Breast cancer: in laboratory animals, marine-derived omega-3s are more effective than plant-derived omega-3s in fighting the disease
Omega-3s could have a preventive effect on breast cancer, specifically EPA and DHA contained in fish appear to be eight times more effective in inhibiting tumor development and growth than those contained in plant-derived foods such as, for example, flaxseed. A recent study, conducted in laboratory mice, showed that consumption of marine-derived omega-3s reduced the number of tumors by 30 percent the size by 60-70 percent, and that larger doses of plant-derived omega-3s are required to achieve the same effect.
The protective of omega-3 in the occurrence of breast cancer
Breast cancer is the most common cancer among women worldwide and accounts for 29% of all cancers affecting the female sex. In Italy it represents the most frequent neoplasm, affecting one in eight women over a lifetime, with 53200 new cases in 2018 alone.
According to much research there is a link between the occurrence of breast cancer and poor eating habits.
In addition, more and more scientific evidence testifies to the importance of healthy nutrition in preventing disease and recurrence.
In particular, fatty acids appear to play a role on the risk of this cancer. Confirming this, epidemiological studies have found significant differences in the incidence of the disease between populations following Asian and Western diets.
Asian-style diets generally include high consumption of fish, which is rich in omega-3 fatty acids and is associated with a lower incidence of breast cancer, compared with populations that consume typically Western foods.
Omega-3s are not only found in fish, however, but can also be taken from plant sources; linoleic acid (ALA), for example, is found in edible seeds such as flaxseed and in oils such as soybean, rapeseed, and hemp, while EPA and DHA are mainly of marine origin and are contained in fish, algae, and phytoplankton.
Although a number of studies have associated omega-3 consumption with a reduction in breast cancer risk, the totality of the evidence and the specific mechanisms responsible for the protective effects still remain inconclusive.
Omega-3s of marine origin are more effective than those of plant origin
Canadian researchers, led by Professor David Ma investigated the role of omega-3s of different origins in the onset of breast cancer, using animal models, and studying the effect of feeding different types of omega-3s in mice with a highly aggressive form of human breast cancer, called HER-2, which affects 25 percent of women and has a poor prognosis.
It is known that EPA and DHA can inhibit breast cancer growth, but no one had directly observed the efficacy of these omega-3s and ALA.
Research results revealed that marine-based omega-3s are eight times more effective in inhibiting tumor development and growth, so even though omega-3s from plant sources still appear to fight cancer, a higher dose of them is needed.
"This study is the first to compare the potency of plant versus marine omega-3s on breast cancer development," said Professor Ma; "There is evidence that both omega-3s from plants and those from marine organisms are protective against cancer, and we wanted to determine which form is more effective," he continued.
The special feature of the study was that the mice were "exposed" to the different types of omega-3s while still in the womb, thus before the tumors developed, which allowed them to compare the role of fatty acids in preventing disease.
Emerging research, in fact, suggests that early exposure to omega-3s, during the critical period when the mammary gland is undergoing remodeling, may alter cancer susceptibility during adulthood.
EPA, DHA, and ALA, previous studies show, prevent and fight cancer by activating genes associated with the immune system that block tumor growth pathways.
According to the researchers, therefore, omega-3s can also fight other types of cancer, and it is desirable to consume two to three servings of fatty fish per week to maximize omega-3 intake.
Some details about the processes that led to the discovery
To carry out the study, researchers used normal mice and mice with the mutations responsible for mammary cancer.
The animals were divided into 4 groups, which were randomly assigned diets enriched with the following oils: safflower oil, flaxseed oil (at 3% and 10%), and fish oil. All diets were isocaloric with 20% kcal provided by protein, 58% kcal by carbohydrates, and 22% kcal by fat.
Diets with 3% and 10% flaxseed oil contained different levels of ALA and were used to test the dose-response relationship between plant omega-3 exposure and cancer occurrence.
The results showed that lifelong exposure to omega-3, from plant or marine sources, can delay breast cancer onset and improve cancer outcomes. In addition, they revealed the dose-dependent effects of ALA-containing plant fatty acids especially at the highest dose of 10%.
The tumor inhibitory effect due to ALA was found to be about eight times less potent than that of marine-derived EPA and DHA.
The first recommendation? Increase fish consumption
According to the researchers who conducted the study, the results reveal that plant forms of omega-3 have the same impact as fish sources but larger doses are needed. The indication, therefore, is to increase fish consumption, especially among Western populations who eat a diet rich in saturated fatty acids.
According to Dr. Ma, the significant positive effects that omega-3s may have in fighting a highly aggressive form of breast cancer suggest that omega-3s are likely to be useful in fighting other types of malignancies as well, and more research in this area will therefore be needed.
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Source: Liu et. al. "Marine fish oil is more potent than plant-based n-3 polyunsaturated fatty acids in the prevention of mammary tumors" The Journal of Nutritional Biochemistry, 2018, Pages 41-52.
