Home | Obesity and its Causes »
Diet and Cancer
 Printer Friendly Version |
Diet and Cancer
Arthur Price gives an introduction to cancer and some of the evidence for dietary prevention of cancer.
What is cancer?
About 1 in 3 people in the UK will get some form of cancer during their lifetime, and most people know someone who has died or suffered from cancer. Cancer is a disease where a cell in the body is no longer regulated properly and grows in an uncontrolled way, often spreading from one part of the body to another, a process known as metastasis. In all forms of cancer something has gone wrong in the cell to cause the excess growth. There are genes inside every cell made of DNA which give the cell instructions to prevent it from growing too fast, and cause damaged cells to stop growing. Cancer can begin if these genes are changed or mutated. Scientists think that two or more mutations may be necessary to cause cancer1. This is part of the reason why older people are more at risk of cancer, as mutations accumulate over time. There are many possible mechanisms for the damage to DNA which leads to cancer. Some substances are known carcinogens, i.e. can directly cause cancer, for example ionising radiation, or chemicals such as benzene2. Mutations may also occur in everyday life during normal bodily functions.
The link between diet and cancer
There is evidence that a diet high in fruit and vegetables can protect against a range of cancers. There is a vast amount of evidence from experiments and studies looking at cancer rates in different groups of people. Some studies contradict others, but most give the same broad message. Several studies have shown that people who eat the least amount of fruits and vegetables have about twice the risk of developing cancer, compared to the 25% of people who eat the most fruit and vegetables3. There is an array of evidence that healthy eating is protective against many types of cancer. Current theories suggest that by eating healthily breast, prostate and colorectal cancers could be reduced by 60-70%, and even lung cancer rates could drop by up to 30-40%3. Current research also suggests that a large number of different dietary factors may influence cancer development.
There are several possible reasons for the protective effect of fruit and vegetables against cancer. Antioxidants, which are found in a number of foods, can protect against cancer because they are able to prevent some of the damage to DNA. One example of an antioxidant is lycopene. Lycopene is found in high concentrations in tomatoes, and may give them their red colour. Studies have shown that eating a large amount of tomatoes or tomato sauce may reduce someone’s risk of prostate cancer by up to 23% 4,5,6. People with high levels of lycopene in their blood have also been found to have a lower rate of aggressive fast-growing prostate cancers6. Fruit and vegetables also contain the mineral selenium (found in brazil nuts). Selenium helps in many processes in the body, including in the immune system, and may help to prevent carcinogens (chemicals which cause cancer) forming3. Chlorophyll found in green vegetables has also been shown to prevent cancer in laboratory studies3, as have vitamins such as vitamin C (found especially in oranges and citrus fruits) and vitamin E.
Another commonly talked about cancer-diet link is that between cancer of the colon and fibre. Studies since the 1980s have suggested that a high fibre diet might prevent this type of cancer. For example, there is no difference in the rate of colon cancer among first generation Japanese people who move to
Other dietary factors may also play an important role in cancer prevention. There is evidence that an imbalance of omega-3 and omega-6 fatty acids may be linked to breast cancer, with omega-3 being cancer protective3. Flax seed is known to be a good source of omega-3, and may protect against a range of cancers including breast and prostate cancer3. In addition, over-consumption of calories leading to obesity is linked to an increased risk of death among people who already have cancer 3. Sustained high blood sugar levels have also been suggested to increase the risk of cancers of the digestive tract, endometrium and ovaries3. Thus a diet low in refined sugars or carbohydrates may be best for cancer protection because it will not increase blood sugar levels so much, as well as being high in fibre.
In conclusion, diet may be vital to prevent cancer, one of the biggest killers in the UK today. Prevention is better than cure, and with a good diet we may be able to reduce the incidence of several types of cancer. Scientists believe that antioxidants play an important role, since they prevent damage to DNA. Obesity and a high sugar intake may also increase the risk of cancer. Fibre is known to prevent colorectal cancers, as it mops up some of the bodies’ own damaging carcinogens. This evidence all supports the view that we should try to cut down on refined processed foods and sugar, and eat more fruit, vegetables and high-fibre foods.
References
1. Robbins and Cotran Pathological basis of disease 7th ed; Kumar, Abbas, Fausto;
2. Robins, King, Harlow: Cancer biology 3rd ed; Pearson Prentice Hall, 2006
3. Donaldson, M. S., Nutrition and cancer, a review of the evidence for an anti-cancer diet; Nutrition Journal 2004, 3:19 doi:10.1186/1475-2891-3-19
4. Barber N. J., and Barber J., Lycopene and prostate cancer; Nature 2002, volume 5, number 1, pp 6-12
5. Giovannucci E., A Review of Epidemiologic Studies of Tomatoes, Lycopene, and Prostate Cancer;; Experimental Biology and Medicine 227:852-859 (2002)
6. Campbell, J.K., Canene-Adams, K., Lindshield, B. L.,Boileau, T. W-M., Clinton S.K., Erdman, J. W. Jr; Tomato Phytochemicals and Prostate Cancer Risk; Journal of Nutrition; 2004 Dec;134(12 Suppl):3486S-3492S
7. Reddy, B. S., Dietary fibre and colon cancer; epidemiological and experimental evidence; Can Med Assoc J. 1980 November 8; 123(9): 850–856.
Topics: Articles (Food and Health Information) |
