Colorful Evidence Linking Fruits, Vegetables, and Lower Breast Cancer Risk

2012-12-11 11:30
fruits and vegetables, cancer risk, breast cancer

The American Cancer Society recommends eating at least five servings of fruits and vegetables each day to reduce the risk of many types of cancer. While all plant foods have plenty of health benefits, those that are more colorful have additional nutrients known to decrease the risk of disease. New research finds that a diet rich in fruits and vegetables containing carotenoids can lower the risk of breast cancer in women.

Carotenoids are plant pigments that give fruits and vegetables a deep red, yellow or orange color. The nutrient group contains compounds such as alpha- and beta-carotene, lycopene, lutein, and zeaxanthin. Fruits and vegetables rich in carotenoids include carrots, sweet potatoes, tomatoes, and winter squash. Dark leafy greens such as spinach and kale are also good sources; however, the chlorophyll in the leaves hides the yellow-orange pigment.

Researchers with Brigham & Women’s Hospital and Harvard Medical School have found that women whose blood carried higher levels of carotenoids were at a lower risk of developing breast cancer. The link is strongest for ER-negative breast cancers, which tend to be more aggressive, have fewer prevention and treatment options, and have a poorer prognosis.

For this study, lead author A. Heather Eliassen and colleagues analyzed data collected from 8 cohort studies including a total of 7,000 women. These studies covered 80% of the currently published data on the correlation between carotenoids and breast cancer. The researchers also re-analyzed the blood samples collected in order to standardize the carotenoid levels reported.

Women whose blood carotenoid levels that were in the top 20% of the measured ranges had a 15 to 20% lower risk of breast cancer compared with those in the lowest category. “It looks like it is a linear relationship,” says Eliassen. ”The higher you go, the [lower] your risk is. There is some benefit at a moderate level of carotenoids and there is even more benefit at a higher level.”

Carotenoids are believed to protect by metabolizing into retinol, which regulates cell growth and gene expression and may slow tumor growth. The nutrients may also improve cell communication and enhance the immune system function, thereby increasing the body’s ability to suppress abnormally growing cells.

However, Eliassen warns against taking dietary supplements in place of increasing fruit and vegetable intake. “We are not at a point to recommend supplements,” she says. “We know from other studies that certain supplements can increase the risk of lung cancer among smokers. We are not going to go in that direction clearly, but increasing fruit and vegetable intake clearly can provide lots of health benefits and may also reduce the risk of breast cancer.”

The American Cancer Society offers the following tips to increase fruit and vegetable intake to reach the minimum of 2 ½ cups per day (five servings at one-half cup each):
• At each meal, fill at least half your plate with fruits and vegetables
• Have a piece of fruit or crunchy vegetable as a snack
• Enjoy ½ cup (4 ounces) of 100% fruit or vegetable juice once or twice a day. Mix with club soda or unsweetened seltzer water if you like fizz
• Layer lettuce, tomatoes, beans, onions, and other vegetables on sandwiches and wraps
• Add tomato sauce and extra vegetables to pastas and vegetable soups
• Check out the vegetarian sandwiches when you visit restaurants for lunch
• With your carotenoid-rich meal, it is suggested to include a fat source, as these nutrients are fat-soluble and therefore absorption is improved with the addition of, say, a little oil and vinegar on your sandwich or a canola-oil based dressing on your salad.

Try new vegetables from the produce aisle, frozen foods section, or farmer’s market, especially focusing on the following high-carotenoid choices:
• The orange-colored fruits and vegetables include carrots, apricots, mangoes, squash, papaya, and sweet potatoes. These contain significant amounts of beta-carotene, alpha-carotene, and beta-cryptoxanthin.
• Green vegetables, especially spinach, kale, and collard greens, also contain beta-carotene, and are the best sources of lutein.
• Lycopene is found in tomatoes, guava, and pink grapefruit.
• (Note: Salmon, shellfish, milk, and egg yolks also provide carotenoids.)

Journal References
A. Heather Eliassen et al. Circulating Carotenoids and Risk of Breast Cancer: Pooled Analysis of Eight Prospective Studies. JNCI J Natl Cancer Inst (2012)doi: 10.1093/jnci/djs461First published online: December 6, 2012
Shellen R. Goltz et al. Meal triacylglycerol profile modulates postprandial absorption of carotenoids in humans. Molecular Nutrition & Food Research Volume 56, Issue 6, pages 866–877, June 2012

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