pros and cons of soya and other off limits foods

[Hashiboy]

Hi there, a recent thread asked about advice on going vegan.   superb_lulu I thought that was a really interesting question. I realised that I'm pretty ignorant on the topic and wondered what the evidence was for avoiding things like Soya, caffiene and cruciferous veg. I know there are few books by people with strong ideas on what to eat for thyroid or autoimmune problems but don't know what's actually reliable and what's based on good evidence.

For example, I came across this review on soya and thyroid problems that suggests quite a complex picture and that there are health benefits as well as possible problems in eating soya if you are hypothyroid.

pubmed.ncbi.nlm.nih.gov/308...

Does anyone know of a recent scientific review that seperates fact from fiction? I'm beginning to think that perhaps we need to put a non biased honest review together.

[Forestgarden]

I was under the impression that soy can reduce levo absorption, but wasn't aware that it can raise TSH (as the article says):Soy supplementation has no effect on the thyroid hormones and only very modestly raises TSH levels, the clinical significance, if any, of the rise in TSH is unclear.

But I would be a little concerned about the rise in tsh! I'll be following this thread.

I think caffeine reduces levo absorption too. Personally I drink decaf/no caf because its hard enough trying to maintain a certain amount of energy without a caffeine high and crash. Similarly I mostly avoid alcohol.

I think the cruciferous veg thing is to do with goitrogens, but that you'd need to eat acres of the stuff before it had any effect.

Again, interested in reading any proper scientific literature about this.

[radd in reply to Forestgarden]

Forestgarden,

Thyroid hormones have many stages to go through before becoming active including what is in the blood stream being transported into the cells where it binds with nuclear receptors and turns on gene expression.

Soy is known to impede the ability of the cell in up- taking thyroid hormone , so although you have enough in the blood stream (evidenced by your labs), it isn't being allowed to become useful (active).

It can also impede the uptake of iodine by the thyroid gland, and in those people not medicating replacement meds or medicating very low doses, this risks reducing thyroid hormone levels and TSH rising in response.

[Forestgarden in reply to radd]

Thanks for this. Do you have any links to papers?

[Lalatoot in reply to Forestgarden]

If you type soy and thyroid into Google it comes up with scientific papers

[Forestgarden in reply to Lalatoot]

Is there anything more recent than the 2019 paper mentioned? There are a lot of sites which talk about it, but few papers that I can find

[radd in reply to Forestgarden]

Forestgarden,

Lots of reference papers here. ...... thyroidpharmacist.com/artic....

[Hashiboy in reply to Forestgarden]

Yes its completicated isn't it? My nephews girlfriend is hypo and when I asked if she avoids caffiene she says is doesn't really matter if you consistently take a dose that's high enough to compensate for any absorption issues. I can see that she's quite right. I think we need much more nuanced and maybe personalised advice.

I just used soya as an example of how confusing nutrition advice is in general. For example as a male already on T3 and T4 do I need to worry about research on people without a thyroid problem?

I suppose the answer is that it's complicated and individual

[greygoose in reply to Hashiboy]

Well, she is right about the absorption issues. But, what's really a problem with caffeine is that it can lower TSH if you drink it before a blood draw. And there's no compensating for that!

For example as a male already on T3 and T4 do I need to worry about research on people without a thyroid problem?

Depends what the research is on, but I would have thought that, as a hypo, you should be especially worried about soy impeding the up-take of thyroid hormone at a cellular level. It's difficult enough to get doctors to prescribe enough thyroid hormone to get decent levels in the blood without some substance that stops it getting into the cells.

[Hashiboy in reply to greygoose]

Thanks for the tip about coffee and blood tests.

[radd in reply to Hashiboy]

Hashiboy,

If you are feeling symptomatic surely it is best to avoid any possible negative interaction with precious thyroid hormones.

However, once everything is working and your body is managing to maintain wellbeing, then perhaps more flexibility can be exercised. I always eat soy at a friends who cooks lots of it but would never cook it myself. I drink several coffees a week as opposed to a day, and eat cruciferous vegetables coz I love them.

It's a balance isn't it.

[Hashiboy in reply to radd]

That sounds really sensible and balanced

[Blissful]

I understand the issue with soy is that it behaves as a phyto-oestrogen and can cause what is called oestrogen dominance - imbalanced oestrogen (from any reason) impedes T4. I'm talking about non GMO soy by the way - GMO anything can never be a healthy option.