糖尿病风险随着饮食质量提高而下降

旧金山——哈佛大学公共卫生学院的Sylvia H. Ley博士在美国糖尿病学会（ADA）年会上指出，即使仅较小程度地改善饮食质量，也有助于避免罹患糖尿病。

具体而言，根据对3项纵向观察性研究、184,417名受试者的数据分析，饮食质量评分提高至少10%的成年人，在未来4年内罹患2型糖尿病的风险将降低9%，而饮食质量评分恶化至少10%的成年人，风险将增加18%。糖尿病风险的上述变化有统计学意义。

Sylvia H. Ley博士

研究者分析了护士健康研究Ⅰ、护士健康研究Ⅱ和卫生专业人员随访研究中随访至少20年的受试者数据。研究者每2年询问这些受试者的糖尿病发病情况，每4年了解其饮食内容。Ley博士及其同事采用替代健康饮食指数来评价饮食质量。

结果显示，在超过200万人年的随访期间，共报告了近1万例新发2型糖尿病。亚组分析显示，饮食改变与糖尿病风险之间的关联影响到所有人，不论他们的饮食质量是好、一般还是差。“不论你现在的饮食状态如何，改善饮食质量均有助于预防糖尿病。”饮食质量改善带来的糖尿病风险降低，独立于体力活动或体重降低的影响。

替代健康饮食指数关注11种成分的摄入：红肉、坚果、含糖饮料、水果、蔬菜、多不饱和脂肪、反式脂肪、ω脂肪、乙醇、钠和全谷物，每种成分的摄取量最多计为10分。最佳饮食为110分，所以只要提高11分即意味着饮食质量提高10%。

Ley博士指出，将饮食质量提高10%“并不那么难”。在这项研究中，几乎所有受试者最初的饮食质量均较差，但之后有很多受试者的饮食质量评分提高了10%以上。她说：“我认为健康饮食仍然有些抽象，人们仍然不太理解它意味着什么。向人们提供更多有关健康、优质饮食的信息是有助益的。”

Ley博士及其同事在另一项研究中发现，饮食的质量比数量更重要，多种不同的饮食策略均可降低糖尿病风险（包括地中海饮食、素食、低糖指数饮食，或适度低碳水化合物饮食），原因是这些饮食均富含全谷物、水果、蔬菜、豆类、坚果，以及中低量的酒精、细粮、红肉或加工肉和含糖饮料（Lancet 2014;383:1999-2007）。

既往其他的随机对照研究已显示，限制饮食中的热量有助于避免糖尿病的发生，但是人们难以维持这样的饮食策略。“这使得我们转而采取更多以食物为基础的方法。”此外，这些研究主要观察糖尿病风险较高的人群，而本项研究则关注正常的健康人群。

除非开展进一步研究，否则上述研究结果不能外推至总体人群，原因是本项分析纳入的3项研究的受试者是受教育程度相对较高的医务人员，98%是白人。

Ley博士报告称无相关利益冲突。

专家点评：讨论饮食时细节很重要

Melinda Marynuik

如果我们能向人们清晰地说明什么是优质营养，以及具体该吃什么，将会很有意义。我认为优质营养意味着更多的水果和蔬菜，更多的谷物、饱和脂肪水平更低的蛋白质来源，以及脂肪水平更低的乳制品。有越来越多的科学证据支持我们的观点，这难道不是一件很好的事情吗？如果我们再稍稍深入挖掘一下，就会发现该研究引出了一些问题。我们目前如何评估饮食质量？

Melinda Marynuik是教育学硕士、注册营养师，担任波士顿Joslin糖尿病中心的临床教育项目主任。她披露称无利益冲突。

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By: SHERRY BOSCHERT, Internal Medicine News

SAN FRANCISCO – Even small improvements to the quality of diet can help stave off diabetes.

More specifically, adults whose diet quality scores improved by at least 10% were 9% less likely to develop type 2 diabetes in the next 4 years, and those whose diet quality scores worsened by at least 10% were 18% more likely to develop diabetes, according to an analysis of data from three longitudinal observational studies involving 184,417 people.

Those changes in diabetes risk were statistically significant, Sylvia H. Ley, Ph.D., reported at the annual scientific sessions of the American Diabetes Association.

They analyzed data on participants in the Nurses Health Study I, Nurses Health Study II, and the Health Professionals Follow-Up Study who were followed for at least 20 years in each study and asked every 2 years about incident diabetes and every 4 years about the contents of their diet, among other topics. Dr. Ley and her associates used the Alternative Healthy Eating Index to assess diet quality.

Nearly 10,000 new cases of type 2 diabetes were reported during more than 2 million person-years of follow-up, Dr. Ley of Harvard University’s School of Public Health, Boston, said in a press briefing.

The associations between dietary changes and diabetes risk affected all people, whether they ate well or poorly, according to subset analyses of participants grouped as those having the poorest quality diet, medium quality, or highest quality diet. "Regardless of where you start, improving your diet quality is helpful in diabetes prevention," Dr. Ley said.

The reduced diabetes risk from improving diet quality was independent of effects from physical activity or reduced body weight, she said.

The Alternative Healthy Eating Index focused on intake of 11 components: red meat, nuts, sugar-sweetened beverages, fruits, vegetables, polyunsaturated fat, trans fat, omega fats, alcohol, sodium, and whole grains, with up to 10 points for intake of each. A perfect diet score was 110, so a mere 11-point gain provided a 10% improvement in diet quality, she said.

A 10% improvement in diet quality is "not that difficult" to make, Dr. Ley said. Nearly everyone in the study started with a poor-quality diet, and many made more than a 10% improvement in diet quality scores.

The bottom line is that changing one’s diet can be helpful, she said. "I think healthy eating is somewhat abstract, and that people still have difficulty understanding what that means," Dr. Ley said. "I think it’s helpful to provide more information on what is healthy and what is better quality eating."

A separate study by Dr. Ley and her associates found that the quality of foods and drinks consumed is more important than the quantity and that a number of different dietary strategies can reduce diabetes risk (including a Mediterranean diet, vegetarian diet, low-glycemic-index diet, or moderately low carbohydrate diet) because they are rich in whole grains, fruits, vegetables, legumes, and nuts, with moderate to low amounts of alcohol, refined grains, red or processed meats, and sugar-sweetened beverages (Lancet 2014;383:1999-2007).

Other previous randomized, controlled studies had shown that restricting dietary calories can help protect against development of diabetes, but that dietary strategy is difficult for people to maintain, Dr. Ley said. "That has led us to take more food-based approaches," she said. In addition, those studies predominantly looked at people who were at high risk for diabetes, whereas the current study looked at a normal healthy population.

The current findings can’t be generalized to the entire population without further study, however, because participants in the three studies in the analysis were relatively well-educated health care professionals and 98% were white.

Dr. Ley reported having no financial disclosures.

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Specifics help when discussing diet

Isn’t it great to have more science to prove what we think makes a lot of sense? If we dig a little deeper, the study raises questions. How are we measuring quality?

 If we can get clear guidelines out to people about what we mean by quality nutrition, that would help. I think that would mean more fruits and vegetables, more whole grains, lower saturated-fat protein sources, and lower-fat dairy sources.

Getting real clarity on what that message is, and how to translate to the general population what exactly to eat, would be progress.

Melinda Marynuik, M.Ed., R.D., C.D.E., is director of clinical education programs at Joslin Diabetes Center, Boston. She disclosed having no financial conflicts.