Can you reduce your risk of cancer?
The answer is yes, kind of. There are many factors involved in determining our risk of cancer, and we only have have control over some of them.
Recent research shows that dietary modification, and nutritional supplementation, is one area that we can use to improve our chances of avoiding and/or surviving cancer.
Vitamin D. According to a recent study, raising the RDA of vitamin D from 400 IU to 1500 IU could cut the number of deaths from cancer by 30%. This is according to American scientists investigating the link between vitamin D levels and cancer risk.
This relationship between vitamin D intake and protection from cancer is not new. It dates from the 1940s when Frank Apperly demonstrated a link between latitude and deaths from cancer, and suggested that sunlight gave "a relative cancer immunity."
The Health Professionals Follow-Up study, a prospective study of over 50,000 US male health professionals, is the first study to examine total cancer incidence and factors that determine 25(OH)D levels. The research, led by Edward Giovannucci from Harvard School of Public Health, used data from 1095 participants who had plasma 25(OH)D levels measured, and then computer-predicted levels for the whole cohort.
What they found was that " . . . a 25(OH)D increment of 25 nanomoles per litre (nm/L) was associated with a 17 per cent reduction in total cancer incidence, a 29 per cent reduction in total cancer mortality, and a 45 per cent reduction in mortality of digestive-system cancer," (Giovannucci, Journal of the National Cancer Institute (vol. 98, pp. 451-459)).
What does "25 nm/L" actually mean? Well, the RDA of 400 International Units (IU), equal to 10 micrograms per day, only raises plasma levels of 25(OH)D by a modest 7 nm/L. "To achieve a level of 25 nm/L," the amount associated with the impressive cancer reduction, you would need "vitamin D supplementation of at least 1500 IU per day, a safe but not generally encouraged level," said Giovannucci."
The best source of vitamin D is from sun exposure, with a fair-skinned person estimated to produce up to 20,000 IU after 20-30 minutes in the sun. However, sun exposure is discouraged due to the risk of skin cancer. This is one reason why researchers are urging that clinical trials of high dose vitamin D supplementation and the risk of cancer should be "undertaken speedily".
"The potential for cancer prevention by vitamin D (in pill form) must now proceed to the clinical trial testing arena," said the editorial. "The biological evidence for inhibition of carcinogenesis is strong and, often, was predicted by the prior epidemiological findings on sunlight exposure."
The vitamin's protection is proposed to be multifaceted, by reducing the formation of blood vessels in tumours (angiogenesis), stimulating the mutual adherence of cells, and enhancing intercellular communication through gap junctions. All this adds up to stop proliferation of cancerous cells by contact inhibition.
One interesting observation in the study was that people taking vitamin D supplements did not have as high a level of active vitamin D (25(OH)D as those getting their vitamin D from dietary sources. According to the researchers, this is "consistent with the common use of the less active vitamin D2 in multivitamins.
We have spoken about this on several occasions in the past, including this radio show (http://www.emailbliss.com/article.aspx?artid=43) . Even though both forms of vitamin D, D2 and D3 are labeled in International Units, and can be converted to the active form by the liver and kidneys, the "animal" form, vitamin D3 (cholecalciferol) seems to be more active.