Can diet help to prevent cancer?

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We’ve had a spate of bad news stories about the health of the nation of late, so it is gratifying to read recent reports that deaths due to some forms of cancer (such as those of the breast and colon) are on the wane. However, these glad tidings are somewhat tempered by data which shows the incidence of cancer is actually showing an upward trend. According to official statistics, the last 30 years have seen UK cancer rates increase by about 20 per cent in men and 30 per cent in women. While earlier detection and treatment seems to be helping to reduce deaths due to a few types of cancer, it seems that our chances of succumbing to the Big C is growing.

The causes of cancer are complex, which means pinning down the factors responsible for its increasing incidence is not easy. Nevertheless, there is some thought that one potential factor in this is the increasing amount and array of synthetic and potentially-toxic chemicals that pervade our food supply and environment. Another important mechanism fuelling the rising rates of cancer may be a decline in our intake of cancer-protective nutrients. For instance, dietary levels of the mineral selenium (which studies suggest has significant anti-cancer properties) have fallen considerably in the UK over the last few decades.

Another dietary factor that is believed to have some bearing on our risk of succumbing to cancer concerns our intake of specific fats. Recent years have seen some scientific focus on the role that the so-called omega-6 fatty acids may play here. The most abundant omega-6 fat in the diet is known as linoleic acid, which is found in vegetable oils such as sunflower, safflower, corn and soya oil. Within the body, linoleic acid can be converted into another fat called arachidonic acid (AA), which itself can be made into substances that have cancer-promoting effects including prostaglandin E2 (PGE2) and hydroxyeicosatetraenoic acid (HETA).

Some scientists have theorised that a surfeit of omega-6 fats in the diet (in the form foods such as margarine, fast and processed foods) may be one factor feeding cancerous potential in the body. Happily, however, it seems that relative protection from this unwanted effect may be had through an increased intake of the so-called omega-3 fats. These fish-derived fats, more usually famed for their heart-healthy properties, have been shown to put a brake on the conversion of AA into cancer-inducing PGE2 and HETA. Omega-3 fats also seem to have the capacity to mute the cancer-triggering effects of the hormone oestrogen in the body. This action may have particular significance in the protection against what are known as ‘hormone-dependent’ cancers, such as those of the breast, womb, ovary and prostate, the rates of which are generally rising most quickly.

Several studies have found significant associations between a higher intake of omega-3 fats and a reduced risk of cancer. Fish rich in these fats to incorporate in the diet include salmon, trout, mackerel, herring and sardine, though supplementing with fish oil is also likely to confer benefit. Another option is to take cod liver oil at a dose of about two teaspoons a day. In addition to being rich in omega-3 fats, cod liver oil also offers vitamin D which itself seems to have important cancer-protective properties. The evidence suggests that eating more in the way of oily fish and/or supplementing with fish oil offers significant potential in keeping cancer at bay.

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