Stable isotope analyses demonstrate that C4 plants played an important dietary role in Eurasian prehistory. Uncertainty remains, however, about when and how crops were integrated into the diet of Central Asian populations. Here, the authors present δ13C and δ15N stable isotope analysis of human and animal bone collagen from Kyrgyzstan, revealing C4 plant—likely broomcorn millet—consumption in the third millennium BC. Combining this evidence with AMS radiocarbon dating and animal collagen peptide fingerprinting demonstrates that broomcorn millet was consumed by humans and animals during the earliest episodes of the westward spread of this crop plant. The results contribute to debates about the timing and means by which domesticated millets were dispersed across Eurasia.

With the popularization of carbon and nitrogen stable-isotope analysis methods used on archaeological samples from Xinjiang, the ancient paleodiet there has been revealed. However, research about isotopic analysis combined with environmental factors is rare, especially in such a variable and complex climate as that of the Tianshan region. We systematically analyzed the δ13C and δ15N results from animals and humans for dietary reconstruction of nomadic pastoralists from the Tianshan region during 3900–1200 cal BP. The δ13C and δ15N values for animals (sheep/goat, horse and cattle; n = 57) have a wide range from –20.8‰ to –14.7‰ for δ13C (–19.2 ± 1.0‰) and 3.2‰ to 9.9‰ for δ15N (7.0 ± 1.2‰). The δ13C and δ15N values from humans range from –19.6 to –12.3‰ (–16.0 ± 1.5‰) and 7.1 to 16.7‰ (–13.6 ± 1.5‰), respectively. The animal δ15N results indicate that the dry environment in the Tianshan region may result in elevated δ15N values. Synthesizing animal and human isotope results suggests that the inhabitants engaged in mobile herding economies subsidized with crops and wild animal meat from the Tianshan Mountains. In conclusion, we found that the regional environment closely relates to crop types, and temporal climate change has an effect on human dietary structure. Therefore, climate condition cannot be ignored when studying human paleodiet.

The Jiaojia site is the earliest city in the Haidai area of China, about 5000 years old. To obtain more accurately the beginning and end of this site, radiocarbon accelerator mass spectrometry (14C AMS) measurements, along with stable carbon and nitrogen isotope data, were collected from 13 bone samples. According to the measured dates, human diet was dominated by C4-based plants, and the Jiaojia site appeared before 2900 BC.

The present study investigated whether consuming dairy products naturally enriched in cis-9, trans-11 (c9, t11) conjugated linoleic acid (CLA) by modification of cattle feed increases the concentration of this isomer in plasma and cellular lipids in healthy men. The study had a double-blind cross-over design. Subjects aged 34–60 years consumed dairy products available from food retailers for 1 week and then either control (0·17 g c9, t11 CLA/d; 0·31 g trans-vaccenic acid (tVA)/d) or CLA-enriched (1·43 g c9, t11 CLA/d; 4·71 g tVA/d) dairy products for 6 weeks. After 7 weeks washout, this was repeated with the alternate products. c9, t11 CLA concentration in plasma lipids was lower after consuming the control products, which may reflect the two-fold greater c9, t11 CLA content of the commercial products. Consuming the CLA-enriched dairy products increased the c9, t11 CLA concentration in plasma phosphatidylcholine (PC) (38%; P=0·035), triacylglycerol (TAG) (22%; P<0·0001) and cholesteryl esters (205%; P<0·0001), and in peripheral blood mononuclear cells (PBMC) (238%; P<0·0001), while tVA concentration was greater in plasma PC (65%; P=0·035), TAG (98%; P=0·001) and PBMC (84%; P=0·004). Overall, the present study shows that consumption of naturally enriched dairy products in amounts similar to habitual intakes of these foods increased the c9, t11 CLA content of plasma and cellular lipids.