A lot of Americans think they're eating a healthy diet these days. But it's easy to be fooled by our assumptions and the ways that food manufacturers play on them.

Take chicken. The average American eats about 90 pounds of it a year, more than twice as much as in the 1970s, part of the switch to lower-fat, lower-cholesterol meat proteins. But roughly one-third of the fresh chicken sold in the U.S. is 'plumped' with water, salt and sometimes a seaweed extract called carrageenan that helps it retain the added water. The U.S. Department of Agriculture says chicken processed this way can still be labeled 'all natural' or '100% natural' because those are all natural ingredients, even though they aren't naturally found in chicken.

Producers must mention the added ingredients on the package -- but the lettering can be small: just one-third the size of the largest letter in the product's name. If you're trying to watch your sodium to cut your risk of high blood pressure, heart attack and stroke, it pays to check the Nutrition Facts label. Untreated chicken has about 45 to 60 mgs of sodium per four-ounce serving. So-called enhanced or 'plumped' chicken has between 200 and 400 mgs of sodium per serving, almost as much as a serving of fast-food french fries.

Adding salt water became widespread when big discount stores began selling groceries and wanted to sell chicken at uniform weights and prices. Plumping packaged chicken helps even out the weight. But that means consumers are paying for added salt water at chicken prices -- an estimated $2 billion worth every year, according to the Truthful Labeling Coalition, a group of chicken producers that don't enhance their products.

Makers of enhanced chicken, including some of the biggest U.S. producers, say many consumers prefer it in blind taste tests and that it stays moister. Ray Atkinson, a spokesman for Pilgrim's Pride, says the company sells both enhanced and unenhanced chicken because consumers ask for it. He also notes that even at 330 mg of sodium, the enhanced chicken qualifies for the American Heart Association's mark of approval.

A survey released this week from Foster Farms, a member of the Truthful Labeling Coalition, found that 63% of consumers are unaware of the practice, and 82% believe that salt-water-injected chicken shouldn't carry the all-natural label. The telephone survey polled 1,000 consumers on the West Coast.

Here are some other foods that may not be as healthy as they appear.

-- Salt substitutes. If you're trying to cut down on salt, check with your doctor before you start using a salt substitute. Most contain potassium chloride, which can exacerbate kidney problems and interact badly with some heart and liver medications.

-- Artificial Sweeteners. Sugar-free gum, mint and candy have fewer calories and are better for your teeth. But they frequently contain sorbitol, a plant extract that isn't completely absorbed by the body and works as a natural laxative. Consuming a single pack of gum or mints can cause bloating, flatulence, stomach pains and diarrhea in people who are sensitive to it. Some diabetics find that such sugar alcohols, which are sweet but have few calories, can raise their blood sugar. Others include maltitol and xylitol.

-- Trans fat. There's been a remarkable reduction in these artery-cloggers in processed foods recently. But manufacturers are allowed to round down: Products labeled zero grams of trans fat can have up to 0.49 gram of fat per serving. You could still be consuming significant amounts of trans fat, 'especially when the serving size is unrealistic,' says Bonnie Taub-Dix, a nutritionist and spokeswoman for the American Dietetic Association, a nonprofit professional organization. If the ingredients include partially hydrogenated oil, hydrogenated oil or shortening, a product isn't completely trans-fat free. And it may have considerable saturated fat as well.

The same rounding principle applies to zero calories, fat and carbohydrates. Walden Farms, which advertises a line of dips, spreads and dressings as 'Fat Free, Sugar Free and Calorie Free,' says its products do have trace calories and up to 0.49 gram of fat and carbohydrates per serving.

-- 'Wheat bread.' This is a meaningless term, since almost all bread is made with wheat. Some manufacturers add to the illusion by using a brown wrapper or darkening bread with brown sugar or molasses. The more healthful stuff is whole wheat, which includes the outer bran and the wheat germ inside, good sources of nutrients and fiber. Check the ingredients. If the first one listed is 'enriched wheat flour,' you aren't getting much whole grain.

A few bread makers are still displaying the USDA's old Food Pyramid on their packages -- the one that recommended six to 11 servings of bread or pasta a day. That's been replaced by a more individualized pyramid that recommends only six carbohydrate servings, three of which should be whole grains.

-- Fiber. Companies are adding fiber to all kinds of products -- including yogurt, ice cream and beverages. In many cases, the added fiber comes from purified powders, not the kind of fiber found in whole grains, beans, vegetables and fruits. The latter have been shown to lower cholesterol, reduce the risk of diabetes and heart disease and may cut the risk of colon cancer. But there isn't much evidence that 'isolated' fibers like inulin, maltodextrin, oat fiber and polydextrose have the same effect, according to the Center for Science in the Public Interest, a nonprofit consumer-advocacy group. The Nutrition Facts label doesn't differentiate between the kind of fiber counted, so check the ingredients.

'The added fiber is probably better than nothing, but it's not as good as fiber from natural sources like fruits, vegetables and whole grains,' says CSPI Executive Director Michael Jacobson.

-- Yogurt. The yogurt aisle is dizzy these days with products that promise to reduce your cholesterol, control your blood pressure, protect your digestive health or boost your immune system. In many cases, it's a single ingredient that provides the benefit, and you can find much more of it in other sources. For example, Promise activ SuperShots say they 'Help Control Blood Pressure' thanks to 350 mgs of potassium. There's much more potassium in a banana, a cup of spinach or a baked potato. DanActive probiotic dairy drink's immunity-boosting claims stem from its L. casei Immunitas active culture. There's lots of research interest in such probiotics, but for now, the marketing is ahead of the science. The friendly bacteria in DanActive has mainly been shown to fight diarrhea in people taking antibiotics.

-- Super water. The Center for Science in the Public Interest sued Coca-Cola Co. earlier this year over claims on its VitaminWater beverages. The center argued that the drinks -- with names like 'defense,' 'rescue,' 'energy' and 'endurance' -- are mainly sugar water with 125 calories per bottle. Coke called the lawsuit 'frivolous' and said its VitaminWater brands are properly labeled. 'Consumers today are savvy, they are educated and they are looking for more from their beverages than simply hydration,' said Coke spokesman Scott Williamson.

Government surveys show that most Americans aren't deficient in many of the vitamins supplied in these drinks. If you consume more than you need, the excess gets excreted.

-- Omega 3. Many foods are adding these essential fatty acids, said to cut the risk of heart disease, cancer and arthritis and help promote brain health. But you can get a lot more from natural foods. You'd need to drink 45 eight-ounce glasses of milk that is fortified with 32 mgs of omega 3 to get as much of these fatty acids as you get in a three-ounce serving of salmon.

Will any of the products mentioned here hurt you? No, but they may not help you as much as manufacturers would like you to think. 'Try to buy foods as close to their natural state as possible,' says Ms. Taub-Dix.

许多美国人以为他们现在吃的东西都算得上是健康食品。不过，我们其实很容易被自己头脑里的那些思维定势和食品生产商们的花言巧语所蒙骗。

以鸡肉为例吧。美国人平均一年要吃上大约90磅鸡肉，这比上世纪70年代增加了一倍以上，原因之一在于美国人如今已经转而吃起低脂肪、低胆固醇的肉类食品来了。不过在美国销售的大约三分之一的新鲜鸡肉都加注过水、盐，有时还要加入一种名为角叉胶的海藻提取物以帮助鸡肉保持添加的水份。美国农业部(U.S. Department of Agriculture)表示，以这种方式处理过的鸡肉仍然可以标上“全天然”或者“100%天然”的字样，因为水、盐和角叉胶这些物质都是天然成份──尽管这些东西并不是鸡肉的天然成份。

生产商必须在包装上注明添加成份──不过这些成份的字体可能会很小：仅相当于标注产品名称所使用的大字体的三分之一。如果你想控制钠的摄入量以降低患高血压、心脏病和中风的几率，那么就别忘了查看营养表。一份四盎司的未经处理的鸡肉含有大约45至60毫克的钠。而一份所谓的“增强型”或者“注水”鸡肉则含有200至400毫克的钠，钠含量几乎和快餐食品炸薯条相当。

加入盐水的作法是在大型折扣店开始销售食品，并设法以统一的重量和价格销售鸡肉的时候开始变得普遍起来的。注水能够使包装好的每盒鸡肉的重量变得更加均衡。不过这意味着消费者为添加的盐水付出了鸡肉的价钱──根据鸡肉生产商联盟Truthful Labeling Coalition的估计，这笔开支每年高达20亿美元。该联盟的生产商们允诺不对鸡肉产品进行加工处理。

“增强型”鸡肉的生产商，其中包括某些美国最大的生产商表示，许多消费者在不知情的情况下在比较产品口味时，都更喜欢增强型鸡肉，此外增强型鸡肉能够更好地保持水份。鸡肉生产商Pilgrim's Pride的发言人雷•阿特金森(Ray Atkinson)表示，该公司既销售增强型鸡肉，也销售未经加工的鸡肉，这是为了满足消费者的需求。他还指出，即便是330毫克的钠含量，增强型鸡肉也仍然符合美国心脏协会(American Heart Association)的认证标准。

Truthful Labeling Coalition成员Foster Farms上周发表的调查报告显示，63%的消费者并不了解鸡肉行业的这种作法。此外，82%的消费者认为，注入盐水的鸡肉不应标有全天然字样。这一电话调查访问了美国西海岸的1,000名消费者。

以下是其他一些实际上或许没有表面看上去那么健康的食品：

食盐替代品：如果你正在努力减少盐的摄入量，那么在开始使用食盐替代品之前先和医生咨询一下。大多数此类替代品都含有氯化钾，该物质可能加重肾脏问题，与某些心脏和肝脏药物还会产生不良反应。

人造甜味剂：无糖的口香糖、薄荷糖和其他糖果的卡路里更低，而且有益于你的牙齿健康。不过这些产品一般都含有一种植物提取物──山梨糖醇。这种物质不能被身体完全吸收，而且还是一种天然的轻泻药。对于那些对山梨糖醇敏感的人来说，吃一包口香糖或者薄荷糖就可能引发肠胃气胀、胃部疼痛和腹泻。有些糖尿病患者发现，此类有甜味但卡路里更低的糖醇──其中还包括麦芽糖醇和木糖醇──可能会令他们的血糖升高。

反式脂肪：近来，这种可能引发动脉阻塞的物质在加工食品中的用量已经大为减少。不过生产商们可以有四舍五入的上下浮动空间：只要每份食品的反式脂肪含量在0.49克以下，那么该产品在包装上仍可注明不含反式脂肪。因此你可能仍在摄入大量的反式脂肪，“尤其是在每份的含量不切实际的情况下，” 非营利性的专业机构美国饮食营养学会(American Dietetic Association)的营养学家兼发言人邦妮•陶蒂(Bonnie Taub-Dix)表示。如果产品的成份中含有部分氢化油、氢化油或者起酥油，那么这样的产品就不能说是100%的不含反式脂肪，而且其中还可能含有大量的饱和脂肪。

同样的四舍五入浮动原则也适用于零卡路里、零脂肪和零碳水化合物产品上面。Walden Farms宣传该公司旗下一系列调味酱、果酱和沙拉酱是“不含脂肪、糖和卡路里”。该公司表示，这些产品确实含有少量卡路里以及每份至多0.49克的脂肪和碳水化合物。

“小麦面包”：这种叫法毫无意义，因为几乎所有的面包都是由小麦制成的。有些生产商通过使用棕色包装或者加入红糖或者蜜糖的深色面包更是增加了人们的这种误解。更为健康的产品是全麦面包，这种面包中包含粗麸皮和小麦胚，这些都是营养元素和纤维的上好来源。查看一下成份，如果第一项成份标明的是“强精粉”，那么里面就不会含有太多全麦的成份。

一些面包生产商在包装上仍然印有美国农业部过去使用的食品金字塔──这一指标推荐每天食用6至11份面包或意大利面。而现在它已经被一项更为个人化的金字塔所取代，新指标建议人们每天食用六份碳水化合物，而且其中三份最好是全麦食品。

纤维：食品公司正在向各类食物中添加纤维成份──包括酸奶、冰淇淋和饮料。在许多时候，添加的纤维物质取自纯化粉，而不是那种来自全麦谷类、豆类、蔬菜和水果中的纤维。而后者已经被证明能够降低胆固醇、减少患糖尿病和心脏病的风险，还可能有助于预防结肠癌。不过，据非营利性消费者权益组织公众营养健康科学中心(Center for Science in the Public Interest)的研究，并没有太多证据表明那些单一纤维，比如菊粉、麦芽糊精、燕麦纤维和聚葡萄糖具有同样的效果。而营养表并不会将这些纤维物质区分开来，所以别忘了查看成份表。

公众营养健康科学中心主任迈克尔•雅各布森(Michael Jacobson)表示，“添加纤维或许比不加要更好，但这不及来自水果、蔬菜和全麦谷类的天然纤维那样营养健康。”

酸奶：现在商场货架上的酸奶产品之丰富简直让人眼花缭乱，而产品功能包括降低胆固醇、控制血压、保护消化器官健康，或者是提高免疫力。以上的种种益处在许多时候往往仅是由酸奶中的某一种成份提供的，而且你可以从其它食品中摄取多得多的此类营养。比如说，Promise activ SuperShots酸奶宣称因为内含350毫克的钾，该产品“有助于控制血压”。其实，在一根香蕉、一份菠菜或者是一个烤土豆里面含有更多的钾元素。DanActive益生菌乳制品宣称自己能够提高免疫力的原因是该产品添加了干酪乳杆菌菌株。现在有许多对此类益生菌的研究，不过眼下，市场营销显然走在了科学的前面。科学研究表明，DanActive所含益生菌的主要作用是帮助那些服用抗生素的人们防止腹泻。

超级水：美国公众营养健康科学中心今年年初因可口可乐公司(Coca-Cola Co.)对旗下维他命饮料的宣传起诉了这家公司。该中心表示，这些冠名以“防护”、“拯救”、“能量”和“耐力”的饮料不过是每瓶能量125卡路里的糖水。可口可乐称这一诉讼毫无意义，并表示该公司生产的VitaminWater品牌的标识并无不妥之处。可口可乐公司发言人斯科特•威廉森(Scott Williamson)表示，“现在的消费者非常精明，他们都受过教育，而且希望喝到的饮料不仅仅能够补水。”

政府调查显示，大多数美国人并不缺乏这些饮料中所提供的维生素。如果吸收了过剩的维生素，那么多余部分也会被排出体外。

欧米加-3：许多食品都添加了这种人体必需的脂肪酸，欧米加-3据说可以减少患心脏病、癌症和关节炎的风险，还有助于大脑健康。不过你可以从自然的食品中得到更多的欧米加-3。如果每杯8盎司的牛奶中添加了32毫克欧米加-3，那么喝掉45杯这样的牛奶，其摄入量才相当于吃掉3盎司的三文鱼。

以上提及的产品有没有什么坏处呢？没有，不过这些东西或许并不像生产商所宣传的那样好。陶蒂说，应该尽量多买些更接近其自然状态的食品。