How we rate
“Strong” = several concordant meta-analyses or systematic reviews. “Moderate” = one synthesis, or several controlled trials. “Limited” = early trials only. The rating is about the quality of the studies, not about how useful the supplement is.
Copper
An essential mineral, but as a supplement it changes neither cholesterol, nor bones, nor memory in trials: it mainly raises copper-dependent enzymes. EFSA does not anticipate accumulation up to 5 mg per day.
Benefits
- Copper status: in 16 young women, 3 mg per day for 4 weeks increased blood copper and the activity of a copper-dependent enzyme; 6 mg did not do any better.
- Copper enzymes: in 8 female students, 2 mg per day for 8 weeks increased caeruloplasmin by 9% and diamine oxidase by 75%, and decreased an oxidative stress marker by 39%, in a small pilot trial.
- Adults with slightly high cholesterol: 2 mg per day for 8 weeks raised two copper-dependent enzymes, without changing CRP, homocysteine or cholesterol.
- Coagulation: in 16 young women, 6 mg per day reduced by about 30% a factor that inhibits the dissolution of clots; no other cardiovascular marker changed.
- Mainly in those who start out low: in 20 men, 2 mg per day for 4 weeks changed nothing overall, but raised two copper-dependent enzymes in the 10 men who had the lowest baseline values.
Precautions
Accumulation: it is the accumulation of copper in the liver that heralds toxicity, sometimes sudden; EFSA does not anticipate any up to 5 mg per day from all sources. Zinc: too much zinc taken over a long period causes a copper deficiency, with anaemia and gait disturbances; in a 76-year-old woman, the neurological disorders persisted despite the correction of the anaemia. Iron: in 14 women, copper taken with vitamin C cancelled out the boost in iron absorption provided by vitamin C, at a copper-to-iron ratio of 8 to 1. Limits: cholesterol: a meta-analysis of 5 trials (176 participants) finds no effect on total cholesterol, LDL or HDL; nor did 8 mg per day for 6 months in 60 men. Bones: no effect on markers of bone turnover in 6 weeks in 24 adults; in 224 postmenopausal women, copper and zinc for 2 years did not slow down bone loss, which was actually greater in this group and attributed to the zinc. Alzheimer's: 8 mg per day for one year changed nothing regarding the cognition of 68 patients. LDL oxidation: 3 to 6 mg per day changed nothing in a European project conducted in four centres. Small and short trials (8 to 224 participants), which measure blood markers rather than health.
Recommended dosage
2 to 3 mg per day in trials in healthy adults; do not exceed a total of 5 mg per day, the level without accumulation established by EFSA.
How to take it
- For whom: trials mainly involve healthy adults; none show any benefit on health itself, only on blood markers.
- Dose: 2 mg per day as glycinate, or 3 to 8 mg per day as sulphate, for 4 weeks to 6 months depending on the trials.
- Upper limit: EFSA anticipates no accumulation of copper in the body up to 5 mg per day, and sets the tolerable upper intake level at 0.07 mg per kilo of body weight.
- What you already eat: in a trial, adults obtained about 1.4 mg per day (men) and 1.1 mg (women) from their diet.
- Form: copper sulphate, glycinate and orotate have been tested; no trial in this fact sheet compares their effects on health.
Did you know?
In a patient with a copper deficiency caused by an excess of zinc, two months of oral copper corrected nothing: intravenous copper was required, because the excess zinc, which is slow to eliminate, was still blocking its absorption.
What the studies say
This meta-analysis, pooling 5 randomized clinical trials and 176 participants, examined the effect of copper supplementation on blood lipid levels. The results showed no significant difference in total cholesterol, LDL-cholesterol, and HDL-cholesterol between the copper-supplemented and control groups. In conclusion, copper supplementation had no impact on blood lipids in this analysis.
Wang S, Wang N, Pan D, Zhang H, Sun G. — Biological trace element research (2021) — View the source study
For information only: not a substitute for medical advice. Dietary supplements are not a replacement for a varied, balanced diet. Learn more