Selenium, Zinc, Copper and Manganese: The Minerals Behind Antioxidant Enzymes
How selenium, zinc, copper and manganese help the body's own antioxidant enzymes, what supplement trials found, the risks of excess, and where each mineral is covered in full.
Content last updated . This page has not been medically reviewed.
What the minerals do
The National Center for Complementary and Integrative Health notes that antioxidant enzymes are the most important components of the body's defense system. [2] Where each mineral fits:| Mineral | Role in antioxidant enzymes | Source |
|---|---|---|
| Selenium | Helps the body make special proteins called antioxidant enzymes. [3] The NCI says its antioxidant effects are most likely due to selenium-containing proteins. [1] | MedlinePlus; NCI |
| Zinc | Needed for making new cells and enzymes. [4] Copper and zinc bind to the enzyme superoxide dismutase 1, which breaks down superoxide radicals. [5] | NHS (2020); MedlinePlus |
| Copper | Works with iron to help form red blood cells. [6] Also part of the copper-zinc enzyme above. [5] | MedlinePlus |
| Manganese | Helps make and activate some of the enzymes in the body. [4] The sources we read did not name specific manganese antioxidant enzymes, so we do not describe them. | NHS |
What supplement trials found
Evidence labels: "no good evidence of benefit", "evidence of harm", "promising but limited" and "insufficient evidence". Study amounts are what researchers gave participants, not recommendations.| Question | What the source found | Label |
|---|---|---|
| Selenium and cancer (Cochrane, 10 trials, 27,232 people) | Supplements did not reduce overall cancer incidence (RR 0.99, 95% CI 0.86 to 1.14). [7] | No good evidence of benefit |
| Selenium side effects in trials | Hair loss (alopecia) and dermatitis were more frequent in the largest trial, and a slightly increased risk of type 2 diabetes was seen in trials. [7] | Evidence of harm |
| Selenium in SELECT (healthy men) | Study amount: 200 μg a day from L-selenomethionine. [8] Prostate cancer hazard ratio 1.09 (99% CI 0.93 to 1.27), not statistically significant. [8] | No good evidence of benefit |
| Selenium and deaths from any cause | In low-risk-of-bias trials the result was not significant (RR 0.97, 95% CI 0.91 to 1.03). [9] | No good evidence of benefit |
| Eye disease already present (AREDS formula) | The formula contained vitamins C and E, beta-carotene, zinc and copper; it reduced the risk of advanced macular degeneration by about 25 percent in people with intermediate disease. [2] A specific formula in a specific group: do not assume one mineral alone gives this result. | Promising but limited (specific formula) |
| Selenium, zinc, copper or manganese alone for other conditions | Proper evidence not found in the sources we read for this page (we searched NCI, NCCIH, MedlinePlus, the NHS and Cochrane/PubMed for the trials above). | Insufficient evidence |
The Cochrane authors of the antioxidant mortality review found no evidence to support antioxidant supplements for primary or secondary prevention. [9] NCCIH reports that the U.S. Preventive Services Task Force judged evidence insufficient for supplements of other single nutrients, including selenium. [2]
When there is a real shortage, the picture changes. Lack of selenium is rare in the United States, but Keshan disease, a heart muscle condition, is caused by a lack of selenium. [3] Deficiency diseases need a clinician. Never diagnose one from symptoms and do not treat a suspected shortage on your own. MedlinePlus says taking a selenium supplement in addition to food sources is not currently recommended for the cancer and heavy metal conditions it discusses. [3] See deficiency testing and its limits.
Too much: what the sources say
- Selenium: too much causes selenosis, which can lead to loss of hair and nails. [4] MedlinePlus lists hair loss, nail problems, nausea, irritability, fatigue and mild nerve damage. [3]
- Zinc: high doses reduce the amount of copper the body can absorb. [4] This can lead to anaemia and weakening of the bones. [4]
- Copper: in large amounts copper is poisonous. [6] The NHS lists liver and kidney damage with long-term high intake. [4] A rare inherited condition, Wilson disease, causes copper deposits in the liver, brain and other organs, so people with it need a clinician's guidance. [6]
- Manganese: high doses for long periods might cause muscle pain, nerve damage and other symptoms. [4] The NHS also notes older people may be more sensitive. [4]
Where each mineral is covered
- Selenium: roles, food sources, evidence and toxicity
- Zinc: roles, food sources, evidence, excess and copper and zinc forms compared
- Copper: roles, food sources, deficiency and excess
- Manganese
- Vitamins C and E: what the antioxidant role means
- Wider context: antioxidants explained and the minerals directory
Frequently asked questions
Are selenium and zinc antioxidants?
They are minerals used to build or run antioxidant enzymes. The NCI says selenium's antioxidant effects are most likely due to selenium-containing proteins, not selenium itself. [1] MedlinePlus says copper and zinc bind to the enzyme superoxide dismutase 1. [5]
Does selenium prevent cancer?
A Cochrane review of 10 supplement trials found no reduction in overall cancer incidence. [7] Trials also saw hair loss, dermatitis and a slightly increased risk of type 2 diabetes. [7]
Can I take zinc and copper together or separately?
We do not give schedules. The NHS says high-dose zinc reduces how much copper the body can absorb, [4] so ask a pharmacist or clinician before using either as a supplement.
What is manganese for?
It helps make and activate some of the enzymes in the body. [4] High doses for long periods might cause muscle pain and nerve damage. [4]
Do these minerals interact with medicines?
Proper evidence not found in the sources we read for this page; we searched NCI, NCCIH, MedlinePlus and the NHS. That is not proof of safety. Ask a pharmacist, and see medication interactions.
More details: evidence, limits and cautions
The details behind this page: cautions, limits of the evidence and where sources disagree. Open any note to read it.
Who should ask a clinician or pharmacist first
References
- Antioxidants and Cancer Prevention. National Cancer Institute (US). Read 2026-10-23.
- Antioxidants: In Depth. National Center for Complementary and Integrative Health (US). Read 2026-10-23.
- Selenium in diet. MedlinePlus Medical Encyclopedia (US National Library of Medicine). Read 2026-10-23.
- Vitamins and minerals: Others (selenium, zinc, copper, manganese). NHS (UK). Read 2026-10-23.
- SOD1 gene. MedlinePlus Genetics (US National Library of Medicine). Read 2026-10-23.
- Copper in diet. MedlinePlus Medical Encyclopedia (US National Library of Medicine). Read 2026-10-23.
- Selenium for preventing cancer. Cochrane Database of Systematic Reviews, 2018. Read 2026-10-23.
- Vitamin E and the risk of prostate cancer: the Selenium and Vitamin E Cancer Prevention Trial (SELECT). JAMA, 2011. Read 2026-10-23.
- Antioxidant supplements for prevention of mortality in healthy participants and patients with various diseases. Cochrane Database of Systematic Reviews, 2012. Read 2026-10-23.