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  • Ever counted calories using nutritional labels?


  • But just how accurate are they anyway?


  • Hey, guys, Julia here for DNews.

    大家好,我是 DNews 的 Julia。

  • Food labels are great.


  • They give you an estimate of how many calories are in any certain food.


  • But they have a teeny bit of a flaw.


  • They fail to take into account cooking.


  • So we end up with a system that likely overestimates the calories available in unprocessed foods and underestimates the calories in processed food.


  • The way we currently count calories is based on the Atwater System, which is at least a hundred years old.

    我們目前是基於「艾特瓦特系統」去計算卡路里,而它至少有 100 年的歷史了。

  • The System standardized the idea of the amount of energy available in food, 9 calories in a gram of fat or 4 calories in every gram of protein.

    這個系統訂定各種食物中成份固定量所含的能量,脂肪每克 9 大卡,蛋白質每克 4 大卡。

  • But this measures the availability of energy in food, not the digestibility.


  • A calorie is a unit of energy.


  • It's technically the amount of energy needed to heat up a kilogram of water by 1 degree Celsius.

    理論上來說,1 大卡是使 1 公斤的水提高 1℃ 所需要的能量。

  • Our body burns calories in food through metabolizing the carbohydrates and proteins and whatnot into smaller molecules our body can use as energy.


  • Cooking food changes how many calories are digestible.


  • Take potatoes for example.


  • When raw, the sugar molecules in potatoes are too tightly packed for our digestive system to handle.


  • Cooking causes the starches in the potato to gelatinize.


  • That process allows us to access the sugars stored in the starch, so we get more calories out of the cooked potato.


  • On top of that, the type of cooking method might change the chemistry of food as well, whether it's boiled, baked, or microwaved.


  • On the other hand, digesting raw food takes work: A stick of celery might have 10 calories, but the chewing and digesting burns about half of them.

    另外,消化生食時會需要額外的能量,像是一根芹菜裡可能有 10 卡路里,但在嚼它和消化它的過程中可能就先消耗掉 5 卡路里了。

  • All that work means there are fewer calories for your body to absorb for energy.


  • But before you go nibbling on an all-carrot diet, consider this:


  • For our ancestors, cooking meant the difference between life and death.


  • The invention of a cooked meal might have changed everything.


  • Cooking food provided more energy and led to humans with bigger brains and bigger babies.


  • And people who consume an all-raw diet now might not be getting enough calories, even when eating food packed with nutrients.


  • Some women on an all-raw diet get irregular menstrual cycles—a sign of undernourishmentnot to mention the bacteria of your gut steal a few of the calories for themselves.


  • So the exact number of calories you're getting is affected by way too many factors for those labels to be truly accurate.


  • But while modifications to the Atwater system have improved it some over the years, there's still no real alternative.


  • So until nutrition scientists come up with a better calorie counting system, take food labels with a grain of salt.


  • See what I did there? Grain of salt? It's a... pun... ok.

    看我做了什麼?一撮鹽 / 持保留態度?這是...雙關語...

  • Switching gears for a second, I wanted to let you know that tomorrow, Trace, Amy, and Ian are gonna be chatting with a real-live astronaut about what it's like to live and work in space.

    題外話一下, 我想跟你們說,就在明天 Trace、Amy 跟 Ian 就要訪談一位太空人,聊聊真正在太空中工作和生活是什麼感覺。

  • And if you wanna hang out with us space nerds, be sure to RSVP using the link we've got in the description.


  • That's at 3 p.m. Eastern time, noon Pacific.


  • So, do you trust nutritional labels?


  • Do they need to be updated?


  • Leave your thoughts and comments below, and don't forget to subscribe for more DNews everyday.


Ever counted calories using nutritional labels?


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B2 中高級 中文 美國腔 標示 食物 能量 消化 馬鈴薯 分子

運動健身正夯!你真的可以相信食物上的熱量標示嗎?(Can You Trust The Calorie Counts On Food Labels?)

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    Derrick Chen 發佈於 2020 年 05 月 16 日