News & Health Information :: Events 2008

Breast Cancer

By Nicola Drabble
Registered Dietitian

Many conflicting ideas exist in the media about what the best diet is to reduce the risk of breast cancer development.  Some swear by certain "super foods" and vitamin and mineral supplements, others are concerned about food products such as coffee, food additives, sweeteners and pesticides - but there is no evidence that suggest these foods are either "super" or a risk factor. 

In November 2007, the American Institute for Cancer Research and the World Cancer Research Fund released their second report: "Food, Nutrition, Physical Activity and the Prevention of Cancer: A Global Perspective".   After compiling scientific research into cancer, results showed that the cause of breast cancer is not just a result of our genes, but is strongly linked to our weight, diet, fitness and lifestyle, indicating that in most cases, breast cancer is a preventable disease.   

Because we all eat different foods in varying amounts, there is no way to identify exactly which foods are culprits and which will aid in prevention. What we do know, however, is that oestrogen, an endocrine hormone which occurs naturally in the body, is a promoter of breast cancer.  Therefore women who have a higher than average oestrogen level, have an increased risk for developing breast cancer.   High oestrogen levels can be linked with dietary intake in the following ways:

Overweight

After menopause, oestrogen converts to its active form in body fat.  Therefore, overweight post menopausal women have a higher than average risk of breast cancer, as oestrogen levels are linked to the amount of body fat.  The more body fat, the higher the oestrogen levels, and therefore the higher the risk of developing breast cancer.  Staying within the recommended Body Mass Index range of between 20 -25 will decrease that risk.

Alcohol consumption

– There has been a definite link between alcohol and breast cancer. It has been estimated that alcohol causes about 2,000 cases of breast cancer every year in the UK, as it increases the level oestrogen in the body. Cancer research UK, found that with each additional daily measure of alcohol consumed in women, there was a 7% increase in breast cancer risk.  Some studies have also shown that alcohol increases the risk even more if women are on Hormone Replacement Therapy (HRT).  It is not the type of alcohol that makes a difference, but the quantities in which it is consumed.  There is no evidence to indicate that alcohol in moderation is a risk factor.  Staying within the recommended guidelines of 14units/week will decrease the risk – 1 unit is half a pint of beer/cider, 1 glass of wine, or 1 measure of spirit.   

Dietary fat

Dietary fat and breast cancer has been studied a great deal but has provided conflicting results.  It is thought that dietary fat increases oestrogen levels. From recent studies though, it seems that women who have diets high in saturated fats (fats from animal products) specifically, are at a higher risk of developing breast cancer, although high intakes of total fat will lead to obesity which, as previously mentioned, is a definite risk factor for breast cancer development.

There are of course other foods which have shown to be beneficial.  Eating wheat bran fibre has been found to lower the levels of oestrogen in the blood in premenopausal women.  Researchers are not quite clear why, but it may not be an effect of the fibre itself. Instead it may be that high fibre diets contain less fat, and more antioxidants, than low fibre diets.

Phytoestrogens are plant oestrogens which are similar in structure to female oestrogen. It is thought that these mimic and compete with the action of female oestrogen in the body, therefore weakening the total effect of female oestrogen.  Evidence supporting their use is uncertain. Soy bean products for instance which contain the phytoestrogens isoflavones, only seem to have effective preventive properties if they are consumed from adolescence.  Lignans the phytoestrogens in fibre, fruit and vegetables seem to have a protective effect although whether the protective effect is caused by the phytoestrogens in the diet, or whether they are only components of a healthy diet, has not been established.

Fruit and vegetables also contain many different vitamins, minerals and antioxidants which are all known to decrease the risk of breast cancer.  There is strong evidence that they do not have the same effect when they are taken as supplements. In 2008, an organisation called the Cochrane Collaboration reviewed the results of 67 clinical trials of vitamin supplements. It found that these supplements either have neutral or harmful effects. If you take supplements instead of eating more fruit and vegetables, you wont benefit from other substances they contain that may help to prevent breast cancer.

Scientists are uncertain at the moment about some of the links between diet and breast cancer.   Following the balance of good health below, will not only ensure you maintain a healthy weight, but may also protect you from many other chronic health conditions such as diabetes, other cancers and heart disease.

Include a starchy food at each meal especially those high in wholegrains and fibre

Eat at least five portions of fruit and vegetables a day and try and choose a variety of colours

Limit foods that contain a lot of fat, especially saturated (animal) fat – replace these with polyunsaturated fats (vegetable oils) and monounsaturated fats (olive oil).

Only drink alcohol in moderation

Stay within a healthy weight range (Body Mass Index = 20 - 25)

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