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Vitamin D downgrade as scientists advise there is no real proof it fights cancer
Last updated at 23:07pm on 30.10.07
The cancer-fighting abilities of the 'sunshine food' are being questioned
Vitamin D, once heralded as a major weapon in the war on cancer, in fact does little to cut the risk, a study has discovered.
The sunshine vitamin has been widely credited with warding off cancer, strengthening bones and cutting the risk of heart disease and diabetes.
But a ten-year study of thousands of men and women has questioned its cancer-fighting properties. It was found that those with high levels were no less likely to die of the disease than others.
The statistics for bowel cancer were the only ones to show a clear benefit from taking the vitamin. Cancer experts who carried out the U.S. government-funded research said not enough is known about the benefits and limitations to use it for the prevention or treatment of disease.
They looked at how vitamin D affected the health of almost 17,000 men and women and started by measuring the amount in their blood.
A decade later, 536 of the volunteers had died from cancers ranging from lung cancer to breast cancer. Analysis carried out at the National Cancer Institute in Maryland did not find a link between the risk of death from all types of cancer and vitamin D.
Those with high levels of the vitamin were, however, 72 per cent less likely to die of bowel cancer which claims 16,000 lives a year in Britain. Only lung cancer kills more.
It was recently estimated that almost 30,000 cases of breast and bowel cancer could be prevented each year if Britons spend more time in the sun.
Although it is found in food, particularly oily fish such as salmon, mackerel and tuna, most of the vitamin D in our bodies is made when our skin is exposed to sunlight.
Researchers from the Office of Dietary Supplements in the U.S. said: "Health professionals and the public should not assume that vitamin D is a magic bullet and consume high amounts of it.
"More definitive data on both the benefits and potential adverse effects of high doses are urgently needed."
In Britain, the Food Standards Agency says most of us should get all the vitamin D we need from a combination of a balanced diet and a little sunlight.
It recommends that pregnant and breastfeeding women take a 0.01mg supplement each day.
Ed Yong, of Cancer Research UK, said: "This is a large study, but it's only one piece of the jigsaw. It is still unclear how big a part vitamin D plays in the fight against cancer, or how much vitamin D you need for good health.
"The best advice is to get a variety of different nutrients through a healthy, balanced diet, rather than relying on supplements."
Reader views (6)
My husband and I have been taking Vitamin D daily at 4,000 to 5,000 units a day for over 2 years and we have not had a cold or flu since. I am a sub for teachers and when I began subbing I was getting several colds and/or flu a year.
- Virginia Lee Dubon, Saginaw, Texas USA
Since when is a 72% reduction considered "no real proof it fights cancer"? There are also other studies that also show vitamin D has impressive anticancer effects.
This study may fail to detect other anticancer vitamin D effects. The people were measured ONCE and then monitored for 12 years. Vitamin D status varies enormously with diet and lifestyle. A single measurement at one point in time will be very weakly corrected with vitamin D levels over the following 12 years.
- Dan Steinberg, USA
"More definitive data on both the benefits and potential adverse effects of high doses are urgently needed."
What a load of rubbish. Once again, the government is discouraging people from taking beneficial and safe supplements. 2000IU-4000IU vitamin D is safe and very effective. The risk is essentially zero. This amount restores D blood levels to where they should be if you were in the sun frequently. Vitamin D deficiency is an epidemic.
- Dan Steinberg, Virginia, US
The study was fundamentally flawed in that it collected blood samples from the South in the Winter and from the North in the Summer. The seasonally difference between Summer and Winter status is roughly 30nmol/l thus the study was not comparing like with like.
The study fails to appreciate that 20 women with low vitamin d status died from breast cancer while only 8 of those with status above 80nmol/l while only 8 in the high status died, they may not think a 30% reduction in Breast cancer is significant but others are not so biased I bet if the 20 women who got breast cancer were in the higher vitamin D group they would have had something to say.
More than 90% of our vitamin D comes from sun exposure, between October and March no UVB reaches the ground in the UK so our vitamin D status drops from a summer high of 70nmol/l to a winter low of 40nmol/l.
Remember those with the 72% lower incidence of colon cancer were all above 80nmol/l.
Each 400iu of vitamin d3 raises your vitamin d status by 9nmol/l. To raise from 40nmol/l to 80nmol/l requires 2000iu/daily.
"The urgent need to recommend an intake of vitamin d that is effective" shows a united call from Vitamin d scientists to raise the current levels.
"Risk assessment for Vitamin D" shows the safety of up to 10,000iu/daily. In fact adverse events have only been recorded above 40,000iu/daily.
- Edward Hutchinson, Louth Lincs UK
10 years ago I had a polyp remove, 2 years after that I had another polyp removed. After that I had become quite disabled with Rheumatoid Arthritis and hadn't been able to have another colonoscopy until just recently. I began taking cod liver oil daily 3 yearsl years and now I'm walking again without the assistance of a cane or walker. I did have a knee replacement 2 years ago. I needed both done but no longer need the second knee done. For the past 5 months I've been taking a liquid vitamin D drops instead of the cod liver oil. Two weeks ago I had a colonscopy, the first one since I had the polyps 8-10 years ago and I am free of polyps which I attribute to the vitamin D I've been getting from cod liver oil and more recently the Ddrops.
- Evelyn Collins, Sydney,N.S.,Canada
Vitamin D does help prevent cancer, as your article goes on to explain. A 72% reduction in bowel cancer is a huge success. Probably more effective than any current medication and certainly safer.
- Dr Sykes, Chiswick
