核桃为何有益健康?原来与肠道细菌有关……
2017/08/06
食用核桃与很多健康益处有关,包括降低心脏病和癌症风险。那么,核桃究竟是如何发挥健康保护作用的呢?近日发表的一项研究称,这可能与其对肠道菌群的调节有关。


核桃因富含omega-3脂肪酸、抗氧化剂等成分被称为“超级食物”。食用核桃与很多健康益处有关,包括降低心脏病和癌症风险。

近日,发表在The Journal of Nutritional Biochemistry杂志上题为“Changes in the Gut Microbial Communities Following Addition of Walnuts to the Diet”的研究发现,饮食中的核桃改变了肠道细菌的组成。

研究小组在啮齿动物模型中开展了这一研究。其中,一组动物的饮食中被添加了核桃,而另一组动物的饮食中不含核桃。之后,研究小组检测了大鼠降结肠(descending colon)中肠道细菌的类型和数量。结果发现,核桃组大鼠的肠道细菌数量、种类以及功能都发生了变化。

具体来说,食用核桃增加了厚壁菌门(Firmicutes)的丰度,降低了Bacteriodetes的丰度;同时,饮食中添加核桃丰富了益生菌微生物群,包括乳酸菌(Lactobacillus)、Ruminococcaceae和Roseburia。此外,核桃组大鼠肠道中的Bacteroide、Anaerotruncus和Alphaproteobacteria也降低了。

领导该研究的Lauri Byerley博士说:“这一结果证明,饮食中的核桃能够增加肠道细菌的多样性。而一些非相关性研究已经表明,细菌多样性的缺乏与肥胖和其它疾病有关。”

研究人员认为,核桃对肠道微生物群的调节作用可能是其带来健康益处背后的一种新机制。


除上述研究外,小编注意到,今年1月发表在Molecular Carcinogenesis杂志上的一篇论文认为,坚果之所以对健康有着积极的影响,因为它们参与激活了机体去除活性氧的自身防御。

活性氧由紫外线照射、各种化学物质或不同食物代谢物产生,能够造成DNA损伤,导致癌症的发生。研究人员表示,机体有一系列使活性氧变得“无害”的保护机制,而坚果及其所含的物质刺激了这些机制。

论文调查了包括核桃在内的五种不同坚果。研究者们将这些坚果在试管中进行了人工“消化”(digested),然后分析了消化产物对癌细胞系的影响。结果证实,被处理的细胞中,保护性的过氧化氢酶和超氧化物歧化酶的活性增加了。此外,消化产物诱导了癌细胞的程序性细胞死亡。

领导这项研究的Michael Glei教授称,这一研究显示,被研究的所有类型坚果都介导了上述作用。

参考资料:

Study finds walnuts may promote health by changing gut bacteria

Changes in the Gut Microbial Communities Following Addition of Walnuts to the Diet

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  • Changes in the Gut Microbial Communities Following Addition of Walnuts to the Diet

    Walnuts are rich in omega-3 fatty acids, phytochemicals and antioxidants making them unique compared to other foods. Consuming walnuts has been associated with health benefits including a reduced risk of heart disease and cancer. Dysbiosis of the gut microbiome has been linked to several chronic diseases. One potential mechanism by which walnuts may exert their health benefit is through modifying the gut microbiome. This study identified the changes in the gut microbial communities that occur following the inclusion of walnuts in the diet. Male Fischer 344 rats (n=20) were randomly assigned to one of two diets for as long as 10 weeks: 1) walnut (W), and 2) replacement (R) in which the fat, fiber, and protein in walnuts were matched with corn oil, protein casein, and a cellulose fiber source. Intestinal samples were collected from the descending colon, the DNA isolated, and the V3-V4 hypervariable region of 16S rRNA gene deep sequenced on an Illumina MiSeq for characterization of the gut microbiota. Body weight and food intake did not differ significantly between the two diet groups. The diet groups had distinct microbial communities with animals consuming walnuts displaying significantly greater species diversity. Walnuts increased the abundance of Firmicutes and reduced the abundance of Bacteriodetes. Walnuts enriched the microbiota for probiotic-type bacteria including Lactobacillus, Ruminococcaceae, and Roseburia while significantly reducing Bacteroides and Anaerotruncus. The class Alphaproteobacteria was also reduced. Walnut consumption altered the gut microbial community suggesting a new mechanism by which walnuts may confer their beneficial health effects.

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