Bowel cancer and vitamin D

Dr Paul Clayton 2003


Research from the Portland VA Medical Centre in Oregon saw over 3000 people screened for polyps in the colon. (These polyps are a common precursor to full-blown colorectal cancer, which can often be prevented if the polyps can be removed early enough). Some interesting findings ensued; it transpired that those who ate a diet rich in Vitamin D (645 IU/day or more) were significantly protected; as were those who consumed 4g or more of cereal fibre, or took daily aspirin. Multivitamins helped to a lesser extent. Conversely, in cigarette smokers, the risk increased by 85%.

These important findings indicate that the risk of colorectal cancer, a major killer in the UK, can be dramatically reduced by simple life-style changes. Don’t rely on screening; stop smoking, take a micronutrient support program containing Vitamin D, take aspirin (unless you have a good reason not to) and eat more fibre – particularly the resistant starches.


References

Lieberman D et al, JAMA 290:2959-2967, 2003.

The evidence for carotenoids

Dr Paul Clayton 2006


Lutein and zeaxanthin are carotenoids found in such yellow foods as corn and egg yolks. They are also found in green vegetables and fruits. Examples include avocados, broccoli, green beans and kale. They are strongly linked to protection against Age-Related Macular Degeneration (Moeller at al ’06).

They are also associated with a reduced risk of coronary artery disease(Osganian et al ’03, Dwyer et al ’04). Moreover, data suggests that they may reduce the risk of certain kinds of cancers. This includes non-Hodgkin Lymphoma(Kelemen at al ’06).

In this last study, a link was established between vegetables and non-Hodgkin lymphoma. People who ate the most servings of vegetables had an incidence of non-Hodgkin lymphoma less than half of that in the group which ate the least vegetables.

There are several possible mechanisms which could explain this reduction in risk. For example, the carotenoids are antioxidants, and reduce free radical damage. They also have the ability to force cancer cells to redifferentiate (i.e.normalise) or enter the apoptotic sequence (commit ‘suicide’).

It is also possible that the carotenoids are merely markers for a diet containing high levels of fruit and vegetables. Especially those which contain other chemo-protective compounds. Like the sulphur compounds that increase the body’s ability to excrete certain carcinogens.

In fact it is likely that all these mechanisms play a role. Thus, from the average consumer’s point of view, it is enough to know that a diet rich in fruit and veg is strongly cancer-protective. It reduces the risk of most of the degenerative diseases.

How many portions should you eat per day? The government says 5-a-day. It seems to be enough to reduce the risk of heart disease. But the American cancer Association recommends up to 9 portions a day to reduce the risk of cancer.

It all seems academic, however, when you realise that the average intake in the UK is around 2.5 portions a day. This statistic is clearly linked to our poor public health.

We need to find easier ways to increase our fruit and vegetable intake. The government needs to find ways of making fruits and vegetables less expensive. Will they do this? Or will pigs continue to fly in the airspace over Westminster?


References

1 Kelemen LE, Cerhan JR, Lim U, Davis S, Cozen W, Schenk M, Colt J, Hartge P, Ward MH. Vegetables, fruit, and antioxidant-related nutrients and risk of non-Hodgkin lymphoma: a National Cancer Institute-Surveillance, Epidemiology, and End Results population-based case-control study . Am J Clin Nutr. 2006 Jun;83(6):1401-10.

2 Moeller SM, Parekh N, Tinker L, Ritenbaugh C, Blodi B, Wallace RB, Mares JA; CAREDS Research Study Group. Associations between intermediate age-related macular degeneration and lutein and zeaxanthin in the Carotenoids in Age-related Eye Disease Study (CAREDS): ancillary study of the Women’s Health Initiative. Arch Ophthalmol. 2006 Aug;124(8):1151-62.

3 Osganian SK, Stampfer MJ, Rimm E, Spiegelman D, Manson JE, Willett WC. Dietary carotenoids and risk of coronary artery disease in women. Am J Clin Nutr. 2003 Jun;77(6):1390-9.

4 Dwyer JH, Paul-Labrador MJ, Fan J, Shircore AM, Merz CN, Dwyer KM.. Progression of carotid intima-media thickness and plasma antioxidants: the Los Angeles Atherosclerosis Study. Arterioscler Thromb Vasc Biol. 2004 Feb;24(2):313-9.