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.

許多美國人以為他們現在吃的東西都算得上是健康食品。不過，我們其實很容易被自己頭腦里的那些思維定勢和食品生產商們的花言巧語所蒙騙。

以雞肉為例吧。美國人平均一年要吃上大約90磅雞肉，這比上世紀70年代增加了一倍以上，原因之一在于美國人如今已經轉而吃起低脂肪、低膽固醇的肉類食品來了。不過在美國銷售的大約三分之一的新鮮雞肉都加注過水、鹽，有時還要加入一種名為角叉膠的海藻提取物以幫助雞肉保持添加的水份。美國農業部(U.S. Department of Agriculture)表示，以這種方式處理過的雞肉仍然可以標上“全天然”或者“100%天然”的字樣，因為水、鹽和角叉膠這些物質都是天然成份──盡管這些東西并不是雞肉的天然成份。

生產商必須在包裝上注明添加成份──不過這些成份的字體可能會很小：僅相當于標注產品名稱所使用的大字體的三分之一。如果你想控制鈉的攝入量以降低患高血壓、心臟病和中風的幾率，那么就別忘了查看營養表。一份四盎司的未經處理的雞肉含有大約45至60毫克的鈉。而一份所謂的“增強型”或者“注水”雞肉則含有200至400毫克的鈉，鈉含量幾乎和快餐食品炸薯條相當。

加入鹽水的作法是在大型折扣店開始銷售食品，并設法以統一的重量和價格銷售雞肉的時候開始變得普遍起來的。注水能夠使包裝好的每盒雞肉的重量變得更加均衡。不過這意味著消費者為添加的鹽水付出了雞肉的價錢──根據雞肉生產商聯盟Truthful Labeling Coalition的估計，這筆開支每年高達20億美元。該聯盟的生產商們允諾不對雞肉產品進行加工處理。

“增強型”雞肉的生產商，其中包括某些美國最大的生產商表示，許多消費者在不知情的情況下在比較產品口味時，都更喜歡增強型雞肉，此外增強型雞肉能夠更好地保持水份。雞肉生產商Pilgrim's Pride的發言人雷•阿特金森(Ray Atkinson)表示，該公司既銷售增強型雞肉，也銷售未經加工的雞肉，這是為了滿足消費者的需求。他還指出，即便是330毫克的鈉含量，增強型雞肉也仍然符合美國心臟協會(American Heart Association)的認證標準。

Truthful Labeling Coalition成員Foster Farms上周發表的調查報告顯示，63%的消費者并不了解雞肉行業的這種作法。此外，82%的消費者認為，注入鹽水的雞肉不應標有全天然字樣。這一電話調查訪問了美國西海岸的1,000名消費者。

以下是其他一些實際上或許沒有表面看上去那么健康的食品：

食鹽替代品：如果你正在努力減少鹽的攝入量，那么在開始使用食鹽替代品之前先和醫生咨詢一下。大多數此類替代品都含有氯化鉀，該物質可能加重腎臟問題，與某些心臟和肝臟藥物還會產生不良反應。

人造甜味劑：無糖的口香糖、薄荷糖和其他糖果的卡路里更低，而且有益于你的牙齒健康。不過這些產品一般都含有一種植物提取物──山梨糖醇。這種物質不能被身體完全吸收，而且還是一種天然的輕瀉藥。對于那些對山梨糖醇敏感的人來說，吃一包口香糖或者薄荷糖就可能引發腸胃氣脹、胃部疼痛和腹瀉。有些糖尿病患者發現，此類有甜味但卡路里更低的糖醇──其中還包括麥芽糖醇和木糖醇──可能會令他們的血糖升高。

反式脂肪：近來，這種可能引發動脈阻塞的物質在加工食品中的用量已經大為減少。不過生產商們可以有四舍五入的上下浮動空間：只要每份食品的反式脂肪含量在0.49克以下，那么該產品在包裝上仍可注明不含反式脂肪。因此你可能仍在攝入大量的反式脂肪，“尤其是在每份的含量不切實際的情況下，” 非營利性的專業機構美國飲食營養學會(American Dietetic Association)的營養學家兼發言人邦妮•陶蒂(Bonnie Taub-Dix)表示。如果產品的成份中含有部分氫化油、氫化油或者起酥油，那么這樣的產品就不能說是100%的不含反式脂肪，而且其中還可能含有大量的飽和脂肪。

同樣的四舍五入浮動原則也適用于零卡路里、零脂肪和零碳水化合物產品上面。Walden Farms宣傳該公司旗下一系列調味醬、果醬和沙拉醬是“不含脂肪、糖和卡路里”。該公司表示，這些產品確實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。

“小麥面包”：這種叫法毫無意義，因為幾乎所有的面包都是由小麥制成的。有些生產商通過使用棕色包裝或者加入紅糖或者蜜糖的深色面包更是增加了人們的這種誤解。更為健康的產品是全麥面包，這種面包中包含粗麩皮和小麥胚，這些都是營養元素和纖維的上好來源。查看一下成份，如果第一項成份標明的是“強精粉”，那么里面就不會含有太多全麥的成份。

一些面包生產商在包裝上仍然印有美國農業部過去使用的食品金字塔──這一指標推薦每天食用6至11份面包或意大利面。而現在它已經被一項更為個人化的金字塔所取代，新指標建議人們每天食用六份碳水化合物，而且其中三份最好是全麥食品。

纖維：食品公司正在向各類食物中添加纖維成份──包括酸奶、冰淇淋和飲料。在許多時候，添加的纖維物質取自純化粉，而不是那種來自全麥谷類、豆類、蔬菜和水果中的纖維。而后者已經被證明能夠降低膽固醇、減少患糖尿病和心臟病的風險，還可能有助于預防結腸癌。不過，據非營利性消費者權益組織公眾營養健康科學中心(Center for Science in the Public Interest)的研究，并沒有太多證據表明那些單一纖維，比如菊粉、麥芽糊精、燕麥纖維和聚葡萄糖具有同樣的效果。而營養表并不會將這些纖維物質區分開來，所以別忘了查看成份表。

公眾營養健康科學中心主任邁克爾•雅各布森(Michael Jacobson)表示，“添加纖維或許比不加要更好，但這不及來自水果、蔬菜和全麥谷類的天然纖維那樣營養健康。”

酸奶：現在商場貨架上的酸奶產品之豐富簡直讓人眼花繚亂，而產品功能包括降低膽固醇、控制血壓、保護消化器官健康，或者是提高免疫力。以上的種種益處在許多時候往往僅是由酸奶中的某一種成份提供的，而且你可以從其它食品中攝取多得多的此類營養。比如說，Promise activ SuperShots酸奶宣稱因為內含350毫克的鉀，該產品“有助于控制血壓”。其實，在一根香蕉、一份菠菜或者是一個烤土豆里面含有更多的鉀元素。DanActive益生菌乳制品宣稱自己能夠提高免疫力的原因是該產品添加了干酪乳桿菌菌株。現在有許多對此類益生菌的研究，不過眼下，市場營銷顯然走在了科學的前面。科學研究表明，DanActive所含益生菌的主要作用是幫助那些服用抗生素的人們防止腹瀉。

超級水：美國公眾營養健康科學中心今年年初因可口可樂公司(Coca-Cola Co.)對旗下維他命飲料的宣傳起訴了這家公司。該中心表示，這些冠名以“防護”、“拯救”、“能量”和“耐力”的飲料不過是每瓶能量125卡路里的糖水。可口可樂稱這一訴訟毫無意義，并表示該公司生產的VitaminWater品牌的標識并無不妥之處。可口可樂公司發言人斯科特•威廉森(Scott Williamson)表示，“現在的消費者非常精明，他們都受過教育，而且希望喝到的飲料不僅僅能夠補水。”

政府調查顯示，大多數美國人并不缺乏這些飲料中所提供的維生素。如果吸收了過剩的維生素，那么多余部分也會被排出體外。

歐米加-3：許多食品都添加了這種人體必需的脂肪酸，歐米加-3據說可以減少患心臟病、癌癥和關節炎的風險，還有助于大腦健康。不過你可以從自然的食品中得到更多的歐米加-3。如果每杯8盎司的牛奶中添加了32毫克歐米加-3，那么喝掉45杯這樣的牛奶，其攝入量才相當于吃掉3盎司的三文魚。

以上提及的產品有沒有什么壞處呢？沒有，不過這些東西或許并不像生產商所宣傳的那樣好。陶蒂說，應該盡量多買些更接近其自然狀態的食品。