What it's actually good for
Copper is an essential trace mineral your body uses as a cofactor for cytochrome c oxidase (mitochondrial energy production), lysyl oxidase (the enzyme that cross-links collagen and elastin into functional connective tissue), ceruloplasmin (iron transport), and superoxide dismutase (antioxidant defense). Most people get enough from shellfish, organ meats, nuts, seeds, and whole grains — beef liver alone supplies more than ten times the RDA in a single serving, according to the NIH Office of Dietary Supplements. Outright dietary copper deficiency is rare in people eating a normal diet.
The realistic case for supplementing isn't performance or "more energy" — it's correcting or preventing a shortfall, most commonly one caused by something else you're taking. Zinc is the culprit: it competes with copper for the same intestinal transporter, and sustained high-dose zinc intake depletes copper stores over weeks to months. That's the scenario copper supplements exist to solve.
What the research says
Energy and connective tissue markers (Grade B). The mechanistic case is solid — copper-dependent enzymes are genuinely required for mitochondrial ATP production and collagen cross-linking — but direct human trial evidence is thin. A placebo-controlled pilot by DiSilvestro et al. (2010) gave 16 young women 2 mg/day of copper for 8 weeks and found a 62% rise in a urinary collagen crosslink marker and a 39% drop in a marker of oxidative stress, alongside improved ceruloplasmin activity. That's one small trial in non-deficient subjects, not a body of evidence — encouraging, not conclusive.
Bone density (Grade B). Eaton-Evans et al. (1996) followed 73 women aged 45-56 for two years and found 3 mg/day copper prevented the vertebral bone density loss seen in the placebo group. It's a real, well-controlled trial, but it's also the only one of its size and duration showing this effect, and copper combined with high-dose zinc in other trials has shown neutral or even negative bone outcomes. Treat this as preliminary, not a reason to add copper for bone health on its own.
Deficiency has real consequences. When copper deficiency does happen — usually after bariatric surgery or from excess zinc — it can cause anemia, low white blood cell counts, and a neurological syndrome called myeloneuropathy (nerve damage causing gait and sensory problems). A 2017 case review by Wazir and Ghobrial notes the blood abnormalities reverse with copper repletion, but the neurological damage often doesn't fully resolve. This is the strongest practical argument for supplementing in the specific population it applies to — long-term high-dose zinc users and post-bariatric-surgery patients — not for the general population.
How much, and which form
The RDA is 900 mcg/day. Multivitamins commonly include 1-2 mg. When copper is used specifically to offset zinc-induced depletion, 2 mg/day is the typical dose, matching what was used in the DiSilvestro trial. Copper bisglycinate and copper gluconate are well-absorbed chelated/salt forms; copper oxide is poorly absorbed and best avoided.
Safety & interactions
The margin between the RDA (0.9 mg) and the tolerable upper limit (10 mg) is wide, but copper accumulates, and chronic excess is a real concern — it's been loosely linked to Alzheimer's risk in observational studies and can act as a pro-oxidant. People with Wilson's disease, a genetic disorder of copper accumulation, should avoid copper supplements entirely. High-dose zinc (50+ mg/day) is the main reason anyone needs standalone copper; high-dose vitamin C can also reduce copper absorption. This is informational, not medical advice — check with a clinician before starting, especially if you're managing a chronic condition.
How we picked the brand
A copper product earns a spot when it uses a well-absorbed form (bisglycinate or gluconate, not oxide), states the dose clearly, and passes independent third-party testing. Thorne's copper bisglycinate meets that bar — NSF Certified for Sport, chelated for absorption, dosed at 2 mg to match the level used in the deficiency-correction research above.