低脂饮食对女性心脏病无益

科罗拉多州埃斯蒂斯帕克——在美国科罗拉多大学主办的内科学会议上，该校妇产科主任Nanette Santoro博士指出，女性健康计划随机对照饮食调节试验(Women’s Health Initiative Randomized Controlled Dietary Modification Trial)最不为人知的结果也许是：结构性低脂饮食干预完全不能降低冠心病、卒中和结肠癌风险。

该试验从美国的40个中心纳入48,835例年龄50~79岁的绝经后女性，并按40:60的比率随机分入低脂饮食干预组和对照组。低脂饮食干预组实施强化行为干预，第1年举行18次小组会议，此后每季度举行1次维持会议，并辅以个体化沟通。目标是通过增加水果和蔬菜的摄入来降低膳食脂肪摄入，即每日食用至少5份水果蔬菜，此外，每日还需食用至少6份谷物。该研究的设计时间为20世纪90年代，当时肥胖还不十分流行，因此未将体重降低作为研究目标。

在平均随访8.1年期间，两组在冠心病(比值比=0.97)、卒中(1.02)和心血管疾病(0.98)发生率方面均无显著差异(JAMA 2006;295:655-66)。同样，在整个研究期间，两组的心血管预后和结肠癌事件发生率曲线也基本相同，未发现低脂饮食具有短期或长期益处的证据(JAMA 2006;295:643-54)。低脂饮食组和对照组的非侵袭性乳腺癌年发生率分别为0.42%和0.45%，前组风险相对后组降低9%(JAMA 2006;295:629-42)。Santoro博士表示，如果要说低脂饮食有什么益处的话，那就是可能在一定程度上有助于降低乳腺癌风险。

饮食干预能够有效持续改变饮食习惯。在低脂饮食干预组中，基线时，脂肪占每日总能量摄入的38%，1年后，该比例降至24%。6年时，低脂饮食干预组和对照组脂肪占每日能量摄入的比例分别为29%和37%；鉴于受试者样本量大且种族和背景多样，因此Santoro博士认为此差异明显。低脂饮食干预组基线时每日平均食用3.6份水果和蔬菜，6年时为4.9份，而对照组为3.8份。然而，鼓励增加谷物摄入的结果并不理想。干预组基线时每日平均食用4.7份谷物，6年时为4.3份，而对照组为3.8份。

该研究获美国心肺血液研究所资助。Santoro博士声明从拜耳公司获得研究资金。

爱思唯尔版权所有  未经授权请勿转载

By: BRUCE JANCIN, Clinical Endocrinology News Digital Network

ESTES PARK, COLO. – Perhaps the least-known finding of the landmark Women’s Health Initiative was the complete failure of a structured low-fat diet intervention to lower the risks of coronary heart disease, stroke, or colon cancer.

"This has gotten very little press. But the results made me very happy because it gave me one less thing to worry about, which is eating a low-fat diet. It doesn’t seem to have the same magnitude of effect in women as it does in men," Dr. Nanette Santoro said at a conference on internal medicine sponsored by the University of Colorado.
 

Nanette Santoro博士

The Women’s Health Initiative Randomized Controlled Dietary Modification Trial involved 48,835 postmenopausal women aged 50-79 at 40 U.S. centers who were randomized 40/60 to a low-fat diet intervention or a control group.

During a mean follow-up of 8.1 years, the diet intervention and control groups didn’t show any significant differences in rates of coronary heart disease (hazard ratio, 0.97); stroke (1.02); or cardiovascular disease (0.98) (JAMA 2006;295:655-66).

Similarly, the event-rate curves for cardiovascular outcomes as well as for colon cancer in the intervention and control arms were virtually identical the entire time, with no hint of either early or late benefit for the low-fat diet (JAMA 2006;295:643-54).

There was a nonsignificant trend for less invasive breast cancer in the low-fat diet group, where the annualized incidence rate was 0.42%, a 9% relative risk reduction compared with the 0.45% rate in controls (JAMA 2006;295:629-42).

"So if there’s any possible benefit to a low-fat diet, there might be some for breast cancer," commented Dr. Santoro, professor and chair of the department of ob.gyn. at the university.

The diet intervention entailed an intensive behavioral modification program with 18 group sessions during year 1 and quarterly maintenance sessions thereafter, with supplemental individualized contact. The goal was to reduce dietary fat intake by boosting consumption of fruits and vegetables to at least five servings daily, along with at least six servings of grains daily. Weight loss goals weren’t part of the study, which was designed in the 1990s before the obesity epidemic was apparent.

The intervention was effective in terms of accomplishing lasting dietary change. At baseline, fat accounted for about 38% of total daily energy intake. After 1 year, this figure dropped to 24% in the diet intervention arm. At year 6, fat accounted for 29% of daily energy intake in the diet group compared with 37% in controls, a difference Dr. Santoro called "huge" in light of the enormous number of participants and the women’s diverse ethnicities and backgrounds.

The intervention group averaged 3.6 servings per day of fruits and vegetables at baseline and 4.9 by year 6, compared with 3.8 in controls. Efforts to increase consumption of grains were unsuccessful, however. The intervention group averaged 4.7 servings per day at baseline and 4.3 at year 6, compared with 3.8 in controls.

The Women’s Health Initiative Randomized Controlled Dietary Modification Trial was funded by the National Heart, Lung, and Blood Institute. Dr. Santoro reported that she has a research grant from Bayer.