Friday, December 10, 2010

Should we swap aspirin for vegetables? Not just yet.

Two cancer studies grabbed the headlines this week, causing nutritionists' hearts to sink and pharmacists to cheer. One suggested that vegetables and fruits offer scant protection against cancer; the other indicated that taking low daily doses of aspirin may cut our risk of dying of this dreaded disease. So, should we simply give up on vegetables and fruits, and pop the little white pill instead? I think not.

In the first article published in the British Journal of Cancer, Oxford University Professor Tim Key summarized evidence from several dozen long-term research projects looking at the amount of fruit and vegetables people eat and their overall cancer risk. He found little, if any, connection between eating lots of fruits and vegetables and the likelihood of developing cancer.

Meanwhile, the Lancet published a study showing that people who took a low dose of aspirin daily to lower their risk of cardiovascular disease were 20% less likely after 20 years to die of solid tumor cancers than those who had been taking placebo pills during the clinical trials, and their risk of gastrointestinal cancer death was 35% lower. The risk of lung cancer death was 30% lower, that of colorectal cancer death was 40% lower and that of esophageal cancer death was 60% lower.

The inflammation connection

Aspirin is thought to act on cancer through its ability to reduce inflammation, which plays a role in the development and spread of cancer cells. In animal studies, aspirin has been shown to block the synthesis of prostaglandins, chemicals that mediate inflammation and promote early tumors.

Whether aspirin systematically protects humans from cancer is uncertain, however. Indeed, the study notes that the results of observational studies in humans "have been conflicting, with more rigorous studies yielding weaker associations." Since few women took part in the trials studied, it is also unknown whether aspirin protects against breast or uterine cancer.

What we do know is that prolonged aspirin use can have negative side-effects, including gastrointestinal bleeding and bleeding in the brain. Non-steroidal anti-inflammatory drugs (NSAIDs) like aspirin can also disrupt the gut flora and increase intestinal permeability, thereby in fact increasing the body's inflammatory burden. (See this paper, this and this). So don't start a regimen of aspirin without first weighing up the potential benefits and risks of such a treatment with a doctor.

Those who can't or won't take a daily dose of aspirin may wish to turn their attention to ways in which food can be used to regulate inflammation. Many of those much-maligned vegetables and fruits, as well as spices, herbs and fats with a healthy omega-3-to-6 ratio, are thought to help cool inflammation, as well as providing antioxidants and a plethora of other compounds that work in different ways to protect the body against cancer.

Alas, these foods are woefully lacking in our western convenience-food diets, which are characterized by inflammation-promoting sugar and refined carbohydrates, trans fats in processed foods, oils with a high proportion of omega-6 fatty acids (e.g. corn, soy, safflower) and meat, eggs and milk from intensively-reared animals fed corn, rather than grass and hay.These should be replaced by foods that can reduce inflammation, such as:
  • Vegetables like peppers, broccoli and broccoli sprouts, Brussels sprouts, cabbage, cauliflower, chard, collards, fennel, garlic, onions, kale, leeks, spinach, sweet potatoes
  • Fruits such as acerola cherries, apples, avocados, black currants, blueberries, kiwifruit, lemons, limes, mulberries, oranges, raspberries and strawberries
  • Herbs and spices like ginger, turmeric, curry mix, basil, cayenne and chili peppers, cinnamon, cloves, cocoa, mint, oregano, parsley, rosemary and thyme
  • Nuts and seeds containing healthy fats, like olives, almonds, flaxseed, hazelnuts and walnuts (olive oil has been found to contain a compound called oleocanthal that acts similarly to the NSAID ibuprofen)
  • Oily fish, such as sardines, mackerel, herring, anchovies and wild salmon which are rich in soothing omega-3 fats, and a healthy omega-3-to-6 ratio in the overall diet
In addition to containing natural anti-inflammatory compounds, vegetables and fruits do act in some indirect and hard-to-measure ways on cancer risk.

"People who eat a large proportion of fruit and vegetables are less likely to be overweight or obese, which is a major cancer risk factor," notes Dr Rachel Thompson, deputy head of science at the World Cancer Research Fund. Most fruits and vegetables are low in calories and contain fiber which helps to make us feel full and hence stops us eating too much and gaining weight, she explains. The World Cancer Research Fund has issued a list of ten recommendations to reduce cancer risk.

Even cigarette smokers, the most at-risk from cancer, are protected if they eat vegetables and fruits. A recent study (which I wrote about here) showed smokers who ate the greatest variety of fruits and vegetables were 27% less likely to get squamous cell lung cancer than those with the least variety. (Of course, not smoking at all confers much greater protection!)

So before you rush to the drug store to stock up on aspirin, may I suggest you head into the kitchen and cook yourself a nice vegetable-and-fish curry. I made one last night that contained red onions, leeks, carrots, broccoli, mushrooms and salmon, swimming in a coconut-milk sauce spiced with turmeric, ginger, garlic, ground coriander, pepper and chili flakes. It was warming, quick and easy to prepare.

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