There are two ways that fruit and vegetables are thought to help protect against cancer:
- Directly through specific anti-carcinogenic (anti-cancer) agents
- Indirectly by helping to mantain a healthy body weight
Fruit and vegetables are rich in fibre, vitamins, minerals, antioxidants and phytochemicals, whose actions in the body help to protect against cancer. It is most likely that the combination of these nutrients found in whole foods help to reduce the risk of certain cancers rather than one anti-cancer component. Fruit and vegetables can also protect against cancer indirectly by helping to maintain a healthy body weight. Fruit and vegetables are rich in nutrients and low in kilojoules and are therefore great food choices for individuals trying to maintain or lose weight. People who eat lots of fruit and vegetables are less likely to be overweight or obese.
Excess fat around the stomach and obesity are well documented risk factors for some cancers of the bowel, breast, oesophagus, kidney and endometrium. Reducing weight by even 5-10% for overweight/obese individuals greatly decreases the chances of developing cancer.
Are all fruit and veg protective?
Yes! However, there is no one “super” fruit or vegetable that protects against cancer. They all contain varying amounts of fibre, vitamins, minerals, antioxidants and phytochemicals, therefore it is important to eat a variety. Fruit choices should include citrus fruits, berries and coloured fruit particularly red, orange and yellow. Vegetable choices should include cruciferous varieties (e.g. broccoli, cabbage, Asian greens) allium varieties (e.g. onions, leeks), dark-green leafy vegetables and red, yellow, & orange varieties.
Eating a variety of both cooked and raw vegetables is encouraged as there are some cancer-fighting agents which are better absorbed from cooked fruit or vegetables. Good methods of cooking include steaming, stir frying, grilling and roasting. These use as little water as possible preventing nutrients and vitamins leaching out into the water.
What happens if I have already been diagnosed with cancer?
Eating fruit and vegetables is not a cure for cancer. For people already diagnosed with cancer, there is some evidence that a diet high in fruit and vegetables is of no significant benefit, but it is very unlikely to be harmful. This is still an active area of research, however we do know that eating well and being active can help you feel better, have more energy and help reduce the risk of cancer returning.
What about fruit juice?
The cancer protective nutrients are preserved in fresh fruit and vegetable juices and some may be more available in juices than whole fruits and vegetables. However fibre is removed in most vegetable and fruit juices and also in dietary supplements. As fibre is thought to be protective against colon cancer, fruit and vegetables are best consumed whole, rather than juiced or as nutrients, in a supplement form.