Plasma copper concentration as marker of copper intake from food

Copper concentration in blood plasma is used mainly as an indicator for alimentary copper supply. This has some limitations because copper concentration in plasma fluctuates with age, exercise and health status and does not increase after a meal nor decrease during short-term fasting. The Austrian Study on Nutritional Status (ASNS) provides data on nutrient intake and corresponding plasma concentrations, permitting to evaluate the suitability of copper plasma concentration as a marker of copper intake. Copper intake and intake of relevant nutrients and food groups were evaluated from 7-day weighed food records from 2,400 preschool and schoolchildren between 4 and 19 years of age. Blood samples were collected from a subgroup of 1,400 of these children. The copper concentration in plasma was measured by graphite furnace atomic absorption spectrometry. Correlations between plasma concentrations and intake of nutrients and food groups were calculated using a stepwise linear regression model. The results showed that the determination of copper plasma concentrations are inadequate to predict copper intake from dietary records. A better indicator for copper supply may be the evaluation of those food items, which are the predominant sources of copper intake at the population level. The highest influence on copper plasma concentration was found for the intake of meat, representing not only the most important food group for copper supply but also the most important food group for fat and protein supply. The individual copper status can only be estimated accurately when information on characteristic enzyme activities under control of additional factors of influence or even body stores of copper are available.