is soy protein connected to breast cancer

i have recently had my post operative results and it seems that my test for hormone stimulated cancer was positive. i have heard that soya has a lot of oestrogen, as i am vegetarian i do eat quite a lot. does anybody know if eating soya can make the cancer worse, and should i stop eating it. up until now i had thought that i have a really healthy diet. now i don’t know what to think.

Hi Dawn

Whilst you await replies you may find it useful to type ‘soy’ into the search facility at the top of this page and you can read previous threads on this subject.

You may also be interested in a factsheet which Breast Cancer Care produces called ‘Diet and breast cancer’, as it contains some information about soya.

I have given the link below to the publication which you can read online or order via the helpline on 0808 800 6000. You are welcome to call the helpline for further information, the line is open Mon-Fri 9am-5pm and Sat 9am-2pm.

Best wishes

I was er+ and was told to avoid soya products.

I used to use loads of soy and soy products because I didn’t want to use dairy. I am now convinced that too much soy may well have contributed to my breast cancer which was also oestrogen stimulated. Now I use Oatly and still avoid eating too much dairy. We’ll see what happens!

Hi all, I am also vegetarian and do eat quorn products does anyone know if these are ok to eat, thanks and hope everyone is ok junieliz

Hi Junieliz

I have posted below for you BCC’'s factsheet on diet which you may find useful.

Jo, Facilitator

There are several ingredients derived from the soya bean that are used in some foods, such as soya protein, soya oil, and soya lecithin (an emulsifier). None of the above are phytoestrogens - those would be found in anything made from whole soya beans such as soya flour, soya milk, and tofu, also in dietary supplements containing soya isoflavones.
Quorn is not made from soya beans and does not contain phytoestrogens as far as I know.
Hope this helps… I too have an ER+ bc and I wonder if my risk was increased by eating a lot of soya!

Gosh you have really started me thinking, prior to diagnosis and after i used to eat a lot of soya, soya milk on my cereals, soya desserts and loved it, when it first came about that perhaps soya was not advisable after a diagnosis i also switched to Oatley and find that just as good, i ran out the other day and found some soya milk in the cupboard still in date so used that but found i prefered the oatley. You can buy it from Tesco and sometimes they do a 2 for a £1, when they do i usually buy up the shelf!

I must admit that if i was to watch everything i ate i would turn paranoid, i do try to avoid the soya but sometimes it is hard, i love bean curd and i am sure that is soya too but that is what i have when i eat out in my favourite chinese restaurant. Phyto also means plant oestrogens and i am not sure if they are different to the oestrogens humans produce. Also cows are meant to produce oestrogen in their milk, and so it goes on…My consultant told me to carry on eating soya even though i was also ER+ but told me to stop using anti perspirant!!!

I am sure though at the end of the day (and this is just me trying to be rational) that nothing any of us has done has caused our BC we were just terribly unlucky like my brother in law who has battled mouth cancer twice and has never had any tobacco product in his mouth in his life!

Best wishes


Anyone here vegan? Soy products are a huge part of my diet and have been for 20 odd years. I’m ER- but still am concerned about soy products. I heard one of the nutritionists from the Penny Brohn Cancer Center speak recently and she still advocated the use of soy in the form of tofu, miso, and tempeh, but suggested that processed soy products like milk, desserts, yogurts, etc., were not the best things to have because they’re so altered from their original state.

Hi Cat I’m a newbie on here and was very interested with this discussion on soya. I was vegan and still am at home but impossible to eat out as one! Consequently I have eaten lots of soya over the last 18 years. I used to drink calcium fortified soya milk every day to keep osteoporosis away. I gave the soya milk up about 3 years ago as I heard about the bad reports. However I still eat othe soya products. I would find it very difficult to give up as a virtual vegan.
I also have breast cancer!!

ps. My G.P. is also vegetarian and she says af the phytos ars from a plant sorse they are perfectly safe.

unbeliveable really. I am a meat eater and since being diagnosed I have read what I thought was an amazing book ‘your life in your hands’ by J Plant. and she insists that dairy products contribute to breast cancer and swears by soya products, so I stopped eating dairy. I think that we have to face the fact that this dreaded disease can get anybody at anytime and my consultant even said to me that if she knew why I got the disease she wouldnt do the job she was doing. LETS FIGHT IT GIRLS XXXXX

My sister and I were dx 2 days apart in July 06. Not sure about this soya malarky because neither of us have ever used soya products only the hidden ones in some foods. After all my treatment had finished, I decided to use soya milk etc to reduce dairy which I found out may be a contributory factor to this disease only to find out that we should avoid soya if on Tamoxifen. I have coeliac disease so can’t use the Oat milk so I’m back on good old fashion milk with fingers crossed.
I’m now wonder what if something I’m eating/drinking caused mine but I don’t think anyone really knows. I agree with flygirl lets fight it girls xxxxxxxx

hi there

i too was worried about soya perhaps contributing to my breast cancer. i had been taking soya tablets for mood swings and menopausal symptoms, which it did help with but it makes you wonder if it does make matters worse as far as bc, because evidently bc is affected by hormones, which soya does work on. who knows? but i suppose now we have it we just have to fight it, like flygirl said.

take care.

I too am ER+, just finished chemo, during which time I gave up dairy-on my consultants advice. I switched to soya, but am now thinking I may switch to the oatly mentioned on this thread! I Know for myself that I have considered everything I have eaten and drunk in the past and agonised at times about whether or not they have been contributing factors, but I think flygirl’s post is right, we just have to keep fighting.

Hi cupoftea, I am interested in your comment that your consultant advised you to stop eating dairy products. Can you give any more info? (did your consultant mention any recent research studies, etc.)? Has anyone else been advised by their oncologist not to eat dairy …

…aahhh I have just reread your post!!! Was the advice ONLY for during chemotherapy or more general advice?

I have been a vegetarian for almost 26 years and ate TONS of soya. Whilst I don’t believe that soya caused my cancer (which was strongly ER+) I also don’t believe that it gave me any protection against breast cancer. Obviously I do not have any faith in Jane Plant’s writings. I don’t believe that any one food item/group is responsible for my cancer or future health. I think we all have to be wary of beating ourselves up about what may or may not have caused our cancer.


Hi all

Just to say, that my onc, who is a Professor and heavily into research and extremely well respected in his field, has a very interesting take on all this.

When I asked him about all the reports in the media about the effect of diet etc and possible causes of breast cancer, his professional reply was ’ it is b----cks’. Made me laugh in a very trying time. Seriously, his advice was have a healthy diet and I think he is probably right. Why drive ourselves mad trying to make sense of something that all the experts with the millions of pounds of research cash they have at hand still can’t…

Hope this doesn’t sound flippant.

Hi not flippant at all, just plain good old fashioned common sense. Echos what i wrote earlier really that nobody knows the reasons why some people get BC and others don’t. I don’t drink, smoke and at the time of diagnosis was certainly not overweight (1 1/2 stones on now due to Arimidex) I was also veggie and loved fruit and veg, i could tick all the boxes for not getting the disease and yet still did. Once again nothing any of us did gave us the disease, we were just very very unlucky!

Lets enjoy our lives, have a little bit of what we fancy and stop beating ourselves up about it. Soya, dairy, Oat milk, thousands of people have this in their diet and never get BC their whole lives. In japan where they eat a lot of soya the incidence of BC is very low, could be they have a healthier diet anyway but i think that is the important thing, the prof was right!