Diet has a significant impact on human health, and many medical conditions can be prevented by modifying diet, or in other words, many foods and drinks can lead to certain medical conditions. The foods and drinks we consume daily constitute our diet and may increase or decrease the risk of developing disorders like heart problems, diabetes, hypertension, obesity, cancer, etc. Cancer is one of the leading causes of death worldwide. Dietary factors have a significant impact on increasing or decreasing the risk of cancers. It is seen that diet and obesity are factors related to 30 to 35 percent of cancer deaths. A review published in 2011 suggested that cancer incidence and progression is influenced by total caloric intake. The current scientific evidence supports linking dietary factors with the cancer of the mouth, pharynx, larynx, esophagus, breast, liver, stomach, colorectal, and ovaries.
Dietary factors account for approximately 30 percent of cancers in developed countries, while cancer risk in relation to diet is lower (20 percent) in developing countries. Diet is also considered second to tobacco as a potentially preventable cause of cancer. Epidemiological studies carried out as early as 1960 also showed a strong correlation between certain cancer types and dietary factors. For example, regions with higher intakes of meat have a higher incidence of colorectal cancer. Experiments were done on animals also showed that cancer rates could be altered by diet, supporting the strong relation of the diet with cancer incidence.
How Can Diet Increase the Risk of Cancer?
Cancer is started by a process termed carcinogenesis that is triggered by carcinogens. A carcinogen can be any factor that induces mutations or DNA damage at the cellular level. These factors can also be called genotoxic as they induce toxic alterations in the human genome. All carcinogens are genotoxic and specific for a specific cancer type. These carcinogens or genotoxic factors can be direct-acting, procarcinogen, or can induce DNA changes during replication. All these have different mechanisms for promoting carcinogenesis in humans. Direct-acting factors act directly with the DNA. Procarcinogens require activation through metabolic processes that ultimately lead them to act like direct-acting carcinogens. Diet-related carcinogens promoting cancer in humans include,
● Carcinogens present in tobacco and alcohol cause cancer of the mouth, esophagus, pharynx, and larynx.
● Hepatitis viral infection can cause hepatocellular carcinoma.
● Polycyclic hydrocarbons cause cancer of the lungs.
● Aromatic amines and smoking can cause bladder cancer.
Diet and Carcinogenesis
Few examples of diet-related carcinogens are mentioned above, but our diet contains various mutagenic and carcinogenic substances. These can be present naturally in food ingredients or can result from other sources that are environmental pollution, pesticide residues, food additives, processing and preparation procedures, or contamination. Most herbal teas contain tannins that are naturally occurring carcinogens. Edible mushrooms contain hydrazines, spices, and flavorings, have safrole and natural alkenyl benzene. Naturally occurring flavonoids are present in many edible plants and fruits that are mutagenic. Stored food can be contaminated by a fungus that produces a potent carcinogenic mycotoxin called aflatoxin. Another significant carcinogen in the human diet is Nitrosamine that is present naturally in meats, plants, and dairy. Nitrosamines are also present in the preservatives used for salted fish and smoked fish. The studies have shown an association between nitrite and nitrate consumption with increased esophageal and stomach cancer incidence. Alcohol consumption is also largely linked to oral, pharyngeal, esophageal, and stomach cancer. A high protein diet is linked with an increased incidence of breast, pancreas, colon, and prostate cancer.
Factors Affecting Carcinogenesis
Carcinogenesis is not a single-step process. It is a multistage process and occurs over a period of time. It also depends on a number of variable factors that include the frequency, duration, and dose of the carcinogen or mutagen. The locally prevailing dietary traditions in different regions of the world account for the occurrence of specific cancer types. In the Orient region, smoked, salted, or pickled food is linked to a higher incidence of stomach cancer. In the West, low fiber and high-fat food are associated with the pancreas, breast, colon, ovary, endometrium, and prostate cancer.
Eating Too Much of Certain Foods Increases the Incidence of Cancer
It is difficult to prove any single food to be cancer-causing, but there are many observational studies that consuming certain foods and drinks may increase the risk of developing cancer.
Sugar is not directly linked to cancer but eating too much sugar causes obesity, which is the leading cause of cancer. The Centre for Disease Control and Prevention reports that at least 13 types of cancers have obesity as a causative factor. Researchers have found that a diet that increases blood glucose levels is linked to an increased risk of cancers, including breast, stomach, and colorectal. Insulin stimulates cell growth, supporting the growth and spread of cancer cells, making them difficult to eliminate. According to the American Heart Association, these are the most common sources of added sugars in American’s diet:
● Soft drinks.
● Cookies, pies, and cakes.
● Milk and dairy desserts (ice cream, sweetened milk, or sweetened yogurt).
● Fruit drinks.
A particular food item’s labels also tell about the ingredients, which are the forms of added sugars, for example, honey, barley malt, high fructose corn syrup, dextrose, maltose, rice syrup, coconut sugar, cane sugar, and caramel. For protection against cancer, foods or drinks high in sugars must be avoided.
2. Processed Meat
Meat that has been processed to preserve flavor by undergoing procedures like salting, smoking, or curing. Processed meat largely includes hot dogs, bacon, ham, salami, chorizo, and deli meats. The International Agency for Research on Cancer (IARC) considered processed meat as a group 1 carcinogen. The other group 1 carcinogens include tobacco, alcohol, and UV radiation. It is believed that carcinogenic properties are due to the cooking of meat at high temperatures. Cooking at a high temperature, the amino acids present in meat interact with the heat to form polycyclic aromatic hydrocarbons and heterocyclic amines, both are carcinogenic compounds. Processed meat also increases cancer risk by the preservatives used for preserving them. The use of preservatives containing nitrites and nitrates is also known to increase the risks of developing cancer. For instance, 30 studies carried out on colorectal cancer, the third most diagnosed type of cancer in men, concluded that the risk of colorectal cancer is increased by 20 percent by only consuming 50 grams of processed meat daily. Some studies also suggested that cancer risk is also increased by consuming large amounts of red meat. Keeping this in view, consumption of processed and red meat must be in moderation with one serving per week or less than that.
3. Hot Drinks and Overcooked Food
Cooking foods at higher temperatures by grilling, barbecuing, sauteing, frying, or broiling can produce heterocyclic amines and advanced glycation end products (AGEs). These compounds are harmful and known to induce inflammation in the body. The inflammatory response, in turn, if not controlled, may have a role in the development of cancer. Animal-based and processed foods containing higher amounts of fats and proteins are most likely to produce carcinogenic compounds when cooked at higher temperatures. These include red meat, fried eggs, cheese, cream cheese, margarine, butter, oil, and nuts. To minimize the risk of cancer development, it is recommended to use gentler cooking methods for such foods as steaming, boiling, or stewing.
Similarly, hot beverages are also linked to increasing the risk of esophageal cancer. A study published in the International Journal of Cancer showed that people who drink hot beverages (tea or coffee) at a temperature of 140°F (60°C) have a 90 percent more chance of developing esophageal cancer.
Studies have shown that alcohol consumption is linked to the increased risk of certain types of cancer, including mouth, pharynx, esophagus, liver, breast, liver, and colorectal. A study recently done has shown a strong correlation of colorectal cancer with excessive beer drinking. An increase in the incidence of breast cancer has also been reported in women who are moderate drinkers as compared to nondrinkers. This risk is especially higher in women drinking before 30 years of age. The International Agency for Research on Cancer considers categorizing alcoholic beverages as carcinogens based on the analysis from various epidemiological and observational studies. The believed mechanism behind alcohol carcinogenicity is that it induces cellular DNA damage. In addition, alcohol is a type of sugar and is considered the fifth-largest contributor to higher caloric intake in U.S adults. This higher caloric intake can contribute to obesity that also increases the risk of certain types of cancer. The guidelines for cancer prevention from the American Cancer Society recommend limiting alcohol intake to not consuming more than two drinks per day for men and not more than one drink per day for women.
Several research studies have shown that increased consumption of dairy products increases the risk of prostate cancer. A study conducted on 4000 males suffering from prostate cancer showed an increased risk of disease progression and death with a higher intake of whole milk. A review of 23 studies published in the American Journal of Clinical Nutrition also linked excessive amounts of dairy to prostate cancer. The theories suggest the possible link of increased intake of calcium, estrogen, or insulin-like growth factor (IGF-1) from pregnant cows, all of which are linked to prostate cancer. In 2014 researchers studied the impact of dairy on 22,000 lactose intolerant individuals. The results showed that lactose-intolerant people have a lower risk of developing breast, lung, and ovarian cancers.
A study carried out in 2018 in Hong Kong revealed the presence of two carcinogens in margarine, glycidol, and 3-MCPD that arise from the heating of vegetable oil at high temperatures. These two compounds are known to alter the DNA genome (genotoxic) and cause liver problems. However, these carcinogenic compounds are present in small quantities. The European Food Safety Authority stated that consuming approximately 24 spoons of margarine to have carcinogenic effects. Consuming margarine in moderation is highly recommended.
7. Foods With High Glycemic Index
The Glycemic index is a measure of how fast consumed carbohydrates turn into sugar in the blood. And as sugar is one of the risk factors for certain types of cancer, consuming high amounts of foods that have a high glycemic index will ultimately increase the risk of having cancer. A study conducted involving 3100 people in 2016 and presented at the Experimental Biology forum found an 88% greater risk of prostate cancer by consuming foods with a high glycemic index. Items with a high glycemic index include sugar fruit juices, sweetened drinks, and processed foods. Another study published in 2015 showed a link between a diet with a high glycemic index and an increased risk of lung cancer. The study concluded that there is an almost 50 percent increased risk of cancer in individuals consuming diets with a high glycemic index as compared to those consuming lower glycemic index diets.
Diet can be a preventive factor in preventing cancer development. The environment, pollutants, and food processing are common factors making the commonly used food items carcinogens. It doesn’t mean to cut off these food items from your diet completely but to consume them in moderation. The food items of daily usage contain ingredients that can act as carcinogens, so it is essential to look for the ingredients on the label before consuming them. The American Institute of Cancer Research recommends increasing intake of a plant-based diet as compared to an animal-based diet. Restricting an animal-based diet will provide some protection against cancer. Similarly, limiting the intake of packaged and processed foods will also lower the risk of certain types of cancer. Apart from dietary factors, lifestyle changes are also protective factors. Further studies are still required in this field of food, causing or increasing the risk of cancer to know the presence of carcinogens and their risk of causing cancer. Modifying diet can prevent or stop the progression of cancer.