Soya with thyroxine

[Gofaster]

Hi, I'm currently on 150mg thyroxine and just found out soya will reduce its efficiency/effectiveness? I was looking at supplementing my Vit D during winter and was told I shouldn't take a particular product as it said "may contain soya". Is this true?

[helvella Administrator]

The phrasing "may contain [ some substance ]" is often used when the product you are looking at is manufactured in a factory which also handles that substance.

This is frequently seen where the substance of concern is gluten (wheat) or nuts/tree nuts/peanuts - as well as soy.

If none of the ingredients of the product is a soy derived substance, you are only seeing that to protect against allergy. Not because it has a significant, realistically measurable, amount of the substance or of soy itself. A serious warning if you know you could suffer anaphylactic shock from exposure to soy and soy derivatives. But insignificant to the rest of us.

A typical soy derivative might be soy lecithin or soy protein isolate.

[Gofaster in reply to helvella]

Thank you for your comprehensive reply. This point I understand, so my next question is does Soy in any form reduce the efficiency of thyroxine?

[helvella Administrator in reply to Gofaster]

Yes.

But the level of impact varies from:

No impact beyond a possible slight increase in TSH

to

A significant impact

Clearly, dose and precise form are important. The odd dash of soy sauce, or a little soy lecithin in a chocolate is of much less significance than eating tofu and drinking soy milk every day.

But I find the slight increase in TSH being ignored not at all helpful, potentially confusing and misleading. TSH rises primarily because there is less thyroid hormone in the blood. Not entirely separately as seems to be implied.

Medications and Food Interfering with the Bioavailability of Levothyroxine: A Systematic Review

A retrospective cohort study revealed elevated TSH levels in the soy diet group compared to the non-soy diet group (p=0.02).102 The interaction between LT4 and soy diet was supported by several case reports.103–105 Notably, both soy milk and soy-based formula can impaired the bioavailability of LT4 in congenital hypothyroid infants.104 Since those infants were less able to maintain their thyroid homeostasis, the effect soy supplements in babies was more severe in comparison with adults on LT4. A long duration of soy supplements was associated with higher risk of thyroid dysfunction, as revealed by a systematic review.135 Interestingly, soy isoflavones were revealed to transiently increase reverse levels in a randomized controlled trial.136 The phenomenon could be explained by inhibited deiodinase 1 and/or 2 activities by isoflavone supplements.

dovepress.com/medications-a...

[Gofaster in reply to helvella]

Thank you so much. I didn't know about any impact of soy but I don't consume soy milk and only rarely have tofu, but may think again about eating this.Providing I can get the right brand of thyroxine all is well but I have struggled when this brand wasn't available. And this took ages to work out! I think some additional Vit D could be helpful but worry about upsetting my current "applecart" Do you have any suggestions? I am on HRT so hoping this is helping my bone health.

[helvella Administrator in reply to Gofaster]

Sorry - I really don't know what vitamin D supplements there are. I have some in the cupboard and cross my fingers that they are helping.

I see you have not posted in quite a while!

Just in case it is of any help, I have a document that details all UK licensed thyroid hormone medicines.

helvella's medicines documents (UK) can be found here:

helvella - Thyroid Hormone Medicines

helvella has created, and tries to maintain, documents containing details of all thyroid hormone medicines licensed in the UK and, in less detail, many others around the world. There is now a specific world desiccated thyroid document.

I highly recommend viewing on a computer screen, or a decent sized tablet, rather than a phone. Even I find it less than satisfactory trying to view them on my phone.

helvella - Thyroid Hormone Medicines - UK

The UK document contains up-to-date versions of the Summary Matrixes for levothyroxine tablets, oral solutions and liothyronine available in the UK. Includes injectables and descriptions of tablet markings which allow identification. Latest updates include all declared ingredients for all UK-licensed products and links to Patient Information Leaflets, Dictionary of Medicines and Devices (dm+d), British National Formulary, NHS Drug Tariff, etc. PLUS how to write prescriptions in Appendix F.

Also includes links for anti-thyroid medicines (but not product details).

📄 dropbox.com/s/bo2jzxucgp9hl...

helvella - Excipients

Details of excipients are in my Excipients document. This includes all excipients identified in UK-licensed thyroid hormone medicines.

📄 dropbox.com/scl/fi/tud6r8f5...

helvella.blogspot.com/p/hel...

If the last updated date of a copy your have downloaded isn’t very recent, please download a new copy!

Last updated 17/10/2024

[Gofaster in reply to helvella]

Thank you and you're right about not posting in a while. That's because I've been fine 😊 and I feel well on Teva thyroxine so no need to change that.No worries about Vit D supplements - I'd joined a Facebook group for Vit D and to be honest the advice was questionable so I've already left!

[helvella Administrator in reply to Gofaster]

I'm glad you have been well!

Also quite glad that you are specifically doing well on Teva. A sizeable proportion of members who have tried Teva have not got on well with it. It has (wrongly in my opinion) become something often actively avoided - simply because some don't tolerate it well.

Yet, for those for whom it works, it seems very good. And we have no known way of identifying who will be fine, and who won't, other than trying it.

So you saying that helps to add balance to the negative reports.

(PS I didn't tolerate it! Even in a tiny dose alongside other makes.)

[Gofaster in reply to helvella]

It took me absolutely ages to work out that Teva was good for me because the pharmacist kept giving me different brands, and sometimes a mix of brands. But I've now been on Teva for nearly 5 months and all the random rushing to the loo has stopped. I looked at everything I was eating, including wondering if it was the different brand of HRT, and only when Teva was re-introduced did I clock it!! Phew!!

[Karen-Eleanor in reply to Gofaster]

Teva works well for me too!

[Jefner]

I have always used this one over the winter months with the odd test inbetween to check levels and it works a treat proactivehealthcare.co.uk/v...

[Gofaster]

Thank you, I'll take a look. Does your GP check your levels?

[helvella Administrator in reply to Gofaster]

Jefner

[Fizzyinch]

better you and bare biology do a vitamin D spray.

Soy is a phytoestrogen so may mimic oestrogen in the body and cause hormonal imbalances

[Suzi-B]

No idea…… i’m vegan so i do have soya, i take my meds around 3am when i wake up with water, for a trip to the toilet, by the time i get up in the morning my meds are absorbed so if soya interferes my body has absorbed my levothyroxine and there is NO interaction! al my bloods come back ok. hope this helps??