Effect of long-term selenium supplementation on mortality: Results from a multiple-dose, randomised controlled trial

[helvella]

Opinions vary on selenium supplementation.

A few years ago, many people were saying that people should take 400 micrograms a day. More recently, the most commonly recommended dose at present appears to be 200 micrograms.

The paper linked below certainly questions higher doses. For myself, I would not take more than 100 micrograms - on the basis that our diets almost certainly contain some selenium and it is the total intake that seems important. If we get 40 or 50 micrograms from our diets (which would still represent selenium deficiency because we probably need around 70 to 80 micrograms), adding 100 would get to about 150 micrograms. Which is around double the usual estimate of our requirement.

Effect of long-term selenium supplementation on mortality: Results from a multiple-dose, randomised controlled trial

Margaret P.Raymana

Kristian Hillert Wintherb Roberto Pastor-Barriusoc Frederick Coldd Marianne Thvilumb Saverio Strangesef Eliseo Guallarg Søren Coldd

doi.org/10.1016/j.freeradbi...

Abstract

Background

Selenium, an essential trace element, is incorporated into selenoproteins with a wide range of health effects. Selenoproteins may reach repletion at a plasma selenium concentration of ~ 125 µg/L, at which point the concentration of selenoprotein P reaches a plateau; whether sustained concentrations higher than this are beneficial, or indeed detrimental, is unknown.

Objective

In a population of relatively low selenium status, we aimed to determine the effect on mortality of long-term selenium supplementation at different dose levels.

Design

The Denmark PRECISE study was a single-centre, randomised, double-blinded, placebo-controlled, multi-arm, parallel clinical trial with four groups. Participants were 491 male and female volunteers aged 60–74 years, recruited at Odense University Hospital, Denmark. The trial was initially designed as a 6-month pilot study, but supplemental funding allowed for extension of the study and mortality assessment. Participants were randomly assigned to treatment with 100, 200, or 300 µg selenium/d as selenium-enriched-yeast or placebo-yeast for 5 years from randomization in 1998–1999 and were followed up for mortality for a further 10 years (through March 31, 2015).

Results

During 6871 person-years of follow-up, 158 deaths occurred. In an intention-to-treat analysis, the hazard ratio (95% confidence interval) for all-cause mortality comparing 300 µg selenium/d to placebo was 1.62 (0.66, 3.96) after 5 years of treatment and 1.59 (1.02, 2.46) over the entire follow-up period. The 100 and 200 µg/d doses showed non-significant decreases in mortality during the intervention period that disappeared after treatment cessation. Although we lacked power for endpoints other than all-cause mortality, the effects on cancer and cardiovascular mortality appeared similar.

Conclusions

A 300 µg/d dose of selenium taken for 5 years in a country with moderately-low selenium status increased all-cause mortality 10 years later. While our study was not initially designed to evaluate mortality and the sample size was limited, our findings indicate that total selenium intake over 300 µg/d and high-dose selenium supplements should be avoided.

sciencedirect.com/science/a...

[Treepie]

Very interesting as I just ordered 200mcg tabs!

[butcher3]

I'm deficient in selenium, I'm currently taking the higher 400 ug dose for a period of 3/4 months before 're testing . This dose started at 50ug & raised every 3 days. I've noticed a remarkable improvement in my mood & body heat.

[helvella Administrator Thyroid UK in reply to butcher3]

You are right to mention that you were tested before, and will be tested again.

One issue with the approach to supplementation is that they will prescribe (or advise), get you into range, then stop.

Your level will then drop over time and no-one will notice.

If nothing else changed, whatever was behind your low selenium will very likely cause low selenium again.

Quite possibly, you need would be best having a (very?) low dose indefinitely?

(This is the pattern we have seen described so, so often for iron.)

[butcher3 in reply to helvella]

I agree that a consistent lower dosage will be needed life long. I have had trouble metabolising my food due to gut issues. This should improve in time. However for the last 6 months the nutrition has not been getting through for sure ( according to my OAT Test )

[Marz]

When my GP in Crete suggested Selenium she also mentioned stopping it for a few weeks now and again. Cannot remember the exact length of time to stop so when I run out I do not rush to re-order !

Thank you for this post ...

[Ozzyfudge in reply to Marz]

Hi Marz I have just been to see my endocrinologist and he has put me on selenium 50 mgs a day I have had a blood test also , I only took one selenium and I felt wired .. hyper I suppose a little strange so have stopped it until I get my blood result .. 😊

[helvella Administrator Thyroid UK in reply to Ozzyfudge]

I hope that is 50 micrograms (not milligrams).

[Ozzyfudge in reply to helvella]

Sorry yes micrograms ! Does it give you energy ? Only I felt strange when I took it ?

[LAHs in reply to Ozzyfudge]

Well it will improve your conversion of T4 to T3 and that increased T3 level will give you more energy.

[helvella Administrator Thyroid UK in reply to LAHs]

Possibly only if you do not have enough?

I really do not know whether taking more than is your basic need makes any such difference.

Research into the research on selenium is itself being performed!

Effect of Selenium on Thyroid Disorders: Scientometric Analysis

ncbi.nlm.nih.gov/pmc/articl...

A list of references to selenium research papers appears at the end of this paper.

[Ozzyfudge in reply to helvella]

Thank you 🙏

[Ozzyfudge in reply to LAHs]

Thank you 🙏

[Lindsayf]

Thank you for this... I take 200mcg every night but will reduce to 100mcg instead.

[Angel_of_the_North]

However, it doesn't say whether selenium was measured before start of trial, or whether amount of selenium in diet was measure during trial. They are assuming that everyone would have low dietary selenium, but did they really know that for the whole 10 years? Lifestyles and food availability can change a lot in 10 years. And I'm always dubious of all-cause mortality as that includes being run over by a bus or drowning. That said, I suspect selenium supplementation should be short term in response to something specific

[Jasma]

I was taking 200mcg + an additional 50mcg in a fertility multi (I know! I've stopped the multi now). I recently had a blood test done and was well over the upper limit. It's hard to tell what causes symptoms as there's so much crossover (hair loss anyone?) but I had a burning sensation halfway across my lower lip that stopped almost immediayely after I stopped all supplementation. I was advised to take it by a gynaecologist without testing although I'd have had a fairly high selenium diet. I think most doctors just see ""hypothyroid and think "selenium". Every book and resource I read seemed to say to take it but I think it's a good to get checked unless you're sticking to a low dose.

[helvella Administrator Thyroid UK in reply to Jasma]

Thanks for that - I know that few have had selenium tested. And that there are around the internet an awful lot of recommendations to take a selenium supplement - often, in my opinion, too high a dose.