You have probably heard that Japan has among the highest life expectancy(预期寿命) in the world and that the island of Okinawa(冲绳) has the greatest concentration(浓度) of centenarians(百岁老人). But do you know that two-thirds of the centenarians are still functioning independently? That means they are in their own homes, cooking their own meals and living their lives fully - at about 100 years old!

The elders there are less likely than their counterparts in the United States to have heart disease, dementia(痴呆) or certain cancers. Their bones are stronger than those of similarly aged people around the world. Many of these residents are the subjects of one of the largest studies of centenarians ever conducted. Since 1976, nearly a thousand centenarians on the islands have been studied.

More than anything, the Okinawa diet has long captured the headlines. Before knowing what the Okinawans eat, there is a valuable lesson in how they eat.

Remember this term: hara hachi bu. It is translated into English as “Stop eating when you are 80% full.” With hara hachi bu, the philosophy is that you should still be a little hungry when you push the plate away. You are also advised to reduce your portion(食物的分量) sizes, use smaller plates and eat more slowly.

There is a basic biological (生物学的) reason this works. It takes about 20 minutes for the stomach to send signals to the brain that it is full. Unfortunately, most people can shovel down another several hundred calories in that short time. Instead, if you push the plate away and just wait, you will have eaten less and still feel satisfied.

Eating less is associated with longevity, but of course, that also depends on what you eat. Okinawans typically eat seven different fruits and vegetables and 18 different foods a day, and more than 200 different foods and spices regularly in their overall diet.

However, the younger generations are eating more meat and fast food instead of fish and soy. The elderly there are still widely revered(崇敬), but there are fewer of them, and they are less often living to 100 than in decades past.

From the moment we’re born, we acquire, and develop an internal ecosystem of microbes (微生物), trillions of them in all, which are living together with us in our body. In fact, there are roughly as many microbial cells in our bodies as human cells. This prosperous microbial world is called our microbiome.

While some microbes can make us ill, we need our microbiome to survive. Combined, they are every bit as essential as our heart, our lungs or our brain. We have microbes living all over our skin and in every other parts of our bodies. But most of the microbiome is found in our guts (肠道). Our gut microbes are essential for digestion. They also help regulate hormones and they can improve our immune system (免疫系统).

Our microbiome contains a wide range of microbes, some of which have beneficial effects on our health and some of which are detrimental. A healthy collection of microbes seems to be vital for our wellbeing, protecting against some of the biggest health threats, like heart disease, obesity, diabetes, arthritis and even depression.

On the other hand, having an unhealthy microbiome may be a contributing factor for many common diseases. Our modern lifestyles, western diets and overuse of antibiotics might all be having a harmful effect on our internal ecology.

So how do you develop a healthy microbiome? Well, it seems that the more diverse your microbial population is, the better. And the best way to increase your diversity is to eat a wide range of plant- based foods. Research shows that people who have at least 30 plant- based elements in their diet every week have a wider range of microbes in their gut, and that’s linked to better weight management, better heart health and better mental health.

For centuries, tea has been used for far more than overcoming thirst. Around the world people drink it to relax and restore energy.

Green, oolong and black tea come from the same plant — Camellia sinensis (茶树). Green tea, however, is processed in a different way, which results in higher levels of some of the compounds that scientists believe have positive effects on our mental health.

A 2017 review of more than 100 studies found that green tea can impact the brain in three ways: reduce anxiety; focus attention; and improve brain function, especially memory. However, it was cautioned that the effects aren’t large, and current evidence is mainly provided by small-scale studies.

There are also suggestions that tea could improve the symptoms of depression, dementia (痴呆) and Down syndrome (唐氏综合征).

A 2018 study conducted in South Korea found that frequent green tea drinkers were 21% less likely to develop depression than those who were non-drinkers. However, as an observational study, it couldn’t establish cause and effect, only association.

Tea also has some benefits for our physical health — it’s linked to a longer life, could reduce some risk factors for cardiovascular (心血管的) disease such as heart attack and stroke, and may also have a weight-losing effect.

“We need better data to truly assess the benefits of tea on our mental and physical well-being,” said Gunter Kuhnle at the University of Reading, “however, with the exception of green tea pills, which have been linked to liver damage, and burning tea, which has been linked to esophageal (食道的) cancer, there’s no real downside to a cup of tea. I think most people enjoy rituals (仪式感). It’s a comforting thing. If there’s anything wrong, here it’s a cup of tea that’s needed.”