Binding versus excretion
Selenium binds mercury in tissue and leaves the excretion rate where it was
The selenium/mercury ratio measures selenium available to form mercury-selenium complexes. The research behind it also records what selenium binding leaves unchanged.
Trace Elements, Inc. sets the selenium/mercury (Se/Hg) minimum at 0.8:1 in its 2010 toxic-ratio set. Its ideal selenium level is 0.08 mg%, and its mercury upper limit is below 0.10 mg%.
Those three numbers fit together exactly: 0.08 divided by 0.10 is 0.8. At the ideal selenium level, the ratio meets its minimum only while mercury stays at or below its upper limit. At a mercury reading of 0.05 mg%, selenium of 0.04 mg% or more meets the ratio. At a mercury reading of 0.20 mg%, selenium would need to reach 0.16 mg%, twice the ideal. The mercury level itself, and its zinc and iron pairings, are covered on the mercury on a hair test page.
Selenium binds mercury. The Trace Elements paper on selenium lists silver, arsenic, cadmium, mercury and thallium as selenium antagonists, citing Ganther, and records that selenium binds mercury and cadmium and renders them less damaging. The ARL toxic-metals text records that mercury-selenium complexes form, and that selenium in tuna protects against the tuna's own mercury.
The same ARL text records that selenium and cysteine, given at the same time as mercury, delayed or blocked the onset of mercury toxicity in the studies it cites.
Both lineages record the limit. Trace Elements states that selenium binds mercury and cadmium but does not increase their excretion. The ARL toxic-metals text records that neither selenium nor cysteine increased fecal or urinary mercury excretion, and that selenium given after mercury exposure probably cannot increase elimination.
The ARL text records one further effect: selenium decreased kidney mercury but increased mercury deposition in the liver and brain. So a satisfactory Se/Hg ratio reads as enough selenium to complex the mercury present, not as mercury leaving.
ARL records biliary excretion as mercury's preferred route. Zinc induces metallothionein, which complexes mercury, and the Trace Elements zinc/mercury minimum is 200:1. In acute poisoning mercury excretion runs about 1 percent per day, while sequestered mercury remains in storage for years.
ARL also records a sequence: mercury inhibits copper absorption, yet people with mercury toxicity often later show copper toxicity, and as mercury is eliminated, copper elimination commonly follows. On a retest, a copper rise after a mercury rise fits that recorded order.
The ARL toxic-metals text records hair mercury at about 300 times the blood level, and that segments of one hair sample can give a chronological account of mercury excretion. Only about 7 percent of ingested inorganic mercury is absorbed, against at least 95 percent of methylmercury, the form in fish.
Blood and hair selenium are closely related, according to the Trace Elements selenium paper. One source of error is specific: a shampoo study Trace Elements cites (Leblanc and colleagues) found that of the shampoos tested, only one, formulated with selenium sulfide, seriously contaminated hair, and ARL notes a high selenium reading can come from a selenium shampoo. A high selenium figure is checked against shampoo use before the Se/Hg ratio is read.
Selenium is a component of glutathione peroxidase and of the deiodinase enzyme that converts T4 to T3 in the liver and kidney, which ties it to thyroid activity. The Trace Elements paper gives a safe and adequate intake estimate of 50 to 200 mcg per day for adults, and classes selenium as a stimulatory, sympathetic mineral.
Supplement toxicity is recorded as hair loss, nail changes, fatigue and irritability, and zinc and selenium are recorded as antagonists. Magnesium deficiency increases the effects of selenium excess, because magnesium is required for glutathione synthesis. So the Se/Hg ratio is read beside the selenium level and the zinc level, not as a target to raise alone.
A hair tissue mineral analysis is a screening test for nutritional and toxic-element patterns. It does not diagnose, it does not establish a cause, and it does not measure what is circulating in blood today. Each mineral reading reflects roughly 2 to 3 months of hair growth. Where the laboratory literature describes a trend, that trend belongs to the mineral pattern rather than to any person reading about it. Anything medical belongs with your own licensed provider.
I read Se/Hg as a measure of selenium available to form mercury-selenium complexes, and I read the zinc/mercury ratio beside it, because zinc-induced metallothionein is the recorded route that complexes mercury. A satisfactory Se/Hg with a Zn/Hg under 200:1 is still a chart I follow closely.
Then I check the selenium level against shampoo use, and on the retest I watch copper after mercury, because the recorded sequence is mercury first and copper after.
Selenium divided by mercury. Trace Elements sets the minimum at 0.8:1, with an ideal selenium of 0.08 mg% and a mercury upper limit below 0.10 mg%.
The recorded research says selenium binds mercury and renders it less damaging, but does not increase its excretion. ARL's text records that selenium lowered kidney mercury while raising liver and brain deposition.
ARL records biliary excretion as mercury's preferred route and zinc-induced metallothionein as complexing mercury. The zinc/mercury minimum is 200:1.
Yes. Of the shampoos tested in a study Trace Elements reviewed, only one with selenium sulfide seriously contaminated hair, and ARL notes a high selenium can come from a selenium shampoo.
A full hair tissue mineral analysis reports selenium, zinc and mercury on one page, so the Se/Hg and Zn/Hg ratios can be read side by side on every test.
Published 2026-10-07 · Updated 2026-10-07
By Eileen Durfee — Practitioner, NBS (Nutritional Balancing Science), NASM-CPT; wellness educator, inventor and author.
These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure or prevent any disease. Hair tissue mineral analysis is a screening test and is not diagnostic; anything medical belongs with your own licensed provider. Wellness Shopping Online is operated by Nuco Enterprise Solutions LLC.
