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Role of Dietary Factors in Cancer

9Dec 2022

Role of Dietary Factors in Cancer

Many studies have looked at the role of dietary factors in increasing or reducing the risk of cancer. Most studies have shown that dietary factors are only associated with a change in cancer risk, but not completely responsible for it. To prove association of a dietary factor and cancer is challenging as there are numerous dietary constituents and numerous cancers. Many dietary factors may not act in isolation and it may be their interaction with other dietary, lifestyle and/or genetic factors. 

Dietary Factors and Cancer Risk

Dietary factors have been thought to contribute to about 30% of cancers in Western countries, making diet second only to tobacco as a preventable cause of cancer. The contribution of diet to cancer risk in developing countries has been considered to be lower, perhaps around 20%.

What is the role of calories in causing cancer?

The most important impact of diet on the risk of cancer is mediated through body weight. Overweight, obesity, and inactivity are major contributors to cancer risk (visceral obesity). Obesity causes increased estrogen synthesis, insulin resistance. And altered adipokine and cytokine production. These factors cause increased angiogenesis, cell proliferation and survival, predisposing to various types of cancer.
Cancers most commonly caused are colorectal cancer, breast cancer, uterine cancer, pancreatic cancer, and gallbladder cancer.

How does alcohol increase the risk of cancer?

Besides body weight, alcohol consumption is the best established dietary risk factor for cancer. If alcohol is consumed, it should be done in moderaton. Moderate alcohol consumption refers to 2 drinks per day in men and 1 drink per day in women. Heavy alcohol consumption is 5 or more drinks any day or 15 or more drinks in a week for men, and 4 or more drinks any day or 8 or more drinks in a week for women. The risk of alcohol associated cancers increase with the duration and amount of alcohol intake. 

Cancers predisposed with alcohol intake are breast, liver, esophagus, pharynx, oral cavity, larynx, and rectum.

What is the role of dietary fat in causing cancer?

Dietary fat and breast cancer – High dietary fat gets converted to heterocyclic aromatic hydrocarbons that can cause cancer of breast. Also, increased obesity may lead to excessive production of estrogen that is carcinogenic for breast tissue. On the other hand, there is an inverse association between monounsaturated fat (eg. Olive oil) and breast cancer.

Dietary fat and colon cancer - High dietary fat causes increased excretion of bile acids which causes ROS mediated DNA damage. Also, heterocyclic aromatic hydrocarbons produced from fat, heme iron in meat and anabolic hormones used for meat production may promote carcinogenesis.

Dietary fat and prostate cancer - Animal fat strongly associated with the incidence of aggressive prostate cancer, and may cause the transition from indolent form to the more lethal form of this malignancy.

To summarize, High intake of animal fat early in adult life may increase the risk of premenopausal breast cancer, increased risk of colorectal cancer. And prostate cancer, particularly the aggressive forms. 

Is a diet deficient in fruits and vegetables risk factor for cancer?

Although fruits and vegetables supply less than 5% of total energy intake, the concentration of micronutrients in these foods is greater than in most others. They are rich in Antioxidants, Minerals, Fiber, Potassium, Carotenoids, Vitamin C, Folate and other vitamins. 

Consumption of fruits and vegetables appears to be less important in cancer prevention than previously assumed. With fortification of breakfast cereal, flour, and other staple foods, the frequent consumption of fruits and vegetables has become less essential for cancer prevention. Though, a high consumption of fruits and vegetables during childhood and adolescence could be more effective in reducing cancer risk than consumption in adult life due to the long latency of cancer manifestation. 

What is the protective role of carotenoids and lycopene?

Carotenoids are antioxidants prevalent in fruits and vegetables. They enhance cell-to-cell communication, promote cell differentiation, and modulate immune response. But studies have not revealed evidence of a protective effect of beta-carotene.

Lycopene is a carotenoid mainly found in tomatoes and has antioxidant properties. Frequent consumption of tomato-based products may be associated with a decreased risk of prostate, lung, and stomach cancers.

How effective are soy products and nuts in cancer prevention?

Soybeans contain isoflavones, phytoestrogens that compete with estrogen for the estrogen receptor. In Asian countries, which have a high consumption of soy foods, breast cancer rates have been low. Soy consumption may affect estrogen concentrations differently depending on the endogenous baseline level. Studies have shown that there is a modest decrease in the risk of breast cancer with soy consumption, with childhood consumption being more effective. In a recent meta-analysis of 18 epidemiologic studies, including over 9,000 breast cancer cases, frequent soy intake was associated with a modest decrease in risk (odds ratio = 0.86; 95% CI, 0.75 to 0.99). Wu et al. observed that childhood intake of soy was more relevant to breast cancer prevention than adult consumption.
Nuts are rich in unsaturated fatty acids, high-quality protein, Fiber, vitamins (e.g., folate, niacin, and vitamin E), minerals (e.g., potassium, calcium, and magnesium), and phytochemicals (e.g., carotenoids, flavonoids, and phytosterols). 

They have anticarcinogenic, antiinflammatory, and antioxidant properties. Studies have shown their consumption to reduce the mortality with breast and pancreatic cancer. In two large, independent cohorts of nurses and other health professionals, the frequency of nut consumption was inversely associated with total and cause-specific mortality, independently of other predictors of death for breast cancer and pancreatic cancer.

What is the role of dietary fiber?

Dietary fiber contains plant polysaccharides and lignin which are resistant to hydrolysis by the digestive enzymes. They have the following effects-

  • “Bulking” effect, which reduces colonic transit time
  • Binding of potentially carcinogenic luminal chemicals
  • Fiber may also aid in producing short-chain fatty acids that may be directly anticarcinogenic
  • Fiber may induce apoptosis.

Role of Vitamin D

Activation of vitamin D receptors by 1,25(OH)2D induces cell differentiation and inhibits proliferation and angiogenesis. Studies have shown that Vitamin D levels may particularly affect colorectal cancer prognosis and may reduce mortality. High intake and high plasma levels of vitamin D have been associated with a decreased risk of several other cancers, including cancer of the breast, prostate, pancreas, and lymphoma.

Other Factors

In cancers of the oral cavity, pharynx and esophagus, dietary factors that may be protective are fruits and vegetables, micronutrients like riboflavin, folate, vitamin C and zinc. Consuming drinks and beverages at high temperature may be causative. 

Nasopharyngeal cancer particularly common in Southeast Asia is associated with a high intake of Chinese style salted fish, especially during early childhood. Chinese-style salted fish is a special product which is usually softened by partial decomposition before or during salting. 
Ingestion of foods contaminated with the mycotoxin aflatoxin is an important risk factor for Hepatocellular carcinoma. 

For More Information And Personalised Guidance, Connect With Oncoexperts  For All Cancer Related Needs:- +91 9686813020
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Sunny Garg
Dr. Sunny Garg

Best Oncologist in Gurgaon & Cancer Specialist - Oncoexperts

Dr Sunny Garg is a renowned Medical Oncologist in New Delhi with an experience of more than 10 years of treating cancer patients.

He has studied in one of the most reputed educational institutes of India. He has done his MBBS and MD Internal Medicine from Institute of Medical Sciences, Banaras Hindu University. Thereafter, he has undergone training in Medical Oncology (DM Medical Oncology) from Kidwai Memorial Institute of Oncology, Bengaluru. He has worked in leading cancer centers in Delhi, and currently practicing at Manipal Hospital, Dwarka, New Delhi.

Dr Sunny Garg has extensive knowledge and experience in the field of oncology, and has treated all cancer types, in various stages, including hard to treat cases. He is well versed with various modalities for cancer treatment like Chemotherapy, Immunotherapy, Targeted Therapy, Hormonal Therapy and Personalised Cancer Therapy.