Regular consumption of soy can prevent chronic prostate problems. Soy products can also contribute to an improvement in existing benign or malignant changes in the prostate.
Soy in the diet – and the prostate cancer rate decreases
Soy has become very popular in recent years. Not so long ago, soy products were only available in organic and health food stores. Soy milk and tofu are now available in almost every supermarket – not least because it is believed that Asians ar
Because people in the Asian regions not only have less breast cancer but also less prostate cancer than people in the West – but only if they live in their home countries. When Asians migrate to the West, they are more likely to be diagnosed with prostate cancer than their stay-at-home compatriots.
Asians who eat Western food are more likely to get prostate cancer
On the one hand, it is said that many Asian countries do not have the medical diagnostic options that are usual in the West and that many cases of prostate cancer are therefore not discovered in the first place. However, that alone is not the reason. Diet also contributes to the risk of cancer – and this is completely different in the West than in Asia. As soon as Asian men stop eating soy products in their new home (Europe or the USA), stop drinking green tea, and perhaps eat fewer vegetables, their risk of prostate cancer increases, which is particularly noticeable in the second generation.
Therefore, in 2012, researchers in the Chinese Journal of Cancer wrote:
“Consumption of soy products is particularly common in Asian populations and is associated with a 25 to 30 percent reduced risk of prostate cancer.”
The reduced risk relates in particular to non-fermented soy products – according to Spitznagel et al. in a 2009 meta-analysis, which is particularly interesting given the widespread claim that fermented soy products are healthier than unfermented ones.
Fermented and non-fermented soy products
The non-fermented soy products include e.g. B. soy milk and tofu. However, there is now also fermented tofu, some of which taste fantastic (e.g. the vegan herbal cream cheese Soyananda from Soyana). Examples of fermented soy products include soy sauce, miso, natto, and tempeh.
Does soy only work for Asians?
Then it is said again that the preventative effect of soy may work on Asian men, but not on men from western regions. If you look at the studies, however, with e.g. For example, when European men were carried out, it is noticeable that the amounts of soy that are effective in Asian men were not used here, but much lower ones – because those who are considered to be high soy eaters in Europe would be considered very little soy in Asia -Count eaters.
While in Asian studies the soy-typical active ingredients (e.g. genistein) are given and consumed in mg amounts, in European studies it is only µg amounts – understandable that no effect can be shown here.
And it is understandable that in studies with higher soy consumption, effects can definitely be observed – even in non-Asians, e.g. B. in an older study with US and Canadian participants (Adventist Health Study). In this study, the risk of prostate cancer is reduced by up to 70 percent if soy milk is drunk regularly (more than once a day).
How Much Soy Do Asians Eat?
Since it is repeatedly claimed that people in Asia do not eat that much soy, the average consumption of soy products in Asian countries was examined and it came to the conclusion that 6 – 11 g soy protein or 25 to 50 mg soy isoflavones are consumed there per day. Here you will find a clear table with the isoflavone content of various soy products.
Example: 40 mg soy isoflavones are located e.g. B. in 100 g regular tofu and 200 ml soy milk.
The active ingredients in soy – the isoflavones
It is assumed that it is the isoflavones in soybeans in particular that lead to the cancer-preventing effect mentioned. Isoflavones (also called isoflavonoids) are secondary plant substances from the group of flavonoids, which also includes anthocyanins – the dark blue plant pigments from blackberries, aronia berries, blue grapes, or red cabbage.
Flavonoids have long been known for their antioxidant, anti-inflammatory, vascular-protecting, and anti-cancer effects.
The isoflavones are found in relevant amounts not only in soybeans but also in other legumes (chickpeas) and red clover. The isoflavones of the soybean are called u. Daidzin (or Daidzein) and Genistein.
Isoflavones have a weak estrogen-like effect (100 to 1000 times weaker than endogenous or even pharmaceutical estrogens) and are therefore also called phytoestrogens, which means something like plant estrogens.
Isoflavones can thus influence hormone balance and are associated with a reduced risk of hormone-dependent cancers – breast cancer, uterine cancer, and prostate cancer.
Isoflavones: promising agents for cancer prevention and therapy
As early as 2003, the Cancer Investigations article Soy Isoflavones and Cancer Prevention read that both in vitro studies and in vivo studies (studies on animals and humans) had shown that genistein – the dominant isoflavone in soybeans – a promising means of preventing or treating cancer.
Men who have soy products in their diet automatically have higher isoflavone levels than those who do not like soy products. Particularly high isoflavone levels can be detected in the prostate since the substances accumulate there.
In the blood, on the other hand, isoflavones only circulate for a short time, which means that isoflavones are quickly transported to where they can be useful, while possible undesirable effects on other organs can no longer occur as a result.
The effect of isoflavones
The following properties and mechanisms of action are attributed to the isoflavones of soybeans:
- Isoflavones from soy have a strong antioxidant effect – as you are used to from flavonoids: They remove oxygen radicals that would otherwise have harmful effects and can have a cancer-promoting and pro-inflammatory effect.
- Isoflavones affect the hormonal balance. However, they do not lower the testosterone level, as is often feared, but prevent e.g. B. Benign prostatic hyperplasia (BPH, benign prostate enlargement) through their estrogen-like effect, with which they can compensate for an excessive testosterone effect. They also inhibit the conversion of testosterone into DHT (dihydrotestosterone). DHT is the active form of testosterone that can stimulate cell proliferation in the prostate and thus contribute to BPH.
- Soy isoflavones can act like estrogens in estrogen deficiency and therefore reduce the effects of a corresponding deficiency. However, they can also reduce the strong endogenous estrogen effect in the event of an excess of estrogen, since they bind to the estrogen receptors instead of the endogenous estrogens, where they have an estrogen-like effect but are many times weaker than the “real” estrogen.
- In March 2014, researchers at the University of Chicago, Illinois published a review specifically explaining how soybean isoflavones can prevent and fight prostate cancer. It includes reading that soy isoflavones inhibited the development of prostate cancer in animal and cell experiments because they hinder cancer cells from growing and promote apoptosis (cancer cell suicide program).
- It is also described that soy substances also have a positive effect through their ability to promote DNA repair and also inhibit angiogenesis (formation of new blood vessels that nourish tumors) and metastasis formation.
- Soy isoflavones can also accompany radiation and chemotherapy. They should be able to enhance the desired effect of radiotherapy and chemotherapy while at the same time reducing their side effects.
The influence of soy on PSA levels
An important blood value that is always closely checked in prostate cancer is the PSA value. PSA is short for Prostate Specific Antigen. It is an enzyme produced by the prostate and keeps the semen fluid and the sperm motile. PSA also enters the blood, where it is used as a marker of prostate health. If the PSA value suddenly increases noticeably and continuously, this can indicate prostate cancer or benign prostatic hyperplasia.
However, one should be careful when specifying guide values for the PSA, because firstly the PSA value can be influenced by many factors, secondly, it can differ greatly from man to man even in healthy men and thirdly the development of the PSA is more decisive than a one-time reading.
The procedure is therefore as follows: From a PSA of 4 ng/ml, is checked at regular intervals. If it rises, there is a need for clarification. However, a PSA of less than 4 ng/ml does not rule out prostate cancer. The PSA value is therefore not suitable to serve as the only diagnostic tool for prostate diseases. Nevertheless, the success of BPH and prostate cancer therapies is always checked using the PSA value. If the value drops or can at least be stabilized, the doctor and patient are relieved.
Genistein lowers PSA
In 2011, a study appeared in the Southern Medical Journal that asked 10 men to eat commercial soy products for two years. They continued to show rising PSA levels after a prostatectomy (removal of the prostate) and radiation therapy. After the end of the study, the PSA levels in half of the participants had fallen under the influence of soy products.
In a randomized, placebo-controlled, and double-blind phase II clinical study, scientists from Oslo University Hospital/Norway gave their participants (who all suffered from prostate cancer) 30 mg of genistein or a placebo preparation daily in the weeks before their total surgery. There were 23 subjects in the genistein group and 24 in the placebo group.
The PSA value decreased by 7.8 percent in the genistein group compared to only 4.4 percent in the placebo group. However, while the PSA value in the placebo group only decreased in the tumor tissue but not in the healthy tissue, it was reduced in the genistein group both in the tumor tissue and in the healthy tissue.
At the same time, the genistein men enjoyed lower cholesterol levels, which was not seen in the placebo men. It was also important that the genistein had neither influenced the sex hormone levels nor the thyroid hormone values.
How much genistein is in soy products?
Since 30 mg of genistein can be easily ingested with a diet containing soy, the researchers involved recommend doing so – not least because of the positive effects on cholesterol levels that can be expected at the same time and the lack of undesirable side effects on the hormone balance.
Isoflavones stop PSA levels, which continue to rise despite conventional medical therapies
A study was published in Nutrition and Cancer some time ago (2003) in which 41 patients with prostate cancer took part. They were divided into three groups:
Group 1 with newly diagnosed and untreated prostate cancer and rising PSA levels.
Group 2 with prostate cancer, which, despite basic treatment (radiation, etc.), led to ever-increasing PSA levels.
Group 3 with prostate cancer, which led to ever-increasing PSA values even despite hormone therapy.
All patients received 100 mg isoflavones twice daily over a period of 3-6 months. Although the participants’ PSA level could not be reduced, it was stopped and stabilized in 83 percent of the patients in Group 2, which was a remarkable achievement given that PSA levels had continued to rise despite conventional medical efforts.
In group 3, this result was achieved in 35 percent of the patients. In this study, too, the plant substance from soy did not affect the testosterone levels of the participants in the slightest – even with a very high dose of isoflavone over a long period of time.
The researchers concluded that soy isoflavones may provide significant benefits for some prostate cancer patients – even when standard therapy fails.
Soy milk reduces severe PSA rises
In a study by the University of Florida from 2008, 20 prostate cancer patients drank 250 ml of soy milk three times a day for one year (corresponding to a total of 141 mg of isoflavones according to the study design). All patients had already received therapy – 11 had had their prostate removed and 9 had undergone radiotherapy.
Before the study, despite previous therapies, PSA levels had increased by an average of 56 percent per year. Under the influence of soy milk, the value only rose by an average of 20 percent.
The following study shows that soy products can also be taken very well alongside conventional medical therapy:
Isoflavones support radiation therapy and reduce its side effects
In 2010, researchers published a study in the journal Nutrition and Cancer examining the benefits of soy isoflavone intake for patients undergoing radiation therapy for prostate cancer.
Since soy isoflavones not only have an effect on the prostate through their hormone-like properties but also have antioxidant and anti-inflammatory properties, it was hoped that the isoflavones would reduce the side effects of radiotherapy.
42 patients received 200 mg isoflavones or a placebo preparation daily for 6 months. It was found that soy isoflavones were able to alleviate many side effects of radiation therapy, such as gastrointestinal disorders, sexual dysfunction (impotence), and problems with the urinary tract (urinary incontinence). Because the placebo group suffered significantly more from these symptoms than the soy group.
Soy isoflavones can also be used in addition to conventional therapies and in this way make the therapies more pleasant.
Soy and green tea: A sensible combination
A study by Oregon State University was published in the same year. It was discovered that it would make a lot of sense to include soy products in the diet together with green tea. Because the combination of both was able – at least in the participating rats – to reverse prostate enlargement and protect against prostate cancer better than soy or green tea alone.
Again, the researchers suspect that both foods lead to this health benefit, particularly due to their antioxidant and anti-inflammatory effects. Because prostate cancer and benign prostate enlargement are closely related to chronic inflammatory processes.
In contrast, the combination of lycopene and genistein (tomato and soy) doesn’t seem to work as well. Here, lycopene works better on its own than in combination with soy:
Lycopene stabilizes PSA levels better than soy
In vitro studies had shown that lycopene – the secondary plant substance from e.g. B. tomatoes – and genistein from soybean were able to initiate apoptosis (cancer cell suicide program) and inhibit cancer cell growth – in both hormone-sensitive and hormone-insensitive prostate cancer cell lines.
Since an earlier phase II study with prostate cancer patients had already shown that the intake of soy isoflavones could stabilize PSA levels, researchers at Wayne State University in Detroit conducted another clinical phase II study in 2007 to see if lycopene from tomatoes could further enhance the beneficial soy effect.
Participants were 70 men with continuously increasing PSA levels or a minimum PSA level of 10 ng/ml. All men had either already had local therapy or were undergoing hormone therapy.
They received either one capsule of tomato extract (15 mg lycopene) twice a day or the same capsule plus one capsule of 40 mg soy isoflavones twice a day for 6 months.
In neither of the two groups was it possible to achieve a decrease in the PSA values. However, 22 out of 33 men in the combined group had their PSA level stabilized, which is a good result. However, the result in the lycopene group was even better. Here the PSA value stabilized in almost all participants.
Incidentally, 15 mg of lycopene can be easily ingested through the diet. It is not necessary to take lycopene capsules. 500 g fresh tomatoes, 350 g watermelon, 200 ml tomato juice, or a tomato sauce made from 50 g tomato paste are sufficient.
Soy for prostate cancer
The bottom line of the above explanations is that you can include foods made from soy (tofu, tempeh, soy milk, etc.) in your diet at any time and with a clear conscience – whether you have prostate cancer or not. The worst that can happen is that you don’t notice any particular effect – either positive or negative.
As we have shown, there are many studies that also confirm that isolated soy isoflavone preparations have a helpful effect on prostate cancer. But there are also studies that show no effect here.
Adverse effects have generally been found in studies using very high concentrations of isoflavone that cannot be achieved with a diet containing soy. Dietary supplements with isolated soy isoflavones should therefore be avoided or chosen with care (in low doses).
Soy foods have the best preventive effect if you are used to them from childhood as part of a plant-based diet rich in vital substances (of course only AFTER infancy) and eat them in manageable quantities throughout your life (e.g. 100 g tofu and/or 200 ml soy drink per day).
A plant-based diet is the best choice for other reasons too, as both animal fats and some dairy products have been linked to an increased risk of prostate cancer. If you also take care of a good vitamin D supply, consume enough omega-3 fatty acids, and frequently eat cabbage vegetables with turmeric, you can expect a very good preventive effect on prostate cancer from your diet.