How long does selenium stay in the system after a selenium overdose (eg eating too many brazil nuts)?

[Alex K Chen]

Am curious. also my melatonin supplements have way too much selenium in them too, and I sometimes take large amounts to reduce Adderall neurotoxicity (i should like just try pure melatonin powder but am worried about the sleep)

some time ago, I swear i saw a paper showing that the highest blood levels of selenium increased mortality. I can't find the source again rn..

https://honey-guide.com/2012/11/19/brazil-nuts-and-selenium/
 

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The concentration of selenium in Brazil nuts has been reported to depend on the selenium concentration of the soil and the ability of the tree to absorb selenium from the soil. This can depend on a variety of factors including the chemical form of selenium in different Amazonian soils, the rain intensity, the genetics of the tree, the forms of selenium containing proteins in the nut and even the position of the nut on the tree (Lisk 1989; Pacheco 2007).

There is an interesting difference in the selenium content of Brazil nuts produced in different geographical regions of Brazil and nuts originating from countries to the east of Brazil. From the study results Brazil nuts growing in the Eastern Amazon regions of Brazil appear to contain much higher concentrations of selenium than those growing in the Western Amazon regions including Peru and Bolivia. The chart below shows the Brazil nuts with known geographical place on origin arranged by their mean selenium concentrations. It can be seen that as you move from east to west across South America the amount of selenium in the Brazil nuts produced there tends to decrease.

It has been reported that soils of the Eastern Amazon region are much richer in selenium than the Western regions (Chang 2005; Pacheco 2007). This may explain the observation that shelled Brazil nuts have often been found to contain considerably less selenium than unshelled nuts. Rather than being due to any effect of the shelling process, it seems that nuts exported unshelled often come from the east of Brazil while shelled nuts often come from the west (Pacheco 2007). However, exported products are prepared by factories using raw nuts from different Amazon sites making it difficult to determine their exact origin.

It is interesting to consider how this variability in selenium content relates to the ability of Brazil nuts to act as a good source of dietary selenium. This was investigated by Thomson (2008) in a study carried out in New Zealand, a country with low intakes of selenium. The participants were given 2 Brazil nuts a day or a 100 mcg selenium supplement in the form of selenomethionine. They found that 2 Brazil nuts each day were as effective as the supplement at increasing plasma selenium concentrations and glutathione peroxidase activity during the 12 weeks of the study. This was despite a large amount of variability in the selenium content of the nuts tested in the study. The values listed in the table above for this study are from composite samples as the authors report that they were unable to accurately test individual nuts due to the extreme variation in selenium content, ranging from 0.816 to 1390 mcg/gram. However this extreme variation did not seem to matter as over the duration of the study the intakes appeared to have averaged out to a more reasonable level.

While selenium is an essential trace mineral that plays an important role in maintaining good health it also has the potential to be quite toxic if consumed in excess. Recommended intakes for selenium vary by country with the RNI in the UK of 70 and 60 mcg/day for men and women respectively and in the USA the DRI for adults is 55 mcg/day. It can be seen from the table above that in most cases this can easily be fulfilled by one or two Brazil nuts. Selenium is known to be toxic at high intakes although there is some uncertainty as to what this level is. As a precaution the tolerable upper limit for selenium intakes has been set at 400 mcg/day. This could easily be exceeded by a high intake of Brazil nuts particularly if combined with selenium supplements.

 

 

Edited February 25 by InquilineKea

[Alex K Chen]

• SELENIUM
  (mcg/L)
• • 170 H
    Mar 2024
  • Range: 63-160

To be fair, this isn't *that* bad after taking SO many melatonin pills full of selenium

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In spline regression models, all-cause mortality decreased with increasing serum selenium levels up to 130 ng/mL (Figure 1). At the higher levels (> 150 ng/mL), however, there was a gradual increase in mortality with increasing selenium levels.Feb 25, 2008

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An inverse association between serum selenium level and cancer risk is biologically possible. Selenium could reduce oxidative stress through antioxidant selenoproteins such as glutathione peroxidase, selenoprotein P, and thioredoxin reductase.^2,9 Selenoprotein-mediated effects, however, are dose dependent. With the possible exception of selenoprotein P, the levels and activity of selenoproteins are maximized at plasma selenium levels of 70 to 90 ng/mL,²⁷ and additional selenium intake above these levels does not result in additional glutathione peroxidase activity. Instead, higher serum selenium levels mainly reflect the nonspecific incorporation of selenomethionine replacing methionine in albumin and other serum proteins.^1,9,28 Because most Americans have serum selenium levels of greater than 95 ng/mL,⁹ it is possible that the inverse association between serum selenium levels and cancer that we observed at low levels (< 130 ng/mL) is related to other mechanisms, including the production of methylselenol, a selenium metabolite that may induce apoptosis of cancer cells and may alter gene expression,³ and the inactivation of carcinogenic metals such as cadmium or arsenic.^29,30

 

Edited March 22 by InquilineKea