Dogs, cats, and humans have been able to evolve together for good reason. Humans and their pets have the ultimatesymbiotic relationship. The simple task of feeding a pet and looking out for their health and safety is a small price to pay for all the good they can do for us. Here are six ways four-legged friends bring good health and happiness to their humans, simply by being themselves.

　　狗狗、猫咪和人类已能够很好地共生。人类和宠物存在着极强的共生关系。比起宠物能带给我们的好处，喂养并保证它们的健康和安全所需要的费用，根本不值一提。以下是这些四只腿的小伙伴带给我们健康和幸福生活的六种方式，仅仅它们是小猫小狗本身这一点就能给予。

　　Calming critters

　　平静心灵的小精灵

　　A study in the Journal of Psychosomatic Medicine showed that pets can help decrease blood pressure and stress in an individual, even better than a significant other or a friend can. Researchers believe this is because there is no fear of judgement or criticism from a pet; perhaps even the most supportive spouse or friend is no match for the unconditional love of a dog or cat.

　　《身心医学杂志》上有一项研究表明宠物有助于降低个人血压，甚至比另一半或朋友来得更有用。研究者认为这是因为宠物不会让人担心被议论和批评，有时候甚至最信任的配偶或朋友都比不上狗狗或猫咪所能给予的无条件的爱。

　　Disease detectives

　　疾病探测器

　　With their keen sense of smell, some dogs can be trained to detect low blood sugar in diabetics just by smelling their breath. Canines are currently also being trained to identify the odor of volatile organic compounds (VOCs) that may indicate cancer. So far, dogs have been able to detect melanoma, bladder, lung, prostate, breast, and ovariancancers.

　　狗狗都有很敏锐的嗅觉，通过训练，有些狗狗能够通过嗅闻糖料病者的呼吸探测出低血糖。如今狗狗也在被训练来识别挥发性有机化合物的气味，从而预知潜在的癌症。至今，狗狗已经能识别出黑色素瘤、膀胱癌、肺癌、前列腺癌、乳腺癌以及卵巢癌。

　　Stop sniffles

　　预防呼吸疾病

　　No matter how irresistible it is to snuggle a cute little furball, sometimes it's just not worth it if their dander causes debilitating symptoms like scratchy eyes, a stuffy nose, and relentless sneezing. But ironically, early exposure to pets can actually stop allergies from developing! Kids exposed to animals when they're very young build a tolerance and prevent respiratory issues like allergies and asthma in the future.

　　无论小动物有多么大的诱惑力，当它们的毛屑导致一些健康衰弱的症状：眼睛发痒、鼻噻、不停打喷嚏，你就会觉得不值得了。但讽刺的是，早期接触宠物确实是可以防止过敏症状的加重。儿童早一点接触动物能在体内形成抗体，防止以后过敏、哮喘等呼吸系统疾病的产生。

　　Love unleashed

　　爱的释放

　　Giving a dog a good petting can release oxytocin in the human's body, lowering blood pressure and cortisol. This means less stress, and also less belly fat, which is correlated to cortisol levels. Oxytocin is also released when dogs and their owners look into each others' eyes, like a mother and baby.

　　轻轻拍打狗狗能释放人体荷尔蒙、降低血压以及皮质醇。这就意味着压力的降低、以及腹脂的减少，这些与人体内皮质醇水平密切相关。当狗狗与主人有眼神交流时，就像妈妈和孩子一样，同样也能够使皮质醇得到释放。

　　Social butterflies

　　交际花

　　People who own dogs — and walk them — are in better shape and are less likely to be obese than people who don't, since exercise is built in to their routines. In turn, this can also reduce the risk of heart disease as well as other diseases linked to a sedentary lifestyle, including diabetes, hypertension, and osteoporosis. Heading outside with a pup in tow also means an increased absorption of vitamin D from sunshine.

　　养狗的人会经常遛狗，大多数人身材很好，相比其他人不容易发胖，因为运动是他们的日常习惯。相应地，这也会降低由久坐而引起的心脏病以及其它疾病的发病率，包括糖尿病、高血压和骨质疏松症。遛狗也能使人沐浴阳光，补充维他命D。

　　Quality control

　　生活质量保证

　　A puppy or kitten waiting to be fed at home can be enough to inspire some people to think twice about engaging in risky behavior. This is one way to increase odds of longevity. But caring for a pet can also heighten a person's self worth and sense of purpose.

　　家里有小狗或小猫咪等着被喂养，能让人反复思考某些有风险的行为。这是增加寿命的方式之一。但是照顾宠物也能提升个人的自我价值和目标感。

　　It's a simple truth: Dogs and cats can improve quality of life all around. They won't ask for much in return, but kind gestures in the form of healthy, tasty food and fun toys to keep them active can ensure a pet friend will keep living the dream for a long, long time.

　　这是一个简单的事实：宠物让我们的生活更美好。它们不求回报，只需要我们真诚的对待：健康、美味的食物和有趣的玩具，让它们永远生活在梦想之中。

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（编辑：何莹莹）