Confused about Soya and BC

Hi all,
I’ve been on tamoxifen for about 3months and my GP suggested trying soya milk to help with hot flushes. But having thought about it and read a bit am now confused…if soya can have an effect on hormones and help symptoms then surely I should’t have it if I’m 95% oestrogen positive? Forgot to ask my onc at last appt so just wondered if anyone could answer this question or shed any light.
Tessa x

You may find reading the following interesting:
I think the jury is still out on this, my medical team advised against
soy/phytoestrogens as a possible proliferating effect can not be discounted. Would definitely check with your onc or medical team. I agree though, the hot flushes are awful and I am so hot&unsettled at night, can’t remember the last time I slept well.xxxTina

My oncologist advised against large amounts of phyto-oestrogens, especially soya.


Like Ann, my oncologist also advises against soya because of the very high amounts of phyto-oestrogens.

This study suggests soya protects against breast cancer:

My take on reading numerous studies is that a moderate dietary intake is fine and possibly beneficial, but a high level intake through supplements should be avoided.

In any case, without drinking soya milk most people will be eating soya anyway as it is included in so many processed foods.

The study relates to Asian Women, do you have any data/study links on how this translates to Western Women?

From the abstract:

In contrast, soy intake was unrelated to breast cancer risk in studies conducted in the 11 low-soy-consuming Western populations whose average highest and lowest soy isoflavone intake levels were around 0.8 and 0.15 mg per day, respectively. Thus, the evidence to date, based largely on case-control studies, suggest that soy food intake in the amount consumed in Asian populations may have protective effects against breast cancer.

I’m not sure what the significance is of Asian women vs western women in this instance. My understanding is that Asian women have no genetic protection against bc, as is demonstrated by the statistics showing that Asian women moving to the west very soon (within 3 generations) have the same risk of bc as their adopted country.

I believe that there is some evidence that the protective nature of soy is linked to lifetime exposure - ie if you ate soy from childhood it has a higher correlation with lower rates of bc, which would obviously be more of a factor in Asian countries.

Thanks finty, I supppose with further studies being done, there will be
one day more conclusive evidence and hopefully clearer understanding.

Hi Tina

Hopefully, but I think these things are so very hard to prove one way or another, as it is so difficult to isolate the effect of one food on these large population studies.

Having said that, it is known that the phyto-oestrogens bind to receptors on oe+ve bc cells. If they were cancer promoting, surely we would expect to see proportionately more hormone positive bc’s in the asian population? In fact we see the opposite - not only lower levels of bc in general, but relatively fewer hormone positive, and those that are +ve tend to be less aggressive than seen in western women. So I’m inclined to go with some very basic reasoning - at the very least it doesn’t appear to do any harm to asian women, and may be very beneficial.

Of course it may well be something else in the asian diet that is providing protection. That doesn’t overly concern me personally, as I try to eat a similar diet anyway - so whatever it is that works for them, will hopefully help me too. Very simplistic, I know.

finty x

i was dx with bc in Aug 2009. I used to drink soya milk until about 2008. Anyway, i asked my oc team- and was told not to drink soya milk/soya based products any more. My bc was er +

My BC was hormone negative, but I was also advised no soya products by all of the oncologists I saw. I found this to be another area where my GPs didn’t really have much knowledge. When it was suggested to me I should be trying soya for some post menopausal symptoms I was experiencing, I told the female GP I saw what the oncologists had told me and she just looked at me in amazement and went “did an oncologist really tell you that?” If BC wasn’t so serious I would laugh, but I found the ignorance of this disease at GP level pretty shocking.

Thanks for all your comments and advice, it goes with my gut feeling so will stay off the soya! Generally my GP has been fantastic and a great support but on this one obviously didn’t have her facts right.
Tessa x

The subject of soya is a difficult one. Here is a very good article on up to date research which discusses some of the difficulties:

One of the problems is that it is far easier in Western countries where soy isn’t a staple to say a blanket ‘don’t eat too many phyto oestrogens or soy’. Soy isn’t of course the only phyto oestrogen.

I have opted not to have dairy and I do drink soya milk. Basically though I try to avoid as much as possible any processed food be it soya, meat or anything.

bw, Elinda

Elinda - Thank you for the interesting link. As you say, it shows the difficulties of this type of research.

I don’t think this should or would reassure anyone about consuming soya products. The research has not been done in the UK; the soya products are different; the Chinese diet is different. How can anyone say that it is the soya that is making a difference. It could be absolutely anything, eg rice! There are so many variables as to make the results of any study like this scientifically invalid.

Ann x

Ann, I don’t think that’s quite right as they looked at different amounts of soy intake and that’s where they found the difference in death and recurrance rates. This is a substantial piece of research and I’ve found a better link which explains the actual research:

Of course there are other variables and these are documented above.
bw, Elinda

Great links- thanks Elinda.

finty x

The chinese diet is in fact very different from ours as Ann points out so pinpointing Soya as making the difference seems far too simplistic to me,for a start the eastern countries eat a lot of fish as one example.
In fact, the people of China, Japan, and other countries in Asia eat very little soy. The soy industry’s own figures show that soy consumption in China, Indonesia, Korea, Japan, and Taiwan ranges from 9.3 to 36 grams per day. That’s grams of soy food, not grams of soy protein alone. Compare this with a cup of tofu (252 grams) or soy milk (240 grams).
Many in the west today think nothing of consuming a cup of tofu, a couple glasses of soy milk, handfuls of soy nuts, soy “energy bars,” and veggie burgers. Babies on soy formula receive the most of all, both in quantity and in proportion to body weight.
Soya also contains many Toxins which the soya industry refers to as anti-nutrients such as protease inhibitors to name but one, yet Soya is hailed as a wonder food that will cure all manner of illnesses.
For anyone who is interested in the Soya issue try doing a google search on the Darker side of Soya it may surprise you, i found it quite alarming there are many articals on the subject.
The link below makes very interesting reading and definately reinforces why i will not be giving up dairy in favor of Soya.


I have agonised over this subject a lot as I am vegan and have been consuming a lot of soya milk especially the last two years. The subject was on my mind again as I was dx with BC week before last. I went to see a nutritionist and the way she explained it is parly relative to the amount of soya consumed but most importantly seems to relate to the specific soya products. The Japanese eat Miso and another soy product(whic i’ve forgotten)but due to the fermentation process they undergo are ok in moderation.less than 80 grams daily. However soya products in the west have been heavily processed and are therefore damaging. The advice given to me by more than one nutritionist and the advice i would pas on is to stay away from soya milk and other processed soy foods such as tvp.

Linda - Thanks for the interesting link. I’m with you.

Ann x

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