Villalpando Salvador, Del Prado Martha, Cienfuego Edith, Morales Pedro
Center for Research on Nutrition and Health, Instituto Nacional de Salud Pública, Cuernavaca, Mexico.
Ann Nutr Metab. 2014;64(1):44-9. doi: 10.1159/000360405. Epub 2014 Apr 26.
C4 plants (e.g. corn and sugar cane) have greater (13)C enrichment than C3 plants (e.g. wheat and sugar beet).
To assess whether (13)C enrichment of CO2 in the breath and breast milk of women on diets based on C3 and C4 foods changes from one diet to the other.
Six breast-feeding women were studied at 5-6 months postpartum. They ate a controlled C4 diet on days 1 and 2 followed by a C3 diet on days 3 and 4. Diet duplicates, breast milk on days 2 and 4 and hourly breath samples were collected over 4 days. (13)C enrichment was measured by isotope-ratio mass spectrometry. Values of δ(13)C were calculated from the international PDBV standard (δ(13)CPDBV). Differences between means were compared by paired t test or t test for repeated measurements.
δ(13)CPDBV values were significantly higher in the C4 diet than in the C3 diet composites (p < 0.01). In breath CO2, the δ(13)CPDBV value was greater on days 1 and 2 (range -15.4 to -13.2, respectively) and declined on days 3 and 4 (range -20.0 to -21.8, respectively, p < 0.01). The lipid and milk serum fractions of breast milk had significantly higher δ(13)CPDBV on the C3 diet than on the C4 diet (p < 0.01).
Subjects eating a C4 diet have a higher δ(13)CPDBV value in the breath and breast milk fractions, which diminish rapidly on a C3 diet. Further studies focusing on individual nutrients are warranted.
C4植物（如玉米和甘蔗）的碳-13富集程度高于C3植物（如小麦和甜菜）。
评估食用基于C3和C4食物饮食的女性，其呼出气体和母乳中二氧化碳的碳-13富集程度是否会随饮食变化而改变。
对6名产后5至6个月的哺乳期妇女进行研究。她们在第1天和第2天食用受控的C4饮食，随后在第3天和第4天食用C3饮食。在4天内收集饮食复制品、第2天和第4天的母乳以及每小时的呼气样本。通过同位素比率质谱法测量碳-13富集程度。根据国际PDBV标准（δ(13)CPDBV）计算δ(13)C值。均值差异通过配对t检验或重复测量t检验进行比较。
C4饮食的δ(13)CPDBV值显著高于C3饮食组合（p < 0.01）。在呼出的二氧化碳中，第1天和第2天的δ(13)CPDBV值较大（范围分别为-15.4至-13.2），而在第3天和第4天下降（范围分别为-20.0至-21.8，p < 0.01）。母乳的脂质和乳清部分在C3饮食时的δ(13)CPDBV值显著高于C4饮食时（p < 0.01）。
食用C4饮食的受试者呼出气体和母乳部分的δ(13)CPDBV值较高，而在C3饮食时会迅速降低。有必要针对个体营养素进行进一步研究。
