The risk of developing cancer depends on several factors. In addition to genetic predisposition and age, nutrition and environmental factors such as smoking also play a role. Scientists estimate that by appropriate nutrition the risk for breast cancer can be reduced by about half. In the case of colon and stomach cancer, it can probably be reduced by up to 90 percent through a healthy diet; After all, it is still about 20 percent for lung, mouth, throat, bladder and uterine cancer.
As early as the 1980s, various studies on larger population groups suggested the connection between diet and cancer. Meanwhile, there are numerous studies that indicate that a predominantly consisting of plant foods diet can protect against cancer or that too low a consumption of vegetables and fruits increases the risk of tumors. Especially in the Mediterranean countries such as Greece or Italy, where a lot of fruits and vegetables are eaten, far fewer people die from colon cancer than, for example, in the Czech Republic, where the consumption of these foods is much lower.
- Natural colors and aromas prevent
Nutritionists blame various ingredients for the preventive effects of a predominantly plant-based diet. In addition to some vitamins, minerals and fatty acids, they also attribute a cancer-preventing effect to bioactive substances. These include phytonutrients, fiber and substances in fermented foods such as sauerkraut or sour milk products. The secondary plant compounds are compounds that occur only in low concentrations in exclusively plant foods, for example as flavorings, fragrances or dyes. Many studies on the bioactive substances indicate that the compounds can intervene in the cancer process via various mechanisms. However, the investigations are predominantly made on animals and cell cultures. They are therefore only conditionally transferable to humans and rather as indications to understand.
- Model of carcinogenesis
Carcinogenesis is a very complex process. Model it can be divided into three phases. In the first phase, the initiation, the genetic information in the cell is changed. Triggers may be radiation, viruses, various food ingredients such as nitrosamines and polycyclic aromatic hydrocarbons (PAH) or cigarette smoke. Normally, the genetic damage in the cells is repaired by the organism so that no tumor can develop from it. However, cancer-promoting substances, also called promoters, affect the damaged cells, so that a tumor forms. The promoters support the division of the cancer cells and contribute to the fact that daughter cells multiply with genetic damage uncontrolled to a tumor. Promoters may include, for example, certain fatty acids, Alcohol or an excessive intake of nutritional energy. This section of carcinogenesis is called promotion. In the last phase, the progression, the tumor enlarges and metastases (secondary tumors) can form.
- Plant substances intervene
Secondary plant compounds can interfere with the cancer process, for example by B. prevent inactive precursors of carcinogenic substances (procarcinogens) into the active form (carcinogens) to convert. Some of the causative agents, such as mold toxins, PAHs and nitrosamines, are present in the diet as procarcinogens. They are first converted into effective carcinogens in the body with the help of enzymes. Various phytochemicals are able to inhibit these enzymes to form less carcinogenic compounds. This effect has been demonstrated inter alia for phenolic acids, glucosinolates and sulfides, the z. B. occur in various cabbage vegetables or garlic. Experts suspect that they attach themselves to the enzymes and thus block them for further reactions. Like vitamins C and E, certain phytochemicals prevent the formation of carcinogenic nitrosamines, which are produced either during food preparation or in the human digestive tract from amines and nitrite. Scientists at the Federal Research Center for Nutrition in Karlsruhe observed in a study with several subjects that contained in tomato juice phenolic acids inhibit nitrosamine formation.
As a further defense against carcinogenic compounds, our body has enzymes that paralyze already activated carcinogens. The harmless compounds are excreted by the organism via bile and urine. Secondary plant compounds such as glucosinolates, monoterpenes, sulfides and polyphenols can stimulate these detoxification enzymes. Other phytochemicals interfere with carcinogenesis by binding to the already activated carcinogens and thus turning them off. Particularly effective in this regard are the phenolic acids ellagic acid, ferulic acid and caffeic acid, which react with carcinogenic hydrocarbons (PAHs). In animal experiments, they were able to suppress carcinogenesis in a certain dose. In addition, carotenoids, polyphenols and flavonoids are able to to attach to the DNA in the nucleus, to which would otherwise be bound carcinogens. In this way, they protect the genetic information from changes and thus intervene in the initiation phase of carcinogenesis.
- Antioxidants stop free radicals
An important contribution to cancer prevention is made by substances that counteract free radicals, the so-called antioxidants. The free radicals are very reactive compounds that can damage or even destroy the cell wall and genetic material in the body. The radicals arise in the metabolism or are supplied to the body from the outside, eg. B. about the food, tobacco smoke or fumes. Some antioxidants prevent these reactions by stabilizing the radicals. This applies to vitamins C and E. Other antioxidants such as carotenoids, however, bind free radicals and are therefore referred to as radical scavengers.
Particularly well studied is the effect of beta-carotene, a carotenoid contained in yellow-red and green vegetables. Numerous studies prove the connection between a high intake of beta-carotene and a low risk of cancer. They not only act as antioxidants but can also inhibit tumor formation. Other carotenoids such as lycopene, the major tomato dye, and lutein found in green vegetables also have antioxidant capabilities. A study on 23 male subjects showed that a two-week intake of 330 milliliters of carrot, tomato or spinach juice per day reduced damage to genetic information. Flavonoids and phenolic acids also prevent cancer due to their antioxidant effects.
- With carrots and beans against cancer?
In tumorigenesis, communication between individual cells is impaired. Due to the disturbed exchange of information their growth and their differentiation get out of control, so that the cells proliferate uncontrolled. Carotenoids and other phytochemicals can inhibit tumor growth by promoting the flow of information between cells.
Tumor cells can also be stimulated by the body’s own hormones such as estrogens for reproduction. This is particularly true for hormone-dependent cancers such as breast, uterine and prostate cancer. The phytosterates, which are part of the phytochemicals, are able to interfere with estrogen metabolism and inhibit tumor growth. The estrogen-like plant substances include, for example, the isoflavonoids genistin and daidzin, which occur mainly in soybeans. These partially inactive compounds are converted into hormonally active substances in the body and there reduce the negative influence of the body’s own estrogens. Similar to isoflavonoids, lignans and indoles also influence hormone-dependent tumor growth.
- Tumor growth is inhibited
Phytosterols, which act especially in the colon, slow down the proliferation of tumor cells. This leaves the body’s repair mechanisms more time to eliminate damage to the genetic material. Phytosterols occur mainly in high-fat parts of plants and can be found among other things in sunflower seeds and sesame seeds. Also saponins, which are abundant in legumes, inhibit the growth rate of tumor cells in the colon.
Some phytochemicals also have the ability to stimulate single immune functions. You can z. B. promote the formation of signaling substances (cytokines), which are involved in the destruction of tumor cells or increase the number and activity of macrophages (seizure cells). These are cells of the immune system that are responsible for the detection and removal of alien substances. Carotenoids in particular showed immunological effects in studies. But also flavonoids, saponins and sulfides can stimulate the immune system and thus inhibit the development of cancer.
- Dietary fibers defuse carcinogens
Not only phytochemicals can prevent cancer. Dietary fiber also has a variety of protective effects. Scientists have been observing for years that people who eat high-fiber diets are less likely to get colon cancer. Dietary fiber increases the volume of the intestinal contents, thereby reducing both the concentration of carcinogenic ingredients and their contact with the intestinal mucosa. In addition, intestinal bacteria degrade the fiber to short-chain fatty acids, so that the pH value in the intestine decreases. This inhibits various enzymes that activate carcinogenic compounds. Butyric acid, which inhibits the growth of cancer cells in the colon, is also produced when fiber is broken down. In addition, dietary fiber is able to bind carcinogens directly, such. B. secondary bile acids, which forms the body itself and which probably have a carcinogenic effect. In a study on rats, dietary fiber fed wheat bran protects against cancer, despite an otherwise high-fat and low-calcium diet – both risk factors for carcinogenesis.
- Lactic acid inhibits tumor growth
Results of animal experiments show that the lactic acid bacteria contained in sauerkraut, yoghurt and other fermented foods can prevent the onset of cancer, especially colon cancer. Scientists observed that the bacteria bind carcinogenic substances in the intestine, so that damage to the genetic information is prevented. However, this property could be detected only in live, not heat-treated lactic acid bacteria. Other studies that fed yoghurt to animals suggest that lactic acid bacteria inhibit tumor growth through their positive effects on the immune system. However, this only applied if the animals regularly received sufficient quantities of yogurt and the tumor was in an early stage of development. Lactic acid bacteria inhibit the activity of intestinal flora enzymes that convert procarcinogens into carcinogenic compounds. The activity of the enzymes can not be influenced only by fermented foods. Also, a high intake of fiber probably reduces the enzyme performance, while it is promoted by the frequent consumption of meat.
- Prevent with whole nutrition
Nutrition plays an important role in the prevention of cancer. However, no diet can guarantee complete protection against disease. But with a well-balanced diet, you have the potential to reduce cancer risk. Both the phytochemicals contained in fruits and vegetables and the dietary fibers have a high anti-cancer potential. For this reason, a plant-based diet such as the whole-food diet is recommended, at the same time less animal fats are consumed than in the usual mixed diet. Such a diet is not only the best way to prevent cancer, but also protects against other diseases.