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A study published in the British Journal of Nutrition shows that the nutrient combination of calcium and milkfat present in dairy may play a key role in reducing fat absorption and may have the ability to maintain good cholesterol (HDL) while minimizing any increase in bad cholesterol (LDL). The study, designed to explore why dairy products containing saturated fat and high contents of calcium do not seem to significantly affect blood cholesterol levels as much as saturated fat from other sources, lends credence to the notion that milk and other dairy products with a high content of calcium such as cheese, might actually reduce the risk for cardiovascular disease.
The authors noted that, historically, intervention studies have pointed to a relationship between a diet high in saturated fat and increases in total cholesterol and LDL cholesterol. As a result, some nutrition experts have recommended that consumers limit the intake of high-fat dairy products. However, observational studies have found an inverse relation between intake of milk and other dairy products with a high content of calcium and incidence of cardiovascular disease. The researchers aimed to study whether the high calcium content of dairy products influences the effect of dairy fat on the lipid profile.
The study was a small, clinical trial that included nine participants completing four separate diets over a period of 10 days, with each diet differing in the amount of calcium and fat content. Blood variables were measured before and after each diet period, and feces and urine were collected at the end of each diet period. A two-way analysis of variance (ANOVA) was used to examine the effect of calcium and fat intake. Independent of calcium intake, the high-fat diet increased the concentrations of total, LDL, and HDL cholesterol compared with the low-fat diet. However, independent of fat intake, the high calcium diet decreased the concentrations of total and LDL cholesterol, but not HDL cholesterol compared with the low calcium diet. In addition, total:HDL cholesterol was decreased (5%), and HDL:LDL was increased (12%) by the high-calcium diet compared with the low calcium diet.
The researchers concluded that “dairy calcium seems to partly counteract the raising effect of dairy fat on total and LDL cholesterol, without reducing HDL cholesterol.”
参考译文：
《British Journal of Nutrition》期刊发表的一项研究表明，乳制品中存在的营养组合——钙和乳脂，可能在降低脂肪吸收方面起着关键性作用，并具备将有害胆固醇（LDL）的升高降至最小程度的同时维持有益胆固醇（HDL）水平的能力。旨在探索为何含有饱和脂肪及高水平钙的乳制品不会像其他含有饱和脂肪的食品那样显著的影响血液胆固醇水平的本次研究给这样一种观念——钙含量很高的牛奶及其他乳制品如奶酪能有效降低心血管疾病风险提供了凭证依据。
作者指出，根据以往观点，干预性研究已经证明了高水平饱和脂肪的膳食跟总胆固醇和LDL胆固醇值升高之间的联系。也因此，一些营养专家建议消费者应控制高脂肪乳制品的摄入。然而，观察性研究却发现了牛奶及其他高钙乳制品的摄入与心血管疾病发生率之间与上述观点相左的关系。研究者想要验证乳制品的高钙含量是否影响乳品脂肪在血脂分析方面的效应。
该研究是一个包括9名参与者的小规模临床试验，他们于10天内完成4次独立膳食——每一次的钙含量和脂肪含量都不同。在每次进食前后分别测量其血液变量，并于进食结束后收集其粪便和尿液。应用双因子变数分析（ANOVA）来检验钙及脂肪的摄入效应。在不摄入钙的条件下，相对于低脂肪膳食来说，高脂肪膳食增加了总胆固醇及LDL和HDL胆固醇值。然而，在不摄入脂肪的条件下，相对于低钙膳食来说，高钙膳食降低了总胆固醇及LDL胆固醇值并且不会降低HDL胆固醇的值。另外，相对于低钙膳食来说，高钙膳食的总胆固醇：HDL胆固醇值降低了5%，HDL:LDL值升高了12%。
研究者推断“乳品中的钙似乎能部分的抵消乳品中的脂肪对总胆固醇及LDL胆固醇值的影响，并且不会降低HDL胆固醇的值。”
期刊链接：British Journal of Nutrition
