The World's Healthiest Foods

Basic Description

Copper is a key mineral in many different body systems. It is central to building strong tissue, maintaining blood volume, and producing energy in your cells. Yet, for all its critical importance, you don't have much copper in your body—barely more than the amount found in a single penny. And those pennies in your pocket are only 2.5% copper by weight.

In the foods we commonly eat, there are only very small amounts of copper. As much as any dietary mineral, the amount of copper you eat is directly related to the amounts of minimally processed plant foods you get every day.

Of the World's Healthiest Foods, 12 are rated as excellent sources of copper, 37 are very good, and 42 are rated as good.

Role in Health Support

Antioxidant Protection

Copper is one of the co-factors for one form of an enzyme called superoxide dismutase (SOD). SOD is one of the major antioxidant enzymes in the body. As a measure of how important SOD is, amyotrophic lateral sclerosis—also known as Lou Gehrig's disease—is thought to be the result of an underfunctioning (SOD) enzyme.

From recent studies where young volunteers were fed a copper-depleted diet, reduced SOD function was an early result. In fact, these changes were apparent within the first month of the experimental diet.

In more advanced cases of copper deficiency, including people who have undergone gastric bypass surgery, this loss of antioxidant protection over a period of years can lead to irreversible damage to the nervous system. However, this does not appear to occur without the types of unusual deficiency risks detailed below.

Bone and Tissue Integrity

Copper is required to manufacture collagen, a major structural protein in the body. When copper deficiency becomes severe, tissue integrity—particularly bones and blood vessels—can begin to break down.

Luckily, it appears at the present time that a very severe and prolonged dietary deficiency of copper is necessary to lead to overt problems. For example, premature babies with immature gastrointestinal tracts can develop bone problems related to copper deficiency.

At least one recent author has speculated that the marginal copper status of the diets of about one-quarter of adults in the U.S. is related to eventual development of osteoporosis in some members of this group. For adults with borderline copper intake from food, deficient intake of nutrients like calcium and vitamin D is still likely to put them at greater risk than borderline intake of copper. Still, this low copper intake may be increasing their risk of osteoporosis and is very likely to be the subject of future research.

Energy Support

Copper plays two key roles in energy production. First, it helps with incorporation of iron into red blood cells, preventing anemia. Second, it is involved with generation of energy from carbohydrates inside of cells.

Each of these uses of copper also requires iron, and for this reason, the symptoms of copper deficiency can mimic those of low iron intake. Lentils, and sesame seeds are just a few examples of World's Healthiest Foods rich in both iron and copper.

Cholesterol Balance

Animal studies have demonstrated that copper-deficient diets lead to increases in blood cholesterol levels. In humans, this appears to be true in some situations, but not all. This should not be a surprise, as human diets are much more varied than those of laboratory animals. Interestingly, the effect of copper deficiency appears to be through increased activity of an enzyme called HMG-CoA reductase—the same enzyme targeted by the most commonly prescribed cholesterol medications.

Summary of Food Sources

With the single exception of shrimp, all of the very good or excellent sources of copper among the World's Healthiest Foods are plant foods. These best copper sources are varied, however, and come from many different food groups.

Our top three sources of copper are sesame seeds, cashews, and soybeans. Any of these three foods will bring at least three-quarters of your daily copper requirement. Shiitake and crimini mushrooms are also excellent copper sources and will provide 40 to 75% of your daily need.

Many of the excellent food sources of copper are leafy greens, including turnip greens, spinach, Swiss chard, kale, and mustard greens. Asparagus and summer squash are two other excellent vegetable sources of copper.

The good and very good sources of copper include many legumes, whole grains, nuts, and seeds. For example, flax seeds, walnuts, and garbanzo beans are rated as very good sources of copper.

Combining a grain- or legume-based recipe with an excellent vegetable source of copper could very easily provide the entire daily requirement of this mineral. For example, 7-Minute Sautéed Crimini Mushrooms would meet or exceed your daily Recommended Dietary Allowance (RDA) for copper.

Introduction to Nutrient Rating System Chart

Impact of Cooking, Storage and Processing

Storage of foods does not significantly affect their copper content. Like other minerals, copper will stay available in your foods as long as they are properly stored for recommended periods of time.

Processing whole grains into refined ones by removing the outer layers will significantly reduce copper content. For example, refined white flour has less than half the copper content of the whole wheat kernel. This is a large price to pay nutritionally.

Along the same lines, foods that are cooked at high temperatures for extended periods can get brown on the outside. This effect is common with some cooking methods, and can substantially impair our ability to absorb the copper from foods. For more information on why we choose shorter cook times and lower temperatures to enhance the health benefits of foods, read this article.

Cooking vegetables reduces copper content in a manner that increases with both the volume of cooking water and the heating time. Lightly cooking vegetables by steaming should therefore help to minimize copper losses. For example, lightly boiling spinach only reduces the copper content by an insignificant fraction.

Risk of Dietary Deficiency

Between one-quarter to one-half of Americans fail to reach Dietary Reference Intake (DRI) recommendations for copper on a daily basis. In fact, in experimental research where scientists intentionally created copper-deficient diets, the composition of those diets was quite similar to the average U.S. diet. These copper-depleted diets were based largely around meats, refined grains, and dairy foods. As noted above, this common diet pattern was low enough in copper to cause significant detrimental effects to antioxidant enzymes within weeks.

About 5% of U.S. adults eat a diet with less copper than was used in these studies. In fact, this 5% of U.S. adults obtain less copper from their diets on a daily basis than would be found in a single serving of navy beans—a food not even close to the best source of copper in our rating system.

According to a statistical analysis published in 2011, copper deficiency risk has risen substantially over the past 75 years. This is probably most related to modern food processing methods, although copper depletion of soils may also contribute to some extent.

Other Circumstances that Might Contribute to Deficiency

Most of the non-dietary factors that contribute to copper deficiency tend to involve somewhat uncommon medical conditions. Gastric by-pass surgery stomach surgeries are two examples. Certain cancers—like pancreatic cancer—can increase risk of copper deficiency, as can celiac disease when it is poorly managed or untreated.

Relationship with Other Nutrients

Prolonged supplementation with doses of zinc that go beyond normal dietary intake ranges can interfere with copper absorption and utilization, leading to copper deficiency.

Risk of dietary Toxicity

Most U.S. adults struggle to achieve the Dietary Reference Intake (DRI) for copper intake, so the risk of dietary toxicity from copper is really only seen in a person with one of two issues.

The first issue would be a genetic condition that impairs the ability to clear copper from the body, leading to a buildup to toxic levels. The most likely reason for this is a condition called Wilson's disease, an inherited genetic mutation. Wilson's disease is both rare (as few as one case per 100,000 people) and very severe. People with this condition—and other similar genetic mutations that affect copper metabolism—are usually diagnosed by the time they reach adulthood.

A more common reason to see risk of copper toxicity is due to excessive exposure from the water supply. This is not generally caused by excessive amounts in city water supplies—these are monitored by the Environmental Protection Agency (EPA)—but by leaching from old copper pipes and fittings.

The amount of copper that is leached into water from old pipes can be significant, but it varies widely. If you have concern about the amount of copper in your tap water, you can take some simple steps to help reduce the exposure risk. First, the amount of leaching is directly related to the amount of time the water spends in the copper pipe. Use the first gallon or so of water in the morning for non-cooking tasks (for example, cleaning or watering plants). In fact, anytime you are getting drinking water from your tap, you can let the water run until you feel it get noticeably colder. Second, hot water will leach more copper than cold water, so if you want hot water for a beverage, you can use cold water and then heat it up rather than getting hot water out of your tap. Finally, you could install a water filter to remove much of the copper. Both activated charcoal and reverse osmosis filters should remove significant amounts of copper from your water. However, before taking any of these steps, make sure that toxicity risk is a greater risk for you than deficiency risk! You don't want to be lowering the amount of copper in your drinking water if you actually need more copper than you are getting from your food.

Disease Checklist

• Anemia
• High cholesterol
• Fatigue
• Low immune function
• Osteoporosis
• Wound healing
• Cardiac arrhythmia
• Arthritis

Public Health Recommendations

In 2001, the Food and Nutrition Board of the National Academy of Sciences published a set of Dietary Reference Intakes (DRIs) that established both Recommended Dietary Allowances (RDAs) and Adequate Intakes (AIs) for copper. (The recommendations for children under one year of age below are AIs, and all other recommendations are RDAs.)

• 0-6 months: 0.2 mg
• 6-12 months: 0.22 mg
• 1-3 years: 0.34 mg
• 4-8 years: 0.4 mg
• 9-13 years: 0.7 mg
• 14-18 years: 0.89 mg
• 19+ years: 0.9 mg
• Pregnant women: 1.0 mg
• Lactating women: 1.3 mg

The DRI report also established a Tolerable Upper Intake Level (UL) of 10 mg per day for adult men and women.

The Daily Value (DV) for copper is 2 mg per 2000 calories. This is the value that you will see on nutrition labels on foods.

At WHFoods, we use the DRI of 0.9 milligrams for adult men and women 19 years and older as our recommended daily intake level for copper.

References

• Amaro Lopez MA, Moreno Rojas R, Zurera Cosano G, et al. Nutritional changes in the essential trace elements content of asparagus during industrial processing. Food Res Int 1999;32:479-86.
• Doblado-Maldonado AF, Pike OA, Sweley JC, et al. Key issues and challenges in whole wheat flour milling and storage. J Cereal Sci 2012;56:119-26.
• Georgopoulos PG, Wang SW, Georgopoulos IG, et al. Assessment of human exposure to copper: A case study using the NHEXAS database. J Expo Sci Environ Epidemiol 2006;16:397-409.
• Goodman BP, Mistry DH, Pasha SF, et al. Copper deficiency myeloneuropathy due to occult celiac disease. Neurologist 2009;15:355-6.
• Griffith DP, Liff D, Ziegler TR, et al. Acquired copper deficiency: a potentially serious and preventable complication following gastric bypass surgery. Obesity 2009;17:827-31.
• Hoyle GS, Schwartz RP, Auringer ST. Pseudoscurvy caused by copper deficiency. J Pediatr 1999;134:379.
• Hunt CD, Meacham SL. Aluminum, boron, calcium, copper, iron, magnesium, manganese, molybdenum, phosphorus, potassium, sodium, and zinc: Concentrations in common Western foods and estimated daily intakes by infants; toddlers; and male and female adolescents, adults, and seniors in the United States. J Am Diet Assoc 2001;101:1058-60.
• Institute of Medicine. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. National Academy Press: Washington DC, 2001.
• Klevay LM. Is the Western diet adequate in copper? J Trace Elem Med Biol 2011;25:2004-12.
• Marquardt ML, Done, SL, Sandrock M, et al. Copper deficiency presenting as metabolic bone disease in extremely low birth weight, short-gut infants. Pediatrics 2012;130:695-8.
• Mesias M, Seiquer I, Navarro MP. Consumption of highly processed foods: Effects on bioavailability and status of zinc and copper in adolescents. Food Res Int 2012;45:184-90.
• Nations SP, Boyer PJ, Love LA, et al. Denture cream: an unusual source of excess zinc, leading to hypocupremia and neurologic disease. Neurology 2008;71:639-43.
• Turnlund JR, Scott KC, Peiffer GL, et al. Copper status of young men consuming a low-copper diet. Am J Clin Nutr 1997;65:72-8.