I've previously discussed the role of dietary lignans in the reduction of breast cancer risk and improvement in breast cancer survival, based on studies that showed that women with breast cancer who ate the most lignans appeared to live longer (Flaxseeds & Breast Cancer Survival: Epidemiological Evidence and Flaxseeds & Breast Cancer Survival: Clinical Evidence). However, lignans are found throughout the plant kingdom--in seeds, whole grains, vegetables, fruits, berries--so how do we know lignans aren't merely a marker for the intake of unrefined plant foods? For example, those who eat lots of plants--vegetarians--have about eight times the lignan intake than omnivores.
In a petri dish, lignans have been shown to both have direct anticancer growth activity against human breast cancer cells and to prevent cancer cell migration. But it wasn't until 2005 that it was put to the test in people. Researchers from the University of Toronto conducted a randomized double-blind placebo-controlled clinical trial (as seen in my video, Can Flax Seeds Help Prevent Breast Cancer?) of flaxseeds, the world's most concentrated source of lignans in breast cancer patients. The researchers found that flax appears to have the potential to reduce human breast tumor growth in just a matter of weeks. Therefore, I started recommending ground flax seeds to breast cancer patients.
Can lignans also help prevent breast cancer in the first place? High lignan intake is associated with reduced breast cancer risk, but again lignan intake may just be saying an indicator of high plant food intake in general. So researchers from the University of Kansas gave women at high risk for breast cancer a teaspoon of ground flaxseeds a day for a year, and found on average a drop in precancerous changes in the breast.
What about women who regularly eat flax seeds? Outside of an experimental setting, there just weren't a lot of women eating flax seeds regularly to study--until now. Matching 3,000 women with breast cancer to 3,000 women without, a study published in Cancer Causes and Control found that consumption of flaxseed (and of flax bread) was associated with a 20-30 percent reduction in breast cancer risk. The researchers note that, as flaxseeds are packed with lignans, only a small daily serving of flaxseed is required to attain the level of lignan intake associated with a reduction in breast cancer risk. Researchers concluded: "As it appears that most women do not consume flaxseed and that small amounts may be associated with reduced breast cancer risk, interventions to increase the prevalence of flaxseed consumption might be considered."
The latest review summarizes the association between flax and decreased risk of breast cancer, better mental health, and lower mortality among breast cancer patients. The only other study of flax and brain health I'm aware of was an exploration of 100 commonly used drugs and supplements on cognition in older adults, which found that flax is one of the few things that appears to help.
How else may flaxseeds aid in preventing and treating breast cancer? There's an inflammatory molecule called interleukin-1, which may help tumors feed, grow, and invade. Our bodies therefore produce an interkeukin-1 receptor antagonist, binding to the IL-1 receptor and blocking the action of IL-1. The activity of this protective inhibitor can be boosted with the drug tamoxifen--or by eating flax seed. In premenopausal women, the proinflammatory profile of interleukin-1 can be counteracted by a dietary addition of a few spoonfuls of ground flax. One month of flax may be able to increase the anti-inflammatory inhibitor levels by over 50 percent, better even than the drug.
Yes, having one's ovaries removed may reduce breast cancer risk as much as 60 percent, but at the cost of severe side-effects. The drug tamoxifen may reduce the incidence of breast cancer by more than 40 percent, but may induce other severe side effects such as uterine cancer and blood clots. That's why less toxic (even safe!) breast cancer preventive strategies such as dietary modifications need to be developed. These lignan phytoestrogens in flaxseeds may be one successful route given the data showing reduced breast cancer risk and improved overall survival.
Lignans are not a magic bullet to prevent breast cancer--we can't just sprinkle some flax on your bacon cheeseburger--but as a part of a healthy diet and life-style, they might help to reduce breast cancer risk in the general population.
What else can these puppies do? See:
I have another 100+ videos on breast cancer if you want to become an expert and help take care of yourself and/or the women in your life. Here's a few recent ones to get you started:
The Health Benefits of Soy Are Real, While the Ideas of Danger Are Fantasies
Remember the school lesson about how, in fifteenth century Europe, influential thinkers said it was impossible to sail across the Atlantic Ocean? The governing idea was that the earth was flat, and anyone venturing too far west by boat would fall off the end of the world. Well, experience proved that popular opinion wrong, and we can smile at it today.
Yet in the twenty-first century, many are frightened by an equally silly idea - that soy is an unhealthy, even a dangerous, food. The truth is the opposite; moderate amounts of whole soy foods are beneficial. How do we know this? Just as in the case of sailing, we look at experience - in this case, what actually happens to people who consume soy.
Let's take a look at valid studies. Many scary soy myths are based on bad science or profit-driven desire to promote animal foods instead. Researchers may inject large amounts of isolated soy extracts into rats, for example. The effect of a concentrated soy extract injected into a rat has nothing to do with the effect of a human eating a whole, natural soy foods in amounts that consumers would actually enjoy at a typical meal.
What Really Happens When People Eat Whole Soy Foods?
Many of the false alarms surrounding soy are concerned with phytoestrogens, which are a variety of substances found in many plants. Phytoestrogens may, under some circumstances, have feeble estrogenic effects (that is, have an effect similar to estrogen, but significantly weaker). Phytoestrogens may also have anti-estrogenic effects (that is, counter the effects of estrogen in people). Soy phytoestrogens, called isoflavones, are alleged by certain myth-makers to raise the risk of breast cancer and other hormone-related issues.
Credible published research on this question compares groups of people who routinely eat whole soy foods with those who seldom do. Mark Messina, PhD, published an excellent analysis in 2010 in Journal of Nutrition. He reviewed, in depth, twenty years of soy research in people.
Alkylphenols are industrial chemicals that are found in hair products, spermicides, cleaning products and detergents. They are considered endocrine disruptors. For more information on alkylphenols, check out my video Alkylphenol Endocrine Disruptors and Allergies.
Concern about alkylphenols first surfaced decades ago when a group at Tufts observed an excessive proliferation of human breast cancer cells in certain types of plastic containers, something that would normally only be seen if the cells were exposed to some type of estrogen. They identified an alkylphenol leaching from the plastic as the culprit, having "estrogen-like properties when tested in the human breast tumor cells." Excessive proliferation of human breast cancer cells is never good, so countries in Europe started banning and restricting the use of these chemicals. However, the U.S. EPA has been slow to respond.
One study, highlighted in my video, Dietary Sources of Alkylphenol Endocrine Disruptors, examined the Japanese food supply to find out which foods had these potentially allergy-exacerbating endocrine disruptors. The researchers found that chicken and fish had the highest levels. Water animals and birds concentrate these compounds to levels several thousands of times greater than those in the environment because these are fat-soluble chemicals. "Therefore, they can easily contaminate foods of animal origin, which are thought to represent the most important source of human exposure to many organic pollutants," not just the alkylphenols. Another research group also found that fish was the worst.
Which kind of fish? Anchovies, mackerel, salmon and cod seem to have the highest levels. In fact, salmon was the only food found contaminated with nonylphenol diethoxylate, which is even more potent than regular nonylphenol. The levels of contamination in fish were at the concentrations that start to make breast cancer cells go crazy in vitro.
These findings are consistent with the fact that seafood consumption has been associated with severe asthma, current and severe rhinoconjunctivitis, (seasonal pollen allergies), and current and severe eczema (an allergic-type disease of the skin) in adolescent populations around the globe.
If these synthetic xenoestrogens are playing a role, what about natural phytoestrogens, such as those found in soy foods? It turns out that in patients with asthma, consumption of a diet with moderate to high amounts of soy phytoestrogens is associated with better lung function and better asthma control. If anything then, it's these chemical pollutants, which come down in the rain, contaminate the soil, the plants, and then concentrate up the food chain in the fat of animals. We're now the animals at the top of the food chain, like the polar bear or bald eagle, building up higher levels of these synthetic xenoestrogens.
Thankfully, there aren't many cannibals around anymore. However, there is one group that continues to feed off human tissues--babies (See The Wrong Way to Detox). Alkylphenols have been found to concentrate in human breast milk, particularly in women who eat fish. The highest levels of these endocrine-disrupting pollutants were recorded in milk samples from mothers who said they ate fish at least twice a week, consistent with the fact that seafood consumption represents an important source of alkylphenol intake. Even these "slightly elevated levels of endocrine disruptors in the milk of mothers with a seafood-rich diet may be associated with adverse effects on neurological development, fetal and postnatal growth, and memory functions on breastfed infants, because these contaminants may interfere with the endocrine [hormonal] system."
Since these toxins concentrate in fat, the highest concentrations may be found in straight animal fat, such as chicken fat, lard, tallow, or fish oil. Consumption of fish oil capsules and processed fish products has been associated with alkylphenol concentration in mothers' milk, again due to bioaccumulation up the food chain. And then we recycle the leftover remains of farm animals into farm animal feed, so the levels can get higher and higher in animal products.
As one commentator noted, while these pollutants do contaminate human milk, they also contaminate cow's milk--humans and cows live in the same polluted world. In fact, infant formula was found to be over five times more contaminated, so breast is still best, absolutely. But these kinds of studies are important in order to provide good suggestions for food choices to nursing mothers to prevent excess exposure to these pollutants in their infants.
We can kind of cut out the middlefish and move lower down the food chain in hopes of decreasing our exposure to industrial toxins.
Endocrine disruptors have also been linked to conditions such as male infertility (Male Fertility and Diet and Xenoestrogens and Sperm Counts) and early onset of puberty (Protein, Puberty, and Pollutants and Xenoestrogens and Early Puberty).
What other industrial pollutants build up in the aquatic fish chain? See, for example:
- Fukushima and Radioactivity in Seafood
- Fish Intake Associated With Brain Shrinkage
- Mercury vs. Omega 3s for Brain Development
- Food Sources of PCB Chemical Pollutants
- Food Sources of Perfluorochemicals
- Obesity Causing Pollutants in Food
- The Problem with Organic Salmon
- Food Sources of Flame Retardant Chemicals
- Dioxins in the Food Supply
Farmed Fish vs. Wild Caught. Which is worse?
-Michael Greger, M.D.
PS: If you haven't yet, you can subscribe to my free videos here and watch my live year-in-review presentations Uprooting the Leading Causes of Death, More Than an Apple a Day, and From Table to Able.
Image Credit: Andrea Pokrzywinski / Flickr