According to a new study led by researchers from Harvard Teaching Hospital – Chan School of Public Health, women who eat a high amount of fruits and vegetables each day may have a lower risk of breast cancer, especially of aggressive tumors, than those who eat fewer fruits and vegetables. In their findings, cruciferous vegetables such as broccoli, and yellow and orange vegetables, had a particularly significant association with lower breast cancer risk.
Although prior studies have suggested an association, they have been limited in power, particularly for specific fruits and vegetables and aggressive subtypes of breast cancer,” said first author Maryam Farvid, research scientist in the Department of Nutrition. “This research provides the most complete picture of the importance of consuming high amounts of fruit and vegetables for breast cancer prevention.”
The researchers analyzed diet questionnaires submitted every four years by participants in the Nurses’ Health Study (88,301 women, starting in 1980) and the Nurses’ Health Study II (93,844 women, starting in 1991). Data on other potential breast cancer risk factors such as age, weight, smoking status, and family cancer history were taken from biennial questionnaires.
They found that women who ate more than 5.5 servings of fruits and vegetables each day had an 11% lower risk of breast cancer than those who ate 2.5 or fewer servings. (A serving is defined as one cup of raw leafy vegetables, half a cup of raw or cooked vegetables, or half a cup of chopped or cooked fruits.)
To find out whether the benefits of fruit and vegetable consumption differed among various types of breast cancers, the researchers conducted an analysis by tumor hormone receptor status and molecular subtype.They found that higher consumption of fruits and vegetables was particularly associated with lower risk of more aggressive tumors including ER-negative, HER2-enriched, and basal-like tumors.
Previous work by this research group linked reduced breast cancer risk with higher fiber intake, but the benefits of fruits and vegetables found in this study appear to be independent of their fiber content, according to the researchers. This suggests that other constituents of these foods, such as antioxidants and other micronutrients, may also be important in reducing breast cancer risk.
“While a diet with lots of fruits and vegetables is associated with many other health benefits, our results may provide further impetus for women to increase their intake of fruits and vegetables”, the researchers said.
How fruits and vegetables help protect against cancer
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 maintain a healthy body weight.
Fruit and vegetables are rich in fibre, vitamins, minerals, antioxidants and phytochemicals, which help to protect your body against cancer. It is most likely the combination of these nutrients found in whole foods that help to reduce the risk of certain cancers rather than one anti-cancer component.
Fruit and vegetables also protect against cancer indirectly by helping to maintain a healthy body weight. They are rich in nutrients and low in kilojoules and are therefore great food choices if you’re 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 stomach, bowel, breast (post-menopausal), oesophagus, liver, kidney, gallbladder, pancreas, endometrium, ovary and prostate (advanced).
Are all fruit and vegetables 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. Try and ‘eat a rainbow’ – eat as many different coloured fruit and vegetables as possible, it will help keep your diet interesting and give your body the best protection.
Eating a combination of both cooked and raw vegetables is best, 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. While there is some evidence that a diet high in fruit and vegetables is of no significant benefit if you already have cancer, 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.