Prevention
Although we don’t know how to prevent someone developing cancer, we do know that you can reduce your risk by making lifestyle choices. For example, not smoking, avoiding sun damage to your skin and not drinking heavily can all reduce the risk of developing some cancers. Also, eating a well balanced diet, that includes five portions of fruit and vegetables, and taking regular exercise may reduce your risk.
In this section, there are a number of questions and answers about how to reduce your risk of developing cancer.
I have heard that taking selenium supplements can reduce the risk of getting some types of cancer. Is this true?
In the early 1980s doctors in America started a clinical trial to see if giving selenium supplements (taken as tablets of brewer's yeast) reduced the risk of skin cancer. People taking part in the study were given either the selenium or a placebo tablet with no selenium.
More than 10 years later the results showed that there was no effect as far as skin cancer was concerned. But it was found that the death rate in the group taking selenium was lower than in those who had the placebo tablet.
Looking at the results more closely the doctors found that this reduction in mortality was because there were fewer cases of lung cancer, bowel cancer and prostate cancer in the group taking selenium.
These findings raise the possibility that selenium might help prevent these major cancers but results from more trials will be needed before this can be certain.
The American study did, however, show that taking selenium supplements in recommended doses did not cause any side-effects and so if you do feel you would like to take them they are perfectly safe, although it is still not clear just how beneficial they might be in reducing the risk of lung, bowel and prostate cancer.
I am a smoker but I do try and have a healthy diet, so I take regular vitamin supplements. A friend has said this could be dangerous. Surely he is wrong?
Some years ago studies of diet suggested that taking large amounts of food rich in vitamin A might reduce the risk of some cancers, particularly lung cancer.
As a result of these reports several large clinical trials were started in which people who were thought to be at risk of getting lung cancer (mainly smokers) where either given vitamin A supplements (or a substance called beta-carotene, which the body converts into vitamin A) or placebo tablet with no vitamin content.
To everyone's surprise the first two of these trials, which involved large numbers of people in Scandinavia and the USA, actually showed that the group taking the vitamin A or beta-carotene actually developed more lung cancers than those taking the inactive placebo.
As result of these findings the other trials were stopped because of the risk that the vitamin supplements might actually be causing rather than preventing the cancers.
These trials only looked at vitamin A and beta-carotene and so don't tell us anything about other vitamin supplements and lung cancer.
Also, these results do not tell us anything about the effects of vitamin A supplements on non-smokers but they do suggest that smokers should avoid them.
At the end of the day the best way for a smoker to reduce their risk of getting lung cancer is to stop smoking!
We keep being told that we should eat five portions of fruit and vegetables every day as part of a healthy diet. Can you tell me how much a portion is?
The Department of health is running campaigns to encourage us all to eat more fruit and vegetables in our diet. There is good evidence that doing this can help reduce the risk of getting certain cancers, including cancer of the stomach, cancer of the colon, cancer of the rectum and possibly even cancer of the breast. It also helps reduce the chance of having heart attacks or strokes and can help in the control of some other illnesses like asthma and diabetes.
The advice is to takes five portions of fruit and vegetables in our diet each day. Fresh, frozen, chilled canned and dried fruit and vegetables all count, as does 100% fruit juice. (With fruit juice, although a glass of juice counts as 1 portion you are only allowed to count juice as 1 portion, however much you drink, because it has very little fibre in it, and it often contains natural sugars. So dinking, say, 4 or 5 glasses of fruit juice in a day still only counts as ‘1 portion’.)
Potatoes don’t count in the ‘5 a day’ portions, because they are too starchy. Beans, and other pulses, such as chick peas and lentils, only count as 1 portion a day, however much you eat, because although they contain lots of fibre they don’t have the same mix of vitamins and minerals as fruit and vegetables.
The Department of Health gives a complete list of portion sizes for different fruits and vegetables on it’s web site at
These are some examples:
Fruit and vegetables making up 1 portion include:
1 fresh apple
3 whole dried or fresh apricots
½ an avocado pear
1 banana
2 clementines
8 segments of canned grapefruit or ½ a fresh grapefruit
150ml of a fruit smoothie
2 medium plums
6 canned prunes or 3 dried prunes
1 tablespoon of raisins
7 fresh strawberries or 9 canned strawberries
5 spears of asparagus
3 heaped tablespoons of broad beans
2 spears of broccoli
8 Brussel sprouts
1 cereal bowl of mixed lettuce leaves
16 medium okra
1 medium onion
3 heaped tablespoons of fresh, frozen or tinned peas
8 spring onions
1 medium sized fresh tomato or two whole tinned tomatos
On some food packets (but not all) there is a '5 a day portion indicator'. It shows how many portions of fruit or vegetables are found in a typical serving.
The logo shows 5 squares, each representing 1 portion. For example, if one square is coloured in, you will know that 1 serving of this food counts as 1 portion towards your 5 a day target. If 2 squares are filled in, 1 serving counts as 2 portions and so on.
To get the best out of a ‘5 a day diet’ you should really take a mixture of different fruit and vegetables to get a good balance of all the vitamins and minerals your body needs for a healthy life.
Eat and enjoy!Is it true that taking aspirin regularly can help reduce the chance of getting a breast cancer?
In recent years there has been quite a lot of interest among scientists and doctors about the idea that aspirin could help prevent certain types of cancer.
Several studies have looked at this in breast cancer, where it is possible that aspirin might reduce the level of oestrogen in a woman’s body, which could help lower her chances of getting a breast cancer.
A recent study from the USA has looked at nearly 3000 women, half with breast cancer, and half who did not have the condition. It found that those women who had previously taken at least one aspirin tablet a week for six months or more, seemed to have a lower risk of getting breast cancer. This only applied to those cancers which were sensitive to hormones (oestrogen-receptor positive, or ER+, tumours), suggesting that there could be a link between taking aspirin and lowering oestrogen hormone levels. Those breast cancers without oestrogen receptors (ER- tumours) were equally common in both groups of women.
Although this study is interesting, and some other studies have reported similar results, aspirin can have side-effects, and until there is more certain scientific evidence for its benefits it is really too soon to say for certain that taking the drug is a good way of reducing a woman’s risk of getting breast cancer.
What are antioxidants?
For many years it has been widely accepted that a diet rich in fruit and vegetables is healthy and can protect against illnesses like heart disease and reduce the risk of cancer.
As a result of this scientists have worked hard to look for chemicals in plants which might be the reason for these benefits. So far several thousand different plant chemicals (or phytochemicals) have been discovered although only a hundred or so of these have been studied in any detail.
Phytochemicals which might have an effect in reducing the chances of cancer developing fall into several groups. These include:
n antioxidants: these work by removing harmful chemicals, called free radicals, from the body. Free radicals can damage the DNA in the cell's nucleus and this might lead to cancer formation. Antioxidants are found in vegetables like broccoli, cauliflower, brussels sprouts and cabbage. Lycopene is an antioxidant found in tomatoes, red peppers and red grapefruit and has been claimed to protect against prostate and lung cancer in particular.
- carotenoids: these cause the orange colour in a number of fruits and vegetables, like carrots and apricots.
- anthocyanins: found in grapes, aubergines and red cabbage.
- sulfides: found in garlic and onions.
- lutein & zeaxanthin: found in spinach
- flavonoids: these are actually a subgroup of a larger group of phytochemicals called polyphenols. They are found in a wide range of fruits, cereals and vegetables. Some flavonoids (found in soy beans, chickpeas and tea) have a similar action to the female hormone oestrogen and are called phytoestrogens.
Phytochemicals are present in almost all the fruit and vegetables we normally eat. Most of these will contain a mixture of compounds, for example it has been estimated that carrots contain over 100 different phytochemicals.
This means that eating a balanced diet rich in a range of fruit and vegetables should provide all the phytochemicals needed to promote health and minimise the risk of cancer. Although many phytochemicals are available as supplements in various forms there is no evidence that these have any additional benefit over eating the natural fruit and vegetables from which they come, indeed they are probably less effective.
I understand that green tea is rich in antioxidants, and that antioxidants may protect against cancer. Does this mean that drinking green tea can reduce the risk of breast cancer?
At present there is no good evidence that drinking a lot of green tea reduces a woman’s chances of getting breast cancer.
Although green tea is rich in antioxidants, and some laboratory studies have shown that its extracts can damage cancer cells, but these studies have only been done in laboratories and there is no clear evidence that it can be used to treat or prevent cancer.
Some studies have also looked at whether women who drink a lot of green tea are less likely to develop breast cancer than other women, but these have shown no difference in the breast cancer risk between the two groups.
Can using sunscreens prevent skin cancer?
Overall there is some very limited evidence from studies done in Australia (where the frequency of skin cancer in fair skinned people is very high) that sunscreens might help protect against the risk of skin cancer. But this is not conclusive and the best advice for people in the UK is to use sunscreens as part of an overall programme of skin protection. Other sensible measures to take - such as avoiding prolonged exposure to strong sunlight and wearing a hat and appropriate protective clothing if going out at the hottest times of day - certainly sunscreens shouldn't be used to allow excessive sunbathing.
Skin cancer is becoming increasingly common in the UK with more than 40,000 new cases being diagnosed a year.
There are three main types of skin cancer: rodent ulcers (also called basal cell carcinomas or BCCs), malignant melanomas and squamous cell carcinomas (SCCs). Rodent ulcers are by far the commonest of the three.
Excessive exposure to sunlight is a risk factor for the development of all types of skin cancer but the pattern is slightly different. For melanomas, excess exposure to sun as a child, especially if this caused sunburns, increases the chances of the growth developing in adult life. For both BCCs and melanomas intermittent, intensive, exposure, again especially if there is burning, increases the risk. For SCCs, however, it seems that long term, more or less continuous exposure to the elements (for example people with outdoor jobs, like farmers) seems more important. Being fair skinned and/or having light coloured or red hair also increases the chances of getting skin cancer.
Although there is no doubt that the ultraviolet radiation in sunlight is a cause of skin cancer, there must be other factors involved, which are not yet properly understood. Skin tumours do sometimes develop in people who have had very little exposure, and some occur on parts of the body which are usually covered.
Ultraviolet radiation in sunlight is made up of two types: UVA and UVB. The older types of sunscreens, which were intended simply to prevent sunburn, only protected against UVB. Today's sunscreens protect against both types of radiation and come in varying 'strengths'. Protection against UVB is measured by a sun protection factor (SPF) and this needs to be at least 15 to offer useful protection. Protection against UVA is measured by a rating system using one to four stars. The higher the number of stars, the better the level of protection. Theoretically, if you use a SPF15 sunscreen properly, your risk would be a fifteenth of the normal risk (around 7% of normal), but in practice, because we rarely use them properly, we probably only gain a 20 / 50 % reduction of the normal risk.
Sunscreens have few side effects although some people find they cause stinging or skin irritation. Their main danger is that people might feel they give false security and spend longer in strong sunlight than they should do because they are using a sunscreen, thereby increasing their skin cancer risk.
I take statins to prevent a heart attack. Someone has said this means I am less likely to get bowel cancer. Is this true?
Statins are drugs that lower the level of cholesterol in the blood, and are now often given to people with high cholesterol levels, in order to reduce their risk of getting a heart attack.
In laboratory tests statins have been shown to stop the growth of cells from colorectal cancers, and this has led scientists to wonder whether the drug might actually prevent this type of cancer developing.
A recent study has looked at people who took statins for more than 5 years and found that they did seem to get far fewer large bowel cancers than other people. Although this study is encouraging it is too soon to be sure that statins really do reduce the risk of getting bowel cancer, in fact some reports in the past have suggested it might actually increase the risk. At least this study offers the reassurance that those other reports where probably wrong, but it would premature to suggest that people should be taking statins to help prevent bowel cancer.
I am expecting my first baby. A friend has told me that she has read that if young babies play with other children they are less likely to get leukaemia. This sounds very strange, is it true?
Leukaemia is the commonest form of cancer to affect children, but in most cases the cause remains a mystery. It has been suggested, however, that the leukaemia might develop as an abnormal response to an infection. As a result there is a belief that children who are exposed to a variety of infections very early in life might actually be at less risk of getting leukaemia than other children.
A recent British study has tested this theory, working on the theory that babies who go to regular childcare in the the first months of their lives will be more likely to come into contact with infection than children who are looked after mainly at home. This study has actually shown that those children who do mix a lot with others in their first few months seem to have about half the likelihood of developing leukaemia compared to those who lead more sheltered early lives.
So this report does lend weight to the belief that exposure to infection in early childhood may actually help protect against getting leukaemia a few years later.
Can taking antioxidant tablets help prevent cancer?
For many years it has been widely accepted that a diet rich in fruit and vegetables is healthy and can protect against illnesses like heart disease and reduce the risk of cancer.
As a result of this scientists have worked hard to look for chemicals in plants which might be the reason for these benefits.
One group of plant chemicals that have been suggested as being beneficial are the antioxidants. Antioxidants remove harmful chemicals, called free radicals, from the body. Free radicals can damage the DNA in the cell's nucleus and this might lead to cancer formation. Antioxidants are found in vegetables like broccoli, cauliflower, brussels sprouts and cabbage.
Clinical trials are underway in a number of countries to see whether giving supplements of antioxidants in the diet might help prevent heart disease and cancer.
One of these studies has published its results. Over 20,000 people between the ages of 40 to 80 were divided into two groups. One group received daily doses of three antioxidants: vitamin C, vitamin E and beta-carotene, for five years, the other group received placebo tablets with no antioxidants.
The study looked at the number of people who got coronary artery disease, strokes, diabetes or cancer. Overall there was no difference between the two groups. The people taking the antioxidants had the same risk of developing any of these illnesses, including cancer, as those who had no dietary supplements.
The study did show that there was no obvious harm from taking the antioxidants.
Although this was a large trial it still is not possible to say for certain that antioxidants don't help prevent cancer and the results of other studies will help answer this question once and for all. For the moment, however, there is no strong evidence of a benefit from taking these particular dietary supplements although there is also no evidence that they do any harm.
Reference:
- Heart Protection Study Collaborative Group. MRC/BHF heart protection study of antioxidant vitamin supplementation in 20 536 high-risk individuals: a randomised placebo-controlled trial. The Lancet, 2002; 360: 23-33.
