Plasma amino acids in Greenlanders and Danes: influence of seasons, residence, ethnicity, and diet.

Basal metabolic rate is elevated among circumpolar populations. It has been our hypotheses that this is reflected in the levels of plasma amino acids, that amino acid concentration in plasma differs between Greenlanders and Danes, and that this difference is related to residence, ethnicity, diet, and season. The purpose of the study was to measure plasma amino acids in Greenlanders and Danes and to analyze the influence of residence, ethnicity, diet, and season. Amino acids in plasma were measured in four groups of healthy subjects both during summer and winter: Group 1, Danes living in Denmark consuming European food; Group 2, Greenlanders living in Denmark consuming European food; Group 3, Greenlanders living in Greenland consuming European food; and Group 4, Greenlanders living in Greenland consuming mainly traditional Greenlandic food. Amino acids were determined by pre-column derivatization with o-phthaldialdehyde and reverse-phase high-performance liquid chromatography with gradient elution and fluorescence detection. Most plasma amino acids were lower during summer than winter in Greenlanders living in Greenland. Comparison of the four groups showed that residence in Greenland was the most important influencing factor for the concentration of plasma amino acids, whereas ethnicity and diet had only a very modest or no effect. These findings could not be attributed to changes in thyroid function. However, the level of physical activity was significantly higher in Groups 3 and 4 than in Groups 1 and 2. Because exercise reduces the amino acid pool in plasma, it is possibly that the higher physical activity among Greenlanders living in Greenland explains the reduction in plasma amino acids during summer. It is concluded that plasma amino acids were lower during summer than winter in Greenlanders living in Greenland compared with Greenlanders in Denmark and Danes. This difference might be due to the higher level of physical activity among Greenlanders in Greenland during the summer period. Am. J. Hum. Biol. 18:99-111, 2006. (c) 2005 Wiley-Liss, Inc.