guest post from susan macfarlane, registered dietitian nutritionist
The Zinc:Copper Ratio
There has been a lot of discussion in the Cronometer forums about the ideal ratio of dietary zinc to copper. A quick Google search suggests that an inability to achieve the correct ratio is a risk factor for a myriad of diseases ranging from depression and fatigue, to childhood ADHD.
However, a closer look at the research suggests that achieving this dietary ratio may not be as important as meeting minimum daily intakes for each nutrient.
Read on to find out more!
What Is Zinc?
Zinc is an essential mineral used by more than 300 enzymes in the human body. It provides cell structure, regulates communication between cells, influences gene expression, supports a healthy immune system, and promotes normal growth and development in children. Zinc also helps other nutrients to work in the body. For example, it is part of a protein that transports vitamin A into the bloodstream and is needed for the absorption of folate (1).
Zinc deficiency is classified as either severe or marginal. Severe cases of zinc deficiency are only seen in rare medical conditions where absorption of zinc from the diet is limited. The condition is characterized by growth stunting and delayed sexual maturation (in children), severe diarrhea, a compromised immune system, night blindness, hair loss, and taste alterations.
Marginal zinc deficiency is commonly found in developing countries and among those with malabsorption conditions, such as Crohn’s disease. Detecting marginal zinc deficiency is challenging since blood levels of the nutrient are kept constant. In these cases, milder symptoms of deficiency may be present (1).
Zinc Deficiency
Zinc deficiency is classified as either severe or marginal. Severe cases of zinc deficiency are only seen in rare medical conditions where absorption of zinc from the diet is limited. The condition is characterized by growth stunting and delayed sexual maturation (in children), severe diarrhea, a compromised immune system, night blindness, hair loss, and taste alterations.
Marginal zinc deficiency is commonly found in developing countries and among those with malabsorption conditions, such as Crohn’s disease. Detecting marginal zinc deficiency is challenging since blood levels of the nutrient are kept constant. In these cases, milder symptoms of deficiency may be present (1).
How Much Zinc Do I Need?
Zinc requirements for various age groups can be viewed below. This requirement was set to match zinc losses, and will meet the needs of ~98% of a healthy population (2).
| Age Group | RDA (mg/day) | UL (mg/day) | |
| Male | Female | ||
| 0-6 months | 2* | 2* | 4 |
| 7-12 months | 3 | 3 | 5 |
| 1-3 years | 3 | 3 | 7 |
| 4-8 years | 5 | 5 | 12 |
| 9-13 years | 8 | 8 | 23 |
| 14-18 years | 11 | 9 | 34 |
| 19->70 years | 11 | 8 | 40 |
* Recommendation is an AI (Adequate Intake) For requirements needed in pregnancy/breastfeeding, please click here. Source: Institute of Medicine. Dietary Reference Intakes: The Essential Guide to Nutrient Requirements. Washington D.C.: The National Academies Press; 2006. Zinc; p 402-413. |
A special note for vegans & vegetarians
Phytic acid is a storage form of the mineral phosphorus found in grains, legumes, nuts, and seeds. Due to its structure, phytic acid interferes with the body’s ability to absorb certain nutrients, including zinc.
As a result, the Institute of Medicine suggests that vegans may require 50% more zinc than non-vegans. However, studies have failed to demonstrate any discrepancy in zinc status between vegans and non-vegans (3). The effect of phytic acid can be reduced by soaking, fermenting, sprouting, and leavening (4).
Can You Consume Too Much Zinc?
Total zinc (i.e. from food and supplements) should not exceed 40 mg per day for adults aged 19 years and older. At levels above this, zinc can interfere with the absorption of copper (since these nutrients compete for the same absorption site), potentially leading to a copper deficiency (2).
Foods Containing Zinc
| Plant-based | Wheat Germ | ¼ cup | 4.8 |
| Pumpkin Seeds | ¼ cup | 2.7-4.4 | |
| Baked Beans | ¾ cup | 4.3 | |
| Hemp Seeds | 3 tbsp | 3 mg | |
| Tempeh | ¾ cup | 2.4 | |
| Lentils | ¾ cup | 1.9 | |
| Peas (chickpeas, black-eyed, split) | ¾ cup | 1.1-1.9 | |
| Sunflower Seeds | ¼ cup | 0.6-1.8 | |
| Tofu | ¾ cup | 1.2-1.7 | |
| Animal-based | Oysters | 75 g | 24.9-59 |
| Beef | 75 g | 4-8.6 | |
| Liver | 75 g | 3-6 | |
| Pork | 75 g | 2.0-6.5 | |
| Chicken | 75 g | 1.3-2.2 | |
| Cheese | 50 g | 1.2-2.2 | |
Source: Dietitians of Canada. Food sources of zinc. 2017. Available from: https://www.dietitians.ca/Your-Health/Nutrition-A-Z/Minerals/Food-Sources-of-Zinc.aspx . Values for zinc are shown in mg. | |||
What Is Copper?
Like zinc, copper is an essential trace mineral with many roles in the human body. For example, copper is involved in the transportation of iron, energy production, and the pigmentation of skin, hair, and eyes. Copper is also found in a powerful antioxidant that stops cell damage caused by free radicals (5).
Copper Deficiency
Copper deficiency is rarely seen outside of genetic mutations that interfere with the ability to absorb copper. However, pre-mature/malnourished infants and individuals with malabsorption (i.e. Crohn’s, celiac, short-bowel syndrome) may be at risk of developing copper deficiency. Symptoms of copper deficiency include anemia, low white blood cell count, loss of pigmentation, impaired growth and in infants, osteoporosis (5).
How Much Copper Do I Need?
Copper requirements for various age groups can be viewed below. This level of intake was set to maintain copper status and account for copper losses, and will meet the needs of ~98% of a healthy population (6).
| Age Group | RDA (mg/day) | UL (mg/day) | |
| Male | Female | ||
| 0-6 months | 0.2* | 0.2* | Unknown |
| 7-12 months | 0.22* | 0.22* | Unknown |
| 1-3 years | 0.34 | 0.34 | 1 |
| 4-8 years | 0.44 | 0.44 | 3 |
| 9-13 years | 0.7 | 0.7 | 5 |
| 14-18 years | 0.89 | 0.89 | 8 |
| 19->70 years | 0.9 | 0.9 | 10 |
* Recommendation is an AI (Adequate Intake) For requirements needed in pregnancy/breastfeeding, please click here. Source: Institute of Medicine. Dietary Reference Intakes: The Essential Guide to Nutrient Requirements. Washington D.C.: The National Academies Press; 2006. Copper; p 304-311. | |||
Can You Consume Too Much Copper?
The body does an excellent job of regulating copper to prevent deficiency and toxicity. At high intakes (i.e. 7.5 mg per day), copper absorption is reduced and excretion is increased, with the opposite occurring at lower intakes of copper.
Nonetheless, copper from food, supplements, and water should not exceed 10,000 mcg or 10 mg per day, as it could result in liver damage (5, 6).
Foods Containing Copper
| Plant-based | Cashews | ¼ cup | 0.7-0.8 |
| Pumpkin or sunflower seeds | ¼ cup | 0.6-0.7 | |
| Lentils | ¾ cup | 0.4-0.7 | |
| Walnuts | ¼ cup | 0.4-0.5 | |
| Mushrooms (cooked) | ½ cup | 0.4-0.5 | |
| Beans | ¾ cup | 0.3-0.5 | |
| Tofu | ¾ cup | 0.3-0.4 | |
| Hummus | ¼ cup | 0.3 | |
| Avocado | ½ fruit | 0.1-0.5 | |
| Animal-based | Liver | 75 g | 10.9-11.3 |
| Oysters | 75 g | 1.1-4.3 | |
| Lobster | 75 g | 1.2 | |
| Crab | 75 g | 0.5-0.9 | |
| Goat Cheese | 50 g | 0.3-0.4 | |
| Source: Practice-based evidence in Nutrition. Dietary sources of copper [pdf]. 2016. Values are shown in mg | |||
Checking Your Omega 6: Omega 3 Ratio In Cronometer
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Scroll all the way to the bottom of your Daily Report or Nutrition Report, and you’ll find your Omega : Omega 3 nutrient ratio.
The Ideal Zinc:Copper Ratio
This is a difficult question to answer for several reasons. The first being that there is a difference between the dietary ratio of zinc to copper and the blood (or serum) ratio of zinc to copper, and it is the latter that seems to be more relevant in health and disease (7). In addition, it is fairly easy to alter your ratio of dietary zinc to copper through food or supplements, but this doesn’t necessarily result in a shift in blood levels of zinc and copper, unless intake becomes extreme, or an inflammatory condition is present (1,5).
Secondly, there are other nutrients, most notably iron, that interfere with the absorption of copper and zinc, thereby altering the ratio of zinc to copper in the blood, but not the diet (1,5).
Nonetheless, it is common practice to recommend a ratio of 8-15 mg of zinc for every 1 mg of copper consumed. However, this ratio seems to be more important when supplementing zinc and copper, compared to meeting needs through diet alone (7).
Tips For Perfecting Your Zinc:Copper Ratio
Aim To Meet Zinc & Copper Requirements Through Your Diet
Many people rely on vitamin and mineral supplements to meet their requirements of essential nutrients. However, it is best to avoid supplementing, unless indicated, given that nutrients are often absorbed in higher concentrations from supplements and can interfere with the absorption of other important vitamins and minerals.
For example, many women are advised to supplement iron, but at high doses, iron can interfere with the absorption of zinc, thereby altering the ratio of zinc to copper. And if high doses of zinc are supplemented, copper deficiency is known to occur (although elevated copper does not seem to interfere with zinc absorption, provided zinc intake is adequate (1,5,7).
To avoid this issue, your best option is to strive to meet your iron, zinc, and copper intake from food. If you follow an omnivore diet, aim for an intake at the RDA shown above. If you are eating a plant-based diet, you may want to aim for an intake of iron and zinc slightly above the RDA (50-80% higher for iron and 25-50% higher for zinc). Provided you are including foods rich in both iron and zinc, such as beans, lentils tofu, nuts, and seeds, meeting this higher level on a plant-based diet should not be a problem.
If Supplementing Iron, Consider A Zinc Supplement As Well
In some situations, supplementation with iron is necessary. If you are supplementing with more than 65 mg of elemental iron per day, it is wise to also take 10-15 mg of zinc, ensuring that total intake does not exceed 40 mg per day (1).
To maximize absorption of each nutrient, take them at least 4 hours apart. Omnivores may also consider adding a copper supplement to this regimen, but vegans should not need to, given their relatively high intakes of copper. This protocol is summarized in the diagram below.
References:
- Linus Pauling Institute. Zinc. 2015. Available from: http://lpi.oregonstate.edu/mic/minerals/zinc
- Institute of Medicine. Dietary Reference Intakes: The Essential Guide to Nutrient Requirements. Washington D.C.: The National Academies Press; 2006. Zinc; p 402-413.
- Macfarlane, S. Optimizing your micronutrients [PowerPoint]. 2016.
- Gupta RK, Gangoliya SS, Singh NK. Reduction of phytic acid and enhancement of bioavailable micronutrients in food grains. J Food Sci Technol. 2015;Feb;52(2): 676-684. Abstract available from: https://www.ncbi.nlm.nih.gov/pubmed/25694676
- Linus Pauling Institute. Copper. 2014. Available from: http://lpi.oregonstate.edu/mic/minerals/copper
- Institute of Medicine. Dietary Reference Intakes: The Essential Guide to Nutrient Requirements. Washington D.C.: The National Academies Press; 2006. Copper; p 304-311.
- Osredkar J, Sustar N. Copper and zinc, biological role and significant of copper/zinc imbalance. J Clinic Toxicol. 2011; S3:001. Available from: https://www.omicsonline.org/copper-and-zinc-biological-role-and-significance-of-copper-zincimbalance-2161-0495.S3-001.php?aid=3055
