You've heard it over and over: Eat your vegetables and plenty of them. A vegetable-packed diet has been linked to a lower risk of high blood pressure, heart attack, stroke, cataract, macular degeneration and cognitive decline.
Now, a study published online last month in the American Journal of Clinical Nutrition suggests the benefits of eating more vegetables extend to breast-cancer prevention.
The research, part of a larger research project called EPIC (European Prospective Investigation into Cancer and Nutrition), explored the association between vegetable and fruit intake and breast-cancer subtypes, hormone receptor-positive and hormone receptor-negative cancers.
Doctors test breast-cancer cells to see if they have hormone receptors. If breast-cancer cells have hormone receptors, the cancer is said to be hormone receptor-positive. If cancer cells do not have hormone receptors, it is called hormone receptor-negative breast cancer.
For the study, European researchers followed 335,054 healthy women, average age 51, to determine the association between vegetable and fruit intake and breast-cancer risk. Upon entering the study, participants were asked about their usual diet over the previous 12 months.
After 11.5 years of follow-up, 10,197 women developed breast cancer.
Compared to women with the lowest intake of vegetables (one serving per day), those who ate the most (at least 5.5 servings daily) were 13-per-cent less likely to develop overall breast cancer.
The protective effect of vegetables, though, was most apparent for hormone receptor-negative breast cancer. High vegetable consumers had a 26-per-cent reduced risk of this type of cancer compared to women who ate few vegetables. Fruit intake was not associated with breast-cancer risk.
Hormone receptor-negative breast cancers don't respond to hormonal treatment and are typically more aggressive than hormone receptor-positive tumours.
It's thought that phytochemicals in vegetables, many of which differ from those in fruit, may reduce the level of proteins involved in the development of hormone receptor-negative breast cancer. Fibre in vegetables may also play a role.
These new findings are consistent with a large study called the Pooling Project, published in 2013. Among nearly one million women followed for 11 to 20 years in 20 observational studies, high vegetable consumption was tied to a 20- to 25-per-cent lower risk of hormone receptor-negative breast cancer.
Both studies, observational in nature, don't prove that a high vegetable diet guards against breast cancer. Their findings do, however, strongly suggest there's a connection and provide yet another reason to boost your vegetable intake.
Aim to eat at least five vegetable servings each day. One serving is equivalent to one-half cup of cooked or raw vegetables or one cup of salad greens. The key to meeting your daily quota: fitting vegetables into every meal – including breakfast – and snacks.
Seven easy ways (beyond salad) to eat more vegetables
Try the following to eat a minimum of five daily vegetable servings (i.e., at least 2.5 cups of cooked or raw vegetables).
1. Include them in breakfast. Add chopped bell pepper, mushrooms and green onion to scrambled eggs and omelettes. Stir shredded carrot and zucchini into muffin, pancake and waffle batters.
2. Blend them into smoothies. Make a green smoothie by adding raw or cooked spinach or kale. (Compared to raw, cooked greens offer more antioxidants and minerals.)
3. Fortify meals. Add chopped carrot and celery to chili and soups (homemade and store-bought). Top pizza with roasted vegetables or garnish with baby arugula.
4. Jazz them up. Splash raspberry or champagne vinegar over steamed spinach. Sprinkle grated Parmesan cheese over steamed or roasted broccoli and cauliflower.
5. Add spinach to (just about) everything. Throw an entire container of baby spinach into soups, stews, casseroles, chili and pasta sauces. For a change, try chopped kale.
6. Use leafy greens for bread. Wrap lettuce leaves around tuna, salmon and chicken salad for a low-carb sandwich.
7. Replace white carbs with vegetables. Top shepherd's pie with mashed cooked cauliflower instead of potatoes.
Leslie Beck, a registered dietitian, is based at the Medisys clinic in Toronto.