Author Dan Buettner has traveled the globe visiting "blue zones," where people tend to live longer and lead healthier lives. Cheryl Tiegs/National Geographic Books hide caption

itoggle caption Cheryl Tiegs/National Geographic Books

It's important to talk to your vet about any changes in your dog's behavior or diet, says veterinarian Nicholas Dodman. iStockphoto.com hide caption

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Carlos Eire is a professor of history and religious studies at Yale. Free Press hide caption

itoggle caption Free Press