前情提要
这对吃货们而言绝对是一个好消息，爱尔兰《乳制食品摄入形式、身体成分与代谢健康指标：全国成人营养调查结果》为那些爱吃乳制品的人带来了福音。人们之前一直认为诸如黄油、奶油、奶酪、全脂牛奶这些高脂肪乳制品的饱和脂肪含量很高，如果想要保持健康，只能偶尔吃一次。但是，该研究的结果恰恰与人们的想法相反。
2017年2月20日，英国《自然》旗下《营养学与糖尿病》在线发表都柏林大学学院、科克大学学院的爱尔兰全国成人营养调查研究报告，发现乳制品摄入量较多，体内脂肪含量和体重指数反而较低，黄油、奶油、奶酪、全脂牛奶也未必使甘油三酯或胆固醇升高。
血液低密度脂蛋白胆固醇水平高可能增加心脏病的风险，每年大约有一万名爱尔兰人死于心脏病，与世界上的心脏病死亡率基本相同。该研究发现，奶酪和其他高脂肪乳制品可能并非罪魁祸首。
既往研究分析乳制品摄入量与代谢健康之间相关性的结果存在分歧，部分原因可能为：对乳制品的定义不同，或者仅仅孤立分析单一类型乳制品。
本研究分析了乳制品食物摄入量与代谢健康之间的相关性，确定了乳制品食物摄入形式，并确定了乳制品饮食形式是否与代谢健康结局有相关性。
该研究入组1500位18～90岁生活自理的爱尔兰健康成人，使用4天食物日记，记录食物和饮料摄入的乳制品（定义为牛奶、奶酪、酸奶、奶油、黄油），收集空腹血样897份，并进行人体测量，通过协方差分析检验乳制品摄入量三分位数及其形式的代谢健康指标差异，使用归类分析确定不同脂肪含量乳制品摄入形式。
结果发现，根据性别、年龄、社会阶层、吸烟程度、能量摄入进行校正后，较高的乳制品总摄入量，与较低的体重指数、身体脂肪百分比、腰围、腰臀比（P＜0.001）、收缩压（P=0.02）、舒张压（P＜0.001）有相关性。当分别考虑牛奶和酸奶摄入量时，观察到类似趋势。
而且，较高的奶酪摄入量，与反映胰岛β细胞分泌功能的C肽水平较高（P＜0.001）有相关性。虽然酸奶摄入量最多者的血脂水平最低，但是与奶酪摄入量最多者相比，新陈代谢指标无显著差异。
此外，根据饮食形式分析，可以将乳制品摄入分为三种形式类型：全脂牛奶、脱脂牛奶和酸奶、黄油和奶油。其中，脱脂牛奶和酸奶类型的健康饮食指数评分最高、脂肪和饱和脂肪的摄入量较低，但是与甘油三酯（P=0.028）和总胆固醇（P=0.015）水平较高有相关性。常吃奶酪的人与不吃或吃较少奶酪的人相比，虽然饱和脂肪摄入较多，但是低密度脂蛋白胆固醇水平却无显著差异。
因此，这些结果表明，虽然摄入脱脂牛奶和酸奶有利于人体，但是作为低脂高碳水化合物饮食形式摄入时，对血脂谱较不利。
这到底是怎么回事？是爱尔兰人侥幸，还是为了健康，我们也应该开始喝全脂牛奶、吃奶酪？
其实，相关性未必等于因果性，因此我们可能会发现那些摄入低脂肪食物者也可能摄入了一些引起胆固醇升高的食物。此外，研究者让研究对象自己记录饮食，可能无法证明记录是否有遗漏或有偏差，而且食物日记也可能使人改变自己的饮食习惯。
营养科学极其复杂，如同营养学家至今无法确定禁食疗法是否可行、无麸质饮食是否增加糖尿病风险。因此，我们需要考虑的不仅仅是营养素本身，还有我们摄入营养素的形式，以及饮食的总体结构，也就是说，不仅需要考虑摄入的食物，还要考虑各种食物的搭配。
为此，需要开展更多研究以更好地了解此相关性。现在，这个问题仍然悬而未决，营养学家需要进行更多研究、更长时间、寻找更多元化人群，以弄清楚：当我们享用吐司上的美式奶酪、英式干酪或稀奶油制成的新鲜软质奶酪时，体内到底发生了什么？
不过，趁现在尚无定论，我们可以先抛开内疚，开心地吃点奶酪、喝点全脂牛奶。
做人呢，最重要的就是开心，祝大家周末愉快！
Nutr Diabetes. 2017 Feb 20;7(2):e243.
Patterns of dairy food intake, body composition and markers of metabolic health in Ireland: results from the National Adult Nutrition Survey.
Feeney EL, O'Sullivan A, Nugent AP, McNulty B, Walton J, Flynn A, Gibney ER.
University College Dublin, Dublin, Ireland; University College Cork, Cork, Ireland.
BACKGROUND: Studies examining the association between dairy consumption and metabolic health have shown mixed results. This may be due, in part, to the use of different definitions of dairy, and to single types of dairy foods examined in isolation.
OBJECTIVE: The objective of the study was to examine associations between dairy food intake and metabolic health, identify patterns of dairy food consumption and determine whether dairy dietary patterns are associated with outcomes of metabolic health, in a cross-sectional survey.
DESIGN: A 4-day food diary was used to assess food and beverage consumption, including dairy (defined as milk, cheese, yogurt, cream and butter) in free-living, healthy Irish adults aged 18-90 years (n=1500). Fasting blood samples (n=897) were collected, and anthropometric measurements taken. Differences in metabolic health markers across patterns and tertiles of dairy consumption were tested via analysis of covariance. Patterns of dairy food consumption, of different fat contents, were identified using cluster analysis.
RESULTS: Higher (total) dairy was associated with lower body mass index, %body fat, waist circumference and waist-to-hip ratio (P<0.001), and lower systolic (P=0.02) and diastolic (P<0.001) blood pressure. Similar trends were observed when milk and yogurt intakes were considered separately. Higher cheese consumption was associated with higher C-peptide (P<0.001). Dietary pattern analysis identified three patterns (clusters) of dairy consumption; 'Whole milk', 'Reduced fat milks and yogurt' and 'Butter and cream'. The 'Reduced fat milks and yogurt' cluster had the highest scores on a Healthy Eating Index, and lower-fat and saturated fat intakes, but greater triglyceride levels (P=0.028) and total cholesterol (P=0.015).
CONCLUSION: Overall, these results suggest that while milk and yogurt consumption is associated with a favourable body phenotype, the blood lipid profiles are less favourable when eaten as part of a low-fat high-carbohydrate dietary pattern. More research is needed to better understand this association.
CONCLUSION: Overall, these results suggest that although milk and yogurt consumption is associated with a favourable body phenotype, the blood lipid profiles are less favourable when eaten as part of a low-fat high-carbohydrate dietary pattern. More research is needed to better understand this association.
PMID: 28218736
DOI: 10.1038/nutd.2016.54
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