Scientists have known for a number of years that consumption of tomato products seems to be associated with a reduced risk of prostate cancer, but the findings are not consistent. Sometimes tomatoes seem to help, and sometimes they don't, although overall the studies hint at a reduction of prostate cancer risk of as much as 20 per cent in men who consume the most tomato products. The National Institutes of Health took a closer look at just which tomato products are most effective.
The National Institutes of Health followed over 30,000 men in the Prostate, Lung, Colorectal, and Ovarian Trial. Cancer-free men aged 55 to 74 were given PSA tests when they entered the study and then follow-up blood work and digital (finger) examinations every year for four years. They were also queried about all the foods they ate on a daily, weekly, and monthly basis.
The scientists learned that the most lycopene was to be found in:
- Tomato juice, and
- Tomato sauce.
And the men in the study consumed more tomato sauce than any other tomato product.
The greatest protection against prostate cancer, however, was found with consumption of:
- Lasagna, and
But more was not necessarily better. In fact, about one serving a week seemed to offer the most protection against cancer. Why would this be?
Lycopene dissolves in fat, not water. Oily foods carry lycopene to the lining of the colon where it can be absorbed, but watery foods simply pass through without the lycopene entering the body.
Lycopene in raw tomatoes is a trans- isomer. Basically, this means there is just one point on the molecule where a human cell can "grab" it and move it inside.
Lycopene in cooked tomatoes is a cis- isomer. This means there are two points on the molecule where it can be attracted to a cell. It is easier for the body to absorb lycopene if the tomato has been cooked a long time (as in sauce) or at high temperature (as in pizza). Additionally, mashing and cooking the tomato bursts the cell walls of the tomato so that the lycopene is more thoroughly released. Cooking makes lycopene easier for the body to take in.
But there are limits, of course, to how much spaghetti, lasagna, and pizza are really cancer-preventive, since they are usually prepared with high amounts of saturated fat. In the National Institutes of Health study, this was about once a week.
Other studies have found little or no benefit for lycopene supplements in preventing prostate cancer. The protection comes from real tomatoes, cooked, but consumed in moderation. And the reduction in risk is 10 to 20 per cent.
You may also be interested in Natural Prostate Cancer Therapies: Moderation Is Key.
Kirsh VA, Mayne ST, Peters U, Chatterjee N, Leitzmann MF, Dixon LB, Urban DA, Crawford ED, Hayes RB. A prospective study of lycopene and tomato product intake and risk of prostate cancer. Cancer Epidemiol Biomarkers Prev. 2006 Jan;15(1):92-8.
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