惊天大逆转！饱和脂肪并不增加心脏病发病风险

　　既往众多研究表明饱和脂肪（如奶油和黄油）不利于健康，关于这一理论结果的建立已有50多年。

　　2016年11月30日，美国营养学会官方期刊《美国临床营养杂志》在线发表挪威海于克兰大学医院、卑尔根大学的随机对照研究报告，发现饱和脂肪并不增加心脏病的发病风险。

　　目前关于饱和脂肪的理论表明，高脂肪低碳水化合物与低脂肪高碳水化合物相比，心脏病风险较高。

　　该研究将46位腹部肥胖男性（年龄30～50岁）随机分为两组，分别给予低碳水化合物饮食、低脂肪高碳水化合物饮食12周，然后测量所有参与者腹部、肝脏、心脏的脂肪质量，还评估了参与者的心血管疾病发病风险因素。

　　结果发现，两组参与者的心脏病发病风险并无显著差异。高脂肪摄入并未增加心血管疾病风险，高脂饮食参与者的重要心血管危险因素也得到极大改善，如异位脂肪储存、血压、甘油三酯、胰岛素、血糖水平。

　　该研究采用富含饱和脂肪的新鲜、粗加工和营养食品，包括大量的蔬菜和米饭，而非面粉制品，脂肪来源也是粗加工，主要是黄油、奶油、冷榨油。

　　两组参与者的能量、蛋白质、多不饱和脂肪酸、食物类型相似，主要差异在于数量。糖的摄入量保持在最低限度水平。

　　两组参与者的能量摄入基本在正常范围内，而那些增加能量摄入的参与者仍然可以发现脂肪储存和疾病风险的降低。

　　该结果表明，只要脂肪质量高、总能量摄入适中，对于大多数健康人，摄入较多饱和脂肪可能无害甚至有益于健康。

　　既往研究认为，饱和脂肪促进心脏疾病的发生是由于增加了血液中“坏”低密度脂蛋白（LDL）胆固醇的水平，而本研究结果否定了这一理论。本研究不仅发现LDL胆固醇未显著升高，还发现高脂饮食与“好”胆固醇水平增加无关。

　　未来仍需更多研究确定哪些人群或患者需要限制饱和脂肪，但是目前来看饱和脂肪的健康风险确实被夸大了，这对于鼓励公众少食面粉制品食物、精加工脂肪食品以及添加糖类食品而言十分重要。

Am J Clin Nutr. 2016 Nov 30. [Epub ahead of print]

Visceral adiposity and metabolic syndrome after very high-fat and low-fat isocaloric diets: a randomized controlled trial.

Veum VL, Laupsa-Borge J, Eng O, Rostrup E, Larsen TH, Nordrehaug JE, Nygard OK, Sagen JV, Gudbrandsen OA, Dankel SN, Mellgren G.

Haukeland University Hospital, Bergen, Norway; University of Bergen, Bergen, Norway.

BACKGROUND: Different aspects of dietary pattern, including macronutrient and food profiles, may affect visceral fat mass and metabolic syndrome.

OBJECTIVE: We hypothesized that consuming energy primarily from carbohydrate or fat in diets with similar food profiles would differentially affect the ability to reverse visceral adiposity and metabolic syndrome.

DESIGN: Forty-six men (aged 30-50 y) with body mass index (in kg/m²) >29 and waist circumference >98 cm were randomly assigned to a very high-fat, low-carbohydrate (VHFLC; 73% of energy fat and 10% of energy carbohydrate) or low-fat, high-carbohydrate (LFHC; 30% of energy fat and 53% of energy carbohydrate) diet for 12 wk. The diets were equal in energy (8750 kJ/d), protein (17% of energy), and food profile, emphasizing low-processed, lower-glycemic foods. Fat mass was quantified with computed tomography imaging.

RESULTS: Recorded intake of carbohydrate and total and saturated fat in the LFHC and VHFLC groups were 51% and 11% of energy, 29% and 71% of energy, and 12% and 34% of energy, respectively, with no difference in protein and polyunsaturated fatty acids. Mean energy intake decreased by 22% and 14% in the LFHC and VHFLC groups. The diets similarly reduced waist circumference (11-13 cm), abdominal subcutaneous fat mass (1650-1850 cm³), visceral fat mass (1350-1650 cm³), and total body weight (11-12 kg). Both groups improved dyslipidemia, with reduced circulating triglycerides, but showed differential responses in total and low-density lipoprotein cholesterol (decreased in LFHC group only), and high-density lipoprotein cholesterol (increased in VHFLC group only). The groups showed similar reductions in insulin, insulin C-peptide, glycated hemoglobin, and homeostasis model assessment of insulin resistance. Notably, improvements in circulating metabolic markers in the VHFLC group mainly were observed first after 8 wk, in contrast to more acute and gradual effects in the LFHC group.

CONCLUSIONS: Consuming energy primarily as carbohydrate or fat for 3 mo did not differentially influence visceral fat and metabolic syndrome in a low-processed, lower-glycemic dietary context. Our data do not support the idea that dietary fat per se promotes ectopic adiposity and cardiometabolic syndrome in humans. This study was registered at clinicaltrials.gov as NCT01750021.

KEYWORDS: CT; computed tomography; food profile; metabolic syndrome; obesity; saturated fat

PMID: 27903520

PII: ajcn123463

DOI: 10.3945/ajcn.115.123463