Food and cancer: the much-needed nuance
In the Netherlands, one in four women and one in three men will develop cancer. If everyone lived healthier lives, we could prevent as many as three quarters of cancer in the western world. Eating better and exercising more: 35 percent less cancer. No smoking: 30 percent. No alcohol: 10 percent.
Whether we are capable of such a drastic change in our lifestyle is of course the question. And there are no guarantees either, because anyone who obediently adheres to all the rules can still get sick.
People who lead an unhealthy life and get cancer are not (entirely) to blame for this either. Because whether you are sensitive to cancer is a matter of pure bad luck.
However, you can greatly reduce the risk of cancer by living healthier now. That may soon matter, because it can take years (sometimes forty years) before a tumor reveals itself.
Those who want to eat healthier are bombarded with – sometimes contradictory – information about the relationship between nutrition and cancer. Soy gives you breast cancer, because it contains hormone-like substances, one claims. No, says another, those substances actually protect against breast cancer. And does red wine help prevent cancer, because of the substance resveratrol it contains, or do you get cancer because of the alcohol it contains?
“The information about this is often confusing,” says Ellen Kampman, professor of nutrition and cancer. High time for her scientific response to a number of statements in recent books and on websites.
Prof. dr. Dr Ellen Kampman (1962) is professor of nutrition and cancer at Wageningen University and conducts research into the relationship between diet, hereditary susceptibility and cancer. She contributed to the analysis of 7,000 international studies of the relationship between diet and cancer by the World Cancer Research Fund in collaboration with the American Association for Cancer Research. The 2007 report contains ‘the real scientific facts about nutrition and cancer’.
FRUIT
‘Fruit does little against cancer’
“That is not true. Fruit does protect against cancer, especially against tumors in the mouth, esophagus, lungs and stomach. These are often caused by smoking. So quitting smoking is the best thing you can do. You cannot prevent these cancers by eating fruit. But those who eat fruit have less chance of it.
What is true is that fruit does less against cancer than we used to think. Initially, the idea was that the antioxidants in fruit would protect against all types of cancer, but the evidence for this is less strong. Perhaps it is other substances in fruit, so-called phytochemicals, that reduce the risk of cancer.
Many people claim that there are superfruits: pomegranates and small forest fruits, such as raspberries, blueberries, cranberries and acai berries. They would protect very well against cancer. But it’s really too early to say that. However, it has already been shown in mice that the phytochemicals from berries and raspberries have a beneficial effect on colorectal cancer, for example. But you can’t just translate that to people. Because we do not know which substances in fruit help against cancer, it is good to vary with different types and try to get the recommended two pieces per day.
Indirectly, eating a lot of fruit (and vegetables) can also reduce the risk of all kinds of cancer related to obesity, such as esophageal, pancreatic, colon, breast, uterine and kidney cancer. Fruit contains few calories and thus reduces the risk of being overweight.”
DAIRY
‘The more milk (calcium), the less chance of colorectal cancer’
“Correct. Calcium binds toxic and irritating substances in the gut and then carries them out. The fact that the World Cancer Research Fund does not yet officially recommend the use of dairy is because a lot of dairy can slightly increase the risk of prostate cancer. But whether this is due to the calcium is not yet clear.
Especially if you have or have had colon cancer in your family, it is wise to regularly use milk products and to follow the recommendations of the Nutrition Center: 450 to 650 ml of dairy for adults per day, depending on the age (up to 50 450 ml, 51 to 70 years 500 ml and from 70 years 650 ml). In that case, especially choose low-fat or semi-skimmed dairy products, to reduce the risk of being overweight.”
SUGAR
Sugar increases the risk of cancer
“It’s not that simple. I can imagine that sugar as a source of calories promotes cancer: the sugar or insulin balance can indeed be disrupted if you are overweight. This has an effect on the ‘growth factors’ that can promote cancer. But it has not been shown that you get cancer from eating sugar. It is of course wise to use as few sugar-rich products as possible, such as soft drinks, because this contributes to obesity.”
VEGETABLE
‘Cabbage varieties help prevent cancer’
“Maybe. The studies contradict each other, which is why cabbage varieties such as broccoli, Brussels sprouts and green cabbage are not recommended in the 2007 report of the World Cancer Research Fund. Moreover, one Brussels sprout is not the same; how many healthy substances (glucosinolates) are in it depends very much on the way of cultivation, storage and distribution. In addition, it is not easy to say how much of it your body absorbs. These kinds of vegetables are certainly healthy, not especially in relation to cancer, because they also contain many other healthy substances.
As for other vegetables: tomatoes protect against prostate cancer, and concentrated products, such as ketchup, even more strongly. It is not possible to indicate exactly how much you should take, but a small piece of tomato (5 mg) already lowers the risk by 3 percent. We don’t know yet whether more is better.
FISH
‘Protect Omega 3 fatty acids’
“That may well be true. It has not yet been proven, but is being seriously investigated. We think that fatty fish reduces the risk of colorectal cancer. For example, research is underway in Wageningen and Norwich (England), funded by the European Union. For six months, a group receives an extra 300 grams of fatty fish (salmon) every week, the second lean fish (cod) and the third no (extra) fish. We examine what happens in the large intestine. Omega-3 fatty acids seem to inhibit inflammation, which plays a role in cancer. We do not know whether this protects fish against cancer. It could also be due to the vitamin D, or the relatively high amount of selenium in fish.”
CURRY
‘Turmeric inhibits cancer’
“You can’t just say this. Turmeric (turmeric, a component of curry), when combined with black pepper, is said to be a powerful anti-inflammatory, helping to prevent all kinds of cancer. Animal studies do indeed show an effect on tumors. Mice, however, then receive very high doses in a short time. We are different from mice, we do not ingest large amounts of turmeric and we also eat all kinds of different things that interact.”
SOYA
‘You can get breast cancer from soy’
“That probably isn’t true, even if you’ve had breast cancer before. Soy contains isoflavones: these are estrogenic substances that influence normal hormone action. Soy has not been shown to increase or decrease the risk of breast cancer. In countries with a high consumption of soy, such as in Asia, there is little breast cancer, but this may also be because the people there have different eating and living habits. I would not recommend dietary supplements containing isoflavones in a dosage much higher than what you can get with the diet (more than 100 mg per day). Breast cancer tissue grows precisely because of this type of supplement, according to research on animals and on human cells in test tubes. This is difficult to study in humans. But you’d better be on the safe side.”
VITAMIN PILLS
‘Nutritional supplements can help’
“No, it could be the other way around. Just try to get all nutrients from your diet and rather not take supplements with high doses, so with more than 100 percent of what you need daily. Certainly not if you have an increased cancer risk, for example because you smoke, are overweight, or if cancer runs in the family.
Supplements often contain substances separately, while you have to ingest them in combination with other substances, if they want to be healthy. Separately, those substances can actually increase the risk of cancer if you take a lot of them.
Beta-carotene, for example, promotes lung cancer in heavy smokers who received it as a supplement. While it can be healthy in carrots, which contain it together with all kinds of other substances in low doses.
However, extra vitamin D may be needed for the elderly and people with dark skin whose skin comes into too little contact with sunlight. It is becoming increasingly clear that vitamin D protects against colorectal cancer and perhaps also against breast cancer. But don’t bake in the bright sun, because that increases the risk of skin cancer.”
MEAT
‘Red meat (especially meat products) increases the risk of colon cancer’
“Correct. Haem iron probably plays a role in this. Haem is the natural coloring agent in red meat. Red meat includes beef, pork, horse and lamb. The report of the World Cancer Research Fund states that 100 grams of red meat per day increases the risk of colorectal cancer by about 30 percent. For processed meats, the risk of colon cancer increases by 20 percent if you eat 50 grams per day. However, long-term Dutch research showed no link between eating meat and colorectal cancer. In the US, meat is smoked more often and barbecued more often, and then there is that connection. Our meat products also have a slightly different composition. Nevertheless, the advice of the World Cancer Research Fund is: few meat products and limit the consumption of red meat to 500 grams per week.”
WINE
‘Red wine is good’
“Absolutely not true. Red wine does contain resveratrol, a flavonoid that may reduce the risk of cancer. But that certainly does not outweigh the cancer-promoting effect of alcohol. This increases the risk of pancreatic cancer, throat, esophagus, colon and breast cancer. It doesn’t matter what kind of alcohol you drink.
Not only do women have a higher risk of breast cancer the more they drink, the breast cancer risk increases by 10 percent per glass per day, but also the earlier they start. In adolescent girls, breast tissue develops rapidly. That is especially vulnerable in those years. I am therefore concerned about their alcohol consumption, quite apart from the possible brain damage that alcohol can cause.
The government advice is: men a maximum of two glasses and women one glass. This is because moderate alcohol consumption reduces the risk of cardiovascular disease. But for cancer there is no safe standard. If you don’t drink alcohol, keep it that way.”
CHOCOLATE
‘Dark chocolate protects, milk chocolate does not’
“That has not been proven. There are catechins in chocolate, especially in dark chocolate. But the link between chocolate and cancer has not been proven. The question is: is the group of people who eat dark chocolate the same who drink green tea, eat a lot of fruit and vegetables and eat fish and soy more often and less often red meat? Is it also the group that is less likely to be overweight? That is the most important thing: eating a lot of chocolate – including dark ones – increases weight and thus increases the risk of cancer.”
GREEN TEA
Green tea protects against cancer
“That is controversial: the studies on this are contradictory. It is certainly not harmful. Maastricht researchers are conducting research into catechins (flavonoids) in green tea, but that is still ongoing. A side note: if you drink tea too hot, it can promote esophageal cancer, a study in China found.”
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- Plus Magazine