低碳高脂饮食并非妊娠期糖尿病最佳选择

芝加哥——美国糖尿病学会(ADA)2013年会上公布的一项针对11例女性妊娠期糖尿病(GDM)患者的随机初步研究结果显示，与食用高复合碳水化合物、低脂肪饮食相比，食用传统低碳水化合物、高脂肪饮食者更多出现胰岛素抵抗，其婴儿发生肥胖的几率也略高。

科罗拉多大学丹佛分校的Teri L. Hernandez博士报告称，上述两种饮食均可控制母体血糖和体重，但组织学数据和空腹血糖水平提示，高脂饮食可加剧妊娠期胰岛素抵抗。


Teri L. Hernandez博士

Hernandez博士及其同事认为，向GDM患者推荐的传统饮食更多关注对碳水化合物(CHO)的限制，但这会导致脂肪摄入较多，进而促进胰岛素抵抗和胎儿肥胖。同时，由于患者依从性不佳和没有对照设计，导致证据并不一致。在一项尚未发表的GDM患者前瞻性随机对照饮食干预试验的系统综述中，Hernandez博士等人发现，患者可耐受高复合碳水化合物/低血糖指数饮食，这种富含未加工碳水化合物的饮食可有效降低餐后血糖升高，减少对胰岛素治疗的需求，改善胰岛素敏感性、糖化血红蛋白A1c以及收缩压。

在这项初步研究中，受试者为其他方面健康的轻度GDM患者，依从性很好且高度匹配，平均体重指数为33.5 kg/m2，年龄29~30岁。她们的所有饮食均由研究人员提供。患者被随机分组，其中5例摄入传统低碳水化合物/高脂肪饮食，6例摄入高碳水化合物/低脂肪饮食。低碳水化合物/高脂肪饮食含有40% CHO、45%脂肪和15%蛋白质，高碳水化合物/低脂肪饮食含有60% CHO、25%脂肪和15%蛋白质。单糖在每日总热量中所占比例≤18%。

结果显示，两组受试者研究期间体重增加相似，血糖指标均低于目标值。但与低碳水化合物/高脂肪饮食组相比，高碳水化合物/低脂肪饮食组6周和7周空腹血糖和空腹胰岛素水平更低(P值分别为0.007和0.06)。

低碳水化合物/高脂肪饮食组餐后游离脂肪酸明显较高(P=0.037)，37周空腹血糖、胰岛素以及母体胰岛素抵抗(HOMA-IR)均明显较高(P 值分别为0.007、0.06和0.02)。

此外，低碳水化合物/高脂肪饮食组婴儿肥胖比例也略高(14% vs. 11%)。不管采用哪种饮食，37周较高的空腹胰岛素和HOMA-IR与高婴儿肥胖比例相关(P＜0.05)。

会议主持人、奥克兰凯撒医疗机构资深研究科学家Assiamira Ferrara博士指出，这是一项很好的研究，但至于上述结果是否及何时会对实践产生影响，现在尚难以确定。我们还需要更大样本量和更多可行性研究以考察女性对这种饮食的依从性。Ferrara博士没有参与该项研究。

研究者认为，两种饮食均不错，迄今尚未出现与饮食相关的不良结局。她们正在进行一项纳入更多患者的研究，迄今获得的数据表明，患者可耐受的碳水化合物比我们想象的要多。“这些女性担心其婴儿太大，因此非常惧怕碳水化合物。上述结果表明，她们真的可以食用烤面包和其他碳水化合物，不但仍有良好结局，甚至还有助于改善其胰岛素抵抗。”

Hernandez博士无利益冲突披露。Ferrara博士受雇于武田全球研发中心并得到武田制药研究经费支持。

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By: NASEEM S. MILLER, Clinical Endocrinology News Digital Network

CHICAGO – Women with gestational diabetes on a conventional low-carbohydrate, high-fat diet were more insulin resistant, and their infants had slightly higher rates of adiposity, than did with women who consumed a diet high in complex carbohydrates and low in fat, according to a randomized pilot study of 11 women.

Both diets controlled maternal glucose and weight. "So, they’re both okay, except that tissue data and fasting levels imply that higher fat content is exacerbating insulin resistance during pregnancy," Teri L. Hernandez, Ph.D., said in an interview after presenting her findings at the annual scientific sessions of the American Diabetes Association.

It’s too soon to tell if and when the findings will have implications on practice. "It’s a good study," said Dr. Assiamira Ferrara, senior research scientist at Kaiser Permanente, Oakland, Calif., who was a moderator and not involved in the study. "But we need a bigger sample size and more feasibility studies on whether women will adhere to the diet" before we try this outside of a research environment.

The conventional diet recommended to women who have gestational diabetes (GDM) has mainly focused on carbohydrate (CHO) restriction. But Dr. Hernandez and her colleagues said that the restrictions result in greater fat intake, which in turn could promote insulin resistance and increase fetal adiposity. Meanwhile, owing to patient noncompliance and a lack of controlled designs, evidence remains confounded, she reported.

In a recent unpublished systematic review of prospective, randomized, controlled trials of diet interventions in women with GDM, Dr. Hernandez and her colleagues found that women tolerated higher complex carb/low glycemic index diets and that diets higher in unrefined carbs effectively blunted postprandial glycemia, reduced the need for insulin therapy, and improved insulin sensitivity, hemoglobin A1c, and systolic blood pressure.

Dr. Hernandez of the departments of medicine and nursing at University of Colorado at Denver in Aurora, said that she has a larger number women in her ongoing study, but the findings so far "lend evidence to the idea that women can tolerate more carb than we thought.

"These women are worried about their baby’s outcome, and they’re afraid their babies are going to be born too big, so they become very fearful of carbohydrates. What this says is that they can actually have toast and other carbs in their diet and still have a great outcome, and it could even help improve their insulin resistance," she said in an interview.

Researchers randomized five women to the conventional low-carb/high-fat diet, and 6 women to the high-carb/low-fat diet.

The low-carb/high fat diet comprised 40% CHO, 45% fat, and 15% protein; the high-carb/low fat diet contained 60% CHO, 25% fat, and 15% protein. Simple sugars made up about 18% or less of total daily calories.

The subjects were rather healthy women with mild gestational diabetes, were highly compliant, and were closely matched, with a mean body mass index of 33.5 kg/m2, and were 29-30 years old. They were provided with all the meals.

During the study period, weight gain was similar in both groups, and their glycemic profiles were below target.

However, the high-carb/low-fat diet group had lower fasting glucose and fasting insulin at 6 and 7 weeks, compared with the low-carb/high-fat diet group (P = .007 and .06, respectively)

Results also showed that the postprandial free fatty acids were significantly higher in the low-carb/high-fat diet group (P = .037). And, at week 37, fasting glucose, insulin, and maternal insulin resistance (HOMA-IR) were significantly higher in the low-carb/high-fat diet, compared with the low-fat/high-carb diet (P = .007, .06, and .02, respectively).

Meanwhile, infant adiposity was slightly higher in the infants of the low-carb/high-fat groups, compared with the high-carb/low-fat group (14% v. 11%). And, regardless of diet, higher fasting insulin and HOMA-IR at 37 weeks were associated with greater infant adiposity (P less than .05).

Dr. Hernandez said that both diets are doing a good job, and thus far, there haven’t been any adverse outcomes because of either diet.

Dr. Hernandez had no disclosures. Dr. Ferrara is an employee of Takeda Global Research and Development and has received research support from Takeda Pharmaceutical.