Selenium and Zinc Together: What to Know

Quick answer

No NIH source describes zinc and selenium changing each other's absorption. Adults need 8 to 11 mg of zinc and 55 mcg of selenium a day. Their limits differ: 40 mg for zinc, set to protect copper, and 400 mcg for selenium, above which long-term intakes can cause hair loss and brittle nails.^1,2,3

Key facts

Adults need 11 mg of zinc a day for men and 8 mg for women, and 55 mcg of selenium.^1,2
The adult upper limits are 40 mg of zinc and 400 mcg of selenium a day, counting food, drinks and supplements.^1,2
About 15% of US adults take in less zinc than the average requirement, while most people get more selenium than they need: the average is 108 mcg a day.^3,4
People who eat vegetarian or vegan diets usually take in less zinc and may take in less selenium.^3,4
In a 12-week trial, blood selenium kept rising for about 10 weeks before it leveled off, while NIH says blood zinc does not always reflect how much zinc a person takes in.^4,5

Two trace minerals with a lot in common

Zinc and selenium are both among the minerals for which the EU permits a statement about normal immune function. Each is a trace mineral that works inside enzymes. Zinc is needed by hundreds of them and for lymphocytes, the immune cells that respond to specific germs, to form and mature. Selenium is built into 25 selenoproteins, some of which protect cells from oxidative damage and some of which convert thyroid hormone to its active form.^3,4,6

They also overlap in food. Seafood, meat and poultry are rich sources of both, while plant foods vary: zinc is held back by phytate, and the selenium in plants depends on the soil they grew in. People who eat no meat tend to run lower in both.^3,4

What each is graded for

Contributes to the normal function of the immune system*^4,7,8

Moderate evidence

A well-established nutrient function. NIH describes zinc as needed for lymphocytes, the immune cells that respond to specific germs, to form, mature and become active, and for the activity of other immune cells. EU regulators permit this wording for foods that are at least a source of zinc. It is about getting enough: NIH notes that when people are not short of a nutrient, routine supplements probably add little.

Amount studied: Recommended intake: 11 mg a day for men and 8 mg for women, from food and supplements

Contributes to normal immune function*^2,3,6

Moderate evidence

NIH lists helping the body resist germs among the jobs selenium is needed for, and the European Union's list of permitted nutrient statements, drawn up after review by the European Food Safety Authority, includes normal immune function for selenium. It describes what enough selenium does, not an effect of taking more than you need.

Amount studied: Recommended intake of 55 mcg a day for adults, from food and supplements

Contributes to normal thyroid function*^2,3

Moderate evidence

NIH describes selenium as a nutrient the thyroid gland needs to make its hormones and work properly, and selenoproteins convert the hormone T4 into its active form, T3. The thyroid holds a higher concentration of selenium than any other organ. This describes getting enough: in a 6-month trial in 368 healthy adults aged 60 to 74, taking 100, 200 or 300 mcg a day raised blood selenium but did not change thyroid function.

Amount studied: Recommended intake of 55 mcg a day for adults, from food and supplements

Side by side

Zinc and selenium for adults, per day^1,2,3,4,9
	Zinc	Selenium
Recommended amount	8 mg (women), 11 mg (men)	55 mcg
Upper limit	40 mg, set to protect copper status	400 mcg; Europe set a lower limit of 255 mcg in 2023, based on hair loss
Richest food	Oysters	Brazil nuts
Typical supplement forms	Sulfate, acetate, gluconate	Selenomethionine, selenium yeast, sodium selenite
Where the body keeps it	Mostly muscle and bone	Skeletal muscle, with the highest concentration in the thyroid

Do they interact, and what about timing?

We looked for any statement that zinc and selenium compete for absorption, and found none in the NIH sheets for either mineral. The documented influences on absorption come from other parts of the meal. For zinc, phytates in beans, whole grains and seeds, and iron supplements of 25 mg or more taken at the same time, lower absorption. For selenium, the one timing study we found involved sodium selenite and vitamin C.^4,10

In the same study, taking the selenite mixed with 1 g of vitamin C on an empty stomach cut the selenium absorbed almost to zero.¹⁰

In a small study of 10 young women given 1 mg of selenium as sodium selenite, a light breakfast had little effect on how much was absorbed, and orange juice appeared to help.¹⁰

Those results come from 10 young women given a large 1 mg dose of selenium as selenite, a form and an amount far from a supplement label. They do not tell us about zinc, and NIH gives no time of day for either mineral.^1,10

How long before anything changes?

People ask how long the two take to work. The sources answer a narrower question: how long the blood level takes to settle. They give no figure for any outcome you would feel or notice.^4,5

In a 12-week trial in 119 adults aged 50 to 64, daily selenium yeast raised blood selenium for about 10 weeks before it leveled off.⁵

Blood zinc is often used to judge zinc status, but it varies with age, sex and time of day and does not always reflect how much zinc a person takes in.⁴

In other words, selenium has a known settling time of about 10 weeks in that trial, while zinc has no reliable one because blood zinc does not track intake well. NIH also notes that supplements do not seem to raise selenoprotein P or glutathione peroxidase unless a person is short of selenium.^3,4,5

Our products

What’s in ours

Men's Multi: Zinc, 15 mg per serving, from the label
Immune Support: Zinc, 11 mg per serving, from the label

What’s in ours

Men's Multi: Selenium, 30 mcg per serving, from the label

Our Men's Multi contains both minerals, and another of our products has zinc only. The cards show the label amounts.

Too much, medicines and who should ask first

Garlic breath and a metallic taste are the earliest signs of too much selenium; hair loss and brittle or lost nails are the most common.³

Zinc has its own ceiling. Too much can cause nausea, vomiting, loss of appetite, stomach cramps, diarrhea and headaches, and 50 mg a day or more for weeks can block copper absorption.^1,4

Ask your pharmacist or doctor first

Cisplatin, a chemotherapy medicine used for several cancers, can lower selenium levels in the blood and hair, and it is not known whether that matters for health. NIH reports that studies of selenium taken during cisplatin treatment are small, and that a Cochrane review found the evidence insufficient to judge them. Ask your cancer care team before taking selenium during chemotherapy.^2,3

Reported in studies

Ask first if you are having chemotherapy, including with cisplatin.^2,3
Ask first if you have a thyroid condition or take thyroid medicine, or are pregnant or breastfeeding with thyroid antibodies.³
Ask first if you are a man over 55 thinking of taking more than the recommended amount of selenium.³
Ask first if you take a quinolone or tetracycline antibiotic, penicillamine or a thiazide water pill, which interact with zinc.¹
Ask first if you have kidney disease or are on dialysis, or already take another product with selenium or eat Brazil nuts often.^2,3

Questions people ask

Can you take selenium with zinc?

The NIH sheets for the two minerals describe no effect of one on the other, and they are sold together in multivitamins. Keep each total under its limit and ask a pharmacist if you take any of the medicines listed above.^3,4

What is the best time to take selenium and zinc?

Our sources name no time of day for either. Meals heavy in phytate release less zinc, and the one selenium timing study used a form and dose unlike a supplement label.^4,10

How long does it take for zinc and selenium to work?

No source gives a time for any outcome. In one 12-week trial, blood selenium took about 10 weeks to level off. NIH says blood zinc does not always reflect how much zinc a person takes in, so it cannot give a time.^4,5

What happens if you take too much selenium?

Long-term intakes above the 400 mcg limit can cause garlic breath, a metallic taste, hair loss, brittle or lost nails, rash, nausea, extreme tiredness and nerve problems. Very high amounts can cause severe stomach and nervous system problems.^2,3

See what we make

Every product shows its whole label and what its lab report covers. The store opens soon.

See the Full Measure line Men's Multi Immune Support

Sources

*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.

This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.