地中海饮食或许还能预防外周血管病变

根据JAMA1月22/29日刊发表的对PREDIMED随机临床试验所做的次要分析，与对照饮食相比，两种改进的地中海饮食与外周动脉病变（PAD）风险较低有关。

西班牙纳瓦拉大学预防医学及公共卫生系的Miguel Ruiz-Canela博士及其在PREDIMED（Prevencion con Dieta Mediterranea）试验中的合作者报告指出，在年龄较大的心血管疾病高危患者中，与遵循对照饮食的患者相比，遵循中位时间为5年的地中海饮食+特级初榨橄榄油（EVOO）与PAD风险降低有关（风险比，0.34）；同样，遵循地中海饮食并额外补充坚果与PAD风险降低亦有关联（HR，0.50）。对于地中海饮食+EVOO而言，预防1例PAD需要治疗的人数为336人，而对于地中海饮食+额外的坚果而言，为448人。



PREDIMED的研究者们募集的受试者为无临床PAD或基线时无心血管疾病但有2型糖尿病或有至少3个心血管危险因素的男性和女性，其年龄分别介于55~80岁和60~80岁。这些患者被随机分配遵循地中海饮食+EVOO（1,154例患者），地中海饮食+混合的核桃、杏仁和榛果（1,240例患者），或建议减少各类型脂肪摄入量的饮食（1,147例对照患者）。PREDIMED的主要终点是心肌梗死、卒中和心血管原因导致的死亡三者构成的复合终点：地中海饮食+EVOO和地中海饮食+坚果与对照相比的危险比分别为0.70和0.72。

研究者们提醒指出，这项分析一定要被视为探索性分析，因为PAD不是PREDIMED的预设终点。在推出因果结论之前，还需要再进行一项以PAD为预设终点的随机对照试验加以验证。研究者们无法确定所观察到的相关性是归因于无症状的PAD发生率减少（真正的一级预防），还是归因于早期PAD向有症状且有临床意义的PAD的转变率降低。

本研究得到了西班牙许多政府和大学方面的资源支持。研究中所使用的辅食由Patrimonio Comunal Olivarero和Hojiblanca公司、加州核桃委员会、Hojiblanca公司以及LaMorella Nuts公司惠赠。Ruiz-Canela医生报告称无利益冲突；一名合作者报告称获得国际坚果理事会的资助并担任其顾问。

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By: MARY ANN MOON, Cardiology News Digital Network

Two variations of the Mediterranean diet were associated with a lower risk of peripheral artery disease, compared with a control diet, in a secondary analysis of the PREDIMED randomized clinical trial, as reported in a Research Letter to the editor in the January 22/29 issue of JAMA.

Among older adults at high cardiovascular risk, following a Mediterranean diet supplemented by extra virgin olive oil (EVOO) for a median of 5 years was associated with a reduced risk of PAD (hazard ratio, 0.34), compared with the control diet. Similarly, following a Mediterranean diet supplemented with extra nuts was associated with a reduced risk of PAD (HR, 0.50), said Miguel Ruiz-Canela, Ph.D., of the department of preventive medicine and public health, University of Navarra, Pamplona (Spain), and his associates in the PREDIMED (Prevencion con Dieta Mediterranea) trial.

Mediterranean diets supplemented by extra virgin olive oil and supplemented with nuts were associated with a reduced risk of peripheral artery disease, Spanish researchers found.
 
The number needed to treat to prevent one case of PAD was 336 for the Mediterranean diet plus EVOO and 448 for the Mediterranean diet plus extra nuts, they said (JAMA 2014;311:415-7).

The PREDIMED investigators enrolled men aged 55-80 years and women aged 60-80 years without clinical PAD or baseline cardiovascular disease but with type 2 diabetes mellitus or at least three cardiovascular risk factors. Those patients were randomly assigned to follow a Mediterranean diet supplemented with EVOO (1,154 patients), a Mediterranean diet supplemented with mixed walnuts, almonds, and hazelnuts (1,240 patients), or a diet advising reduced intake of all types of fat (1,147 control patients).

PREDIMED’s primary endpoint was a composite of myocardial infarction, stroke, and death from cardiovascular causes: The hazard ratios were 0.70 and 0.72 for the Mediterranean diet with EVOO and the Mediterranean diet with nuts, respectively, compared with controls (N. Engl. J. Med. 2013;368:1279-90).

The investigators cautioned that this must be considered an exploratory analysis, because PAD wasn’t a prespecified endpoint of PREDIMED. "Replication by another randomized controlled trial with PAD as a prespecified end point is needed before causal conclusions can be drawn," they noted.

"We cannot ascertain whether the observed association is due to a reduced incidence of asymptomatic PAD (true primary prevention) or to a reduced conversion from this early stage of PAD to symptomatic and clinically meaningful PAD," they added.

This study was supported by numerous government and university sources in Spain. Supplemental foods used in the study were donated by Patrimonio Comunal Olivarero and Hojiblanca, the California Walnut Commission, Borges S. A., and LaMorella Nuts. Dr. Ruiz-Canela reported no financial conflicts of interest; one of his associates reported receiving funding from and serving as a consultant to the International Nut Council.