美国医学会杂志：高植物蛋白质摄入有助减少全因和心血管死亡风险
多吃素少吃肉一向被认为有益健康。2016年10月《美国医学会杂志内科学分册》正式发表麻省总医院（马萨诸塞州综合医院）、哈佛大学医学院、陈曾熙公共卫生学院、西蒙斯学院、布莱根女子医院、南加利福尼亚大学、意大利癌症研究基金会分子肿瘤研究所、麻省理工学院与哈佛大学联合研究所的研究报告，发现多摄入植物蛋白质有助减少全因和心血管死亡风险，而高动物蛋白质则会增加心血管死亡风险。
在研究人群中，饮食所摄入的植物蛋白质主要来源有面包、谷类、意大利面、坚果和豆类，动物蛋白质的主要来源有猪、牛、羊肉等红肉、鸡肉、奶类、鸡蛋和鱼。对人体健康而言，植物蛋白质优于动物蛋白质，而在动物蛋白质中，鸡肉和鱼类优于红肉、奶类和蛋类。高动物蛋白质摄取增加胰岛素生长因子1水平，而高植物蛋白质则降低血管压力，同时提高胰岛素的敏感度。加工过的红肉含有大量的钠、亚硝酸盐和硝酸盐，直接危害人体健康。如果人们选择动物制品，应尽量避免加工红肉，尽量选择鱼或鸡肉。
既往研究主要侧重蛋白质的摄入量，忽略了蛋白质的食物来源。从饮食角度而言，绝大多数摄入的营养素都来自于食物，而每种食物中的营养素又种类繁多。因此，研究蛋白质的食物来源对健康的影响同样重要，作者为此分析了美国两个大型随访研究（1980年至2012年6月1日的护士健康研究、1986年至2012年1月31日的卫生专业人员随访研究）的数据。
这两项研究通过调查问卷收集了131342位参与者（女性、男性分别为85013位、46329位，分别占64.7%、35.3%，平均年龄49±9岁）的饮食、生活方式、健康状况和疾病诊断信息，同时利用家属报告和国家死亡数据库等收集了这些研究对象的死亡信息，并利用统计学模型分析动物蛋白质和植物蛋白质摄入量与死亡率之间的关系。一半参与者从动物蛋白质中获得至少14%的热量，从植物蛋白质中获得至少4%的热量。到该研究结束时，大约有36000例死亡，约8850例心血管疾病和大约13000例癌症。
结果发现，蛋白质的食物来源对健康有重要影响。经过排除主要的生活方式和饮食风险因素（如吸烟、饮酒、肥胖、不运动），每增加10%来自动物蛋白质的能量，全因、心血管死亡风险分别增加2%、8%（风险比分别为：1.02、1.08，95%置信区间分别为：0.98～1.05、1.01～1.16，趋势P值分别为：0.33、0.04）。而每增加3%来自植物蛋白质的能量，全因、心血管死亡风险分别减少10%、12%的风险比分别为：0.90、0.88，95%置信区间分别为：0.86～0.95、0.80～0.97，趋势P值分别为：＜0.001、0.007）。
此外，当3%的能量用植物蛋白质取代来自加工红肉、未加工红肉、鸡蛋的等量蛋白质时，全因死亡风险分别减少34%、12%、19%（风险比分别为：0.66、0.88、0.81，95%置信区间分别为：0.59～0.75、0.84～0.92、0.75～0.88）。
进一步分析显示，高动物蛋白质摄入与死亡风险的正相关性仅存在于生活方式不健康的人群中，比如肥胖或体重过轻、酗酒、抽烟或缺乏锻炼等人群；对于有着健康生活方式的人群，这种相关性并不存在。
目前有关蛋白质食物来源方面的科学研究十分缺乏，该研究很大程度上填补了这一领域的空白。饮食指南不仅应该关注蛋白质的绝对摄入量，更应该关注其食物来源。肥胖人群，以及不良生活方式人群更可能患有潜在的代谢性或炎症性疾病，这些疾病可增加高动物蛋白质摄入的不良影响。
不过，由于该研究为观察性，不能证明蛋白质摄入类型直接影响人们寿命。与摄入动物蛋白质相关的实际死亡率风险很大程度上与加工的肉类相关。其他动物源食品整体似乎相当中立，但却代表了不同的群组，从鸡肉到鸡蛋再到酸奶，为此我们需要了解它们的每一个特殊健康效应，任何单一的营养物质如蛋白质，基于大量证据，摄入大量更健康的植物性食物：水果、坚果、种子、豆类、非淀粉类蔬菜食至关重要的，但不要把注意力放在“植物为为基本成分”本身：很多食物中最糟糕的食物供给是以植物为基本成分的，从炸薯条到汽水再到白面包和白米饭。
JAMA Intern Med. 2016;176:1453-1463.
Association of Animal and Plant Protein Intake With All-Cause and Cause-Specific Mortality.
Song M, Fung TT, Hu FB, Willett WC, Longo VD, Chan AT, Giovannucci EL.
Massachusetts General Hospital and Harvard Medical School, Boston; Harvard T. H. Chan School of Public Health, Boston, Massachusetts; Simmons College, Boston, Massachusetts; Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts; University of Southern California, Los Angeles; FIRC (Italian Foundation for Cancer Research) Institute of Molecular Oncology, Milano, Italy; Broad Institute of Massachusetts Institute of Technology and Harvard, Cambridge.
IMPORTANCE: Defining what represents a macronutritionally balanced diet remains an open question and a high priority in nutrition research. Although the amount of protein may have specific effects, from a broader dietary perspective, the choice of protein sources will inevitably influence other components of diet and may be a critical determinant for the health outcome.
OBJECTIVE: To examine the associations of animal and plant protein intake with the risk for mortality.
DESIGN, SETTING, AND PARTICIPANTS: This prospective cohort study of US health care professionals included 131,342 participants from the Nurses' Health Study (1980 to end of follow-up on June 1, 2012) and Health Professionals Follow-up Study (1986 to end of follow-up on January 31, 2012). Animal and plant protein intake was assessed by regularly updated validated food frequency questionnaires. Data were analyzed from June 20, 2014, to January 18, 2016.
MAIN OUTCOMES AND MEASURES: Hazard ratios (HRs) for all-cause and cause-specific mortality.
RESULTS: Of the 131,342 participants, 85,013 were women (64.7%) and 46,329 were men (35.3%) (mean [SD] age, 49 [9] years). The median protein intake, as assessed by percentage of energy, was 14% for animal protein (5th-95th percentile, 9%-22%) and 4% for plant protein (5th-95th percentile, 2%-6%). After adjusting for major lifestyle and dietary risk factors, animal protein intake was not associated with all-cause mortality (HR, 1.02 per 10% energy increment; 95% CI, 0.98-1.05; P for trend = .33) but was associated with higher cardiovascular mortality (HR, 1.08 per 10% energy increment; 95% CI, 1.01-1.16; P for trend = .04). Plant protein was associated with lower all-cause mortality (HR, 0.90 per 3% energy increment; 95% CI, 0.86-0.95; P for trend < .001) and cardiovascular mortality (HR, 0.88 per 3% energy increment; 95% CI, 0.80-0.97; P for trend = .007). These associations were confined to participants with at least 1 unhealthy lifestyle factor based on smoking, heavy alcohol intake, overweight or obesity, and physical inactivity, but not evident among those without any of these risk factors. Replacing animal protein of various origins with plant protein was associated with lower mortality. In particular, the HRs for all-cause mortality were 0.66 (95% CI, 0.59-0.75) when 3% of energy from plant protein was substituted for an equivalent amount of protein from processed red meat, 0.88 (95% CI, 0.84-0.92) from unprocessed red meat, and 0.81 (95% CI, 0.75-0.88) from egg.
CONCLUSIONS AND RELEVANCE: High animal protein intake was positively associated with cardiovascular mortality and high plant protein intake was inversely associated with all-cause and cardiovascular mortality, especially among individuals with at least 1 lifestyle risk factor. Substitution of plant protein for animal protein, especially that from processed red meat, was associated with lower mortality, suggesting the importance of protein source.
PMID: 27479196
PMCID: PMC5048552
DOI: 10.1001/jamainternmed.2016.4182