Carcinogens

3 types of carcinogens

carcinogen, any of a number of agents that can cause cancer in humans. They can be divided into three major categories: 

1. chemical carcinogens (including those from biological sources), 

2. physical carcinogens, and 

3. oncogenic (cancer-causing) viruses.


1 Radiation

2 In prepared food

3 In cigarettes


Others

Gasoline (contains aromatics)

Lead and its compounds

Alkylating antineoplastic agents (e.g. mechlorethamine)

Styrene

Other alkylating agents (e.g. dimethyl sulfate)

Ultraviolet radiation from the sun and UV lamps

Alcohol (causing head and neck cancers)

Other ionizing radiation (X-rays, gamma rays, etc.)

Major carcinogens implicated in the four most common cancers worldwide

In this section, the carcinogens implicated as the main causative agents of the four most common cancers worldwide are briefly described. These four cancers are lung, breast, colon, and stomach cancers. Together they account for about 41% of worldwide cancer incidence and 42% of cancer deaths (for more detailed information on the carcinogens implicated in these and other cancers, see references[35]).


Foods that may increase your cancer risk

Some foods can increase your risk of type 2 diabetes and obesity, which are associated with certain types of cancer. Other foods contain carcinogens, which are harmful substances that have the capacity to cause cancer.


It’s worth noting that exposure to carcinogens doesn’t always cause cancer, though. It depends on your genetics, as well as the level and duration of exposure to the carcinogen.


1. Processed meats

Processed meat is any type of meat that’s been preserved by smoking, salting, curing, or canning. Most processed meats are red meats. Some examples of red meat that’s been processed include:

hot dogs

salami

sausage

ham

corned beef

beef jerky


The methods used to make processed meats can create carcinogens. For example, according to a 2018 articleTrusted Source, curing meat with nitrite can form carcinogens called N-nitroso compounds. Smoking meat can also lead to carcinogenic polycyclic aromatic hydrocarbons (PAHs).


According to a 2019 reviewTrusted Source, processed meat is a major risk factor for colorectal cancer. A different 2019 reviewTrusted Source also found that it’s linked with stomach cancer.


In a 2018, researchers determined that a high consumption of processed meat was associated with an increased risk of breast cancer.


2. Fried foods

When starchy foods are cooked at high temperatures, a compound called acrylamide is formed. This can happen during frying, baking, roasting, and toasting.


Fried starchy foods are especially high in acrylamide. This includes fried potato products, like french fries and potato chips.


According to a 2018 reviewTrusted Source, acrylamide was found to be carcinogenic in studies done on rats. The International Agency for Research on Cancer (IARC)Trusted Source considers it “probably carcinogenic to humans.”


According to a 2020 study, acrylamide damages DNA and induces apoptosis, or cell death.


Eating a lot of fried food also increases your riskTrusted Source for type 2 diabetes and obesity. These conditions can promote oxidative stress and inflammation, further increasing your cancer risk.


3. Overcooked foods

Overcooking foods, especially meats, can produce carcinogens. According to one 2020 articleTrusted Source, cooking meat with high heat creates carcinogenic PAHs and heterocyclic amines (HCAs). These substances may increase the risk of cancer by altering the DNA of your cells.


You’re more likely to overcook foods when you cook with high temperatures or over an open flame. This includes cooking methods like:

grilling

barbecuing

pan-frying

The Food and Drug AdministrationTrusted Source also states that overcooking starchy foods, like potatoes, increases acrylamide formation.


To reduce your risk of carcinogens from high-heat cooking, try using healthier cooking methods such as:

poaching

pressure cooking

baking or roasting at lower temperatures

slow cooking in a crock pot or slow cooker


4. Dairy

There’s some evidence that dairy may increase the risk of prostate cancer. Dairy foods include products like:

milk

cheese

yogurt

According to a 2014 reviewTrusted Source, eating dairy increases levels of an insulin-like growth factor 1 (IGF-1). This is associated with a higher risk of prostate cancer. IGF-1 may increase the proliferation, or production, of prostate cancer cells.


5. Sugar and refined carbohydrates

Sugary foods and refined carbs can indirectly increase your risk for cancer. Some examples of these foods include:

sugar-sweetened beverages

baked goods

white pasta

white bread

white rice

sugary cereals

Eating a high concentration of sugary, starchy foods may put you at an increased risk of developing type 2 diabetes and obesity. According to a 2020 studyTrusted Source, both conditions promote inflammation and oxidative stress. This may increase your risk for certain types of cancer.


According to a 2019 reviewTrusted Source, type 2 diabetes increases the risk for ovarian, breast, and endometrial (uterine) cancer.


A high intake of sugar and refined carbohydrates may also lead to high blood glucose levels, which according to a 2017 studyTrusted Source, may be a risk factor for colorectal cancer.


To limit the health effects of refined carbohydrates, try to swap these foods with healthier alternatives such as:

whole grain bread

whole grain pasta

brown rice

oats


6. Alcohol

When you consume alcohol, your liver breaks down alcohol into acetaldehyde, a carcinogenic compound. According to a 2017, acetaldehyde promotes DNA damage and oxidative stress. It also interferes with your immune function, making it difficult for your body to target precancerous and cancerous cells. In women, alcohol increases levels of estrogen in the body, according to a 2015 Trusted Source. This is linked with a higher risk for estrogen receptor-positive breast cancer.


Can some foods lower your risk of cancer?

According to scientific research, some foods contain beneficial compounds that may help reduce the risk of cancer. This includes foods like:

Fruits and vegetables. According to a 2017 reviewTrusted Source, fruits and vegetables are rich in antioxidants. These compounds can help protect your cells from oxidative stress and DNA damage.

Nuts. A 2015 studyTrusted Source found that nuts may help reduce inflammation and cancer risk.

Beans. Beans are rich in fiber. According to a 2015 studyTrusted Source, fiber may reduce the risk of colorectal cancer.

Whole grains. Whole grains are associated with a lower risk of cancer, according to a 2020 reviewTrusted Source. Whole grains, like quinoa and brown rice, are rich in fiber and antioxidants.

Fish. Fish offers healthy fats called omega-3 fatty acids. Omega-3 fats may lower the risk of some cancers by reducing inflammation, according to a 2014 studyTrusted Source.


The bottom line

Processed meat, overcooked foods, and fried foods may increase your risk of some types of cancer. That’s because these foods may contain carcinogens, or compounds that cause cancer. Alcohol produces carcinogens when it’s metabolized by your body. Dairy, sugar, and refined carbs may also raise the risk of some types of cancer.


Lung cancer

Lung cancer (pulmonary carcinoma) is the most common cancer in the world, both in terms of cases (1.6 million cases; 12.7% of total cancer cases) and deaths (1.4 million deaths; 18.2% of total cancer deaths).[36] Lung cancer is largely caused by tobacco smoke. Risk estimates for lung cancer in the United States indicate that tobacco smoke is responsible for 90% of lung cancers. Other factors are implicated in lung cancer, and these factors can interact synergistically with smoking so that total attributable risk adds up to more than 100%. These factors include occupational exposure to carcinogens (about 9-15%), radon (10%) and outdoor air pollution (1-2%).[37] Tobacco smoke is a complex mixture of more than 5,300 identified chemicals. The most important carcinogens in tobacco smoke have been determined by a “Margin of Exposure” approach.[38] Using this approach, the most important tumorigenic compounds in tobacco smoke were, in order of importance, acrolein, formaldehyde, acrylonitrile, 1,3-butadiene, cadmium, acetaldehyde, ethylene oxide, and isoprene. Most of these compounds cause DNA damage by forming DNA adducts or by inducing other alterations in DNA.[citation needed] DNA damages are subject to error-prone DNA repair or can cause replication errors. Such errors in repair or replication can result in mutations in tumor suppressor genes or oncogenes leading to cancer.


Breast cancer

Breast cancer is the second most common cancer [(1.4 million cases, 10.9%), but ranks 5th as cause of death (458,000, 6.1%)].[36] Increased risk of breast cancer is associated with persistently elevated blood levels of estrogen.[39] Estrogen appears to contribute to breast carcinogenesis by three processes; (1) the metabolism of estrogen to genotoxic, mutagenic carcinogens, (2) the stimulation of tissue growth, and (3) the repression of phase II detoxification enzymes that metabolize ROS leading to increased oxidative DNA damage.[40][41][42] The major estrogen in humans, estradiol, can be metabolized to quinone derivatives that form adducts with DNA.[43] These derivatives can cause dupurination, the removal of bases from the phosphodiester backbone of DNA, followed by inaccurate repair or replication of the apurinic site leading to mutation and eventually cancer. This genotoxic mechanism may interact in synergy with estrogen receptor-mediated, persistent cell proliferation to ultimately cause breast cancer.[43] Genetic background, dietary practices and environmental factors also likely contribute to the incidence of DNA damage and breast cancer risk.


Colon cancer

Colorectal cancer is the third most common cancer [1.2 million cases (9.4%), 608,000 deaths (8.0%)].[36] Tobacco smoke may be responsible for up to 20% of colorectal cancers in the United States.[44] In addition, substantial evidence implicates bile acids as an important factor in colon cancer. Twelve studies (summarized in Bernstein et al.[45]) indicate that the bile acids deoxycholic acid (DCA) or lithocholic acid (LCA) induce production of DNA-damaging reactive oxygen species or reactive nitrogen species in human or animal colon cells. Furthermore, 14 studies showed that DCA and LCA induce DNA damage in colon cells. Also 27 studies reported that bile acids cause programmed cell death (apoptosis). Increased apoptosis can result in selective survival of cells that are resistant to induction of apoptosis.[45] Colon cells with reduced ability to undergo apoptosis in response to DNA damage would tend to accumulate mutations, and such cells may give rise to colon cancer.[45] Epidemiologic studies have found that fecal bile acid concentrations are increased in populations with a high incidence of colon cancer. Dietary increases in total fat or saturated fat result in elevated DCA and LCA in feces and elevated exposure of the colon epithelium to these bile acids. When the bile acid DCA was added to the standard diet of wild-type mice invasive colon cancer was induced in 56% of the mice after 8 to 10 months.[46] Overall, the available evidence indicates that DCA and LCA are centrally important DNA-damaging carcinogens in colon cancer.


Stomach cancer

Stomach cancer is the fourth most common cancer [990,000 cases (7.8%), 738,000 deaths (9.7%)].[36] Helicobacter pylori infection is the main causative factor in stomach cancer. Chronic gastritis (inflammation) caused by H. pylori is often long-standing if not treated. Infection of gastric epithelial cells with H. pylori results in increased production of reactive oxygen species (ROS).[47][48] ROS cause oxidative DNA damage including the major base alteration 8-hydroxydeoxyguanosine (8-OHdG). 8-OHdG resulting from ROS is increased in chronic gastritis. The altered DNA base can cause errors during DNA replication that have mutagenic and carcinogenic potential. Thus H. pylori-induced ROS appear to be the major carcinogens in stomach cancer because they cause oxidative DNA damage leading to carcinogenic mutations. Diet is thought to be a contributing factor in stomach cancer - in Japan where very salty pickled foods are popular, the incidence of stomach cancer is high. Preserved meat such as bacon, sausages, and ham increases the risk while a diet high in fresh fruit and vegetables may reduce the risk. The risk also increases with age.


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