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Chemistry LibreTexts

17.8: Problems with our Food

  • Page ID
    153910
  • Learning Objectives

    • Identify food substances and cooking processes known to cause cancer.
    • Know common food contaminants and their sources.

     

    Food Substances That May Promote Cancer

    Several foods increase the risk of cancer. Alcohol is one example and increases the risk of mouth cancer, pharynx (throat), larynx (voice box), esophagus, liver, breast, colon, and rectum. People who drink should limit their alcohol intake to no more than 2 drinks per day for men and one drink per day for women. A drink is defined as 12 ounces of beer, 5 ounces of wine, or 1 1/2 ounces of 80-proof distilled spirits (hard liquor). Recent studies suggest there is no safe level of alcohol intake for women who are at high risk of developing breast cancer.

    Scientific studies have shown that people who eat more fruit and vegetable have a lower risk of developing cancer certain cancers. Those individuals that eat less fruit and vegetables may increase their risk of developing cancer. Fruit and vegetables are rich in antioxidants but several studies of antioxidant supplements have not found a lower cancer risk, so the other compounds in fruits and vegetables may confer this protective effect.

    Epidemiological studies have linked a high fat intake with higher rates of breast, prostate, colon, and other cancers. Randomized studies have not found that fat intake increases tumor development or lowers cancer risk either. So, at this time, the evidence is unclear and total amount of fat consumed does not appear to be linked to cancer risk.

    Consumption of large amounts of processed meats has been associated with an increased risk of colorectal and stomach cancer. The exact mechanism is not known but nitrites, used to maintain color and bacterial growth in lunch meats, hams, and hot dogs, may play a role.

    Frying, broiling, or grilling meats, cooking processes that use high heat, form chemicals that may increase cancer risk. These chemicals are polycyclic aromatic hydrocarbons or heterocyclic aromatic amines.

    Eating a lot of foods preserved by salting and/or pickling increase one's risk of stomach, nasopharyngeal, and throat cancer. There is very little evidence that the level of salt used in cooking or flavoring foods or added during ng affect cancer risk.

     

    Figure \(\PageIndex{1}\) Chickenpork and bacon-wrapped corn cooking in a barbecue smoker. Barbecuing and smoking generate carcinogens.

     

    Aflatoxins are poisonous carcinogens that are produced by certain molds (Aspergillus flavus and Aspergillus parasiticus) which grow in soil, decaying vegetation, hay, and grains. They are regularly found in improperly stored staple commodities such as cassavachili pepperscorncottonseedmilletpeanutsricesesame seedssorghumsunflower seedstree nutswheat, and a variety of spices. When contaminated food is processed, aflatoxins enter the general food supply where they have been found in both pet and human foods, as well as in feedstocks for agricultural animals. Animals fed contaminated food can pass aflatoxin transformation products into eggs, milk products, and meat.

     

    Figure \(\PageIndex{2}\) Aflatoxin B1. Source: Wikipedia

    Food As an Anti-Carcinogens

    Dietary fiber and calorie restriction are two anti-carcinogen or anti-promoters that decrease the risk of tumor formation. Dietary fiber is both and is inversely associated with cancer, particularly colon cancer. So the more fiber you eat, the less risk you have of developing colon cancer. One mechanism by which fiber acts is hastening bile acid excretion. Fiber also increases the rate of passage of materials through the colon resulting in decreased production and exposure of the colon to cancer-causing agents, ie dilutes the concentration of carcinogens.

    Animal studies have shown that restricting caloric intake by 30% reduces tumor growth and increases life span. The mechanism is not known but may be due to less oxidation thus damage to DNA.

    Antioxidants can help block the action of initiators or promoters if their mode of action is to damage DNA by oxidation. Vitamin A, C, E, beta-carotene, and selenium are antioxidant nutrients. Some work locally, like vitamin E in the colon, while other work more globally like selenium and vitamin C. Vitamin A appears to work by keeping cells differentiated which slows the growth rate.

    Other compounds in food, particularly fruits and vegetables, have been shown to slow tumor formation. Cruciferous vegetables (eg broccoli, cauliflower, cabbage, and Brussel sprouts to name a few) are rich in nutrients, fiber, glucosinolates which are sulfur-containing chemicals, indoles, and isothiocyanates. Animal studies have found these substances inhibit the development of cancer in several organs in rats and mice (Hecht SS. Inhibition of carcinogenesis by isothiocyanates. Drug Metabolism Reviews 2000;32(3-4):395-411; Murillo G, Mehta RG. Cruciferous vegetables and cancer prevention. Nutrition and Cancer 2001;41(1-2):17-28). Indoles and isothiocyanates help protect cells from DNA damage; help inactivate carcinogens; have antiviral and antibacterial effects; have anti-inflammatory effects; induce cell death (apoptosis); and inhibit tumor blood vessel formation (angiogenesis) and tumor cell migration (needed for metastasis) (National Cancer Institute, Cruciferous Vegetables and Cancer Prevention, 2012, https://www.cancer.gov/about-cancer/...les-fact-sheet). Studies in humans, however, have shown mixed results.

    Dietary Recommendation for Decreasing Cancer Risk

    The American Institute for Cancer Research, American Cancer Society, and National Cancer Institute provide dietary recommendations to reduce cancer risk. These guidelines are remarkably similar and focus on eating more fruits and vegetables, whole grains, and legumes; reducing processed meat and red meat intake; and limit your intake of alcohol. Fruits, vegetables, and whole grains are rich in fiber. Refined grains, such as white rice, are low or devoid of fiber. All types of fibers should be emphasized. Fruits and vegetables contain antioxidants, phytochemicals, and fiber.

    These ten recommendations for cancer prevention are drawn from the WCRF/AICR Second Expert Report. Each recommendation links to more details.

    1. Be as lean as possible without becoming underweight.
    2. Be physically active for at least 30 minutes every day. Limit sedentary habits.
    3. Avoid sugary drinks. Limit consumption of energy-dense foods.
    4. Eat more of a variety of vegetables, fruits, whole grains and legumes such as beans.
    5. Limit consumption of red meats (such as beef, pork, and lamb) and avoid processed meats.
    6. If consumed at all, limit alcoholic drinks to 2 for men and 1 for women a day.
    7. Limit consumption of salty foods and foods processed with salt (sodium).
    8. Don't use supplements to protect against cancer.
    9. * It is best for mothers to breastfeed exclusively for up to 6 months and then add other liquids and foods.
    10. * After treatment, cancer survivors should follow the recommendations for cancer prevention.

     

    Food Contamination 

    Food contamination refers to the presence of harmful chemicals and microorganisms in food, which can cause consumer illness.

    The impact of chemical contaminants on consumer health and well-being is often apparent only after many years of processing and prolonged exposure at low levels (e.g., cancer). Unlike food-borne pathogens, chemical contaminants present in foods are often unaffected by thermal processing. Two major categories of chemical contaminants according to the source of contamination and the mechanism by which they enter the food product are agrochemicals and environmental contaminants.

    Agrochemicals are chemicals used in agricultural practices and animal husbandry with the intent to increase crop yields. Such agents include pesticides (e.g., insecticidesherbicidesrodenticides), plant growth regulators, veterinary drugs (e.g., nitrofuranfluoroquinolonesmalachite greenchloramphenicol), and bovine somatotropin (rBST).

    Environmental contaminants are chemicals that are present in the environment in which the food is grown, harvested, transported, stored, packaged, processed, and consumed. The physical contact of the food with its environment results in its contamination. Possible sources of contamination and contaminants common to that vector include:

    Foodborne illness (also foodborne disease and colloquially referred to as food poisoning)[1] is any illness resulting from the spoilage of contaminated foodpathogenic bacteriaviruses, or parasites that contaminate food,[2] as well as prions (the agents of "mad cow disease"), and toxins such as aflatoxins in peanuts, poisonous mushrooms, and various species of beans that have not been boiled for at least 10 minutes.

    Symptoms vary depending on the cause. A few broad generalizations can be made. For contaminants requiring an incubation period, symptoms may not manifest for hours to days, depending on the cause and on quantity of consumption. Longer incubation periods tend to cause sufferers to not associate the symptoms with the item consumed, so they may misattribute the symptoms to gastroenteritis, for example.

    Symptoms often include vomiting, fever, and aches, and may include diarrhea. Bouts of vomiting can be repeated with an extended delay in between, because even if infected food was eliminated from the stomach in the first bout, microbes, like bacteria (if applicable), can pass through the stomach into the intestine and begin to multiply. Some types of microbes stay in the intestine.

    In the United States, using FoodNet data from 2000 to 2007, the CDC estimated there were 47.8 million foodborne illnesses per year (16,000 cases for 100,000 inhabitants)[68] with 9.4 million of these caused by 31 known identified pathogens.[69]

    • 127,839 were hospitalized (43 per 100,000 inhabitants per year).[70][71][72]
    • 3,037 people died (1.0 per 100,000 inhabitants per year).[71][72]
    Causes of foodborne illness in US[69]
      Cause Annual cases Rate
    (per 100,000 inhabitants)
    1 Norovirus 5,461,731 cases X
    2 Salmonella 1,027,561 cases X
    3 Clostridium perfringens 965,958 cases X
    4 Campylobacter 845,024 cases X

     

    Causes of death by foodborne illness in US[69]
      Cause Annual deaths Rate
    (per 100,000 inhabitants)
    1 Salmonella 378 cases 0.126
    2 Toxoplasma gondii 327 cases 0.109
    3 Listeria 255 cases 0.085
    4 Norovirus 149 cases 0.050

     

     

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    Web Link

    Center for Disease Control and Prevention : List of Foodborne Diseases.

    https://www.cdc.gov/foodsafety/diseases/index.html

    Summary

    • Substances inherent in foods or substances produced during cooking processes that use high heat (e.g. frying, broiling, or grilling meats)  may increase cancer risk.
    • Two major categories of chemical contaminants according to the source of contamination and the mechanism by which they enter the food product are agrochemicals and environmental contaminants.
    • The top four germs that cause illnesses from food eaten in the United States are NorovirusSalmonella,  Clostridium perfringens, and Campylobacter.
    • Many different disease-causing germs can contaminate foods, so there are many different foodborne infections. 

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