Genetic jackpot
中了遺傳大獎
Given these results, there is little doubt that Okinawa has an exceptional population. But what can explain that extraordinary longevity?
鑑於這些結果，毫無疑問地，沖繩的長壽人口眾多。但是，該如何解釋這種驚人的長壽呢？
Genetic good fortune could be one important factor. Thanks to the geography of the islands, Okinawa’s populations have spent large chunks of their history in relative isolation, which may has given them a unique genetic profile. Preliminary studies suggest this may include a reduced prevalence of a gene variant – APOE4 – that appears to increase the risk of heart disease and Alzheimer’s. They may also be more likely to carry a protective variant of the FOXO3 gene involved in regulating metabolism and cell growth. This results in a shorter stature but also appears to reduce the risk of various age-related diseases, including cancer.
遺傳上的好運可能是一個重要因素。由於這些島嶼的地理位置，沖繩人的歷史中有相當長地一段時間都是較為孤立的狀態，這可能給了他們一種獨特的基因組成。初步研究表明，這種基因組成可能包括減少APOE4這種基因變異的盛行率，APOE4會增加患有心臟病和阿茲海默症的風險。他們也更有可能帶有能調節新陳代謝和細胞生長的FOXO3基因的防護型變異。雖然這會導致身材較為矮小，但似乎也會降低各種與年齡有關的疾病(包括癌症)的風險。
Even so, it seems unlikely that good genes would fully explain the Okinawans’ longevity, and lifestyle factors will also be important. The OCS has found that Okinawans are less likely to smoke than most populations, and since they worked predominantly in agriculture and fishing, they were also physically active. Their tight-knit communities also help the residents to maintain an active social life into old age. Social connection has also been shown to improve health and longevity by reducing the body’s stress responses to challenging events. (Loneliness, in contrast, has been shown to be as harmful as smoking 15 cigarettes a day.)
即便如此，好基因也似乎不能完全解釋沖繩人的長壽，生活方式也很重要。OCS發現沖繩人吸煙的可能性低於大多數地區的人，而且由於他們主要從事農業和漁業活動，所以也使他們的身體活動量高。他們密切的社區關係也讓居民即使步入老年期，仍能保持活躍的社交生活。社交連結也能藉由減輕面對挑戰時身體的壓力來促進健康、延年益壽。（相較之下，寂寞所造成的傷害相當於每天吸15支香菸所產生的危害。）
It is the Okinawans’ diet, however, that may have the most potential to change our views on healthy ageing. Unlike the rest of Asia, the Okinawan staple is not rice, but the sweet potato, first introduced in the early 17th Century through trade with the Netherlands. Okinawans also eat an abundance of green and yellow vegetables – such as the bitter melon – and various soy products. Although they do eat pork, fish and other meats, these are typically a small component of their overall consumption, which is mostly plant-based foods.
但是，最能讓我們對健康老化改觀的原因可能就是沖繩人的飲食。與亞洲其他地區不同，沖繩的主食不是米飯，而是番薯，其最初是在17世紀初通過與荷蘭的貿易而引入的。沖繩人也吃大量綠色和黃色的蔬菜，像是苦瓜，以及各種豆製品。雖然它們也會吃豬肉、魚類和其他肉類，但這通常只佔其總體飲食中的一小部分，吃最多得還是植物性食物。
The traditional Okinawan diet is therefore dense in the essential vitamins and minerals - including anti-oxidants - but also low in calories. Particularly in the past, before fast food entered the islands, the average Okinawan ate around 11% fewer calories than the normal recommended consumption for a healthy adult.
因此，傳統的沖繩飲食中富含人體必需的維生素與礦物質(包括抗氧化劑)，但是卡路里卻很低。特別是在速食進入各島之前，沖繩人平均攝取的卡路里比健康成人的正常推薦攝取量少了11％。
For this reason, some scientists believe that Okinawans offer more evidence for the life-enhancing virtues of a “calorie restricted” diet. Since the 1930s, some doctors and scientists have argued that continuously limiting the amount of energy you consume could have many benefits above and beyond weight loss – including a deceleration of the ageing process.
出於這個原因，有些科學家認為，沖繩人進一步證明了「限制卡路里」飲食法有改善健康的好處。自1930年代以來，有些醫生和科學家認為，持續限制攝取的熱量可能可以帶來許多減重以外的好處，包括減緩老化的過程。
In one of the most compelling experiments, a group of rhesus macaques eating 30% fewer calories than the average monkey showed a remarkable 63% reduction in deaths from age-related diseases over a 20-year period. They also looked younger – they had fewer wrinkles and their fur retained its youthful lustre rather than turning grey. Due to practical difficulties, long-term clinical trials in humans have yet to be completed to test the effects on longevity, but a recent two-year experiment, funded by the US National Institute on Aging, was highly suggestive: participants on a calorie restricted diet showed better cardiovascular health – including lower blood pressure and cholesterol.
在一項備受矚目的實驗中，一群獼猴攝取的卡路里比普通猴子攝取的卡路里還少3成，結果顯示在20年之間，因罹患與年齡相關的疾病而死亡的數量明顯減少了63％。牠們看起來也比較年輕，少有皺紋、皮毛保持青春的光澤而非變灰。由於實踐上的困難，目前對人類的長期臨床試驗尚未完成，無法測試長壽的效果，但是最近一個由美國國家老化研究所資助的為期兩年的實驗高度暗示著：進行限制卡路里飲食法的參與者們顯示出更良好的心血管健康，有較低的血壓與膽固醇。
It’s still not clear why a calorie restricted diet would be so beneficial, but there are many potential mechanisms. One possibility is that calorie restriction alters the cell’s energy signalling, so that the body devotes more resources to preservation and maintenance – such as DNA repair – rather than growth and reproduction, while limiting ‘oxidative stress’ caused by the toxic by-products of metabolism that can cause cellular damage.
目前尚不清楚為什麼限制卡路里飲食法會有這麼多好處，但卻有許多潛在機制。一種可能是卡路里的限制改變了細胞的能量訊號，因此人體會投入更多的資源來保存與維護，例如DNA的修復，而不是花在生長與繁殖上，同時限制新陳代謝的有毒副產物所引起的「氧化壓力」，這種氧化壓力會造成細胞的損傷。
The benefits of the Okinawan Diet may not end with its calorie restriction.
沖繩飲食法的好處可能不止於其卡路里的限制而已。
Solon-Biet has conducted a series of studies examining the influence of dietary composition (rather than sheer quantity) on ageing in animals, and her team has consistently found that a high-carb, low-protein diet extends the lifespan of various species, with her most recent study showing that it reduces some of the signs of ageing in the brain. Amazingly, they have found that the optimum ratio is 10 parts carb to one part protein – the same as the so-called Okinawan Ratio.
Solon-Biet進行了一系列的研究，調查飲食的成分（而非只有量）對動物老化的影響，她的團隊持續發現，高醣類、低蛋白的飲食能夠延長各種物種的壽命，她最近的一項研究發現，這種飲食還能減少一些大腦中老化的病徵。驚人的是，他們所發現的最佳比例是10份碳水化合物與1份蛋白質，與所謂的沖繩比例相同。
Although there aren’t yet any controlled clinical trials in humans, Solon-Biet cites epidemiological work across the world that all point to similar conclusions. “Other long-lived populations have also been shown to have dietary patterns that include relatively low amounts of protein,” she says. “These include the Kitavans, [who live on] a small island in Papua New Guinea, the South American Tsimane people and populations that consume the Mediterranean diet.”
雖然目前還沒有任何對人類的對照臨床試驗，但是Solon-Biet指出全球的流行病學研究都有著類似的結論。她說：「其他地區的長壽人口，他們的飲食模式也包含相對較少的蛋白質。這些包括[居住在]巴布亞紐幾內亞小島上的基塔瓦人、南美洲的奇美內人以及進行地中海飲食的人。 」
Once again, the exact mechanisms are murky. Like calorie restriction, the low protein diets seem to promote the cell repair and maintenance. Karen Ryan, a nutritional biologist at the University of California, Davis, points out that the scarcity of amino acids can encourage cells to recycle old material (rather than synthesising new proteins).
不過還是不清楚確切的機制。像卡路里的限制一樣，低蛋白質飲食似乎能夠促進細胞的修復與維持。加州大學戴維斯分校的營養生物學家凱倫萊恩指出，缺乏氨基酸可以促使細胞重複利用舊的材料（而非合成新的蛋白質）。
“Together, these changes may prevent the ageing-associated accumulation of damaged proteins within cells,” she says. This build-up of damaged proteins may usually be responsible for many diseases, she says – but the regular clean up when we eat a low-protein diet could prevent it.
她說：「合起來，這些變化或許能阻止細胞內受損蛋白質產生與老化相關的積聚。」這種受損蛋白質的堆積通常是許多疾病的推手，但是當我們進行低蛋白飲食時，體內的定期清理就可以預防這種堆積的產生。
So should we all start adopting the Okinawan Diet? Not quite. Ryan points to some evidence that low protein intake may limit bodily damage up to the age of 65, but you may then benefit from increasing your protein intake after that point. “Optimal nutrition is expected to vary across the life history,” she says. And it’s also worth noting one study, which found that the relative merits of protein and carbohydrates may depend on the protein's source: a diet higher in plant-based protein appears to be better than a diet rich in meat or dairy, for instance. So the Okinawans may be living longer due to the fact that they are eating (mostly) fruit and vegetables, rather than its high carb, low protein content.
所以說我們都要開始採用沖繩飲食法嗎？也不是這樣的。萊恩指出，一些證據顯示，在65歲以前攝取低蛋白質或許能夠降低對身體的傷害，但是在65歲之後或許能夠因為增加蛋白質的攝取量而得到好處。她說：「人體的最佳營養在一生中都會有所變化。」一項同樣值得注意的研究發現了蛋白質和碳水化合物的相對價值可能取決於蛋白質的來源，例如：富含植物性蛋白質的飲食似乎比富含肉類或乳製品類的蛋白質還要好。因此，沖繩人能活得更長，可能是因為他們（主要是）吃水果和蔬菜，而非其高醣類、低蛋白含量的飲食。
Ultimately, the Okinawans’ health is probably due to a lucky confluence of many factors, Ryan says. “And specific interactions among these factors will also be important.” And we may need many more years of research to understand the importance of each of those ingredients before we finally come up with a true recipe for the “elixir of youth”.
萊恩說，歸根究底，沖繩人的健康可能是由於許多因素剛好匯合在一起。「這些因素之間具體的相互作用也很重要。」在我們終於提出真正的「長生不老藥」配方之前，我們可能還需要更多年的研究來了解每種成分的重要性。
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