By: Bahar Gholipour, LiveScience Staff Writer
Published: 06/27/2013 06:31 PM EDT on LiveScience
A large review of studies concludes that women who consume more omega-3 fatty acids by eating fish were at a lower risk of having breast cancer.
The researchers in China analyzed the results of 26 international studies involving almost 900,000 women, including 20,000 who had breast cancer. The scientists found that those women who had the consumed the highest levels of omega-3 fatty acids from fish were 14 percent less likely to have breast cancer, compared with those who ate the least.
The results also showed what researchers call a dose-response relationship: each 0.1-gram increase in omega-3 per day was linked with a 5 percent lower risk of having breast cancer. For comparison, a serving of an oily fish such as salmon contains about 4 grams of omega-3 fatty acids. Oily fish are those that have high concentrations of omega-3.
Consuming the type of omega-3 found in plants, however, did not appear to reduce the risk.
Omega-3 fatty acids, a type of polyunsaturated fat, have been touted for years for their potential benefits in preventing heart disease and cancer. But not all studies have been able to confirm these claims.
Researchers who conducted a large review of 48 studiesin 2009 concluded that it was not clear whether consuming omega-3 fats, in either the diet or by taking supplements, changed a person's risk of heart problems or cancer. However, those reviewers also said that there wasn't enough evidence to recommend that people should stop eating foods that are rich sources of omega-3.
Other studies have suggested that it's not just the amount of omega-3 that one consumes that matters --the ratio of omega-3s to other fatty acids in foods is important, too. In a 2002 review study, researchers found that women who consumed a balanced ratio of omega-3s to omega-6s (an unhealthy type of fat) were less likely to develop breast cancer.
In the new analysis, researchers looked at studies that measured omega-3 intake in two different ways; either by measuring omega-3 levels with blood tests, or by assessing how much fish people ate.
When looking only at studies that assessed fish diet, the researchers found there was not a significant relationship between eating fish and reduced risk of breast cancer. However, in Asian populations, fish intake did tend to be linked to a lower breast cancer risk, compared with Western populations.
The researchers said perhaps fish intake in Western populations is too low to detect a protective effect against breast cancer.
Other factors may have influenced the findings, too, including differences between sources of omega-3, the researchers said. It is not clear whether eating fish and taking omega-3 supplements have equal benefits.
It is possible too, that other compounds found in fish, such as pesticides and heavy metals from environmental pollution, may reduce the protective effects of omega-3, they said.
The study is published today (June 27) in the British Medical Journal.
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Broccoli And Broccoli Sprouts
Cruciferous vegetables, but broccoli in particular, make for anti-cancer powerhouses thanks in part to a compound called sulforaphane that actually helps the body fight the spread of tumors. Recent research revealed the underlying reason: sulforaphane may inhibit an enzyme, called an HDAC, that <a href="http://www.huffingtonpost.com/2012/02/29/broccoli-cancer-sulforaphane_n_1310634.html">works to suppress the body's tumor fighting ability</a>, as we've previously reported. And sprouts are even more potent: three-day old broccoli sprouts have 20 to 50 times the sulforaphanes as mature broccoli, <a href="http://www.hopkinsmedicine.org/press/1997/sept/970903.htm">according to Johns Hopkins research</a>. For more about the cancer fighting properties of <em>all cruciferous vegetables, check HuffPost blogger Dr. Joel Fuhrman's <a href="http://www.huffingtonpost.com/joel-fuhrman-md/cancer-prevention_b_1624965.html">analysis of cabbage, brussels sprouts, bok choy and more</a>.
Garlic is considered a cancer-fighting food for several forms of the disease, <a href="http://www.cancer.gov/cancertopics/factsheet/prevention/garlic-and-cancer-prevention#r12">according to the National Cancer Institute</a>. One French study found that women who regularly ate garlic had <a href="http://www.ncbi.nlm.nih.gov/pubmed/9928867">a significantly reduced risk of breast cancer</a>. Garlic's mild cousin, onions also had a protective effect, according to the study.
Pomegranates are known for their anti-cancer properties, thanks to a richness in anti-inflammatory antioxidants, polyphenols. But they may offer a specific benefit against breast cancer: research shows that a phytochemical found in abundance in pomegranates, called ellagitannins, interfere in the production of aromatase, an enzyme that, as HuffPost blogger Dr. Nalini Chilkov explained, "<a href="http://www.huffingtonpost.com/nalini-chilkov/pomegranates-cancer-fighting-_b_1078343.html">increases hormone production in breast tissue</a>." That's important because breast cancer is hormone-dependent, meaning that it feeds off of hormones like estrogen to grow and spread. "Hormone dependent cancers such as breast cancer are commonly treated with aromatase inhibitors, which block this enzyme," wrote Chilkov.
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Berries have several powerful antioxidants, primarily anthocyanins and ellagic acid, which have been shown in cell culture studies to <a href="http://www.aicr.org/foods-that-fight-cancer/blueberries.html#research">reduce free radical damage to healthy cells</a>, according to the American Institute for Cancer Research. In separate research, they were shown to slow the growth and shorten the lifespan of breast cancer (as well as mouth, colon and prostate cancer) cells.
Green tea is rich in the polyphenol EGCG (epigallocatechin-3-gallate), which has been shown to slow the spread of breast cancer cells, <a href="http://www.breastcancer.org/tips/nutrition/supplements/known/green_tea">according to breastcancer.org</a>.
Tomatoes are rich in the antioxidant lycopene, which is thought to <a href="http://www.msnbc.msn.com/id/39726407/ns/health-cancer/t/what-you-should-eat-avoid-beat-breast-cancer/#.UHNMJvmMG5M">slow breast cancer cell growth</a>.