By Elizabeth Svoboda for Men's Journal

You already know that eating too much sugar causes your teeth to rot and can lead to diabetes and obesity. But could it also trigger high cholesterol, high blood pressure, heart disease and possibly even cancer? That's the theory of a group of progressive medical researchers who argue that sugar acts as a toxin in the body and is responsible for not only our rising rates of diabetes and obesity but also increasing incidences of heart disease, cancer and other chronic illness. Because sugar is so prevalent in food today -- in obvious items like ice cream, cookies and soda, as well as in "healthy" foods like crackers, energy bars and salad dressings -– experts contend that most people are living in toxic overload.

"Sugar is the biggest public health crisis in the history of the world," says Dr. Robert Lustig, an endocrinologist at the University of California, San Francisco, whose 2009 speech "Sugar: The Bitter Truth" has received more than 2.5 million hits on YouTube. In an opinion paper published earlier this year in the journal Nature, Lustig and colleagues provoked debate when they stated that sugar is so harmful, it should be regulated like alcohol and tobacco. "Every substance of abuse -– cocaine, heroin, you name it -– has required personal or social intervention," says Lustig. "For sugar we have nothing, and my prediction is that we will need both."

At first blush, this antisugar advocacy may seem alarmist. But Lustig and his University of California colleagues argue that sugar is harmful in significant amounts –- not necessarily because it's high in calories but rather because it triggers a toxic chain of reactions in the body that produce harmful fats, hormones and other metabolic by-products.

Sugar is found in nearly every food except meat, oil and butter. But there's a big difference between the sugar that occurs naturally in raw, unprocessed foods like fruits, vegetables, milk and whole grains and the type added to prepared or processed foods. Added sugars include every sweetener imaginable: white sugar, brown sugar, corn syrup, high-fructose corn syrup, dextrose, honey, agave nectar. It's these added sugars that experts say are the root cause of our sugar problem because high amounts of them are found in almost every food we eat, most of which are also high in calories and devoid of nutrients. "Nature made sugar hard to get," Lustig and his colleagues wrote in Nature. "Man made it easy."

Among all the different types of sugar, fructose may be the most harmful, many experts believe. Fructose is found naturally in small amounts in fruit, but is also combined with glucose (the other basic sugar molecule) to make nearly every type of commercial sweetener, including table sugar and high-fructose corn syrup. Why is fructose so harmful? "It's unique," says Dr. Miriam Vos, a gastroenterologist at Emory University. "It's primarily metabolized by the liver," so when you eat it, it's processed and then stays in your liver and starts producing harmful blood fats called triglycerides.

Sugars that don't contain fructose, on the other hand, like pure glucose and corn syrup, are processed by the liver and then sent out into the bloodstream, whether you need the fuel or not. Eat enough fructose and build enough triglycerides, and the result can be a fatty liver and insulin resistance -– when the body can't produce enough insulin to break down the sugar you eat.

For years, researchers have known that insulin resistance can lead to weight gain and diabetes. More recently, though, they've also discovered that it can cause heart disease, in part because eating too much sugar suppresses "good" HDL cholesterol. Eating too much sugar of any kind also seems to increase blood pressure, yet the effect is worse when glucose and fructose are consumed together, which is the case with high-fructose corn syrup and white sugar. Some researchers suspect that the effects of sugar on insulin metabolism may even cause cancer or accelerate its growth. "The cancer story is very early," says Lustig. "But we know that sugar drives insulin resistance, and insulin resistance drives cancer." One theory is that the high levels of insulin drive tumor growth, as the hormone already stimulates cancer cells to grow faster in the lab.

Unfortunately, exercise can't entirely save you from the negative effects sugar has on the body. While exercise may improve your cholesterol numbers by a few points, it's usually not enough to bring levels into a healthy range. "If you're a thin, active person, having a diet high in sugar is still harmful," says Vos. If you're an athlete, you may not want to cut out sugar entirely, especially before and during hard workouts. "There's some evidence for the super-athlete that small amounts of fructose are good," says Dr. Richard Johnson, a nephrologist at the University of Colorado, noting that the effect is beneficial only when sugar is consumed in moderate amounts before or after intense activities.

Other experts insist that sugar isn't as much of a threat to anyone -– including those of us who don't exercise intensely –- as Lustig and others have claimed.

Dr. David Katz, director of the Yale Prevention Research Center, says that while too much sugar isn't great for us, Lustig's dismissal of it as "poison" goes too far, pointing out that our bodies manufacture it naturally as an energy source. "The notion that sugar is toxic is silly," says Katz. "You can show dreadful effects of a high dose, but so what?" He's also skeptical of experts who push elimination of sugar to the exclusion of all else. "This is exactly the sort of dietary boondoggle we've been bogged down in for decades. We fell in love with low-fat; we fell in love with low-carb. If we fall in love with low-sugar, we won't improve our overall nutrition. It's a classic missing-the-forest-for-a-single-tree scenario."

Though Katz does agree that most Americans probably eat too much sugar, he doesn't recommend giving up the sweet stuff entirely because that can lead to food bingeing. Instead, he and most nutritionists advise learning to keep your quantities under control. For men, this means limiting yourself to nine teaspoons of added sugar per day and six for women (a can of cola has eight) if you want to meet the American Heart Association's recommendation. To gauge that limit, start scanning the nutrition labels of the packaged products you eat every day for at least one week. Add up your daily intake, keeping in mind that four grams of sugar on a food label is equivalent to one teaspoon of sugar. If you exceed the recommended limit on a regular basis -– and most of us do -– start by substituting lower-sugar options for foods that shouldn't taste sweet, like crackers and salad dressings. Ditch all sugar-sweetened drinks, like soda and even fruit juice, which packs a condensed amount of fructose without the fiber or other healthy nutrients of real fruit. Finally, prioritize eating whole, unpackaged foods, which don't contain added sugars.


参考译文：
伊丽莎白•斯沃博达发表于《男士期刊》

你已经知道吃过多的糖果会让你的牙坏掉，还能导致糖尿病和肥胖症。但是是否也会引发高胆固醇、高血压、心脏病甚至癌症呢？这个理论来自一群激进的药物研究者，他们认为糖分在身体中扮演的角色是毒素，它不仅要对糖尿病和肥胖症的高发率负责，也增加了心脏病、癌症和其他慢性疾病的发病率。由于糖分在今天的食物中如此常见——存在于明显的食物如冰淇淋、曲奇和苏打水中，也存在于“健康”食物如薄脆饼干、能量棒和沙拉调料中——专家们认为，大多数人都生活在过量的毒素中。

“糖是世界历史上最大的公共健康危机，”罗伯特•拉斯汀博士，旧金山加利福尼亚大学一位曾在2009年发表演讲“糖：苦涩的真相”而在YouTube上获得250万点击量的内分泌学家说。拉斯汀和他的同事今年在《自然》杂志上发布了一篇见解性论文，陈述糖的伤害性，并认为糖应该像酒精和烟草一样被管理起来，进而引发了争论。“任何遭到滥用的物质——可卡因，海洛因，你随便列举——都需要个人或社会的介入，”拉斯汀说，“而对于糖我们哪方面都没有介入，我的预测是我们未来会需要个人和社会都介入。”

许多专家认为，在所有类型的糖中间，果糖是最具伤害性的。果糖天然以小剂量存在于水果中，但也与葡萄糖（另一种基础糖分子）相结合生成几乎任何类型的商业甜味剂，包括蔗糖和高果糖分的玉米糖浆。为什么果糖如此有害？“它是独一无二的，”米里亚姆•沃斯，一位来自埃默里大学的胃肠病学家说，“它主要都进入了肝脏进行新陈代谢，所以你吃的时候，它就会进入肝脏等待处理，然后留在你的肝脏中，并开始生成有害的血液脂肪——甘油三酸酯。”

另一方面，不含果糖成分的糖类，比如纯葡萄糖和玉米糖浆，在肝脏中经过处理后被送入血液，不管你需不需要这种燃料。吃太多的果糖、生成过多的甘油三酸酯，会导致一个肥胖的肝脏，并对胰岛素产生抵抗——身体不再造出足够的胰岛素来化解你吃的糖。

数年来，研究者已经知道胰岛素抗体会导致体重增加和糖尿病。而最近，他们还发现这会导致心脏病，部分因为吃太多的糖会抑制“好的”高密度脂蛋白胆固醇。吃任何糖类过多还会导致高血压，而且如果葡萄糖和果糖一起被消耗，结果会更糟，高果糖分玉米糖浆和白糖就是这样。一些研究者还怀疑糖在胰岛素新陈代谢中的作用有可能会导致癌症，或者加速癌症扩散。“癌症的故事已经很早了，”拉斯汀说，“但是我们知道糖分带来胰岛素抗体，而胰岛素抗体催生癌症。”但有一个理论认为高水平的胰岛素会让肿瘤加速生长，正如在实验中激素会刺激癌细胞生长更快。

不幸的是，锻炼并不能将你从糖的副作用中完全拯救出来。它可能能够提高几个百分点的胆固醇指数，但通常不足以将数值拉回健康范围。“就算你是一个很瘦、而且活跃的人，饮食中糖分过多也是有害的。”沃斯说。如果你是一个运动员，你也许不想完全切断糖分，尤其是在训练前和训练中。“有证据表明对一个超级运动员来说少量的果糖是有益的。”理查德•约翰逊，一位科罗拉多大学的肾病学家说。他指出有益的效果只在糖分剂量合适、并在剧烈活动前后才会出现。

其他专家坚持认为糖并不是对任何人——包括那些不剧烈运动的人——都构成像拉斯汀和其他人所宣称的那样的威胁。大卫•卡茨博士，耶鲁预防研究中心的主任说，虽然过量的糖对我们身体不好，但是拉斯汀对其像“毒”一样的拒绝也太过偏激，因为我们的身体机能天生就需要能量来源。“认为糖是有毒的观念太愚蠢了，”卡茨说，“过量的糖会显示出糟糕的后果，但那又怎样？”他对那些主张在任何食物中消除糖分的专家也持怀疑态度。“这就是一种毫无意义的饮食问题，而我们居然陷入了数十年的争论。我们爱上了低脂肪；我们爱上了低碳水化合物。如果再爱上低糖，我们就没法提高整体的营养了。这是一个典型的只见树木不见森林剧情。”

虽然卡茨同意美国人可能吃了太多的糖，但他并不推荐完全放弃甜食，因为那有可能导致暴饮暴食。他和多数营养学家建议你对糖保持数量上的控制。如果你想遵从美国心脏协会的建议，对于男人来说这意味着一天限制在9勺额外的糖，对于女人来说是6勺（一瓶可乐有8勺）。要判断这个量，就注意浏览你每天吃的食品的外包装上的营养标签，保持一个星期。如果在日常饮食中你已经超过了推荐的量——我们大部分人都超过了——那就开始用糖分低一些的食物来取代吧，比如尝起来没那么甜的薄脆饼和色拉调料。抛弃所有过甜的饮料，比如苏打水甚至果汁，那里头包含了高浓度的果糖，而且没有纤维和其他真正水果应有的健康营养。最后，优先吃完整的、非包装食品，这些食品里不要含额外的糖分。