Copper has had a glow-up. There are copper water bottles on wellness shelves, copper bracelets for sore joints, copper mugs for cocktails, and supplement labels promising energy and a sharper mind. The pitch is always the same: a forgotten mineral you're probably missing.
Reality is stranger. Real copper deficiency is uncommon, and when it does happen, the cause is usually something you'd never connect to copper, sitting in an ordinary bathroom. It disguises itself so well that it has been mistaken for other diseases. And one of the trendiest ways to get more copper is a reliable way to get too much.
What copper does
Your body holds only about the weight of a few grains of rice in copper, and it puts every bit of it to work. Copper sits at the heart of enzymes that do some of the body's most basic jobs.
One of them helps move iron out of storage and into new red blood cells. Another stitches collagen and elastin together, the fibres that give skin, bones and artery walls their strength and stretch. Others help build the insulation around nerves, make the brain's chemical messengers, colour your hair and skin, and mop up the damaging by-products of burning fuel for energy.
Some animals cut out the middleman. Octopuses, crabs and snails carry oxygen with a copper protein, which is why their blood turns blue. Ours runs on iron, with copper as the helper that moves it.
Hair colour is the job you can see. The enzyme that makes pigment depends on copper, and in small groups of teenagers and young adults going grey early, blood copper ran lower than in their peers. It's a link, and grey hair has plenty of other causes, starting with your parents.
The clearest picture of what copper does comes from what happens without it. Babies born with Menkes disease have a faulty copper pump and can barely absorb copper from food. Their hair grows sparse, brittle and oddly kinked, like steel wool, their artery walls weaken, and without treatment most die before the age of three. Every one of those signs traces back to a copper enzyme that had nothing to work with.
Where it comes from
Copper is spread widely through food, and the richest sources are animal ones. A single serving of beef liver carries about two weeks' worth of copper, and a serving of oysters around five days' worth. Tins of keep in the cupboard for the weeks when fresh ones are out of reach. Crab, cocoa, cashews, sunflower seeds, shiitake mushrooms and potatoes all add useful amounts. An ounce of dark chocolate, the 70 to 85 per cent kind, covers more than half a day's copper.
For a healthy adult eating real food, that's usually plenty. In the US, the average diet already brings in more copper than the body needs each day. Liver once a week covers it on its own, with room to spare. If liver on a plate is a step too far, a in capsules is the freeze-dried version. Liver every day overshoots: one serving carries more copper than the daily upper limit for adults, and more than twice the upper limit for vitamin A.
The deficiency hiding behind zinc
When copper deficiency does happen, the cause is often zinc.
Zinc and copper compete in the gut, and zinc wins. Take a lot of zinc for weeks or months, for colds, skin or immunity, and the cells lining the gut start making a protein that grabs copper and holds on to it. Those cells are shed every few days, and the copper leaves with them. It never reaches the blood. A week of zinc lozenges for a cold is a different thing from months of zinc tablets, because the drain builds over weeks.
One supplement already plans for it. The eye vitamins taken for macular degeneration carry a large amount of zinc, and copper was added to the formula on purpose, to stop the zinc draining it.
The strangest source is denture cream. Some brands used to contain zinc, and people who went through them quickly, sometimes several tubes a week to hold loose dentures in place, swallowed enough zinc to drain their copper. They turned up with anaemia, falling white blood cell counts, numb feet and unsteady legs, and the cause sat on the bathroom shelf.
Two other routes run through the gut. Weight-loss surgery that bypasses the upper small intestine skips the stretch where copper is absorbed, and copper deficiency can appear years after the operation. Coeliac disease damages the same stretch of gut, and in one group of 200 people with coeliac disease, 15 per cent were low in copper.
The great impostor
Copper deficiency is easy to miss because it looks like something else.
The blood goes first. Anaemia appears, and it refuses to budge with iron tablets, because the iron is there and the copper enzyme that moves it is idle. White blood cells fall too, which leaves the body open to infection. The bone marrow can look so disordered under a microscope that copper deficiency has been mistaken for a pre-cancerous marrow disease.
Then the nerves. Low copper damages the spinal cord in a pattern almost identical to severe vitamin B12 deficiency: numbness and tingling that start in the feet, an unsteady, wide-legged walk, and trouble knowing where your feet are in the dark. When B12 comes back normal and the symptoms keep going, copper belongs on the list.
Caught early, the blood problems usually reverse once copper is restored. Nerve damage recovers more slowly and sometimes only partly, which is why it pays to think of copper sooner.
Who should get checked
For most healthy adults, food takes care of copper. The people worth checking are the ones with a known route to deficiency: anyone taking zinc supplements for months, anyone who has had weight-loss surgery, people with coeliac or other gut disease, and anyone with anaemia that iron tablets leave untouched, or numbness that B12 fails to explain.
The check is a simple blood test for copper and for ceruloplasmin, the protein that carries most of it. Read the result with care: the pill and pregnancy push blood copper up, and so does any inflammation, so a normal-looking number can hide a shortfall. If you take zinc for the long haul, copper belongs in the same conversation, because the two only work as a pair.
Too much copper
Copper goes wrong in the other direction too, and some of the routes look wholesome.
Water pipes. Copper pipes are safe for everyday use, and water that has sat in them overnight or over a holiday can pick up enough copper to upset the stomach. Blue-green stains around the sink or bath, or a metallic taste to the water, are the signs to look for. Running the tap until the water turns cold flushes out what has been sitting in the pipes, and a shows what your own tap water carries.
Acidic drinks in copper. Copper dissolves into acid far faster than into plain water, which is why copper pans are lined with tin or steel. Food safety rules ban unlined copper from touching anything acidic, including vinegar, fruit juice and wine. That covers lemon water in a copper bottle and the classic copper cocktail mug filled with lime juice and ginger beer. A lined copper pan is fine until the lining wears through and copper shows, and at that point it needs relining or retiring.
Supplements. Copper is a trace mineral for a reason. Adding it on top of a normal diet, without a known shortfall, raises the load on the liver, which is where excess copper ends up. The main way out of the body is the bile, so anyone with liver disease or blocked bile flow clears copper poorly and has the least room for extra.
Copper coils. One worry you can drop: the contraceptive coil releases copper inside the womb, and blood copper barely moves in women wearing one: no change at all over two years in one group, a slight rise in another.
Wilson's disease. In this rare inherited condition, the liver fails to send copper out into the bile, so it builds up in the liver and then the brain. It usually shows itself somewhere between childhood and the mid-thirties, as unexplained liver trouble, a tremor, clumsiness or a change in mood, and it can show up in the eyes as a golden-brown ring around the coloured part. Found early, it's treatable, and a copper blood test is the first step. Treatment uses medicines that pull copper out, and zinc, the same mineral that causes deficiency in everyone else, used here to block copper deliberately.
The copper water pot, in fairness
The copper water vessel deserves a fair hearing, because part of its reputation holds up. When water spiked with the bacteria behind diarrhoea, typhoid and cholera was left overnight in copper pots, the bacteria were gone by morning, and the copper that leached into the water stayed well within drinking water limits.
Bare copper kills on contact. Bacteria and viruses left on it die within hours, and copper was the first solid material the US environmental regulator registered as an antimicrobial. Hospitals have put that to work. When intensive care rooms were fitted with copper bed rails, tray tables and other high-touch surfaces, patients in those rooms caught infections less than half as often as patients in ordinary rooms.
The hard line is milk. In a rural corner of the Austrian Tyrol, 138 young children died of liver cirrhosis between 1900 and 1974, and the milk they drank had been kept in untinned copper or brass pots. In India, milk left in a brass pot for six hours came out carrying more than twenty times its copper.
So a copper pot with plain water is a reasonable old habit. Keep it for water, clean it, and keep milk, lemon, juice and anything fizzy or sour out of it.
Bracelets and big claims
Copper bracelets have been sold for aching joints for generations. When people with rheumatoid arthritis wore a copper bracelet, a magnetic strap and two straps with the magnetism weakened or removed, five weeks each, none of them did better than the stand-ins for pain, swelling or blood markers of inflammation. A bracelet makes nice jewellery.
The bigger claims about hearts and brains run on thinner evidence. Animals starved of copper develop heart problems, and copper levels have been linked with cholesterol, while the findings in people point in different directions. In Alzheimer's disease, both too little and too much copper have been found in the brain, and nobody yet knows which way it runs. These are open questions, and a supplement is a poor way to answer them.
A mineral to balance
Copper was never forgotten. Your body has been managing its few grains of it all along, and it only goes wrong when something tips the balance: months of zinc, a gut that struggles to absorb, a bottle of lemon water, a supplement nobody needed.
So skip the bracelet and the copper pills, keep the copper bottle for plain water, and put liver on the menu once a week. And if you've been taking zinc for months, get your copper checked before your blood or your nerves do the asking.
Taking more than one supplement? Why Your Mineral Supplements Keep Canceling Each Other Out — which minerals compete for the same way in, and how to take them so each one counts.
Wondering which shortfalls are worth testing for? Nutrient Deficiencies: Who's at Risk and Which Test to Get — who tends to run low in what, and the blood test that shows it.
Know someone who's been taking zinc tablets every day for months? Send them this. Their copper may be paying for it.
Disclaimer: This article is general information. For advice about your own health, talk to a qualified health professional. Check any mineral supplement with whoever prescribes your medicines, especially after weight-loss surgery or with liver disease.
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