Introduction.
Soybeans contain lecithin, vegetable protein and fiber, making them a very good health food. In the past, it has been reported that women in areas where soy milk is regularly drunk for breakfast are less likely to develop breast cancer than those who are not accustomed to drinking soy milk, and soy has been considered a very good cancer prevention food.
However, some views now seem to be reversed, with some reports suggesting that soy contains phytoestrogens that can stimulate women to develop breast cancer, or stimulate disease recurrence in patients after breast cancer surgery. A quick search on the Internet reveals a variety of reports with mixed reviews on soy products.
So, should breast cancer patients consume soy products or not?
1.Soybean oil
Soybeans can produce 20% soybean oil after steps such as crushing, extraction and purification. After these processes, soybean oil basically no longer contains phytoestrogens, and the main components are various fatty acids. Of these, linoleic acid is the most abundant, accounting for 51%, and is also called Omega-6, the predominant polyunsaturated fatty acid in all vegetable oils, and is also widely found in other foods, including meat, fruits and vegetables, and cereals.
Because linoleic acid is the raw material of arachidonic acid, which can promote cancer, inflammation, cardiovascular disease and related diseases, there is concern that excessive intake of linoleic acid can lead to the risk of these diseases. At the same time, arachidonic acid increases the activity of “aromatase”, which promotes the conversion of more androgens into estrogens. Animal studies have shown that linoleic acid can promote the growth of breast cancer in mice, therefore, for patients who are taking “aromatase inhibitors”, i.e., anastrozole, letrozole, exemestane, it is advisable to reduce the diet high in linoleic acid.
In fact, linoleic acid and linolenic acid (Omega-3) are both essential fatty acids. However, different ratios of the two can have different effects on the human body. A good ratio will produce anti-cancer effects, while a poor ratio in the long term may promote cancer. The best ratio of Omega-6 (linoleic acid) to Omega-3 (linolenic acid) is 2 to 4:1, while soybean oil is 7:1.
Some studies have shown that people who regularly consume soybean oil and corn oil are 30% more likely to develop breast cancer than those who regularly consume olive oil and canola oil. Therefore, it is recommended that breast cancer patients can try to go for some cooking oils with more reasonable ratios, such as olive oil, canola oil, or supplementation with Omega-3 rich fish oil.
In addition, when cooking, try not to make the oil temperature too high, otherwise it is very easy to produce carcinogenic substances.
2.Tofu and soy milk
Tofu is the most commonly consumed soybean product in our daily lives. Tofu is processed by soaking, grinding, boiling, filtering and solidifying soybeans. During the entire production process, soy isoflavones, or phytoestrogens, have been mostly destroyed, so breast cancer patients consuming tofu do not have to worry about the effects of phytoestrogens.
Not only that, but according to epidemiological studies, people who regularly consume tofu are less likely to develop breast cancer, especially in premenopausal women, so tofu is a recommended food for breast cancer patients. However, breast cancer patients should note that tofu should be consumed sparingly during radiotherapy because it contains a substance called “genistein”, which has a certain role in protecting cells from radiation damage, so its consumption may affect the efficacy of radiotherapy.
Soy milk is a by-product of tofu, and the production process is similar to that of tofu, so it should also be safe. However, it should be noted that some finished soymilk contains an additive called carrageenan, which may be a breast carcinogen, so breast cancer patients who want to drink soymilk should try to do it themselves and drink it now.
3.Soy protein powder/soy protein concentrate
More and more people like to buy health products instead of food for nutritional supplements. Soy protein powder or soy protein concentrate is the removal of fat and carbohydrates from soybeans, increasing the proportion of protein from 40% to about 90%. However, the amount of soy isoflavones contained in soy protein powder varies widely due to the production process.
Studies have shown that soy protein can improve glycemic control, increase sensitivity to insulin and reduce the development of atheromatous plaque in terminally ill women with diabetes. Animal studies have shown that rats fed soy protein extracts are less likely to develop colon cancer when induced by carcinogens than rats fed a regular diet.
Several studies have examined whether soy isoflavones ingested through the consumption of soy protein powder exert an estrogenic effect to prevent the development of osteoporosis in postmenopausal women, but the studies have had very different answers. Some studies have concluded that taking soy protein concentrate improves bone health in postmenopausal women, but others have shown no reduction in the probability of osteoporosis.
It is important to note that soy protein concentrate tends to be high in copper, and excessive copper intake can lead to angiogenesis and metastasis in breast cancer, especially in inflammatory breast cancer and triple negative breast cancer. It has also been shown that the intake of soy protein concentrate by premenopausal women stimulates breast cell proliferation and increases estrogen levels in the blood. The U.S. Food and Drug Administration is currently conducting research on furans in soy protein powder, which are produced during thermal processing and may be a potential human carcinogen.
This shows that soy protein powder or soy protein concentrate products may not be safe for breast cancer patients, so it is not recommended that breast cancer patients get their protein supplement from soy protein powder and can choose other safer enteral supplements.
4.Soybean fermented products
Soybean fermented products are commonly used by the Asian population as condiments, including soybean soy sauce, soybean paste, tempeh and so on, which are the products of fermentation of soybeans through a special process. Through the fermentation process, these products contain more soy flavonoids and genistein than soybeans, substances that have been found to have anti-mutagenic activity. But epidemiological studies in Asia have not seen that soybean paste can reduce the risk of breast cancer in the same way that tofu does.
Not only that, but studies have also observed that people who regularly consume fermented soy products are more likely to develop stomach cancer. However, researchers believe that the development of stomach cancer is still primarily related to the higher salt content of soy fermented products.
There is evidence that breast cancer survivors with tumors have a higher risk of developing gastric cancer, and patients with lobular breast cancer are more likely to develop gastric metastases. Therefore, for breast cancer patients, if they like to eat soy fermented products, it is recommended not to consume too much or avoid these foods with high salt content as much as possible.
Summary.
The results of these studies revealed that the commonly feared soy phytoestrogens do not seem to be the main cause of breast cancer promotion, but rather the various soy products themselves. In fact, Asian races are more likely than Caucasians to metabolize soy isoflavones into substances that have protective functions. The fact that the same study yielded very different results may also be related to the metabolic characteristics of human and animal species.
Thus, the question of whether or not soy products can be consumed for breast cancer is still a matter that requires specific analysis and differentiated treatment. We have to affirm the nutritional value of soy and also guard against its adverse effects, as is the case with any food, so for tumor patients, it is important to try to increase the richness of food, but not to crave for a certain food because you love it more!