Last week, I went down the copper rabbit hole, asking whether a copper deficiency could be the reason your iron supplements aren't working. (If you missed it, that's the place to start.)

But in understanding how copper relates to iron, I'd skipped a much more basic question. I still had no idea where copper comes from in my diet, why it's important, or how to increase it. Nobody really talks about copper as a nutrient in its own right, so the moment someone does, I keep watching because I know nothing about it.

So this time I wanted to look into copper on its own terms, not just as it relates to iron. Where does it actually come from? What does it do in the body? And is getting enough something you and I should genuinely be worried about or just the latest iron thing?

Copper is an essential mineral your body needs in tiny amounts. If you eat a varied diet, you almost certainly get enough. Your body only takes in about 1 mg a day, and that small amount covers most people.

It’s spread across a lot of everyday foods, and even people who eat less than official targets still test as having enough.

Here’s roughly how much copper common sources give you:

(Approximate amounts from USDA food-composition data. They vary by food and serving.)

You don’t need the dramatic sources to get enough. A small handful of nuts plus beans or whole grains across a day adds up fast.

What you eat copper with matters too. Protein and vitamin C help you absorb it, while very large doses of zinc or iron get in the way.

Copper's main job is to switch on enzymes, the tiny machines that run your cells. It's required for more than 30 of them:

You need only a little. Careful intake studies put adult needs at about 1 to 1.25 mg a day to stay balanced. Below roughly 0.8 mg a day you slowly lose copper, and above 2.4 mg a day you build it up.

Official targets exist too, but health authorities don't fully agree on the exact number.

One way to fall short on copper is high-dose zinc. At normal food levels, zinc and iron barely affect copper. But large zinc supplements block copper absorption and can cause a true deficiency.

High-dose zinc switches on a gut protein called metallothionein. That protein grabs copper and holds onto it inside the cells lining your gut. And these cells are shed every few days, and the trapped copper leaves with them.

Very high iron can compete too: in lab studies, copper, iron and zinc together cut copper uptake by about 40%.

For most women, no. Copper deficiency is uncommon in healthy people.

It’s worth a closer look mainly if you:

Here are some takeaways from today:

🥜 Make a 1-oz handful of nuts or seeds a regular snack. An ounce of cashews, Brazil nuts, or sunflower seeds delivers about 0.5–0.6 mg copper, most of the ~1 mg you absorb in a day.

🍊 Eat your copper foods as part of a meal, not on their own.
Protein and vitamin C help you absorb copper, so nuts or lentils alongside lunch beat them solo.

🛑 Tempted to buy a copper supplement after seeing it online? You probably don't need one. Copper is hard to measure, so a "you're low" claim is hard to confirm (standard tests miss mild shortfalls), and a varied diet covers most people.

🔎 Do a 10-second exception check. Copper is only worth a second thought if you take high-dose zinc most days, you've had weight-loss or other gut surgery, or you eat a very narrow diet. If none of those is you, you can stop thinking about it.

⚠️ If you do take copper, keep it small: around 1 mg a day, and well under 10 mg.
More isn't better: your body only uses about 1 mg a day, and too much copper is harmful.