Forsythe W A, Green M S, Anderson J J
J Am Coll Nutr. 1986;5(6):533-49. doi: 10.1080/07315724.1986.10720155.
Different dietary proteins exert different effects on plasma cholesterol concentrations. Animal studies have shown that animal proteins, most notably casein, increase plasma total cholesterol concentrations compared with vegetable proteins, such as soy. Soy protein has been shown to be hypocholesterolemic in rats, swine, primates, and rabbits. Epidemiologic studies have disclosed that vegetarians have lower mean plasma cholesterol concentrations than populations consuming diets of mixed proteins, but it is unclear whether this effect results specifically from the animal or vegetable nature of the protein. In human clinical experiments, substituting soy protein for mixed protein reduces plasma total cholesterol concentration in hypercholesterolemic subjects, but it causes only a small, nonsignificant change in persons with normal plasma cholesterol concentrations. The mechanism responsible for the effects of different proteins on plasma cholesterol concentrations has not been established. One hypothesis suggests that animal proteins, which have a greater content of phosphorylated amino acids than vegetable proteins, interfere with bile acid reabsorption. Another hypothesis suggests that the amino acid content of the protein affects cholesterol absorption, tissue storage, synthesis, and excretion. The dietary protein may also alter cholesterol metabolism by affecting plasma hormone concentrations, either postprandially or over weeks to months. Among the hormones thought to be affected by dietary protein source are insulin, glucagon, and thyroid hormones. Gastrointestinal hormones, such as gastrointestinal inhibitory polypeptide, may also be affected by dietary protein.
不同的膳食蛋白质对血浆胆固醇浓度有不同影响。动物研究表明，与植物蛋白（如大豆蛋白）相比，动物蛋白（最显著的是酪蛋白）会使血浆总胆固醇浓度升高。大豆蛋白已被证明在大鼠、猪、灵长类动物和兔子中具有降胆固醇作用。流行病学研究发现，素食者的平均血浆胆固醇浓度低于摄入混合蛋白饮食的人群，但尚不清楚这种影响是否 specifically 源于蛋白质的动物或植物性质。在人体临床实验中，用大豆蛋白替代混合蛋白可降低高胆固醇血症患者的血浆总胆固醇浓度，但对血浆胆固醇浓度正常的人仅引起微小的、无显著意义的变化。不同蛋白质对血浆胆固醇浓度产生影响的机制尚未明确。一种假说认为，动物蛋白中磷酸化氨基酸的含量高于植物蛋白，会干扰胆汁酸的重吸收。另一种假说认为，蛋白质的氨基酸含量会影响胆固醇的吸收、组织储存、合成和排泄。膳食蛋白质还可能通过影响餐后数周或数月的血浆激素浓度来改变胆固醇代谢。被认为受膳食蛋白质来源影响的激素包括胰岛素、胰高血糖素和甲状腺激素。胃肠激素，如胃肠抑制多肽，也可能受膳食蛋白质影响。
