Selenium Supplementation Suppresses Serum T3 Levels In Man

[paymanz]

Almost every other studies(all on animals) reported positive connection between selenium intake and t3 levels, but this on on humans is opposite!


Dietary selenium intake modulates thyroid hormone and energy metabolism in men. - PubMed - NCBI


Abstract

Most studies of selenium and thyroid hormone have used sodium selenite in rats. However, rats regulate thyroid hormone differently, and selenite, which has unique pharmacologic activities, does not occur in foods. We hypothesized that selenium in food would have different effects in humans. Healthy men were fed foods naturally high or low in selenium for 120 d while confined to a metabolic research unit. Selenium intake for all subjects was 47 microg/d (595 nmol/d) for the first 21 d, and then changed to either 14 (n = 6) or 297 (n = 5) microg/d (177 nmol/d or 3.8 micromol/d) for the remaining 99 d, causing significant changes in blood selenium and glutathione peroxidase. Serum 3,3',5-triiodothyronine (T3) decreased in the high selenium group, increased in the low selenium group, and was significantly different between groups from d 45 onward. A compensatory increase of thyrotropin occurred in the high selenium group as T3 decreased. The changes in T3 were opposite in direction to those reported in rats, but were consistent with other metabolic changes. By d 64, the high selenium group started to gain weight, whereas the low selenium group began to lose weight, and the weight changes were significantly different between groups from d 92 onward. Decreases of serum T3 and compensatory increases in thyrotropin suggest that a subclinical hypothyroid response was induced in the high selenium group, leading to body weight increases. Increases of serum T3 and serum triacylglycerol accompanied by losses of body fat suggest that a subclinical hyperthyroid response was induced in the low selenium group, leading to body weight decreases.

 

[Elephanto]

300 mcg a day is overdose. That's why newer studies found a causal link to prostate cancer with selenium, they used 250mcg daily if I recall correctly, while an older but valid study had found a strongly protective effect with 80 mcg daily (selenized yeast).

So I wouldn't jump to the conclusion that selenium is anti-thyroid as the low dose group had been replete with an optimal dose for 21 days, I think the results rather show a pro-thyroid effect of selenium in adequate doses.

 

[Daniil]

They fed them products with different selenium content. As I understand it, it is impossible to find out the details of various diets here. Most likely, the group with low selenium intake simply had a generally more prometabolic diet. It is also strange that T4 dropped in both groups.

 

[Mauritio]

Interesting study. Weirdly analyzed and interpreted by the authors though.

I dont know why they didn't add a medium dose of selenium after the 21 days in the range of 50-100mcg ,that would have been interesting.

The weight gain is barely significant in the high selenium group, 700g in 3 months. That's really negligible.
TSH increased in both groups ,not just the high group.

They looked at borderline deficient and toxic doses, so the good thing is we get a better picture of what they do in humans. Unfortunately they didn't study the interesting range (50-150mcg) .

The conclusion is: 300mcg/day is too much and 15 probably too little to have a strong effect on our health.

 

[Makrosky]

No surprise. Doses above 80mcg/day can cause hypo symptoms. Someone posted a study about this some years ago.

 

[BigYellowLemon]

They just fed them food not given them the same food but selenium supplements.

Look at what high selenium foods even means and you’ll see your answer. Probably lots of broccoli which is high selenium but also very goitergenic, for mostly different reasons.

 

[Mauritio]

No surprise. Doses above 80mcg/day can cause hypo symptoms. Someone posted a study about this some years ago.

80mcg is surprisingly low. Do you happen to have this study on hand ?

They just fed them food not given them the same food but selenium supplements.

Look at what high selenium foods even means and you’ll see your answer. Probably lots of broccoli which is high selenium but also very goitergenic, for mostly different reasons.

Yes another good point. They fed them beef and rice IIRC.

 

[Makrosky]

80mcg is surprisingly low. Do you happen to have this study on hand ?
Yes another good point. They fed them beed and rice IIRC.

IIRC it was 80mcg supplemental, not from food. And I can't find it sorry mate :-/

Before reading that I would always take 200mcg when supplementing with iodine, after reading that, I try to stay with 100mcg.

But... hey, it was just a study. You cannot extrapolate that. For majority of people 80-100mcg will still be not only not bad but probably ok.

On the old iodine forums it was said that supplementing selenium without iodine could cause hypo symptpms. But people there used to take 200mcg minimum.

Difficult to assess. Also keep in mind it is not the same to use sodium selenite than selenomethionine. The former is probably more problematic than the later.

 

[Makrosky]

@Mauritio I found where I think I got the info. Can't find the thread but I have a sshot. I think the study was posted there, maybe you can find it I am with the cellphone and it sucks.

 

[Mauritio]

@Mauritio I found where I think I got the info. Can't find the thread but I have a sshot. I think the study was posted there, maybe you can find it I am with the cellphone and it sucks.
View attachment 36725

Thanks a lot ! I'll try finding the study elephanto was talking about .

 

[Mauritio]

Thats the study. It doesnt mention TSH ,hypo -symptoms etc.

Correlation between oxidative stress and L-type calcium channel expression in the ventricular myocardia of selenium-deficient mice - PubMed

L-type calcium channels were involved in selenium deficiency-induced cardiomyocyte injury, which was positively related to oxidative stress.

pubmed.ncbi.nlm.nih.gov

That part about 80mcg seems to have been his opinion or at least he didnt post studies confirming it in this post.

 

[Makrosky]

Thats the study. It doesnt mention TSH ,hypo -symptoms etc.

Correlation between oxidative stress and L-type calcium channel expression in the ventricular myocardia of selenium-deficient mice - PubMed

L-type calcium channels were involved in selenium deficiency-induced cardiomyocyte injury, which was positively related to oxidative stress.

pubmed.ncbi.nlm.nih.gov

That part about 80mcg seems to have been his opinion or at least he didnt post studies confirming it in this post.

Excellent. Thanks for clarifying it!