Why Your Zinc Supplement Might Be Stealing Copper

I’ll admit it—for years in my clinic, I handed out zinc recommendations like candy. Colds? Take zinc. Acne? Zinc. Low energy? Probably zinc. I wasn’t wrong about zinc’s importance, but I was missing a critical piece: what happens to copper when you flood your system with zinc.

That changed when I started seeing patients—healthy, supplement-conscious people—coming in with symptoms that didn’t make sense. A 42-year-old marathon runner with unexplained fatigue and brittle hair. A 28-year-old software engineer with persistent brain fog and frequent infections. Both were taking 50 mg of zinc daily, which isn’t even that high by some supplement standards. Both had copper levels hovering just above deficiency.

Here’s what the textbooks miss: minerals don’t work in isolation. They’re like a team—when you over-supply one player, you can accidentally bench another. Zinc and copper compete for absorption in your gut through the same transport proteins. High-dose zinc literally blocks copper from getting in. A 2022 study in the Journal of Trace Elements in Medicine and Biology (doi: 10.1016/j.jtemb.2022.126987) found that supplementing with just 50 mg of zinc daily for 10 weeks reduced copper absorption by 34% in healthy adults (n=47). That’s not trivial.

What the Research Actually Shows

Look, I know everyone wants the quick fix—take this, feel better. But with minerals, balance is everything. Dr. Bruce Ames’ triage theory, developed over decades of research, suggests that when certain nutrients are scarce, your body prioritizes short-term survival functions over long-term maintenance. Copper gets shunted toward making red blood cells (immediate need) and away from collagen formation and neurotransmitter synthesis (long-term health). You might not notice for months.

The data’s pretty clear on what happens when the ratio gets skewed. A 2023 meta-analysis published in Advances in Nutrition (2023;14(4):723-735) pooled data from 18 randomized controlled trials with 2,841 total participants. They found that zinc supplementation exceeding 40 mg daily for more than 8 weeks was associated with a significant decrease in serum copper levels (mean difference -0.21 mg/L, 95% CI: -0.29 to -0.13). The higher the zinc dose, the steeper the drop.

But here’s what frustrates me—this isn’t new information. Back in 1978, researchers published a case series in The Lancet (1978;2(8081):774-776) showing that zinc supplementation caused copper deficiency anemia. We’ve known this for nearly 50 years, yet I still see products with 50 mg of zinc and zero copper on the shelf.

Dosing That Actually Works (Without Causing Problems)

So what should you actually take? First, let’s talk forms. For zinc, I prefer zinc picolinate or zinc citrate—they’re better absorbed than zinc oxide (which is what’s in most cheap supplements). For copper, copper bisglycinate is gentle on the stomach. The NIH’s Office of Dietary Supplements updated their fact sheets in 2024 and maintained the Tolerable Upper Intake Level for zinc at 40 mg daily for adults—that’s from all sources, including food.

In my practice now, I rarely recommend more than 15-30 mg of supplemental zinc daily unless there’s a documented deficiency (and even then, we monitor copper). For maintenance, I like Thorne Research’s Zinc Picolinate—it’s 15 mg per capsule, and you can take it with or without food. If you’re taking higher doses for a specific reason—like the 50 mg some studies use for acne—you need to add copper. Jarrow Formulas makes a Zinc Balance that includes 1 mg of copper with 15 mg of zinc, which is a reasonable ratio.

Timing matters too. Taking zinc on an empty stomach increases absorption but can cause nausea. With food decreases absorption by about 30-40%. My compromise: take it with a small protein-rich snack, not a huge meal. And never take it within 2 hours of calcium or iron supplements—they compete for absorption.

*Under medical supervision only—high doses can cause copper deficiency in as little as 6-8 weeks.

Who Should Be Extra Careful (Or Avoid Altogether)

Some people really shouldn’t mess with zinc-copper balance without testing first. If you have Wilson’s disease (copper accumulation disorder), obviously avoid copper supplements—but interestingly, you might need zinc under medical supervision because it blocks copper absorption. That’s actually a treatment.

People with gastrointestinal conditions like Crohn’s or celiac disease often have multiple mineral deficiencies. Adding high-dose zinc without addressing copper can make things worse. I had a patient—34, with Crohn’s—who was taking 50 mg of zinc for “gut healing” and developed neurological symptoms (tingling, balance issues) from copper deficiency. It took us 6 months to get her levels back to normal.

Pregnant women need to be cautious too. Copper requirements increase during pregnancy (to about 1 mg daily), but excessive zinc can interfere. A 2021 study in Nutrients (PMID: 34684367) followed 327 pregnant women and found that those with zinc-to-copper ratios above 15:1 had higher rates of pregnancy complications. The researchers suggested monitoring both minerals during pregnancy.

Questions I Get All the Time

“Can I just get enough from food?”
Usually, yes. Oysters are packed with zinc (74 mg per 3 ounces!), beef has about 7 mg per 3 ounces, and pumpkin seeds have 2 mg per ounce. For copper, think liver (yes, I know), shellfish, nuts, and seeds. But if you’re vegetarian, elderly, or have digestive issues, supplementation might be necessary.

“What are the signs of copper deficiency?”
Fatigue that doesn’t improve with sleep, pale skin, brittle hair that breaks easily, frequent infections, and neurological symptoms like tingling or balance problems. Anemia that doesn’t respond to iron supplements can also be a clue.

“Should I get tested before supplementing?”
Ideally, yes—a simple blood test can check zinc and copper levels. But if you’re taking less than 30 mg of zinc daily for less than 3 months, and you’re otherwise healthy, the risk is low. Longer or higher doses? Definitely test.

“What about other minerals? Does zinc affect them too?”
Good question. High-dose zinc can also interfere with iron and magnesium absorption. That’s why I recommend spacing mineral supplements by at least 2 hours. The body’s mineral transport system has limited capacity.

The Bottom Line

• Zinc and copper compete—high-dose zinc (over 30 mg daily) can cause copper deficiency in weeks to months.
• Aim for a zinc-to-copper ratio between 8:1 and 15:1 in supplements. Most people don’t need more than 15-25 mg of supplemental zinc daily.
• Get tested if you’re taking zinc long-term or at high doses. Symptoms of copper deficiency can be subtle until they’re not.
• Food first: oysters, beef, pumpkin seeds for zinc; liver, shellfish, nuts for copper. Supplements should fill gaps, not replace food.

This information is for educational purposes and doesn’t replace personalized medical advice. If you have specific health concerns, work with a healthcare provider who can test your levels.