According to a new study, a diet plentiful in vegetables, fruit and legumes help protect women from breast cancer.
The 26 year study of more than 86,000 U.S. women found that women with diets high in plant foods - but low in red meat, sodium and refined carbohydrates - tended to have a lower risk of developing certain breast tumours.
Specifically, they were less likely than other women to develop breast tumours that lack receptors for the hormone estrogen. Such estrogen receptor (ER)-negative tumours account for about one-quarter of breast cancers.
The risk of ER-negative breast cancer was lower among women whose diets most closely resembled the Dietary Approaches to Stop Hypertension (DASH) diet -- an eating plan recommended for lowering blood pressure. It emphasizes vegetables, fruit, whole grains, legumes and nuts and low-fat dairy.
The women who, at the outset, had the highest DASH "score" were 20 percent less likely to develop ER-negative breast cancer than those with the lowest DASH scores.
When the researchers took a closer look, it seemed to be high vegetable and fruit intake that mainly accounted for the protective effect.
Recent research has been suggesting that the risk of ER-negative breast tumours, in particular, may be related to diet. Why that might be is unclear.
Researchers speculate that with ER-positive breast tumours - whose growth is fuelled by estrogen - the hormone's influence may be so important that it overwhelms any potential protective effects of diet.
The study also showed that women with diets high in vegetable protein (e.g. beans, soy, nuts) but low in refined carbs (e.g. white bread, white rice) had a 19 percent lower risk of ER-negative cancer, versus women with the opposite diet pattern.
The link between plant-rich diets and lower breast cancer risk still held when the researchers accounted for factors like weight, exercise habits and smoking.
When it comes to breast cancer prevention, exactly how much any one woman might benefit from eating more vegetables remains unclear.
The DASH diet recommends that the average woman should get 4 to 5 servings of vegetables and 4 to 5 servings of fruit each day. It also recommends 4 to 5 servings of legumes, nuts and seeds each week.
The study was published last month in the American Journal of Epidemiology.
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