The Copper content of Nuts, Seeds, and Legumes

Copper content of nuts, seeds, legumes

Storing foods high in carbohydrates is relatively easy: white long-grain rice and white pasta keep very well and are high in carbs. But stored protein is more problematic. Rice offers about 8% of its calories in the form of protein, and pasta about 14%. By my estimation, your diet should get about 20% of calories from protein. Add some fruits and vegetables to your diet, and the percent protein drops further. So you can’t eat enough rice and pasta to obtain that much protein.

Beans and other legumes are good sources of stored protein. For example, pinto beans (dry) offer about 25% of calories as protein. Other legumes (peas, chickpeas, soybeans, lentils, other beans) are similarly high in protein. Nuts and seeds are another good source of stored protein.

However, legumes, nuts, and seeds are also rather high in copper. As a micronutrient, some copper in the diet is healthy and even essential. But recent studies have shown that excess copper intake is particularly unhealthy.

A 2006 study found that high copper levels increased overall cancer mortality by 40% and all-cause mortality (that’s all causes of death put together) by 50%. Low zinc combined with high copper was even worse, increasing cancer mortality by 2.7 times and all-cause mortality by 2.6 times. And a 2011 study found that high copper intake (from dietary supplements) increased the risk of death from cardiovascular disease by 50%.

The problem with storing protein in the form of legumes, nuts, and seeds is that these foods are all high in copper. The RDA for copper for adult men and women is 0.9 mg/day. Only 3.5 ounces (100 g) of sunflower seeds has twice that amount of copper (1.8 mg). And 4 ounces of walnuts has a similarly excessive amount of copper (1.8 mg). Almonds have 1.1 mg of copper per 3.5 oz portion. Almonds, walnuts, and sunflower seeds are healthy in moderate amounts, more in the range of 4 oz/wk rather than per day.

Soy flour is alarmingly high in copper. Defatted soy flour has over 4 mg of copper per 3.5 oz. A single ounce of soy flour has an excessive amount of copper (1.15 mg). Cashews are also problematic, with 2.2 mg of copper per 3.5 oz serving. Lentils have 1.3 mg copper per 3.5 oz portion. But firm tofu has only 0.2 mg of copper per 3.5 oz serving. So when you are eating from stored foods, with limited food choices, you should be careful not to consume too much of any food high in copper.

The copper content of some additional legumes, nuts and seeds:

  • Pinto beans, dry, 0.9 mg copper/3.5 oz
  • Peas, dry, 0.86 mg copper/3.5 oz
  • black beans, dry, 0.84 mg copper/3.5 oz
  • Soybeans, dry roasted, 0.83 mg copper/3.5 oz
  • Navy beans, dry, 0.83 mg copper/3.5 oz
  • Cranberry beans, dry, 0.79 mg copper/3.5 oz
  • Pumpkin seeds, 0.69 mg copper/3.5 oz
  • Peanuts, 0.67 mg copper/3.5 oz
  • White beans (small dry) 0.63 mg copper/3.5 oz
  • Yellow beans (small dry) 0.64 mg copper/3.5 oz

My suggestions to avoid excessive intake of copper:

Never or rarely:
* liver, oysters, soy flour, spirulina, winged bean seeds, brazil nuts, dietary supplements containing copper.

At most, only one of the following foods and amounts per day:
* 15 g (0.5 oz) maximum: dried shitake mushrooms, dried pepeao mushrooms, cocoa powder, unsweetened baking chocolate, sesame seeds (or paste, butter, tahini).
* 30 g (1.0 oz) maximum: soy chips (or similar snacks), cashews, squid.
* 45 g (1.5 oz) maximum: sunflower seeds (or butter), hazelnuts, mixed nuts, dark or semi-sweet chocolate, soy protein isolate, lobster, walnuts, kale, sun-dried tomatoes.
* 60 g (2.0 oz) maximum: pumpkin seeds, pine nuts, lentils, pistachio nuts, flaxseed, pecans, peanuts, crab, tofu, almonds, buckwheat, sorghum.

Also, be cautious about combining multiple foods from the above list. The copper intake is additive. You can look up the copper content of foods in the USDA National Nutrient Database.

Leave a Reply

Your email address will not be published. Required fields are marked *