Foods That Cause Cancer
The risk of developing cancer increases with age. In developed societies, cancer is the second leading cause of death after cardiovascular disease, and accounts for approximately 25% of deaths. There are variations between less and more developed countries in the incidence of different types of cancer. In the former, cancers of the esophagus, stomach, liver and oral cavity are more frequent, and in the more developed countries those of the lung, colon, breast and prostate.
Epidemiological studies have shown a strong causal relationship between some types of cancer and certain lifestyle habits, such as smoking and exposure to environmental pollutants, and also with the consumption of food. The diet would be the cause of more than a third of the cases. At the same time, some foods and/or nutrients are protective against cancer. The pathogenic role of the diet seems especially important in tumors of the gastrointestinal tract, breast, prostate, and endometrium, although it is difficult to know precisely what is the effect attributable to diet in the origin and development of tumors due to the interrelation of diet with other factors: environmental, genetic and lifestyle.
Dietary recommendations, along with the usual practice of physical activity and maintaining an adequate body mass index, over time, could help reduce the incidence of cancer between 30 and 60%, especially breast (postmenopausal woman), endometrium, colon, kidney, and esophagus. Using the current rates, these measures would suppose the prevention of between three and four million cases per year in the world.
Mechanisms of Action of Nutritional Factors
Risk modification through nutritional factors can occur at different stages of the process of cancer onset; contributing to reducing the effects of environmental carcinogens, directly or indirectly damaging the DNA, or favoring or inhibiting the development of the neoplasm.
Several carcinogens have been identified in foods and beverages. The way of conservation and/or preparation of food results in the formation of compounds with carcinogenic action or are a vehicle of pesticide residues, organochlorine agents, or chemical compounds with a potential carcinogenic effect.
Carcinogens in the Diet
In the diet we can find various substances that are related to the risk of developing cancer:
1. Mycotoxins: compounds produced by some fungi during storage of corn, cotton, and peanuts. The best known are aflatoxins. Aflatoxins appear in poor storage conditions of cereals and nuts and are the most potent liver carcinogens that are currently known.
2. N-nitroso compounds (nitrosamines): nitrosamines are not naturally present in food and are formed as a result of the reaction between the amines of the food and the sodium nitrite used to improve its conservation. The most important production route of nitrosamines comes from the endogenous formation of nitrites in the digestive tract from the nitrates present in some foods such as sausages.
3. Polycyclic aromatic hydrocarbons: are present in foods that have been grown in areas with high environmental pollution due to the combustion of petroleum or coal derivatives, and also in foods that have been prepared on the grill or smoked. Very high temperatures in the preparation of food produce certain cancer-inducing substances. When cooking on the coals and temperatures of 500ºC are reached, the pyrolysis of carbohydrates and fats is produced, generating the appearance of these compounds.
4. Heterocyclic aromatic amines: formed during the cooking of meat and fish by reaction between proteins and carbohydrates.
The Relationship Between Food and Cancer
Food can increase or decrease the risk of cancer. The risk is lower in populations with a high consumption of fruits and vegetables, but the causes of cancer are very complex, and it is difficult to appreciate the importance of the different components of the diet without considering other factors that may contribute to the development of the disease. There are studies that indicate that up to 70% of cancers are related to diet, although checking which food or nutrient can be the cause is complicated.
It is necessary to consider that, at times, several risk behaviors that add up and increase the possibility of developing cancer coexist in the same individual. In this sense, people who smoke and consume high amounts of alcohol have more incorrect diets, and all these factors can enhance the risk of presenting various types of cancer.
Food of Animal Origin
In some studies it has been found that feeding with a high meat content could be associated with an increased risk of gastric cancer. It is particularly important to avoid meats prepared with nitrites. These foods should be consumed only occasionally and accompanied by vitamin C to alleviate the effects of nitrosamines. Several studies have shown that high consumption of red meat increases mortality in patients with lung cancer, colorectal, prostate and breast cancers.
Epidemiological studies indicate that populations that consume diets rich in smoked, salted and marinated foods have a higher incidence of esophageal and stomach cancer, at least in part due to its content in polycyclic aromatic hydrocarbons. There is evidence that preservatives in meats and fish increase the risk of colorectal cancer.
The Effect of Alcohol on Cancer Development
There is convincing evidence that high alcohol intake increases the risk of cancer of the oral cavity, pharynx, larynx, esophagus, liver, colon and breast and, possibly, stomach and pancreatic cancer as well. By combining alcohol with tobacco, the risk of developing cancer increases.
It is very likely that dietary fat (especially of animal origin) is a determining factor in the development of breast cancer. A diet rich in carbohydrates and low in fat may decrease the risk of breast cancer.
In some epidemiological studies it is suggested that diets rich in total fat and saturated fat are associated with an increased risk of lung and prostate cancer.
In general, more than the total amount of fat, what is of most interest is the type of fatty acids. The intake of high amounts of saturated fat may be associated with an increased risk of developing neoplasms. Obesity has been linked to an increased incidence of colon, breast and endometrial cancer. In this sense, it seems advisable to fight against obesity, avoid excessive consumption of calories and fat and increase energy expenditure by performing physical activities appropriate to the age and condition of each subject.
Several researches prove that fruits and vegetables reduce the risk of cancer of the oral cavity, esophagus, stomach and colorectal as well as breast and prostate cancers. In addition, cereals also act as protective factors for colorectal cancer.
In some studies, low consumption of cabbage, broccoli and other vegetables has been found in cancer patients, and it has been pointed out that the regular consumption of this type of food is associated with a reduction in the risk of presenting gastrointestinal cancer. In epidemiological studies, a protective role has been found of the high consumption of fruits and vegetables, especially for leafy and / or colored vegetables (rich in vitamin C and / or beta-carotene), against lung cancer. In a recent prospective European study, an inverse association between fruit consumption and risk of lung cancer was confirmed.
Other studies indicate that the increase in the intake of cereals and vegetables is related to a decreased risk of developing prostate cancer.
The increase in the consumption of other foods of vegetable origin (soy, apples, onions, raw tomatoes, etc.) has been associated with a lower incidence of cancer. Fruits and vegetables contain vitamins, selenium, fiber and other phytochemicals that have antioxidant and anticancer properties. The lycopene content, the red pigment of tomatoes, is a very effective antioxidant and is a protector against cancer.
Lichtenstein P, Holm NV, Verkasalo PK, Illiadon A, Koskenvuo M, Pukkala E, editors. Environmental and heritable factors in the causation of cancer. Analyses of Cohorts of Wins from Sweden, Denmark and Finland. N Engl J Med. 2000;343:78-85
Breslow RA, Graubard BI, Sinha R, Subar AF. Diet and lung cancer mortality: a 1987 National Health Interview Survey cohort of Finnish men. Cancer Causes Control. 2000;11:419-31.
Miller A, Altenburg HP, Bueni B, Boshuizen HC, Agudo A, Berrino F, et al. European Prospective Investigation into Cancer and Nutrition (EPIC). Fruits and vegetables and lung cancer: Findings from the European Prospective Investigation into Cancer and Nutritio. Int J Cancer. 2004;108:945.
Key TJ, Allen N, Appleby P, Overvad K, Tjonneland A, Miller A. European Prospective Investigation into Cancer and Nutrition (EPIC). Fruits and vegetables and prostate cancer: no association among 1104 cases in a prospective study of 130544 men in the European Prospective Investigation into Cancer and Nutrition (EPIC). Int J Cancer. 2004;109:119-24
Steinmetz KA, Potter JD. Vegetables, fruit and cancer prevention: a review. J Am Diet Assoc. 1996;96:1027-39
COMA. Working group on diet and cancer. Nutritional aspects of the development of cancer. UK Department of Health report nº 48. Norwich: HMSO, 1998