“Science hasn’t really dug into copper in the past, but that is changing,” says King. “As the picture of its role in the body becomes clearer, I think we’ll see that it’s as powerful as something like vitamin D.”
How much is enough?
One of the reasons copper has been overlooked is that it’s hard to measure. “It involves a very specialized, very expensive test that is rarely administered in the doctor’s office,” says King. While it may be hard to know for sure if you’re copper deficient, there are plenty of telltale signs that you should try to increase your intake.
“A copper deficiency can resemble an iron deficiency in terms of symptoms, especially fatigue,” says Sonya Angelone, RDN, a spokesperson for the Academy of Nutrition and Dietetics. Achy joints are a common first sign, according to King, and over the long term a lack of copper can contribute to osteoporosis. She warns that people with malabsorption issues—including anyone with celiac disease or chronic diarrhea—have an increased risk of not absorbing enough copper.
The good news is that it isn’t hard to get enough copper—provided you eat a pretty healthy, well-balanced diet complete with lots of veggies. “Copper is found in minimally processed plant foods,” says Angelone, noting that dark leafy greens like swiss chard, mustard greens, and kale are good picks. Nuts (particularly cashews), seeds, whole grains, oysters, and mushrooms contain copper as well.
“One of the richest sources of copper is liver—that’s where copper tends to hang out in any animal,” says King, though she acknowledges liver is a tough sell for many people. You don’t need to eat it to get enough copper, but if you do happen to like it, it’s an easy way to meet your copper quota.
The recommended daily allowance for copper is 0.9 mg. One ounce of beef liver has roughly twice that amount; one ounce of cashews contains 0.6 mg; one cup of cooked kale contains 0.2 mg.
Not planning on having liver for dinner? It’s easy to get what you need by taking in smaller amounts throughout the day, says Angelone. For a copper-conscious meal plan, she recommends the following:
Breakfast: ¾ cup whole grain cereal (0.1 mg), 1 cup strawberries (0.07 mg), low fat milk or milk alternative
Lunch: lentil soup with spinach (0.58 mg), ⅓ cup hummus (0.5 mg), 1 ounce whole wheat crackers (0.1 mg), orange (0.06 mg)
Dinner: grilled fish with ½ cup crimini mushrooms (0.18 mg), 1 cup asparagus (0.3 mg), ½ cup brown rice (0.1 mg), salad with 2 cups lettuce (0.05 mg)
Too much of a good thing
Once you learn how vital copper is to your health, you might be tempted to go out and buy a supplement. Don’t. The upper safe limit for copper is 10 mg a day, and if you get too much it will build up in your liver. “You can get a metallic taste in your mouth, vomiting, and even cirrhosis of the liver,” says King. But this warning only applies to supplements—it’s almost impossible to get a toxic dose by eating copper-rich foods.