| 1. Background:Chinese people’s diet is based on grain, with plant as theirs main protein sources. Population nutrition survey of one province showed that more than90%amino acid pattern is not ideal, with lysine as its first limiting amino acid. Lysine is one of the Essential amino acids for human and the first limiting amino acid in grain. It is very important to identify the body requirement for lysine of the Chinese people. The symptoms due to lack of lysine include fatigue, weakness, nausea, vomiting, dizziness, loss of appetite, growth retardation, anemia, etc. Research about lysine strengthen in cereals has been studied by foreign scholars in order to improve the nutritional value of protein. In the mid-20th century. Mack found that supplement lysine in based dietary to feed children can improve their weight gain and bone density increase, which indicates that lysine can promote growth and calcium calm. However any nutrient intake should follow the principle of proper amount. Harmful effects caused by excessive intake of lysine have also been reported. At present, there is no recommended intake of lysine according to the characteristics of Chinese dietary, and there is little relative research. So it is even more significant to work out the recommended intake of essential amino acids for the Chinese population. In this study, advanced safety indicator amino acid oxidation (13C-phe is the indicator) was used to investigate the physical requirements for lysine of Chinese healthy young males.2. Research purposes:This study was intended to use healthy adult males under the Chinese current dietary pattern as subjects. Through the use of stable isotope tracer technique, with13C-phenylalanine as a tracer, combined with the "2002China National Nutrition and Health Survey" data derived from typical dietary pattern of Chinese population, it explored China’s lysine requirement of healthy adult males and provided a scientific basis for the development of our gender, population recommended intake of essential amino acids and practice support for strengthening our country’s food and clinical amino acid therapy. Meanwhile, through comparison of the results with species Westerners, the study explored lysine requirements on different races and the reasons for similarities and differences and provided the experimental data for further exploring the mechanism of amino acid metabolism in the human body. 3. Methods:Healthy adult males under the Chinese current dietary pattern were used as subjects in research. Through designing five levels of lysine intake:65mg/(kg-d),55mg/(kg-d),45mg/(kg-d),35mg/(kg-d),25mg/(kg-d), Experiments were divided into five consecutive experimental periods, a7-day per period. Seven healthy young men were Chosen as the subjects of study,1-6days for adaptation, Sunday for amino acid metabolism kinetics. Through using of stable isotope tracer techniques to13C-phenylalanine as a tracer for amino acid metabolism in human experiments, the abundance of stable isotopes in exhaled breath and blood were tested to calculate the flow and amino acid oxidation rate. The oxidation of phenylalanine under5different dietary levels of lysine intake was observed to understand the variation of the oxidation of lysine decomposition of the body. Two regression curves between lysine intake and change in oxidation rates of phenylalanine were established, and the inflection point of the regression curve was calculated to determine the physiological requirements of lysine.4. Results:The lysine physiological requirement resulted from the rate of13CO2production is57.08mg/(kg·d)The lysine physiological requirement resulted from the oxidation rate of13C-Phe is53.46mg/(kg·d)5. Conclusions:Under the Chinese current dietary, the physical requirement for lysine of Chinese healthy young males is50-60mg/(kg·d)... |
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