Cancer and Diet: What is the connection?

Last Updated on September 27, 2023 by Shabnam Sengupta

Cancer is one of the leading cause of death in every country of the world in a few years. Although dietary factors are thought to be important in determining the risk of developing cancer, establishing the exact effects of diet on cancer risk has proved challenging.

It has been estimated that 30-40% of all kinds of cancer can be prevented with a healthy lifestyle and dietary measures. Low use of fibres, the intake of red meat and an imbalance of Omega-3 and Omega-6 fats may contribute to increasing the risk of cancer. On the other hand, the consumption of lots of fruits and vegetables may lower the risk of cancer.

Renowned nutrition and wellness consultant, Sheela Krishnaswamy, involves senior Oncologist Dr Manish Singhal and Clinical Nutritionist Shivshankar T. in an exciting discussion about Cancer and Diet.

Dr Manish Singhal is a distinguished oncologist in India and is currently head and senior consultant of the medical oncology department at Apollo hospital, New Delhi. His expertise lies in all modalities of chemotherapy, immunotherapy, and the management of oncological emergencies along with patient medical care.

Shivashankar T. is the Chief Clinical Nutritionist and Dietician at Tata Memorial Cancer Hospital, Mumbai. He is an expert in onco-nutrition and critical care nutrition. He is the vice president of the Indian Association of Parenteral and Enteral Nutrition (IAPEN) and Chief Programme Officer Onco-nutrition, Core Group.


Does cancer have a genetic predisposition? If yes, then to what extent?

Dr Manish Singhal: Yes, cancers do have a genetic predisposition. Our understanding of genetics has increased over a period of time, and so has our ability to do such tests which can tell if a cancer is genetic. The most common cancers which are genetic are breast cancer, ovarian cancer, colon cancer and prostate cancer. Genetic cancers may account for about 15 per cent of the cases of these cancers on the higher side, whereas the lower side is around four to five per cent. Whenever a patient is diagnosed with cancer at a very early age or those who have a strong family history, we suspect genetic cancers in such cases, and we screen these patients for genetic mutations. And then we complete the family tree by doing more testing among the family members to see if there is genetics involved.

The treatment is mostly the same for cancers or tumours which are genetic. However, nowadays, we have therapies which we can direct against specific genes causing cancer. In these cases, we can improve the results by giving certain drugs. So, that is one reason why there is an interest in looking for genetic mutations. There can be therapeutic advantage also, which we can render out to patients who test positive for genetic mutations.

Do gene sequencing tests help in preventing cancer in the family?

Dr Manish Singhal: Yes. In cases in which we are able to detect the mutation in a patient who is already suffering, they receive treatment for the cancer, and sometimes we can use those targeted therapies against the genes.

Once we complete the family tree and we find more mutations in other members of the family, we are able to counsel them for risk reduction surgeries. For example, if there is a female who does not have cancer and tests positive for a mutation which predisposes her to breast or ovarian cancer, then she can undergo mastectomies for both the breasts. She can then opt for the reconstruction of the breasts at an appropriate age later. They can also undergo surgical removal of overies after their reproductive age or after they have completed their family. The importance is a risk reduction surgery. The identification of genetic mutations in the members of a family also plays a significant role in screening and early detection of cancer. We cannot remove a colon, i.e., large intestine if a patient has colon cancer. But we can certainly conduct regular screenings by doing a yearly colonoscopy and detect cancers at an early age or early stage, which can be highly curable. So, the importance of this understanding is quite instrumental in giving them options for reduction surgeries and also screening more stringent screening for early detection of cancer. 

Vegetarian vs. Non-vegetarian. Is there a link to cancer prevention or cancer cure?

Shivshankar T: There are a lot of studies available that very strongly favour the vegetarian diet, specifically for gastrointestinal and colorectal cancers.

The Western diet predominantly consists of red meat consumption and processed meat consumption energy. We observed that there are comparatively more cases of gastrointestinal and colorectal cancers among people who consume a lot of red meats and processed meats. We do not have any such research for white meat as of now.

However, we need more research to ensure whether we should completely avoid processed meat. Also, we have to understand here that the meat processing procedure in our country is different from that of Western countries. 

People these days opt vegan diet and cut off white meat completely, which is a rich source of protein. In India, we consume very little protein and a lot of carbohydrates in our diet. Therefore, asking people to avoid even white meat is not favourable for people here.

So, it is better to keep a check on the quantity of white meat and be careful of its processing. It is better that you get lean meat and prefer white meat. Also, a lot of places that serve meat use certain non-permitted ingredients not permitted. For example, the preservatives, colouring agents, etc. These ingredients and the meat processing procedure that these places may use can lead to gastrointestinal and colorectal cancers. Therefore, it is important to be aware and careful.

Nevertheless, there is no need to be obsessed with vegetarian or vegan diets because of this. You can eat meat in moderation. However, you should prefer white meat over red meat. The best diet which a lot of researchers propose as an ‘anti-cancer diet’ is the Mediterranean diet. In this diet, there is less red meat and good amounts of white meat.

To what extent, does diet play a role in the prevention or treatment of cancer?

Dr Manish Singhal: There’s an old saying that ‘You are what you eat’. Diet definitely has a tremendous role in the occurrence as well as predisposition to cancer. Simply put, red meat predisposes you to cancer. It has a much greater carbon footprint. The body struggles to digest as those who eat meat would tell you that they have to drink a lot of water after they eat it, as it takes a lot of time for the body to digest it, and so does egg protein. It has to do less with whether your diet is vegetarian or non-vegetarian. You should consume a balanced diet. You should keep an eye on high-calorie diets, which have high glycemic index and tend to make you obese because such diets can make you obese.

Those diets which can increase your blood sugar rapidly are definitely a risk factor. Obese people have a high chance of fatty liver disease. And those people who have fatty liver have a higher risk of developing liver cancer. Obese people have different microbes in their gut as compared to people who are not. And these microbes may predispose them to cancer. A lot of research is going on to study gut microbiomes that can increase the chances of cancer in a person.

You have to understand that when you eat something which is high on the glycemic index, like a sugary diet, cream etc., your sugar level rises immediately. This results in increased insulin production by the body, and insulin-like growth factors are responsible for creating tumours. This is an area of ardent research, and researchers are trying to develop targeted therapies against insulin-like growth factors. However, I am not suggesting that one should never consume such diets, but everything should be in balance. A balanced diet is important. Foods meant to be for occasional consumption, like Coke, should not become a part of your regular diet. These days you see children consuming fried foods, and fast food on a daily basis, which is not correct.

What is a healthy meal plan during and after treatment?

Mr Shivshankar T: In cancer patients, when the food intake gets compromised, it impacts the gut health too. It is not easy to revive the health of the gut, and it takes time. The process can take even months, and it may not be completely successful. It is important to add both prebiotics and probiotics to your diet. One has to understand that once your gut health is compromised, no matter how good your diet is, your body will not be able to use all the nutrients. Your gut health will determine the outcome of the nutrition that you are consuming.

How often do you see a bad diet leading to cancer?

Dr Manish Singhal: When we get a patient, we do not look into the diet history of the patient as the damage is already done. However, if you look at the demographics, the regions where people consume more spices have a higher incidence rate of stomach cancer. Obesity is definitely a major risk factor for cancer. Anything that tends to make you obese or increase your BMR (Basal Metabolic Rate) can play a role in causing liver cancers, cirrhosis, pancreatic cancers, uterine cancers, and even breast cancers. People should develop good food habits right from childhood to avoid cancers in the later stages of life.

There is a culture of using different kinds of spices in Indian cuisine. Do you allow your patients to use such spices in their diet?

Mr Shivshankar T: Yes, I allow and encourage my patients to include spices. The thing that we have to understand here is the way they should use these spices. Our kitchen spices, like turmeric, peppers, etc. have anti-cancer properties but we use it in the wrong way. These can harm you if your diet is deficient in fibres. And all these phytonutrients work in harmony. So, if you use only one kind of phytonutrient, then it is not going to benefit you in a wholesome way. There are more than 500 types of phytonutrients and you can easily and cheaply find them in your kitchen itself. We need to understand how to correctly use these so that it benefits our health. For example, I ask my patients to take half of the onion-garlic paste that they were going to use for the curry and sauté it in whichever way they like, and then put the rest just before consumption. In doing so, there will definitely be some flavour there that they may not like, but it is important to do so. This is because the way we sauté this paste actually ensures that the phytonutrients in it get completely destroyed.

What would be your general diet recommendation for cancer patients?

Mr Shivshankar T: Although the diet that we prescribe is based on several factors including the type of cancer they have and the type of treatment they are receiving. In general, the diet should consist of good protein. It should not contain simple carbohydrates and inflammatory proteins. However, the diet advice needs to be altered for every patient according to the requirements of their body.

Can alkaline water prevent cancer?

Dr Manish Singhal: This entire fiasco started with the book called ‘The pH Miracle’. It was based on cell line work, and they showed that when you grow cancer cell lines, the cancer cells grow less in alkaline media. This led to an American author writing this book, in which he promoted that alkaline food and water can treat cancer. This is how this concept came into being. This author was later sued in an American court who then had to serve three years in jail and pay compensation. This is because one of the patients who started an alkaline diet and stopped their oncological treatment suffered and died. The family of the deceased then took legal action against the author.

You have to understand here that our pH is tightly regulated between 7.35 and 7.45 by the kidney. No matter how much alkaline water you drink or the diet you consume, you cannot change the pH value of the blood. There is no way that the alkaline water or food is going to reach the cancerous cells in the body. It is unfortunate that a lot of celebrities are promoting this theory. It is a myth.

What is your take on sugar intake by cancer patients?

Mr Shivshankar T: Firstly, sugar does not have any secondary nutrients. Secondly, it has only harmful carbohydrates. Thirdly, it is an inflammatory nutrient. I do not recommend sugar to cancer patients as cancer is an inflammatory disease, and therefore, such nutrients will be harmful to the patients. Currently, Omega-3 fatty acids are proving to be effective because they lower inflammation. So, if we include Omega-3 fatty acids in a cancer patient’s diet to decrease inflammation, letting them include sugar in their diet would be detrimental to the process. However, by restriction of sugar intake, I mean restricting the intake in excessive amounts. You can consume about 5-10 grams of sugar per day. But consuming sugar more than that will impact your treatment and recovery from cancer. Giving a free hand to the patient to consume as much sugar as they want is wrong. This is because it will limit their protein intake. A high recurrence rate has been observed in patients who consume food with a high glycemic index as compared to those who don’t. 

Nevertheless, there are some patients, where I give patients some liberty with food. These include palliative patients, very aged patients, and/or anorexic patients.

What would be your take-home message for the viewers Dr Singhal?

Dr Manish Singhal: My message to everyone is simply that everything in moderation is fine. You should not do things in excess. There is a saying in Hindi, “Ati ka bhala na bolna ati ki bhali na choop, ati ka bhala na barasna ati ki bhali na dhoop”. Moderation is the way of life and should be your mantra.

Q: What would be your message to the viewers Mr Shivshankar?

Shivshankar T: I would suggest that cancer patients follow the Mediterranean diet. It has been proven and is accepted worldwide.

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