Focus: Kill or cure? - Sunday Times - Times OnlineThe Sunday Times January 01, 2006
Focus: Kill or cure?First we were told to keep out of the sun to avoid skin cancer. Now a study suggests the resulting vitamin D deficiency can give us other cancers. Is health advice doing us harm? Lois Rogers reports
Rachel Jennings is one of millions of women who have invested heavily in protecting their children from the perils of skin cancer.
For years she has taken care to limit their exposure to the sun during the hottest periods of the day; for family holidays to sunny destinations she has always gone weighed down with the latest sunblocks.
Now she is dismayed to discover that while protecting her children from sunburn and skin cancer, she might have also inadvertently put them at risk of other cancers, heart disease and further illnesses by depriving them of sunlight.
This is because the sun’s ultraviolet radiation is our main source of vitamin D — and scientists now believe that vitamin D deficiency is closely linked to a range of cancers and other diseases.
This week an American analysis of 63 studies published over the past four decades concluded that cancer tumours of the colon and breast are linked to low levels of vitamin D. Other studies have found a link between vitamin D deficiency and schizophrenia, multiple sclerosis and lung diseases.
“It really is impossible to know what to do,” said Jennings, 38, who has two sons: Joe, 9, and Charlie, 6. “I don’t necessarily believe that I have increased their risk of all these horrible things, but it is impossible not to worry as a mother.”
Like many other consumers Jennings is baffled: the more health advice that we receive, the more confusing, if not downright contradictory, it can seem.
In the past few months, for example, scientific journals have reported that coffee might cause fatal heart disease — and that it is full of cancer-preventing antioxidants.
Milk, which contains calcium, is good for the bones — but its fat is bad for the arteries. Red meat is bad for the heart — but high-protein diets, claim some, can help to avoid obesity. A high-fibre diet is good — except that an American study now says that it does not, after all, prevent cancers of the digestive system.
Within days of each other last month, one study was published claiming that an aspirin a day reduced heart disease in women by 25% — but another said that one in 10 of those who take aspirin is at risk of intestinal bleeding and a possible early death.
Science is complex and good health involves balancing one risk against another. But for ordinary consumers, sifting the plethora of different advice is becoming an ever more complex task.
“When you see these headlines you can’t help wondering if we should be looking for the vested interests behind all health advice,” said Jennings, a former marketing executive who now works part-time near her home in Hersham, Surrey. “Have we been peddled the scare about skin cancer by a cosmetics industry that just wants to sell more sunblock, and the vitamin D message by the dietary supplement manufacturers who want to sell more pills?
“The trouble is, it is impossible not to be influenced by it.”
THE vitamin D debate illustrates how health advice evolves. A decade ago, doctors discovered that low intakes and blood levels of vitamin D were associated with arthritis and osteoporosis, the bone-thinning disease. Vitamin D assists the body in the absorption of calcium, which is vital to maintain healthy bones.
Tablet supplements of vitamin D were heavily promoted as a method of preventing bone and joint disorders. But after a flurry of excitement, it became clear that some people still get such diseases whatever they do. It was not long before concerns about vitamin D were overtaken by the rush to avoid the risk of skin cancer inherent in sunlight exposure.
The results of scientific research are, however, cumulative. Studies on vitamin D continued and the latest report draws on decades of research. Cancer specialists led by Cedric Garland of the University of California, San Diego reviewed almost every study of the link between vitamin D and cancer published since the 1960s.
As a result, Garland claims that his analysis has proved a clear link between the vitamin and raised cancer risk, and he is exhorting everyone to begin taking daily vitamin D supplements in tablet form.
“The high prevalence of vitamin D deficiency combined with the discovery of increased risks of certain types of cancer in those who are deficient, suggest that vitamin D deficiency may account for several thousand premature deaths from colon, breast, ovarian and other cancers annually,” he said.
It may be the best available information, but there is still a problem. Most studies that link diet or lifestyle with disease are epidemiological rather than empirical: they examine trends among large numbers of people rather than being based on experiments designed to reveal precise causes and effects.
This has its limitations. Karol Sikora, professor of cancer medicine at the Imperial College School of Medicine, says that to prove that a deficiency of vitamin D causes cancer it would be necessary to stage a 20-year experiment involving, say, 1,000 people with 500 receiving high doses of vitamin D and the rest receiving low doses.
In addition, all other aspects of lifestyle and diet would have to be taken into account.
“Quite apart from the logistics, the boredom factor in this kind of research is just too high,” said Sikora, who has participated in several abortive studies of this nature.
The new study on vitamin D also shows just how difficult it is to identify cause and effect in such research.
A huge European study on diet and cancer found lower rates of cancer among Mediterranean people. It prompted experts to advise that a Mediterranean diet high in fish, fruit, vegetables and olive oil was better than the diet high in meat and dairy fat more common in northern Europe.
Although that still holds, there is now a question about how much of the difference in cancer rates might be down not to diet but to higher levels of sunlight and vitamin D in the Mediterranean regions. “The biggest problem with research in this area, is what we call confounding,” said Tom Sanders, professor of nutrition at King’s College, London.
“Fruit and vegetable intake may be just a marker for some other lifestyle factor, like lower alcohol.” He points out another complication: “Fat people may be at greater risk of disease for other reasons, but vitamin D is stored in fatty tissue so they have a greater capacity to hold on to it. Nothing is ever as straightforward as it seems when you are talking about diet.”
Commercial pressures must also be taken into account since scientists and institutions are constantly battling for publicity and funding. Some complain of university press officers ringing research teams to find out if there is any study they can promote, as well as researchers anxious to raise their own status by promoting weak studies.
Others blame the scientific press. “The British Medical Journal and The Lancet will often send out press releases highlighting the research they consider to be most newsworthy, not necessarily the best science,” said Susan Jebb, head of nutrition and health at the Medical Research Council in Cambridge.
Sikora also warns that the public should always look for the vested interest. “There is no such thing as unbiased advice in health,” he said. “People are either promoting an industry, or their own careers, which may depend on promoting a particular theory, or more directly on funding from vested interests.”
He points out that the skin cancer campaign has been funded largely by the cosmetics industry which makes sunscreens and that research promoting the value of vitamins is frequently subsidised by the food supplements industry.
SUCH caveats leave one question: how, armed with suitable scepticism about health messages, can you achieve a healthy diet and lifestyle? The solution seems to be to follow the weight of scientific evidence in areas that have been researched thoroughly over a period. “The two biggest lifestyle killers are smoking and obesity, and alcohol is an increasing concern,” said Sikora. “Most health experts would agree on that.”
Avoidance or moderation is the rule and there is broad agreement on diet, too. “A diet with at least five servings of fruit and vegetables a day, and moderation in everything else, is a philosophy we should all aspire to,” said Frankie Phillips of the British Dietetic Association. “If people keep that in mind, they should be able to cut through the worst scare stories.
“Sugar, fat and processed foods with high additive content should be avoided. Most people know all this already: it is just a matter of doing it.”
Advice from the government’s Food Standards Agency follows the same thread. Snacks should be fruit or vegetables; alcohol intake should be no more than a couple of glasses of wine or a pint of beer a day; meat consumption should be reduced with products such as sausages and bacon eaten only once a week.
Fatty foods such as chips, along with butter, cream and lard, should be generally avoided and sweets should be an occasional treat rather than a daily indulgence.
As for sun: you need some but not too much. Don’t burn.
A similar message applies for exercise: regular, moderate activity is preferable to sudden bursts followed by inertia. Today Sport England is launching an “everyday sport” campaign to reinforce the idea that new year resolutions based on guilt are not the way to achieve long-term change and that exercise should be built into daily life.
It is possibly no coincidence that the world’s longest-living people have tended to be slim and modest in their dietary habits, with many subsisting on Mediterranean-style foods. The record for longevity is held by Jeanne Louise Calment, from southern France, who died in 1997 aged 122.
Mind you, she, too, is confusing for scientists and consumers: she was a lifelong smoker, apart from a few months when she tried to give up when she was 117.
A GUIDE TO THE THINGS YOU NEED TO DO – AND AVOID DOING – TO LIVE A LONG AND HEALTHY LIFE FOOD
A good diet is one that is high in nutrients and which keeps your body mass index (BMI) — a ratio of height to weight — low and stable. Repeated studies suggest that diets high in fresh fruit, vegetables, fish and fibrous, starchy foods such as brown bread, rice and pasta are best. The European Prospective Investigation into Cancer and Nutrition (Epic), one of the biggest studies of its type, also advises against over-consumption of red meats and dairy produce such as full-fat milk and butter, as these are high in animal fats and linked to a greater incidence of illness, including cancer. Also avoid processed foods which tend to be low on nutrients and high in fat, salt and sugar. When cooking try to steam, not boil, and to grill, not fry. Do not char food since this can produce potent mutagens that can cause cancer.
DRINK
Keep yourself well hydrated during the day by regularly drinking water. Milk is rich in calcium, which is particularly important for women who are more prone to bone disease. Intake should be limited, though, because of its animal fat content. Coffee contains antioxidants, believed to reduce the risk of cancer-cell formation, but the consensus is that these benefits are offset by the increased stress that caffeine causes. Office workers are being advised by many doctors to switch to green tea, which is high in antioxidants. As for alcohol, repeated studies have suggested that a small daily intake — especially of red wine — is beneficial and may reduce heart disease by up to 25%.
EXERCISE
People should ensure they build cardiovascular exercise and stretches into their fitness regime, but most experts agree there is no need to go anywhere near a gym. Moderate exercise taken daily has greater long-term benefits, not least because it is more likely to become habitual over time. Swimming, walking, dancing, cycling and using stairs instead of escalators or lifts are all good low-impact options. A nine-month study published last year, involving hundreds of overweight middle-aged Americans, found that those on a walking regime achieved higher levels of fitness than those doing short bursts of intense activity in a gym. The older you get, however, the more important it is to do some light lifting to maintain muscular strength. Stretch each morning.
SNACKS
Britain is at the top of the European league for consumption of crisps and other savoury snacks, sweets and fizzy drinks — almost all of which are full of fat, salt and sugar. The artificial sweeteners used in so-called “diet” drinks may also carry health risks if consumed to excess. Best advice is to stock up early each week on fresh fruit, raw vegetables and nuts so that if you do graze throughout the day you reach for those first. If you must treat yourself, go for dark chocolate as it contains antioxidants (but not too much as it is also rich in caffeine).
SUPPLEMENTS
If your diet is balanced and you spend a good few hours outdoors each week you should not need extra vitamins and minerals. However, the latest research on vitamin D suggests a supplement may be beneficial to those who do not get enough daylight. There is also evidence that fish oil supplements can be beneficial if you do not include oily fish such as herring in your diet. Vitamin E supplements are recommended by some doctors as they contain powerful antioxidants, while aspirin is a supplement recommended to thousands of middle-aged adults because it thins the blood and reduces the risk of strokes. It can cause serious stomach problems, however, so consult a GP first.
