Cancer and diet: Experts decode how food works as supportive therapy

Can diet prevent cancer ?

Researchers have been able to link certain food patterns with a lower risk of developing cancers. For example, consumption of excess calories can lead to obesity, thereby increasing the risk of several cancers such as those of the breast, bowel and liver. A low-fat diet has been linked to a lower risk of breast cancer while a diet high in processed and red meats has been linked to a higher risk of colon cancer. A Harvard study last year also linked a low-carbohydrate diet to 24 per cent reduction in all-cause mortality in diabetics, including deaths due to cancers.

“Diet has a very important role when it comes to cancer prevention because nearly 90 per cent of cancers have environmental causes and only 10 per cent are truly genetic. The environmental factors include diabetes, hypertension, consumption of tobacco and alcohol, air pollution and chemicals, among others,” says Dr Shailesh Shrikhande, head of digestive cancer surgery, Tata Memorial Hospital. Specialising in the treatment of colorectal cancer, where diet is of utmost importance, he says, “A diet with more meat is linked to a higher risk of colorectal cancers, which is three times more likely in the West than in India. High-protein diets, with less fibre, are known to cause constipation, which in turn is linked to an increased risk of colon cancer. The longer these foods stay in the intestines, the more carcinogens are likely to be released, thereby increasing the risk of cancers.” Dr Shrikhande doesn’t ask people to refrain from eating meat but balance it with other food groups.

The American Cancer Society guidelines — followed by many experts in India — recommend including four to five portions of fruits and vegetables in the diet as they are high in fibre, low in calories and contain many vitamins and minerals. Research is ongoing to study cancer-preventive properties of certain groups of vegetables — the dark green and orange vegetables, cruciferous vegetables such as cabbage, broccoli or cauliflower, and allium vegetables like onions and garlic.

The guidelines also suggest consuming more proteins from legumes, poultry or fish rather than red meat sources. The norms suggest limiting or eliminating sugar-sweetened beverages, highly processed foods and refined grain products.

Food as supportive Cancer Therapy

When it comes to cancer treatment, nutrition not only changes the patient’s quality of life but also influences therapy outcomes and prognosis. “Nutrition is crucial for those with oesophageal or gastrointestinal tract cancers who are unable to eat properly. Patients with late stage cancers may develop metabolic syndromes like cachexia (a condition where patients lose weight and muscles because of a faster metabolism) that can derail their treatment,” says Dr Abhishek Shankar, oncologist at the All-India Institute of Medical Sciences (AIIMS), New Delhi. “If a patient loses, for example, 5 kg while undergoing treatment, their chemotherapy dose would have to be changed or they might develop toxicity. For radiotherapy, weight loss could lead to gaps in the thermoplastic meshes that we make to immobilise patients and target the radiation. This could lead to ineffective radiation and more reactions. It is also not possible to do cancer surgeries if the patient weighs less than a recommended level. All of this can delay treatment and change the outcome,” he explains.

Researchers have been able to link certain food patterns with a lower risk of developing cancers.

Therefore, intermittent fasting and restricting dairy and carbohydrates that Sidhu spoke of may not work when a patient is undergoing active cancer treatment. While there are laboratory and animal studies that show some beneficial pathways that may prevent cancer growth through time-restricted eating, maintaining such a diet is practically not possible for a patient. “Cancer and its treatment lead to a breakdown of muscles and other cells in the body. So we have to ensure that patients consume enough calories and proteins to repair them. When a person is unable to consume a normal diet, fasting for several hours a day would mean they are not meeting their daily requirements and could become weaker and anorexic. Patients have to take a lot of medicines through the day, which they cannot have without eating first,” says Ritika Samaddar, regional head of clinical nutrition and dietetics at Max Healthcare.

She designs the diet based on what the patients need and what they can eat, including dairy products, eggs, or lentils and millets to fulfil their protein requirement. For example, those on chemotherapy need to eat small portions slowly and every few hours. They need to avoid fatty, greasy or spicy foods. One advice she has for cancer patients is that they must go to a nutritionist at a tertiary care centre, preferably the same one where they are getting treated. “Treatment has to be a team approach because there are certain foods and supplements that interact with the medicines and have negative effects,” she says.

Dr Eileen Canday, head of nutrition and dietetics at Mumbai’s Sir H N Reliance Foundation Hospital and Research Centre, says there is some evidence suggesting that certain foods can improve treatment outcomes for cancer patients, although the research is still ongoing and the findings are not definitive to revise current protocols. “Curcumin (the active ingredient in turmeric) may inhibit growth of cancer cells and reduce inflammation. Cruciferous vegetables like broccoli and cauliflower may lower the risk of cancer as they contain antioxidants, vitamins and phytochemicals like flavonoids and carotenoids. Omega-3 fatty acids in some fishes and flaxseed have anti-inflammatory properties and may improve immune function. Fermented foods like yogurt and kefir may help mitigate some side effects of cancer treatment,” she says.

Life After Cancer

The role of diet and nutrition remains important even after remission of cancer to keep relapse at bay. “Obesity is a known risk factor for some cancers such as breast cancer. So after treatment, we would put the patient on a negative calorie diet with less saturated fats. In other patients with, say colon or oesophageal cancers, where they lose a lot of weight during the treatment, the focus would be on a calorie-dense diet to help them regain the weight and muscles,” says Samaddar.

Current research is also focussing on using diet — and thereby the body’s own metabolism — as medicine for cancer treatment. What this essentially means is that researchers are looking into diets that either lack or have certain additional substances that work in synergy with newer therapies to improve treatment outcomes. This would make nutrition a key pillar of therapy, but not the magic bullet.