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Over the years, Americans have become inured to salt. Most people have no idea how much salt they consume — onaverage, about 9 to 12 g (or 3,600 to 4,800 mg of sodium) per person per day, according to the American Heart Association (AHA). That's twice the amount recommended by the government.
In the past four decades, Americans' salt consumption has risen 50%, mostly as a result of eating more processed foods and more food prepared in restaurants. "Over time, we have adapted our taste buds and adapted our bodies to crave much, much higher levels of salt than we require to function," says Dr. Kirsten Bibbins-Domingo, an epidemiologist at the University of California, San Francisco.
Some salt is crucial for good health, of course — to regulate blood pressure and assist with muscle and nerve function — but too much (that is, at the levels we currently consume) can lead to hypertension, heart disease and stroke. If Americans halved their salt intake, as many as 150,000 premature deaths could be prevented each year, according to the American Medical Association. And new research presented March 11 by Bibbins-Domingo at the AHA's annual conference shows that even small reductions — as little as 1 g of salt per day — could have dramatic effects, saving 200,000 lives over the course of a decade.
Using a sophisticated computer model to analyze trends in heart disease over time among U.S. adults, Bibbins-Domingo and colleagues discovered that incremental population-wide reductions could drastically improve public health. Cutting out just 1 g of salt (or 40 mg of sodium) per person per day could prevent 30,000 cases of coronary heart disease across the U.S. population by 2019. Reducing consumption by half — a more sizable 6 grams — could prevent 1.4 million cases of heart disease during that same period.
While eating less salt would improve the health of the population across the board, researchers found that the benefits would be greatest for African Americans and women. As a group, African Americans tend to have higher blood pressure than the general population, and "many studies suggest that they may be more sensitive to salt," Bibbins-Domingo says. Her analysis found that a reduction of 3 g of salt per day would reduce heart attacks 8% on average; among African Americans, that rate would drop 10%. A similar result was found in women, whose stroke risk dropped 8% with a 3-g reduction in salt intake; in men, the risk fell 5%.
The numbers certainly offer compelling incentives to cut salt consumption, but that's no easy task. You can put down the salt shaker and cut back on obviously salty snacks, but there's still so much sodium packed into processed foods that trying to extract it from your diet is a tricky business. "It's so pervasive in an average U.S. diet that it's really hard to tell people, 'You have to avoid salt,' " says Bibbins-Domingo.
And there is salt hiding in places you wouldn't think to look. According to a sodium chart from the U.S. Department of Agriculture, a single slice of commercially made whole-wheat bread has 148 mg of sodium; white bread has 170 mg. Cheerios contains 213 mg of sodium per cup; Total Raisin Bran, 239 mg. And then there are the big offenders: processed soups and sauces. Chicken noodle soup, for example, even after it has been diluted with water during preparation, has a whopping 1,106 mg of sodium per cup. "I think people don't have a clue," says Bibbins-Domingo. "The recommended daily amount of salt is about a teaspoon," she says. "It's easy to add that much if you're just adding salt," let alone all of the salt that's in food before we break out the shaker.
If you're dining out, all bets are off. According to the British organization Consensus Action on Salt in Health, a three-course meal in a restaurant can contain more than 15 g of salt, almost three times the recommended daily amount.
Bibbins-Domingo says it's especially tough for families with limited income, who tend to rely more on processed or packaged foods and canned fruits and vegetables rather than fresh foods. Patients tell her they've cut salted nuts, potato chips and pretzels from their diet and started eating more soup instead. "You realize that they're actually consuming more salt in their attempt to make healthy choices," she says.
Any large-scale success in salt-intake reduction would have to involve policymakers and the food industry, say public-health experts. "If you could reduce blood pressure by just a few points, you could reduce hundreds of thousands of deaths," says Dr. Thomas Frieden, commissioner of New York City's Department of Health and Mental Hygiene, who recently announced a national campaign to diminish salt intake 20% in the next five years and 40% in the next decade. Frieden, who has in the past targeted trans fats and led the charge to require chain restaurants to list calorie content on menus, has evoked less animosity from the food and restaurant industries with his desalinization efforts than with his previous initiatives.
"[Frieden] is looking for voluntary guidelines. It's a national movement, and he's working closely with the industry on developing these re-education guidelines," says Rob Bookman, an attorney for the New York State Restaurant Association, but he adds wryly, "I don't know if it's one big happy family."
Frieden points to a successful salt-reduction campaign in the U.K. as a kind of proof of principle. Several years after the British government launched an aggressive national campaign, which included voluntary reductions in salt content by food manufacturers, British citizens had reduced their annual sodium consumption roughly 10%. "If you look at what happened in the U.K., at first the industry was very concerned," Frieden says. "But after a few years, they saw that they could drop their salt content 20% to 30% [without losing customers]."
For Bibbins-Domingo, the issue is less about mandating food production or proscribing salt consumption than enabling people to make better choices. "This is actually something that we can achieve with very little cost to our personal liberties," she says.
But Frieden adheres to a harder line. When asked whether the government should be allowed to influence how or what we eat, he responded with a pointed rhetorical question: "Should industry be allowed to serve us food that makes us sick and kills us?"
这些年来，美国人已经习惯了食用（大量的）盐。大多数人并不知道自己每天摄入了多少盐——据美国心脏协会统计，平均下来，每人每天大概9-12克（相当于3600-4800毫克的钠）。这是政府推荐摄入量的两倍。
在过去的四十年，美国人盐的消费量增加了50%，主要是因为人们更多得食用加工食品，更多得在餐馆就餐。“一直以来，我们都在纵容自己的口味，纵容自己的身体对盐的需要，摄入了大量的盐，远远超过满总生理机能所需的量”旧金山加利福尼亚大学的比宾斯-多明戈博士如是说。
当然，盐对我们的健康至关重要——调节血压，辅助肌肉和神经功能。但是，过量的盐（比如我们目前的摄入量）会导致高血压、心脏病和中风。据美国医学学会称，如果美国人的盐摄入量减半，每年将会有150，000人避免过早死亡。比宾斯-多明戈 3月11日在美国心脏学会（AHA）年度研讨会上公布的最新研究表明，即便微小的调节，比如每天减少1克，都会带来显著的效果——在未来的十年挽救 200，000人的生命。
比宾斯-多明戈和其同事用高性能计算机模型分析了美国成年人心脏病的发展动态，发现全民减少摄入盐能够大幅度提高公共健康水平。如果每人每天减少1克的盐摄入（或者40毫克的钠），在2019年前，能够在全国范围内预防30，000例冠心病的发作；如果盐的摄入量减半——大约6克，在同一时期内，能够预防140万例心脏病的发作。
减少食用盐能够提高国民的健康水平，研究人员发现这种成效在非裔美国人和妇女身上更为明显。比起普通居民，非裔美国人的血压更高，比宾斯-多明戈说：“大量研究表明他们可能对盐更为敏感。”她的分析显示，平均来说，每天减少3克的盐摄入将会降低8%的心脏病发作率；而在非裔美国人中间，这一比例将会是10%。相似的结果出现在女性身上。每减少3克的盐摄入，发病概率降低 8%；而对男性来说，这一比例为5%。
这些数字毫无疑问刺激人们去减少盐的摄入量，但这可不是一个简单的任务。你可以放下盐瓶，放弃明显的咸味点心，但是，在加工过的食品中却含有大量的纳，把他们从你的食谱中剔除会是一件相当棘手的事。比宾斯-多明戈说：“在美国人的日常食物中，它（加工过的食品）是如此的常见，以至于你很难去告诉人们‘你必须远离盐’”。
在一些你永远都不会注意的地方也存在着盐。根据美国农业部的一份钠含量的图表，一片市面上出售的全麦面包含有148毫克的钠；白面包有170毫克。每一杯 Cheerios含有213毫克的钠；Total Raisin Bran,139毫克。钠含量的大户还有：精心熬制的汤和酱。比如说，鸡肉面条汤，即便在烹制期间加水稀释，每杯仍含有惊人的1106毫克的钠。“我想人们毫无头绪”，比宾斯-多明戈说。她说：“推荐的食用量是一汤匙。如果你只是随便加入盐的话，就很容易超量”。一定要把食物里所有的盐弄出来，直到你的振动筛被用坏。
如果你在外边吃饭，那一切都完了。根据英国组织“为了健康 同心抗盐”的调查，餐馆里的三餐含有高达15克的盐——几乎三倍于推荐食用量。
比宾斯-多明戈说，对于收入拮据的家庭，（减少盐的食用量）尤为困难。因为他们更为依赖经过加工包装的食品，更多得食用罐装蔬菜和水果，而不是新鲜的。有病人告诉她，他们已经从食谱中剔除了腌坚果、薯片和椒盐饼干，而开始食用更多的汤。她说：“你能看到他们本想选择更加健康的饮食，实际上却食用了更多的盐。”
公共健康专家称，任何减少盐的摄入量的大规模行动的成功，都必然牵涉到决策者和食品工业。托马斯.弗里登博士说：“如果能够让血压降低哪怕很小的幅度，就能够挽救成百上千的生命。”托马斯.弗里登博士是纽约市健康及心理卫生署署长，他最近公开发起了一项全民运动，目的是在未来的5年内减少盐的摄入量20%，十年内减少40%。弗里登，就是那个曾经把目标指向脂肪，领导了要求连锁餐馆在菜单上列出卡利路含量的那场斗争的人。（他）因除去盐分的努力而招致的食品和餐饮行业的怨恨，比他先前的活动还要少。
“弗里登正在寻找自愿准则。这是一场全民运动，他正在和食品行业紧密合作，制定他们的再培训准则。”纽约餐馆联盟的代理律师Rob Bookman说，但是他略带讽刺得补充说：“我不知道会不会出现皆大欢喜的局面。”
弗里登指出，英国发生的一场成功的“减盐”运动，可以作为重要借鉴。几年前，英国政府发动了一场轰轰烈烈的全民运动，其中包括食品生产厂家自愿减少盐的含量。英国居民盐的摄入量已经减少了大概10%。弗里登说：“如果你观察一下，你会发现，最初企业都很忧虑，经年之后，他们发现即使盐的含量减少了20%- 30%,他们却没有失去买主。”
对比宾斯-多明戈来说，行动的目的是让人们有机会做出更好的选择，而不是苛责食品行业和管制盐的消费。她说：“我们确实可以促进我们的个人自由，只需付出很小的代价”
但是弗里登坚持强硬路线。当被问及政府是否应该被允许去影响我们吃什么、怎么吃时，他尖锐得反问道：“食品行业应该被允许供给会毒害我们的健康甚至杀死我们的食物吗？”
