Actor Dipika Kakar, who is currently battling a cancer relapse in her liver, has lost 2 kg over the past month through a strict diet, nutrition and lifestyle discipline. This approach is necessary, say doctors, for the success of the immunotherapy that she is undergoing.“Immunotherapy, which activates the body’s immune system to fight cancer, works dramatically well in some patients and fails in others who seem clinically similar. A growing body of research is pointing to an unexpected answer: nutrition and lifestyle. What a patient eats, their physical activity levels, the state of their gut microbiome, and their overall metabolic health appear to powerfully modulate how the immune system responds,” says Dr Eileen Canday, HOD, Nutrition & Dietetics, Sir HN Reliance Foundation Hospital, Mumbai.“As immunotherapy triggers the body’s immune system to fight cancer cells, this method has different levels of effectiveness, and thus nutrition and weight management become crucial,” says Dr Nitin Bayas, cancer physician at M|O|C Cancer Care and Research Centre, Borivali, Mumbai.How does nutrition boost the body’s immune system to battle cancer?The immune system needs a lot of energy and nutrients to work properly. Processes like activating the disease-fighting T-cells, producing antibodies, and maintaining Natural Killer (NK) cells depend on a steady supply of fuel, proteins and vitamins. When nutrition is poor, the immune system becomes weaker.“The ideal state for supporting the immune system is called anabolic competence. This means the body is building and maintaining itself well — making proteins, preserving muscle mass, keeping organs functioning and supporting a strong immune response. For treatments like immunotherapy to work effectively, the body needs to be in this healthy, well-nourished state,” explains Dr Canday.Cancer, however, disrupts this balance. It creates conditions that make proper nutrition difficult to maintain. Tumours can cause a condition called cachexia, where the body keeps losing muscle even if the person is eating enough. “This condition also leads to inflammation, problems using nutrients properly, changes in how the body handles sugar and higher energy needs at rest. Because of these effects, nutrition in cancer care has to be carefully planned rather than a general or one-size-fits-all,” she adds.Story continues below this adIn India, poor nutrition and late cancer diagnosis make proper nutrition an important part of treatment. “Patients who receive nutrition counselling along with immunotherapy tend to handle the treatment better and respond more effectively. Optimizing factors like protein intake, digestion and body weight is not just an extra step, it is a core part of cancer care,” says Dr Bayas.Why customised nutrition is critical for immunotherapyDr Canday maintains that nutrition isn’t the same for everyone and newer approaches help tailor it to each person’s needs. “Nutrigenomics looks at how our genes affect the way we process nutrients and respond to different diets. This explains why the same diet may work well for one person but not for another. Metabolomics, on the other hand, shows what’s happening in the body in real time. By measuring small molecules (metabolites), it helps us understand how a person’s body is actually responding to food, illness, or treatment at that moment. This means nutrition can be adjusted to better support the immune system, improve treatment tolerance, and potentially enhance how well the therapy works,” she says.What’s the role of gut microbiome in cancer care?Multiple landmark studies have found that patients with a more diverse gut microbiome have had a stronger immune system response in terms of recognising and attacking cancer cells more effectively. Fibre is the key here; it also negates toxicity and side effects.Story continues below this adCancer puts the body under stress and speeds up how quickly it breaks down and rebuilds proteins. At the same time, the body becomes less efficient at using protein. That’s why cancer patients need more protein than healthy people to maintain their strength. Muscle mass is strongly linked to better treatment tolerance, improved quality of life and higher chances of survival.“That’s why patients are generally advised to consume at least 1 gram of protein per kilogram of body weight per day, and ideally up to 1.5 grams. High-quality protein sources such as animal foods, fish, dairy, and plant-based proteins are recommended. This has to be backed up by key micronutrients,” says Dr Canday. She lists the musts like Vitamin D, which regulates T-cell activation, zinc, which is essential for T-cell development and NK cell activity, selenium, which supports antioxidant defence, vitamin C, which maintains oxidative balance, iron, which boosts immune cell proliferation and Omega-3 fatty acids, which reduce inflammation; at least 2 g/day may improve lean mass, appetite and quality of life.What are evidence-based recommendations?“Eat generously. Vegetables, fruits, whole grains, legumes, nuts, generally foods high in fibre and polyphenols, all of which are needed for the gut microbiome,” says Dr Canday. Omega-3 can be taken in 2-3 portions per week while hydration should be adequate. Dr Canday says an absolute no to ultra-processed foods, refined sugars and high-glycaemic diets. “Maintain a healthy weight: obesity is an independent risk factor for cancer recurrence and worse, survival,” she says.