction in breast cancer (diagnosed after the first 12 months) compared with women who took a placebo (Am J Clin Nutr 2007;85:1568–1591).
Some of the genes vitamin D activates make proteins that halt cancer by inducing apoptosis (programmed cell death), which destroys aberrant cells before they become cancerous, like adenoma cells in the colon and rectum. Others promote cell differentiation and reining in of out-of-control growth of cancer cells (like prostate cancer cells). Vitamin D-expressed genes inhibit angiogenesis, the formation of new blood vessels that malignant tumors need to grow, as studies on lung and breast cancers show. Other genes inhibit metastases, preventing cancer that arises in one organ from spreading its cells to other parts of the body, as studied in breast, and prostate cancers.
Vitamin D also expresses genes that curb cardiovascular disease. One gene controls the renin-angiotensin system, which when overactive causes hypertension (high blood pressure). Others stifle the immune system-mediated inflammatory response that propagates atherosclerosis and congestive heart failure (Curr Opin Lipidol 2007;18:41–46).
Multiple sclerosis (MS) is a neurologically devastating disease that afflicts people with low vitamin D levels. Around 85,000 people in the UK have MS. In Scotland it is estimated that there are 10,500 people with MS – more people per capita than anywhere else in the world.* ....Researchers have shown that the risk of MS decreases as the level of vitamin D in the blood increases .... Studies show that people who live below latitude 35° (e.g., Atlanta) until the age of 10 reduce the risk of MS by 50% (Toxicology 2002;181–182:71–78 and Eur J Clin Nutr 2004;58:1095–1109).
In a study published earlier this year, researchers evaluated 79 pairs of identical twins where only one twin in each pair had MS, despite having the same genetic susceptibility. They found that the MS-free twin had spent more time outdoors in the sun – during hot days, sun tanning, and at the beach. The authors conclude that sunshine is protective against MS.
New research suggests that influenza is also a disease triggered by vitamin D deficiency. ...Randomized clinical trials need to be done to test the vitamin D theory of influenza. With what we know now, however, perhaps an annual shot of 600,000 IU of vitamin D (Med J Aust 2005;183:10–12) would be more effective in preventing influenza than a jab of flu vaccine.
Our species evolved in equatorial Africa where the sun, shining directly overhead, supplies its inhabitants with year-round ultraviolet B photons for making vitamin D. Our African ancestors absorbed much higher doses of vitamin D living exposed in that environment compared to the amount most humans obtain today. A single mutation that occurred around 50,000 years ago is responsible for the appearance of white skin in humans. It turns out that a difference in one rung, or base pair, in the 3 billion-rung DNA ladder that constitutes the human genome determines the color of one’s skin.
The majority of the world’s population now lives above latitude 35° N and is unable to synthesize vitamin D from sunlight for a period of time in winter owing to the angle of the sun. Scotland starts at latitude 55 & heads north At a large solar zenith angle, ozone in the upper atmosphere will completely block UVB radiation. In Seattle (47° N) and London (52° N), from October to April UVB photons are blocked by the atmosphere so one’s skin cannot make vitamin D. (The half-life of circulating vitamin D is approximately one month.)
Except for oily fish like (wild-only) salmon, mackerel, and sardines and cod liver oil – and also sun-dried mushrooms – very little vitamin D is naturally present in our food.
....A majority of Americans have insufficient or deficient vitamin D blood levels. In veterans undergoing heart surgery at the Seattle VA hospital,47 degrees N I found that 78% had a low vitamin D level: 12% were insufficient; 56%, deficient; and 10% were severely deficient.
In order to enjoy optimal health, we should maintain a vitamin D blood level of ≥50–99 ng/ml. Without sun exposure, to reach a level of 50 ng/ml requires taking a 5,000 IU/day vitamin D supplement. There are two kinds of vitamin D supplements: vitamin D3 (cholecalciferol), the kind our skin makes, and vitamin D2 (ergocalciferol), a synthetic variant made by irradiating plants. Vitamin D2 is only 10–30% as effective in raising 25-hydroxyvitamin D blood levels compared to vitamin D3, leading the authors of a recent study conclude, "Vitamin D2 should not be regarded as a nutrient suitable for supplementation or fortification" (Am J Clin Nutr 2006;84:694–697).
Concerns about vitamin D toxicity are overblown, along with those about sun exposure. As one researcher in the field puts it, "Worrying about vitamin D toxicity is like worrying about drowning when you’re dying of thirst." .....
Sensible sun exposure should be encouraged, not maligned. If one avoids sunburn, the sun’s health-giving benefits far outweigh its detrimental effects.... A U.S. Navy study found that melanoma occurred more frequently in sailors who worked indoors all the time.
....The rise in skin cancers over the last 25 years parallels the rise in use of sunscreen lotions, which block vitamin D-producing UVB radiation but not cancer-causing ultraviolet .... 1,500 deaths occur each year from non-melanoma skin cancer, but 1,500 deaths occur each day from other cancers that vitamin D in optimal doses might well prevent.
.... The cost of taking a 5,000 IU supplement of vitamin D every day for a year is £12. I have started getting them at Lidls for £2 a bottle The cost for 5 million Scots taking this supplement would be £60 million. The number and variety of diseases that vitamin D at this dose could prevent, starting with a 50 percent reduction in cancer, is mind-boggling.
Scotland which is indeed northerly (matching Hudson's Bay) maintains a high level of habitability because the Gulf Stream runs offshore, however this also means the west of the country where most of us live, is relatively cloudy.
Scotland also has the honour of being at the top of the listing of all sorts of illnesses like heart attacks & MS. Since I started taking Vitamin D tablets a few weeks ago I wouldn't claim to have become tremendously fit but a sinus problem I have had for ages has improved significantly. This is barely anecdotal evidence on the other hand it is as good one could hope for.
This is where government devolved to our northern latitude could usefully act. Though the free market is effective on many things achieving health care for the entire population is something government can do far more efficiently. It would be within the regulatory power of Holyrood to insist that a sellers of a staple food in Scotland (bread, salt, milk?) should be required to have a sufficient level of D added for a 5,000 IU supplement - the cost of the government providing it would, I suspect, be far less than £12 per person. Unless all the evidence is completely wrong nothing could do nearly as much to improve Scotland's dreadful health record.