The plant compounds that keep breast cancer from coming back

Breast cancer recurrence happens when treatment doesn’t get rid of all the cancer cells in the breast. Treatment can shrink breast cancer tumors until they’re undetectable. However, the weakened cells are still present, and over time, they can regain strength and start to grow, potentially leading to the creation of tumors.

The odds of breast cancer recurring can range between 3 and 25 percent, depending on what treatment is received and whether it has spread to the surrounding lymph nodes. These factors can also affect risk:

• Age. Women who develop breast cancer before the age of 35 are more likely to get breast cancer again.
• Cancer stage: Women with later stages of breast cancer are more likely to develop recurrent breast cancer than those with stage I or stage II breast cancer.
• Cancer type: Aggressive cancers like inflammatory breast cancer and triple-negative breast cancer are harder to treat and more likely to recur.

Research shows specific treatments may reduce breast cancer recurrence risk, including chemotherapy and hormone therapies like tamoxifen or aromatase inhibitors. However, these treatments don’t guarantee prevention of recurrence.

Some investigators are exploring alternative means of prevention. And one international team of researchers may have found a set of natural compounds that could help keep breast cancer at bay….

The power of soy isoflavones

The Johns Hopkins Kimmel Cancer Center co-directed a review of  22 studies examining the impact of specific phytonutrients from plants on breast cancer recurrence and mortality, as well as death from all causes.

In one meta-analysis of six studies, they found soy isoflavones were linked with a 26 percent reduced risk of breast cancer recurrence. The results were most notable among post-menopausal breast cancer survivors.

The most significant risk reduction was seen at 60 milligrams of soy per day. That equals two to three servings per day, where a serving is one cup of soy milk, three ounces of tofu, or a half cup of cooked soybeans.

The effect of soy consumption on death risk was only 12 percent and was most noticeable at 20 to 40 milligrams per day, or about one to two servings.

Another finding reported for the first time in a meta-analysis is related to enterolactone, a substance formed in the gut by the digestion of compounds known as lignans. Lignans are found in a wide variety of plants, with high levels in flaxseeds, cashews, broccoli, Brussels sprouts, and in varying degrees in some berries.

The meta-analysis showed enterolactone reduced the risk of mortality specific to breast cancer by 28 percent and death from any cause by 31 percent. In post-menopausal women, enterolactone had a 35 percent reduced risk of death from any cause.

The researchers say it isn’t possible to calculate the effective dose of lignans in the diet from these findings because the gut microbiome, which plays a role in metabolizing lignans, varies among individuals.

Green tea and lignans

According to the researchers, the findings on lignans and soy were solid enough to recommend that breast cancer survivors include them in their dietary guidelines. Other findings didn’t have enough data behind them for such a recommendation, although the researchers say they were “suggestive.”

For instance, green tea consumption suggests an effect of reducing the risk of breast cancer recurrence by 44 percent in women with stage I or II breast cancer. Two Japanese studies documented the greatest impact from consuming three to five cups of green tea per day.

Among those consuming lignans before breast cancer diagnosis, there was a 34 percent risk reduction in cancer-specific mortality and a 19 percent reduction in risk of all causes of death in post-menopausal women. However, consumption of lignans by premenopausal women suggests an increased risk of mortality. This indicates the effect of lignans could depend on the hormonal environment. The highest intake in the studies reviewed was nine or more servings per day.

“It is critically important to stress that these studies were conducted on women who received medical and/or surgical treatment for breast cancer, and that these foods and phytonutrients should not be considered as alternatives to treatment,” says senior study author Dr. Channing Paller, director of prostate cancer clinical research and an associate professor of oncology at Johns Hopkins University.

Peller says the research highlights the need for more robust studies looking for the most effective dosages of these compounds, and whether starting to consume them after diagnosis has the same effect as a lifelong dietary habit before diagnosis.

When adding soy to your diet, make sure it’s the right kind. Avoid soy meat products, energy bars and other processed soy products, and stick to simple versions of soy like tofu, tempeh or edamame.

Fermented soy foods like tempeh, miso and natto are especially good for you because they contain beneficial bacteria and more easily absorbable nutrients. If you’re concerned about GMOs, you can find non-GMO versions of these products in health food stores.

Flaxseeds and their lignans have been proven in past studies to protect against breast cancer. I have some tips for adding them to your diet here.

Sources:

Natural Compounds Derived from Soy and Other Plants Reduce Breast Cancer Recurrence and Improve Survival, Research Shows — Johns Hopkins Medicine

Phytonutrients and outcomes following breast cancer: a systematic review and meta-analysis of observational studies — JNCI Cancer Spectrum

Breast Cancer Recurrence — Cleveland Clinic