吃红肉与之后糖尿病风险升高有关

《美国医学会杂志》6月17日在线发表的一篇报告显示，4年内红肉摄入量增加与接下来4年内2型糖尿病风险升高有关(JAMA Intern. Med. 2013 June 17 [doi:10.1001/jamainternmed.2013.6633])。

主要研究者、哈佛公共卫生学院营养学系的An Pan博士指出，这项随访12~16年的大规模队列研究显示，不论基线红肉摄入水平如何、总体膳食质量如何、体重如何，这一关联在男性和女性中均很强。

既往研究(主要为横断面研究)已提示摄入红肉与当前糖尿病风险有关，但缺乏长期随访数据。本项研究则首次评估了长期摄入红肉与之后糖尿病风险之间的关联，并且证实了这一关联具有鲁棒性。不过研究者也承认，这项观察性研究尚不足以确定二者间是否存在因果关系。

Pan博士及其同事索使用的数据来自3项大规模队列研究：医务人员随访研究(HPFS)、护士健康研究(NHS)以及护士健康研究Ⅱ(NHS II)。这3项研究均每4年采集1次红肉摄入数据，以及其他的膳食、生活方式和医学相关因素。Pan博士等人共分析了26,357名男性医务人员(基线1986年时的年龄为40~75岁)和122,786名女性医务人员(基线1986年或1991年时的年龄为25~55岁)的数据。

这些受试者报告其摄入标准份量红肉的平均频次。标准分量红肉定义为吃以牛肉、猪肉或羊肉为原料的主菜，或吃汉堡，或吃包含牛肉、猪肉或羊肉的三明治或混合菜，或吃熏肉、热狗、香肠、腊肠及其他加工红肉。受试者报告的频次少至“从不或＜每月1次”，多至“≥每日6次”。

在随访期间共出现7,540例偶发性2型糖尿病：HPFS中发生1,561例，NHS中发生3,482例，NHS II中发生2,497例。

在这3项研究中，与4年期间红肉摄入量相对稳定者相比，摄入量明显增加者罹患糖尿病的相对风险均升高。总体而言，红肉摄入量增加0.5份/d与接下来4年中糖尿病风险上升48%有关。而且这一关联在非肥胖受试者中更强，红肉摄入量增加0.5份/d与糖尿病风险上升65%有关。

在校正同期体重增加这一常与红肉摄入增多相伴随的因素之后，糖尿病风险“轻微”减弱。这提示摄入红肉-罹患糖尿病的关联与体重增加有一定关系，但体重增加并不能完全解释这一关联。

此外研究者还发现，与摄入非加工红肉相比，摄入加工红肉与糖尿病风险之间的关联更强。

令人失望的是，减少红肉摄入量的受试者之后4年内罹患糖尿病的风险并未明显下降。不过，在校正体重指数(BMI)和同期体重增加因素之后，红肉摄入量下降最多(在最初4年内减少超过0.5份/d)的受试者，至16年随访结束时的糖尿病风险降低了10%。

这项研究的局限性在于，受试者增加或减少红肉摄入量的原因不明。而且，受试者主要为白人和受教育程度较高的成人，因此其结果可能难以外推至其他人群。

该研究获得了国立卫生研究院和国立心肺血液研究所的支持。研究者无相关利益冲突披露。

随刊述评：“红肉”的叫法具有误导性

葛兰素史克公司肌肉代谢研究部、杜克大学老年病学系的William J. Evans博士评论指出，为了将肉食分类而将猪肉、羊肉和牛肉统称为“红肉”的做法具有误导性，因为颜色是由肌红蛋白成分决定的。实际上，鸡肉所含的肌红蛋白比猪肉更多，金枪鱼所含的肌红蛋白甚至多达牛肉的2倍(JAMA Intern. Med. 2013 June 17 [doi:10.1001/jamainternmed.2013.7399])。

“蛋白质(或肉)的类型并不是问题的关键所在，真正重要的是脂肪的类型。”也许根据饱和脂肪酸成分来对肉食分类是更好的做法，能够更好地反映吃肉对糖尿病风险的影响。

William J. Evans博士报告称无相关利益冲突。

爱思唯尔版权所有  未经授权请勿转载

By: MARY ANN MOON, Cardiology News Digital Network

Increased consumption of red meat over a 4-year period was associated with higher risk that type 2 diabetes would develop during the next 4 years, according to a report published online June 17 in JAMA Internal Medicine.

This association was strong in both men and women in a large cohort study with 12-16 years of follow-up, regardless of the subjects’ baseline level of red meat intake, the overall quality of their diet, or their body weight, said An Pan, Ph.D., of the department of nutrition, Harvard School of Public Health, Boston, and his associates.

Previous studies, largely cross-sectional, have noted a correlation between the consumption of red meat and current diabetes risk but have had limited duration of follow-up. This is the first study to assess changes in the intake of red meat over time and subsequent diabetes risk, and it confirms the robustness of the association, the investigators said.

However, because this was an observational study, it cannot determine causality, they noted.

Dr. Pan and his colleagues examined the issue using data from three large cohort studies: the Health Professionals Follow-Up Study (HPFS), the Nurses’ Health Study (NHS), and the Nurses’ Health Study II (NHS II). All of these collected measurements of red meat intake every 4 years, as well as other dietary, lifestyle, and medical factors.

For their investigation, Dr. Pan and his associates analyzed data for 26,357 male health care professionals aged 40-75 years at baseline in 1986 and 122,786 female nurses aged 25-55 years at baseline in either 1986 or 1991.

These subjects reported how often, on average, they consumed a standard portion size of red meat, which was defined as beef, pork, or lamb as a main dish; hamburger; beef, pork or lamb as a sandwich or mixed dish; as well as bacon, hot dogs, sausage, salami, bologna, and other processed red meats. The responses ranged from never or less than once per month to six or more times per day.

A total of 7,540 cases of incident type 2 diabetes developed during follow-up: 1,561 in the HPFS, 3,482 in the NHS, and 2,497 in the NHS II.

Compared with people whose intake of red meat was relatively stable during each 4-year period, those who increased their intake were at elevated risk for developing diabetes in all three cohorts, said Dr. Pan, who is also at the National University of Singapore, and his colleagues.

Raising consumption by more than 0.5 servings per day was associated with a 48% rise in diabetes risk during the next 4 years in the study population as a whole. And even among nonobese adults, increasing intake by 0.5 servings per day was associated with a 65% greater risk of diabetes, the investigators said (JAMA Intern. Med. 2013 June 17 [doi:10.1001/jamainternmed.2013.6633]).

Diabetes risk was "modestly" attenuated when the data were adjusted to account for the concurrent weight gain that often accompanied greater intake of red meat. This suggests that weight gain accounted for some, but not all, of the association between red meat intake and diabetes.

In addition, the association was stronger for processed than for nonprocessed red meats.

Unfortunately, study subjects who cut back on red meat did not show a significant reduction in diabetes risk during the ensuing 4 years. However, the highest reduction of red meat intake – decreasing consumption by more than 0.5 servings per day during the initial 4 years of follow-up – was associated with a 10% lower risk of diabetes by the end of the entire follow-up of 16 years after adjustment for BMI plus concurrent weight gain.

This study was limited in that the reasons why subjects increased or decreased their intake of red meat were unknown, and could not be accounted for in the data analysis. In addition, the study subjects were primarily white and well-educated adults, so the findings may not be generalizable to other populations, the researchers said.

This study was supported by the National Institutes of Health and the National Heart, Lung, and Blood Institute. No financial conflicts of interest were reported.

View on the News
'Red Meat' designation misleading

To classify meat according to "redness" and include pork and lamb along with beef may be misleading, because the color is determined by its myoglobin content. Many cuts of chicken have more myoglobin than does pork, and cuts of tuna can have almost twice as much myoglobin as beef, said William J. Evans, Ph.D.

"It is not the type of protein (or meat) that is the problem; it is the type of fat," he noted.

Perhaps a better way to categorize meats that exert the greatest effect on diabetes risk is by their content of saturated fatty acids.

William J. Evans, Ph.D., is in the muscle metabolism discovery unit at GlaxoSmithKline and in the division of geriatrics at Duke University, Durham, N.C. He reported no other financial conflicts of interest. These remarks were taken from his invited commentary accompanying Dr. Pan’s report (JAMA Intern. Med. 2013 June 17 [doi:10.1001/jamainternmed.2013.7399]).