Cancer and diet – a balanced approach
People living with a cancer diagnosis often ask if there are special diets or cancer-fighting foods that can help them, or particular foods they should avoid. With more than a third of us expected to develop cancer during our lifetimes, everyone can benefit from making healthful choices of diet and lifestyle, to prevent cancers. In this article we’ll look at aspects of diet and nutrition that are relevant for people affected by a cancer diagnosis, or at particular risk of developing cancer. We’ll also look at how diet choices can be helpful for people at different stages of their cancer journey. You may also find our articles on Foods that Fight Cancer and Carcinogens helpful, as they discuss some of these themes in more detail.
- After a cancer diagnosis, overall diet quality and choosing particular foods can be very helpful for supporting health and resilience. These choices can also contribute to other aspects of your health and wellbeing
- Dietary needs may change for cancer patients at different stages of their cancer journey, and particularly for patients during some types of cancer treatment
- Studies have identified foods that can help prevent cancer, and foods that may increase cancer risks
- For people living with and beyond cancer, better quality diet is associated with longer survival according to studies.
- Some foods with particular cancer-fighting properties have been identified
- Individual needs may differ, but overall, a higher intake of plant foods is beneficial, providing an array of vitamins and minerals, and particularly phytonutrients, botanical compounds in certain foods are especially valuable as they have anti-cancer properties.
- Reducing or avoiding red and processed meat is advisable as there are compounds in these foods that may trigger cancers to start
- Very recent research suggests that eating plenty of fibre helps to support a healthy population of microbes in the digestive system, and this can have a benefit for immunity.
- Healthy unprocessed fats such as olive oil, and oily fish provide essential fats that help healing and may help reduce inflammation.
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How foods may impact on cancer
Eating well can help your body at all stages of the cancer journey from diagnosis, through treatment and recovery, and for people living with and beyond cancer. At Curve we consider food to be a key element in your armory against cancer following diagnosis, whatever your stage. We say this not to replace treatment, but to support you to get the most out of your treatment and to boost your resilience. There’s no single study proving it will help, and there’s no single food that’s a miracle, but there is enough evidence to suggest that some food choices can be of real benefit. This is not just in how patients feel, but also maximizing your health while living with disease, preventing recurrence, or living well in a palliative situation.
Diet at different stages of the cancer journey1-5
Firstly let’s look at why people in different health situations might be looking at diet with regards to cancer. Studies with many thousands of people have identified dietary factors that may impact on cancer risk. Research on individual foods have begun to identify specific dietary components that can have an impact on the cancer process.
People with a precancerous condition, such as Barrett’s esophagitis, may be looking for ways to reduce their risk of progressing to esophageal cancer. Some studies indicate that diet is helpful for cancer prevention in people with pre-cancerous conditions. Foods with anti-cancer properties can help resist progression from a pre-cancerous condition to cancer1-5. Anti-oxidants from foods can help reduce damage in inflammatory pre-cancerous conditions.
Some people with low-grade early stage cancers, for example prostate cancer, may be following a care plan of ‘watchful waiting’ because they may not yet need treatment for a very slow-growing cancer. They can benefit from good dietary choices of cancer-fighting foods that can help reduce risks of progression.
Cancer patients having treatment may have very different needs to someone who has completed their treatment, and it is always advisable to discuss your questions about diet with your healthcare team. We are all individuals, what’s best for one person may not be right for someone else.
For those who have had cancer treatment and are in remission, they may be looking to reduce their chances of their cancer coming back. Again research suggests that some foods have cancer-fighting properties that can prevent or delay cancer recurrence. Finally, more people are living with cancer, receiving treatment or after treatment, and they seek to maximize their health. Dietary choices can improve resilience and increase the body’s ability to fight cancer.
Studies on diet and cancer prevention have provided some persuasive evidence on some of the best ways to avoid cancer, but very few studies have examined how diet may affect people after they have developed cancer. The strongest evidence we have is that collected by the World Cancer Research Fund (WCRF), which along with the American Cancer Society (ACS) advises that people with a diagnosis of cancer should follow the advice for cancer prevention. One of the reasons for this is that prevention guidelines identify dietary elements, such as processed meats, that may trigger cancer growth. Once cancer has developed, it is sensible to take away known triggers, and to increase known protective factors in the diet. So leading world cancer bodies acknowledge that food probably plays a role in treatment and preventing recurrence, at least for many people. Importantly, some very recent results from a study with people after a cancer diagnosis showed that a better quality diet was linked to longer survival6. In the US National Health and Nutrition Examination Survey, a high intake of vegetables and fruits was strongly linked to longer survival in people who had been diagnosed with cancer6.
The need for balance
Unfortunately there is still uncertainty in many areas of diet and nutrition, and the advice can be contradictory even amongst the ‘experts’. There are many reasons why it’s difficult for research to prove how diet may affect people after a cancer diagnosis. Unlike studies of drug treatments which can be carefully controlled, diets are complex. Individual foods can vary between different varieties and even when cooked in different ways. Against this background of uncertainty, some cancer specialists feel unable to give definitive advice on nutrition for people with cancer, and may even dismiss diet as a factor worth considering. However, balanced against this apparent confusion and uncertainty, is the simple fact that we all need to eat. Your food choices can also impact on other disease risks, like heart disease, and can help with energy levels and mood.
Some risky foods to avoid7,8
Protein is an important part of a balanced diet, and cancer patients having surgery, chemo and radiotherapy need protein to heal. However, persuasive evidence points to a significant risk of developing cancer in people eating processed meats, including cured and smoked meats. These foods contains cancer-causing compounds (carcinogens) that are best minimized. There is still a question about unprocessed red meat, such as beef, lamb and pork, but the strongest evidence is of a risk with processed products. Good quality protein from poultry, fish, eggs, and vegetarian protein foods such as beans and nuts, have not been linked to cancer risk.
Plant foods that can help fight cancer7-9
Nutrition studies have looked at cancer rates in people following many different types of diets around the world, with different culinary traditions. One very strong message emerging from those studies is that a high intake of plant foods offers protection against many types of cancers7,8. Foods with particular cancer-fighting properties include brassica (cruciferous) vegetables9,10 such as broccoli, cabbage, arugula and watercress. These contain particularly beneficial anti-cancer compounds called phytonutrients, such as Sulphoraphane. This compound helps the body to eliminate cancer-causing compounds. Other cancer fighting compounds are found in brightly colored vegetables and fruits such as bell peppers, tomatoes, sweet potatoes and blueberries11-13. They contain compounds such as carotenoids and flavonoids which have an array of anti-cancer properties, such as protecting healthy cells against damage. So having a broad array of brightly colored vegetables and fruits will help you to boost your intake of cancer fighting nutrients. Eating mushrooms and enjoying garlic are tasty ways of boosting cancer-fighting nutrients14-16.
There may be some people living with cancer who cannot eat large amounts of vegetable. For example the bulk of vegetables may be too much for the digestive system after surgery or other treatments. For people with conditions affecting kidney function, it is important to discuss with your healthcare team if you need to restrict potassium which is high in most vegetables.
A grain of truth
It seems clear, therefore, that for people affected by cancer, eating an abundance of plant foods is a healthful choice. The benefits seem to go beyond the various vitamins, minerals, anti-oxidants and other phytonutrients that we have looked at so far, that are an important part of an anti-cancer diet. Population-based studies have shown that eating wholegrains such as wholewheat and oatmeal is linked to a lower risk of several cancers. There are several beneficial components in wholegrains, including anti-oxidants and folate, but studies suggest that one very important contribution of wholegrains and other plant foods is the fiber. This is the indigestible component of plant foods that is important for the regular movement of the bowels. As it passes through the gut, fiber helps remove toxins from the bowel, but it is now evident that some fiber is very good at nurturing beneficial microbes in the digestive system. As we shall see, this is an important aspect of diet for people affected by cancer.
We are mostly human
Inside the digestive system is a collection of microbes, several pounds in a typical adult, and these have an important influence on health. So one aspect of cancer diets that will doubtless receive more attention in the near future, is how dietary components can influence this ‘microbiome’ in cancer patients and people at risk of cancer. It is now understood that various species of microbes in the microbiome communicate with the immune system via the blood cells circulating in the walls of the intestine. Studies with cancer patient receiving some new immune therapy cancer drugs seem to suggest that a healthful diet with plenty of fibre may help some cancer patients to respond particularly well to these treatments19. Much more research is needed to understand these mechanisms and how they can be optimized. However, it is a sensible strategy, unless you have medical advice to the contrary, to include fiber-rich foods in your diet. These can be healthful vegetables, fruits, wholegrains, nuts, seeds and mushrooms9.
Fats in a healthful diet
Healthy unprocessed fats such as olive oil, and oily fish provide essential fats that help healing and may help reduce inflammation. Studies have suggested that an increased intake of omega-3 fats from oily fish such as salmon and mackerel is linked to a lower risk of cancers of the breast, prostate and colon20. One group studying colorectal cancer has suggested that omega-3 fats can have a direct anti-cancer action and may be beneficial to support patients during cancer treatment21. Meanwhile, eating oily fish may also have other health benefits.
After a cancer diagnosis, overall diet quality and choosing particular foods can be very helpful for supporting health and resilience. These choices can also contribute to other aspects of your health and wellbeing. Dietary needs may change for cancer patients at different stages of their cancer journey, and particularly for patients during some types of cancer treatment. Studies have identified foods that can help prevent cancer, and foods that may increase cancer risks. For people living with and beyond cancer, better quality diet is associated with longer survival according to studies. Some foods with particular anti-cancer properties have been identified. Overall, a higher intake of plant foods is beneficial, providing an array of vitamins and minerals, and particularly phytonutrients, botanical compounds in certain foods are especially valuable as they have anti-cancer properties. Reducing or avoiding red and processed meat is advisable as there are compounds in these foods that may trigger cancers to start. Very recent research suggests that eating plenty of fibre helps to support a healthy population of microbes in the digestive system, and this can have a benefit for immunity. Healthy unprocessed fats such as olive oil, and oily fish provide essential fats that help healing and may help reduce inflammation. Individual needs may differ, and dietary changes need to be considered for each person’s situation and taking account of other restrictions they may need to follow.