The links between diet and cancer are widely researched. The World Cancer Research Fund UK (WCRF UK) estimate that lifestyle factors such as being overweight, eating an unhealthy diet and being inactive are responsible for about a third of all cancers in developed countries (1). The WCRF UK are a charity committed to cancer prevention.
A recently published study (2) has found a significant link between eating a diet high in carotenoid rich fruits and vegetables and a reduction in the risk of breast cancer in premenopausal women.
Carotenoids such as alpha and beta carotene, lutein and zeaxanthin are a family of over 700 naturally occurring yellow, red, orange and dark green pigments found in vegetables and fruits. Good sources include carrots, sweet potatoes, tomatoes, squash, peppers, cantaloupe melons, nectarines, papaya, mango and dark green vegetables such as spinach, kale, watercress and asparagus. Introducing a good mix of these fruits and vegetables on a regular basis in the diet will help keep carotenoid levels in the body high.
The study (2) involved 5,707 women with invasive breast cancer (2,363 premenopausal women and 3,516 postmenopausal women) and 6,389 individuals with no breast cancer, control subjects (2,594 premenopausal women and 3,516 postmenopausal women). In an interview, these women were asked about their intake of carotenoid rich fruits and vegetables. The researchers found that pre-menopausal women eating high intakes of vitamin A, beta-carotene, alpha-carotene, lutein and zeaxanthin appeared to have a reduced risk of breast cancer. Eating at least two servings of carotenoid-rich vegetables each day was associated with around a 17% reduced risk of breast cancer. As an association study the results are positive but further studies would be necessary before any firm conclusions could be drawn about the effect of dietary carotenoids on cancer risk.
Carotenoids may be acting to prevent cancer via different means. Carotenoids have been shown to interfere with oestrogen (hormone) signalling which may explain why their cancer-preventing effects would be limited to premenopausal women. In addition to this, carotenoids act as antioxidants in the body and antioxidants have been linked to cancer prevention. Antioxidants prevent damage to the body cells by naturally occurring unstable oxygen molecules, known as free radicals. Antioxidants may help to ‘quench’ or mop-up the destructive free radical molecules and therefore protect against cell-damage (which could lead to cancer formation).
Absorption of carotenoids from foods into the body is greatly affected by fat. Without a fat source carotenoids are not easily absorbed. Fat acts as a carrier for these nutrients to allow them passage from the gut into our blood and bodily cells. This is not a suggestion to drown your vegetables or salads in gallons of oil, however, I am a firm believer in using small amounts of olive oil in dressings and cooking. Including some nuts, seeds or olives in salads may also be helpful in order to gain maximum absorption of these important nutrients.
(1)WCRF/AICR. 2009. Policy and action for cancer prevention. Food, nutrition and physical activity: a global perspective. Washington DC: AICR, 2009.
(2) Mignone LI et al. 2009. Dietary carotenoids and the risk of invasive breast cancer. International Journal of Cancer. 124:2929-2937
Written by Ani Kowal
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