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Say the words “cancer prevention” and you have most people’s attention.
In 2012, 8.2 million people worldwide died from cancer, with 60% of new cases occurring in Africa, Asia and Central and South America. However, an astonishing 30% of cancers could have been prevented, according to the World Health Organization (WHO).
Before we investigate whether antioxidant supplements can help thwart cancer, we’ll take a look at the causes of cancer, and what role antioxidants can play in disrupting this life-threatening process.
What is cancer?
Cancer is a name given to a collection of related diseases that are all characterised by the body’s cells dividing without stopping, and spreading into surrounding tissues, according to the US National Cancer Institute at the US National Institutes of Health..
These American experts explain that the body produces new cells as and when they’re needed, but that this orderly process sometimes breaks down. Old and damaged cells survive when they should die, and new ones grow when they’re not needed. Tumours formed in this way can be malignant and form a solid mass, or they can be more systemic, as in the case of leukaemia. What’s more, cancer cells can evade the immune system, which normally removes damaged cells from the body.
Cancer can be a genetically inherited disease, or it can be the result of damage caused to DNA by certain environmental factors, such as tobacco smoke, or exposure to asbestos. In most instances, a combination of factors is probably at play.
What are free radicals?
When a substance combines with oxygen, there’s a reaction in which the atoms of an element lose electrons. Oxidation causes a change in your cells, and they may die or be replaced with other cells. This is a normal process that carries on right throughout life.
But as oxidation occurs in cells of any type, about one percent of them are damaged and change into free radicals (“free”, because they’re missing a critical molecule and are looking desperately to pair with another one to find it). These free radicals can cause cell damage, says the Harvard School of Public Health, and can lead to a number of diseases, such as heart disease and cancer.
So what are antioxidants?
Antioxidants are substances – either natural or man-made – that may prevent or delay some types of cell damage, according to the US National Institutes of Health. The Harvard School of Public Health adds that these antioxidants “work by generously giving electrons to free radicals without turning into electron-scavenging substances themselves”.
While they do occur naturally in the body, many foodstuffs contain them and they can be taken as supplements. The most familiar antioxidants, says the Harvard School of Public Health, are vitamin C, vitamin E, beta-carotene, selenium and manganese. But there are also many others.
Foods high in antioxidants include grapes, blueberries, red berries, nuts, green leafy vegetables such as broccoli and spinach, sweet potatoes, orange vegetables, green tea, whole grains, beans and oily fish, such as tuna, sardines and mackerel.
The cancer-fighting properties of antioxidants received much publicity in the early 1990s, when scientists began to understand the role of free-radical damage in the development of chronic, non-communicable diseases such as cancer.
Antioxidants and cancer prevention
Research on antioxidants, and their possible cancer-prevention abilities, are ongoing. It must be remembered that conclusive results can take decades, and that few trials have gone on long enough to provide clear answers.
While many human trials on antioxidants remain inconclusive, a great number of laboratory and animal studies have shown that antioxidants from vitamins and food can help prevent the free radical damage associated with the development of cancer, the US National Cancer Institute reports.
Although research by Hoyoku Nishino et al., published in Biofactors in 2004, noted that various antioxidants in foods, including phenolic compounds and carotenoids, seem to protect against cancer, many randomised, controlled clinical trials that have been completed in human subjects over the past decade have yielded mixed results. Overall, they provided little conclusive evidence that antioxidant supplements are beneficial in terms of primary cancer prevention.
Some results were, however, quite promising. In one study, an antioxidant cocktail led to a reduction in cancer risk and all-cause mortality among men. Unfortunately, the same wasn’t demonstrated in women. Harvard also reports on a study of selenium taken by people with skin cancer. The study demonstrated “significant reductions in cancer and cancer mortality at various sites”, including the colon, lungs and prostate. People who had low selenium levels to start with seemed to benefit most.
While people who eat lots of fruit and vegetables have a lower disease risk in general – also for cancer – studies haven’t been able to clearly show that the antioxidants in fruit and vegetables are solely responsible for this positive effect. However, abundant evidence suggests that eating whole fruits, vegetables and whole grains – all rich in networks of antioxidants and their helper molecules – provides protection against many of the scourges of ageing, says the Harvard School of Public Health.
The Cancer Council of Australia confirms that you can lower your cancer risk by enjoying a healthy diet rich in fruit and vegetables, legumes, whole-grains, low-fat dairy, fish, poultry and some meat.
“If you enjoy a wide variety of nutritious foods, you’ll get the nutrients you need, reduce your cancer risk and be less likely to be overweight or obese,” the Cancer Council writes.“For most healthy people, vitamin and mineral supplements are not necessary when they eat well.”
If you think your diet may be deficient in certain vitamins, minerals or antioxidants, it’s best to speak to your doctor.
- (Susan Erasmus)
Sources:
- Harvard School of Public Health, http://www.hsph.harvard.edu/nutritionsource/antioxidants
- US National Cancer Institute at the US National Institutes of Health, http://www.cancer.gov/cancertopics/what-is-cancer
- US National Institutes of Health, http://www.nlm.nih.gov/medlineplus/antioxidants.html
- Cancer council of Australia, http://www.cancer.org.au/preventing-cancer/reduce-your-risk/
- http://www.who.int/cancer/en/
