Soy and hormone therapy

My sister has told me that she has read that you should avoid soy products if undergoing hormone therapy. Does anyone know if this is correct? i have changed from dairy to soy producta as I thought as I read that dairy can be harmful

Hi,there are differing views about soy and dairy on here depending on what people read on the Internet.I have put a link to

" If you are taking hormonal therapy to fight off a hormone-receptor-positive breast cancer, and you are concerned about any phytoestrogen effects, ask your doctor or registered dietitian about how much soy you can eat"
or maybe give the BCC helpline a call and talk to one of the clinical team.

Best wishes Melxx

As Mel says there are very mixed views on soy. Soy is a phyto-oestrogen (plant oestrogen). Many things we eat are phyto-oestrogens although from what I understand soy has higher levels.

Some people argue that eating soy has a protective effect. This is thought largely because rates of breast cancer are low in countries like China and Japan who (up until recently at least not sure of if/how diet has changed in past few years) were not having dairy and eating a lot more soy.

Others argue that its best to avoid completely. Possibly one of the issues is that we tend to have processed soy in this country eg. soya milk, tofu etc.

We have discussed the issue of soy at some length on the thread ‘for those interested in research and diet’ so it’s worth looking back through that if you want to see the findings of latest academic research. We also have current discussion on phyto oestrogens.

In terms of dairy replacements there are other options such as rice milk, oat milk and Kara coconut milk (different from the tinned stuff). Elinda x


I gave up dairy a couple of years ago, then felt I was having too much soya so have cut down on that too. I find the kara coconut milk great - its not at all like sweet coconutty tasting stuff - has no taste at all really and is good in both tea and coffee. I think that it isn’t good to be too reliant on anything at all really - so I do have soya in some things (almost impossible to avoid really), but I try not to have too much of it. Likewise I don’t panic if i happen to have a small amount of milk although I try not to!

Hi nvlmevans,
I agree with Mel on this one ,there are many differing views about soy and dairy on here depending on what people read on the Internet and where the scorces of information comes from.
For the latest and up to date information re the current evidence its always advisable to look at sites such as CRUK ,BCC,Breakthrough, or also which Mel has posted above .
The Soya issues has always been a very contraversial one ,mainly because it was always assumed that Asian countries ate lots of Soya and had much lower rates of BC ,however the Asian countries have only ever used Soya as a “Condiment” not as we do as foods in the west,Asian countries also have very high rates of stomach cancer but now interestinly in recent yrs the Asian countries BC rates have rapidly increased to almost comparable levels so i think proberly the Soya and BC association has been somewhat a bit of a myth.
My own oncologist doesnt advise eating Soya because of the very high amounts of photoestrogens,but there have been some studies that have shown a benifical affect for BC simularly other studies have not and have shown that Soya could have a possible adverse effect so there is no clear evidence either way and it seems the the jury is still out. From what ive read i believe most ladies who are ER+ though should be carefull of too much Soya consumption in their diet because of the very high photoestrogens levels.

Re Dairy, this is another area of controversy and has been studies many times over very many yrs,at this time there is still no evidence that Dairy/Milk ect is connected to BC infact the majority and largest studies have still not found a link between Dairy consumption and Breast Cancer, There has also been a fair amount of research into the “possible benefits” of dairy foods on breast cancer risk.
“To better clarify the relationship between dairy product consumption and breast cancer risk, a recent study analyzed the published literature to date.”

There is also a debate about Dairy ,IGF-I and Breast Cancer risk, a very interesting and comprehensive examination of the effects of INSULIN-LIKE GROWTH FACTOR AND BREAST CANCER is below, this review is for anyone who may be confused about any of these issues and still has any concerns about the eating of dairy products and Breast Cancer.We also of course should bear in mind that there are many different factors which increase our IGF-I levels most of which are non diet related.

EPIC is the latest and largest study ever conducted to date re Diet and BC 500,000 people in ten European countries,and this study also has concluded that there are NO strong links between diet and BC ,therefore personaly i think the current guidelines of a “Healthy Balanced Diet” is proberly still the best advise for all of us,
moderation is key.

All the best to you
Linda x

You should be aware that the article linked to above declaring dairy to be safe is written by the Australian Dairy Council.

Thanks finty for pointing that out though im not quite sure why you found it nessesary to do so as im sure you are aware that this study was also published in the American Journal of Clinical Nutrition and also in Pubmed , i had already posted this discrepancy when raised before on the “Wacky” thread.

Because this study was a review in The American Journal of Clinical Nutrition which looked at the previous research on the topic of dairy and breast cancer risk “The researchers considered nearly all of the largest epidemiology studies that have been conducted to look at how dairy foods might affect risk of breast cancer,After looking at 46 different epidemiology studies on dairy foods and cancer, the researchers concluded that there is no strong association between milk and other dairy products and breast cancer risk.”

I think because of the other “additional” above reputable publications (please correct me if im wrong) we can be very sure that this study was infact unbiased and accurate,

Very good news for anyone who has concerns on the Dairy- BC theory.


I pointed it out because it represents sloppy scholarship, the author is a paid schill for the diary industry who does not declare his interest in the piece, and it is full of misleading information that is directly contradicted by independent research. Other than that, it’s a great piece.


"What do these results mean?

This review is important for several reasons. First, the dairy industry and issues around dairy foods are highly influenced by politics in this country (49,50). Pro-dairy interests work to convince the American public that dairy is absolutely necessary for good health. Anti-dairy groups work to convince the American public that dairy is bad for health and the cause of many chronic diseases, including cancer. In reality, the truth is likely somewhere in the middle: dairy is neither necessary for good health nor the main cause of chronic diseases such as cancer. Likely it is a food that can be included in the diet if desired, but is not absolutely necessary for good health.

The results of this review study help us to understand the big picture on dairy and breast cancer risk (48). It is important to remember that one single study can never answer all of the questions we have about nutrition and cancer. What is more important to consider is whether a given study fits into the big picture of all of the research on that topic. In other words, if many, many studies tell us that a certain factor is related to risk of cancer, then chances are, this factor is indeed related to cancer"

Think the pro-dairy anti-dairy part sums it up as to the feelings some have on here about the subject.

Why is it when some people respond to posts on other threads with differing research or have a view that doesn’t comply they are said to be attacking the thread/post and branded “aggressive” “usual women” “trouble makers”.All seems a bit one sided to me.It also seems ok for some to ridicule a post but not others.

Doesn’t matter what research is put on here regarding dairy,the jury is still out on the dairy breast cancer risk.It’s personal choice you either choose to have dairy or you don’t.


Thanks Flinty for pointing out the flaws in a study on dairy by the Australian Dairy Council - potential conflict of interest?? - Never!!!

Mel, the bits quoted from the report are interesting and well written (but I am guessing should really have quotation marks for clarity perhaps?). Your comments on ridicule are interesting and I understand exactly what you mean as I have often been the target of ridicule, especially as my views are always particularly mainstream…

Dairy consumption post bc is a very personal choice, but still, given the overall evidence it would be very prudent for women to remove as much dairy as possible from their diet.

It’s true that breast cancer rates are increasing in Asian countries particularly younger women. However the research that looked at this did not look at why this might be. Please see the commentary from the Breastcancerorg which reports on these findings. One possibility they suggest is that young Asian women are adopting Western diets and lifestyles. Another possibility they suggest is the increasing levels of pollution.

They also point out that Asian women who move to the US have similar BC rates at those of general US population.

I think it’s very important to look at who is funding any research. I found a fantastic academic research report on the benefits of soy and then discovered after searching that it was funded by the soy industry. Sometimes you have to do considerable searching to find this out. The dairy industry also funds a lot of research into the safety of dairy which isn’t surprising.

Personally I don’t have dairy because it has hormones such as oestrogen and progesterone in it. The dairy industry says that these are safe levels and perhaps they are.
However, there has been some quite worrying research though into the effect of these hormones (this study was in Japan 2010):
As you’ll see serum estrone (E1) and progesterone concentrations significantly increased after drinking cow’s milk.

I just can’t see the point of having something that has animal hormones in it if its something I can easily replace with rice milk etc.
People worry about soy much more it seems probably because it’s not so normal to have it. That said it’s most shop bought loaves of bread particularly white ones.

There is increasing evidence for the benefits of phytooestrogens although particularly in the case of soya it doesn’t appear to be conclusive. elinda x

Thanks for that link Elinda - it confirms the findings of several other independent studies that oestrogen in diary products raises serum oestrogen levels, despite the dairy industry’s denials - something that should concern anyone with hormone positive bc.

But the original question on this thread was about soy and the safety of phyto-oestrogens. It is my personal view that many of those that recommend against eating phyto-oestrogens don’t see past the word oestrogen. Many large scale observational studies have shown benefits from eating soy at normal dietary levels, some have shown no benefits - I’m not aware of any that have shown damage from eating soy.

But observational studies are notoriously prone to influence from confounding variables. Laboratory studies have supported a beneficial affect for soy and other phyto-oestrogens, but that is on cancer cell lines and in animal studies only. So wouldn’t the best way of showing what affect phyto-oestrogens have on breast cancer cells be to take a group of women with breast cancer and have them eat phyto-oestrogens, and then analyse their tumours to see what difference it made? Yes? Well that is exactly what this study did, and the results were startling:

Flax seeds are richer in phyto-oestrogens than any other food. In this study, a small group of post-menopausal women who were diagnosed with primary breast cancer, but had not yet had their tumours removed, were enrolled in a double blind, randomised, placebo controlled diet trial. Half the group were given a 25g per day supplement of flax seeds in the form of a muffin, the other half were given a placebo - no other diet changes were made. When their tumours were surgically removed and analysed, on average 32 days later, and compared with the biopsy data collected before the trial, the following results were found:

In the tumours of the flax seed intervention group compared with the placebo:

  • tumour cell proliferation had DECREASED by 34%

  • apoptosis,the spontaneous death of cancer cells - had INCREASED by 31%

  • the expression of c-erbB2 had DECREASED by 71%. This is a measure of HER+ status, and is in essence a measure of cancer cell aggressiveness - so the researchers characterised this result as reducing the aggressiveness of these cancer cells by 71%.

So here we have direct evidence that a strong phyto-oestrogen is highly beneficial to these post-menopausal women with breast cancer. Of course this study is limited to what it can say about this group of women and this particular phyto-oestrogen only - maybe they will repeat it with soy, I hope so. But it is interesting to note that the 34% reduction in tumour cell proliferation compares to 40% with tamoxifen, the first line drug of choice.

Also think it should be pointed out that it is just one of the links that linda put on here that is written by a research scientist from the Australian Dairy Council.The others are not such as this one

Also Gretchen maybe you need to look more closely at my post as the quotation marks are there.


If anyone actually wants to cut phyto-oestrogens out of their diet, here is the list of things you will need to avoid:

Most breads
Most cereals and grains
Most fruit and vegetables
Virtually all processed food

I’m not sure what that leaves - just meat and sugar I guess.

Mel that meta-analysis you posted is certainly interesting.

I suppose it still leaves me with the question that if there is oestrogen and progesterone in milk and it does raise serum levels of those, what is the actual effect of drinking milk/dairy products on women with ER+ and/or PR+ breast cancer?

I’m baffled as to why so little research is being done to look specifically at hormones in milk and their effect on breast or other tumours.

The Japanese study I posted it is very small and it would be good to see more of that kind of work.

Mel - this isn’t in any way a criticism, but I think when you are quoting from something it is easier to understand if you differentiate the quote from your own words, and say where the quotation comes from, preferably with a link. finty xx

I find it quite alarming that my earlier post is being savagely attacked by the same usual women, so thanks ladies (though i cant say i didnt expect this again ) ,firstly with respect, im not surprised that this particular study has been critisised by some posters on this thread as this study will not be welcomed by those ladies who prefer to encourage Veganisum and breast cancer as clearly encouraged on another thread.
I posted this new research for those ladies who may be interested to know the current up to date findings on Dairy and BC which continues to find no link with Dairy and BC and is supported by ALL the major Cancer organisations and Cancer Charties, therefore ladies can either ignore this study along with the others or take heart that Dairy still to this day after all the endless research remains a safe option for anyone DX with BC,to say otherwise is ludicrous and is just not supported by the medical establishment.
I am also quite staggered to read the comments that this study “represents sloppy scholarship” and would ask what if any medical expertises critisisers of this study ladies on here have? ive seen very little reconised reptuable research for instance on the “diet thread” and find the references to studies there mainly from scorces such as "foodforbreastcancer"which i find extreamly questionable .

Im sure when and if (which is very unlikely it seems) that there is ever any reliable research proving a link to Dairy and BC like there is on Lung Cancer and smoking im sure we will all be the first to be told about it from the medical profession and Cancer Research, in the meantime with all the current evidence considered its totally incorrect for anyone to suggest “Dairy” is bad for Breast Cancer as this is just not true.

I certainly dont want to get drawn into another unpleasant discussion about this topic and would hope that those ladies who dont welcome any current research into diet and breast cancer unless it is about Veganisum will respect other posters space on this forum.

Re Soya here is a more comprehensive list of foods that contain the very highest amounts of Photoestrogens for anyone who may be debating the Soya issue.

Foods high in phytoestrogen content.

Phytoestrogen food sources Phytoestrogen content (µg/100g)
Flax seed 379380
Soy beans 103920
Tofu 27150.1
Soy yogurt 10275
Sesame seed 8008.1
Flax bread 7540
Multigrain bread 4798.7
Soy milk 2957.2
Hummus 993
Garlic 603.6
Mung bean sprouts 495.1
Dried apricots 444.5
Alfalfa sprouts 441.4
Dried dates 329.5
Sunflower seed 216
Chestnuts 210.2
Olive oil 180.7
Almonds 131.1
Green bean 105.8
Peanuts 34.5
Onion 32
Blueberry 17.5
Corn 9
Coffee, regular 6.3
Watermelon 2.9
Milk, cow 1.2

Interestinly Milk has the lowest phytoestrogen content.

Linda x

Ok one thing at a time:

Firstly I’m not a vegan and don’t promote veganism, and I don’t think anyone on this thread that has disagreed with your article is a vegan. So lets dispense with that first falsehood.

Secondly your post wasn’t savagely attacked - my precise words were: “You should be aware that the article linked to above declaring dairy to be safe is written by the Australian Dairy Council”, which are precisely true. So that’s the second falsehood.

Thirdly the article did not represent up to date findings, it pointedly ignored all research that disagreed with it’s premise, and included several outright falsehoods, such as those Elinda highlighted on dairy raising oestrogen and progesterone levels.

It in indeed sloppy scholarship to present research without stating your financial interest in the results - you won’t find any academic that disagrees with that, and you don’t need any special expertise or medical expertise to know that, other than perhaps a tertiary education and being used to reading primary research.

The diet thread does indeed link to some research on the foodfor breastcancer website. So what? All that website does is provide a summary of academic research with links to the original - it doesn’t make it up. There’s nothing remotely questionable about the sources - it isn’t sponsored by a vested interest as your dairy research was. When I post research that I have read there I usually link to the primary research as well, but that is sometimes behind a pay wall, so the summary that ffbc provides is useful. But glad to know you’re reading the thread!

Nobody is stopping anyone posting about anything and nobody has been disrespectful or savagely attacked you or your post - but it is perfectly acceptable to point out flaws in an argument.

Finally - and my last word on the matter - I think it is interesting that you can say with absolute certainty that it is completely safe to eat a product that raises serum levels of oestrogen and progesterone.

I can’t believe Linda that you are accusing anyone of ‘savagely attacking’ your post and making all this personal again. I’ve not written a single disrespectful word. It would seem to me that there is a desire to keep on about previous arguments and picking at healing wounds. It isn’t helpful.

To clarify some of the erroneous comments you’ve made, I am not and never have been a vegan. I eat meat and fish.

Secondly, there is a huge amount of academic research on the research and diet thread. I always go for the primary source where at all possible and always look for academic research.

And furthermore, I don’t think we can have double standards here when some type of research is seen as okay for one side of an argument but not for the other.