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The common saying, “too much of a good thing,” does have a place in nutrition. Excess and deficiencies of vitamins and minerals can lead to imbalances and health problems. Many nutrients also work as antagonists with one another, which can mean that when one is too high, it causes the other to become too low, possibly increasing susceptibility to certain acute or chronic conditions.

No pair better exemplifies this interrelationship than zinc and copper. When the copper-to-zinc ratio becomes too high, it can lead to health problems. Before we go too far into the relationship of these two essential minerals, let’s review the basics.

Zinc 101

Zinc is a trace mineral required for over 300 enzymes involved in cell growth, antioxidant activity, immune response, and more. For example, zinc is a cofactor for superoxide dismutase, an important antioxidant enzyme. The human body also expresses more than 3,000 zinc proteins, which comprise at least 10% of the human proteome, defined as all the human body proteins. The largest depots of zinc in the human body are muscle and bone, and though the body does not have a reservoir for zinc as it does for iron, it can mobilize zinc to tissues with higher requirements.

Zinc plays numerous roles in the body. There are more than 3,000 zinc proteins in the human body, some of which are vital enzymes, and some whose functions are currently unknown. Zinc ions also work as signalers in the body. The body requires specific cellular concentrations of this mineral to ensure the zinc reactions can take place without disrupting the work of other essential ions. Although considered a trace element, in the cell itself, zinc is actually incorporated as a cofactor more often than many other essential vitamins, and the concentration is almost as high as that of ATP, the energy of the cell.

Roles of zinc in the body include:

• Antioxidant
• Bone structure
• Cell division
• Collagen synthesis
• DNA synthesis
• Gene transcription
• Growth and development
• Immune function
• Insulin formation and signaling
• Male fertility
• Protein synthesis
• Thyroid function
• Wound healing

The Recommended Dietary Allowance (RDA) in the U.S. is 11 mg daily for adult males and 8 mg daily for adult females. Pregnant and lactating women, teenagers, children, and infants have different requirements.

Other than a lack of intake, risk factors for zinc deficiency include poor absorption from gastrointestinal disorders such as Crohn’s disease; increased requirements, such as during pregnancy; and increased losses from diuretic use, diarrhea, alcohol use, and burns. Vegetarians and vegans might be at an increased risk of deficiency because plant-based sources of zinc, such as beans, often contain phytates, which inhibit absorption of zinc. In some estimates, vegans and vegetarians may require 50 percent more zinc than non-vegetarians.

Signs of deficiency include:

• Appetite loss
• Brittle hair
• Delayed wound healing
• Diarrhea
• Hair loss
• Impaired taste and smell
• Light sensitivity
• Low bone mineral density
• Male infertility
• Mental illness
• Nail ridging and inflamed cuticles
• Recurrent infections
• Skin issues, including lip inflammation, dermatitis, and lesions

While zinc is essential to health, supplementing in high doses can lead to adverse side effects including nausea, diarrhea, dizziness, headache, appetite loss, and copper deficiency.

Copper 101

Copper also plays a role as a cofactor in enzymes involved in several biochemical processes, including redox reactions, iron metabolism, antioxidant defense, energy production, immune function, and neuropeptide synthesis.

Copper deficiency is uncommon, but causes include a diet low in copper, malabsorption, enteropathies, zinc supplement overuse, and ingesting zinc-containing denture cream. Copper absorption can be decreased by phytates, calcium, zinc, and ascorbic acid. Additionally, Menkes disease is a rare genetic disorder causing copper deficiency.

The RDA for copper is 900 ug/day for adult men and women. As with zinc and most other nutrients, the levels for pregnant and lactating women, teenagers, children, and infants differ.

Some signs of copper deficiency include:

• Anemia
• Neutropenia
• Neurological symptoms (symptoms may resemble B12 deficiency)

Copper deficiency in pregnant women can affect the fetus and lead to underdevelopment of the nervous system, poor growth, and miscarriage. Compared to other organs like the liver and brain, the heart is more sensitive to copper deficiency. Chronic copper deficiency and reduced function of copper transporters and copper-binding proteins (e.g., SOD1 and LOX) may be implicated in heart disease. On the other hand, a meta-analysis found a significant association between heart failure and high serum copper, and evidence for copper’s role in cardiovascular disease appears to be inconsistent.

Despite its importance, excess copper can potentially be toxic and can harm the liver, brain, heart, muscles, bones, and eyes. High levels of copper can contribute to excessive oxidative stress and are implicated in a number of health conditions. A prospective study involving more than 2,800 adults concluded that high serum copper levels are a risk factor for all-cause and cardiovascular disease mortality. In pregnant women, excess copper can contribute to low birth weight, preterm birth, and gestational diabetes.

Copper may increase inflammation and reduce levels of brain-derived neurotrophic factor (BDNF), which can increase the risk of depression. However, the role of copper in depression is controversial as it has been shown to have both positive and negative associations, as well as no association at all. A 2023 cross-sectional study using NHANES data from 2011-2016, totaling 5,419 adults (ages 20 years and older), found that depression symptoms were higher in serum samples with high levels of copper. The association was not significant in a model that adjusted for variables such as gender, race, cigarette smoking, and diabetes; however, results did show that the risk of depression symptoms was worsened by obesity in those with high levels of copper.

Vascular-type senile dementia (VD) occurs after stroke or ischemia when blood flow to the brain is disrupted and glutamate is released due to neuronal excitation. Excess zinc is released with glutamate and plays a role in neurodegeneration in this scenario. It is also hypothesized that long-term neuronal excitation during ischemic conditions allows zinc and copper to coexist in the synaptic cleft, and it is copper that enhances neurotoxicity and ultimately leads to VD.

Excessive amounts of copper may be consumed via acidic foods cooked in uncoated copper cookware and drinking water with high copper levels. Research regarding the effect of copper intrauterine devices (IUDs) on blood copper levels is inconclusive. Wilson’s disease is another rare genetic disorder in which copper accumulates in the body and causes liver- and brain-related issues.

Antagonism between Copper and Zinc

Copper and zinc are antagonists, which means they work against one another and compete for binding sites. When there are excess zinc levels, metallothionein protein production increases in the small intestine to provide a binding site for zinc and prevent toxicity. However, metallothionein proteins have a higher affinity for copper compared to zinc. This increased affinity means that copper binds to the metallothionein proteins, creating a metallothionein‐copper complex in enterocytes, which is then excreted in the feces and may lead to a copper deficiency. On the other hand, excess copper increases oxidative stress via Fenton-type chemistry or by forming a complex with glutathione and reducing glutathione levels.

Zinc and copper work hand in hand in many of their beneficial tasks, so it is important to consider these minerals together to ensure a healthy balance. One way to do this is to consume adequate amounts of both minerals, primarily through diet.

Food Sources of Zinc and Copper 

As with most nutrients, food is the ideal source. Many foods have both zinc and copper, making it easy to maintain a healthy ratio. For example, foods in the nuts, seeds, and legume families often are rich sources of both zinc and copper, and they also have many other benefits. For example, Brazil nuts, known for their high selenium content, are also rich in zinc and copper. The average concentration of zinc in 100 grams of Brazil nuts is 4.72 mg, and the same serving has an average 1.83 mg of copper. Granted, an average serving of nuts is one ounce, which is approximately 5-6 Brazil nuts. One ounce of Brazil nuts contains 1.14 mg of zinc and 0.488 mg of copper. In addition to these nutrients, Brazil nuts provide healthy fat, protein, fiber, phytonutrients, magnesium, calcium, and phosphorus. These work synergistically to promote optimal health further.

Besides Brazil nuts, some food sources of zinc, from highest to lowest, include:

• Oysters
• Beef
• Blue crab
• Fortified breakfast cereals
• Pumpkin seeds
• Pork
• Turkey
• Cheese
• Shrimp
• Lentils
• Sardines
• Greek yogurt
• Milk
• Peanuts
• Brown rice
• Eggs
• Kidney beans

Food sources of copper, also from highest to lowest, include:

• Beef liver
• Oysters
• Cocoa
• Potatoes
• Shiitake mushrooms
• Cashews
• Crab
• Sunflower seeds
• Tofu
• Chickpeas
• Millet
• Salmon
• Whole wheat pasta
• Avocado
• Figs
• Spinach
• Asparagus
• Sesame seeds
• Turkey

Several common foods contain copper, but people eating the typical “SAD,” or Standard American Diet, might still risk deficiency. The number of people presenting with copper deficiency may be more than previously recognized, with possible causes being a change in eating habits, gastrointestinal diseases and surgeries, and excessive zinc consumption.

While it’s important to avoid both deficiency and excess of either nutrient, food sources are not usually the cause of imbalances between copper and zinc. Instead, supplements and other sources like zinc in denture adhesives and copper leached from copper cookware, especially when cooking acidic foods, can contribute to imbalances between zinc and copper. For those using supplements, it is often recommended to include 1 mg copper for every 8-15 mg zinc. This provides a ratio similar to that found in the RDA for copper and zinc.

Final Remarks

Copper and zinc are minerals that should be considered together because of their antagonistic relationship and health consequences of both deficiency and excess. As always, consult with a doctor or other healthcare professional who can guide zinc and/or copper intake and supplementation that ensures adequate amounts of both.