In the 1970s and 80s, everyone was explicitly told to cut down on foods like butter, cheese,

在 1970 和 1980 年代，大家都被明確告知要減少攝取食物像是奶油、起司

and beef, to avoid heart attacks and strokes.

還有牛肉，來防止心臟病發作和中風。

But now, apparently, they're ok?

可是現在這些食物似乎是 ok 的？

Or good for you?

或是對你好？

Or… something?

或者...其他作用？

And it's sugar that's bad!

糖才是不好的！

Sugar's what's killing us!

糖才是個致命的東西！

If we just cut sugar from our diets, we could rid the world of not only heart disease,

如果我們減少糖的攝取，我們不僅可以擺脫心臟病，

but also obesity, diabetes, and even cancer!

還可以擺脫肥胖症、糖尿病甚至癌症！

The change in attitude might seem extreme, but the case against sugar has been building for decades,

態度的轉變看起來似乎蠻極端的，但反對糖攝取的論據已經建立了數十年，

while the one against saturated fat has been weakening.

對於反對飽和脂肪的論據卻一直在減弱。

And yet, though we all love a good villain, when it comes to the health effects of your diet, things are rarely that simple.

但是，儘管越壞的東西我們越愛，但就飲食對健康的影響而言，事情就沒有這簡單了。

Today, we're taking a look back at the complex history of nutrition science to try to understand how saturated fat became public enemy number one.

今天，我們藉由回顧營養科學的複雜歷史來看看飽和脂肪是如何成為大家的第一公敵。

And how, when doctors zeroed in on fat, they overlooked the damaging effects of sugar.

以及當醫生強調低脂的同時卻忽略糖帶給我們的危害。

But that doesn't mean it should be the new saturated fat, or that fat is entirely exonerated.

但這並不表示它應該是個新的飽和脂肪，或者也不是完全不攝取脂肪。

And while there still isn't an easy answer as to what diet is best for losing weight

雖然我們不能定義哪種飲食最適合減重

or preventing heart disease, cutting down on things like saturated fats and refined sugar is probably a good start.

或是防止心臟疾病，減少飽和脂肪和精緻糖的攝取或許是個好的開始。

Back in the late 1940s, Ancel Keys, a physiologist at the University of Minnesota was puzzled by the fact that American businessmen seemed to be dying at an alarming rate from heart attacks.

在 1940 年代後期，一名明尼蘇達大學的生理學家 Ancel Keys 對於當時眾多美國商人死於心臟病感到非常困惑。

These middle-aged men made more than enough money to to afford quality food.

這些中年男子賺的錢都可以負擔的起優等品質的食物。

So why were they the ones keeling over?

所以為什麼他們都成為這些疾病的受害者呢？

He hit upon an idea, often called the diet-heart hypothesis, that would forever alter 20th century food habits.

他提出了一個想法，被稱作為「飲食 - 心臟假說」，這假說永遠改變了二十世紀的飲食習慣。

That's the notion that the amount of fat you eat, specifically saturated fats— the ones where the fatty carbon chains are all connected by single bonds, and therefore maxxed out, or saturated, with hydrogens—

這主張了所吃的脂肪的量，特別是飽合脂肪（這些由單鏈組成的碳鏈的脂肪，這導致氫原子的數量到了達極限或者我們所稱的「飽和」）

leads to high levels of fats in your blood, which then glom onto the walls of your blood vessels to cause coronary artery disease.

，因此血中含有高含量的脂肪，然後這些脂肪將會凝結在你的血管壁上，導致冠狀動脈疾病。

It's kind of like how pouring too much bacon fat down your drain can clog your pipes.

這就像是把太多的培根脂肪倒入排水管會堵塞管道一樣。

Keys was especially concerned about blood levels of the fat cholesterol because it's found in the fatty build ups in blood vessels.

Keys 特別關注血液中的膽固醇水平，因為膽固醇會堆積在血管中。

So he did a few small studies to test his idea, and then decided to go big or go home.

所以做了幾個研究來測試他的想法，然後決定孤注一擲。

In the Seven Countries Study, he and his colleagues looked for correlations between diet and coronary artery disease in about 13,000 middle-aged men in the U.S., Japan, Finland, Yugoslavia, Italy, Greece, and the Netherlands.

在「七國研究」裡， 他和他的同事們在美國、日本、芬蘭、南斯拉夫、義大利、希臘還有荷蘭，約13,000名中年男性中尋找飲食與冠狀動脈疾病之間的關聯性，

By 1970, the early results were in, and total dietary fat didn't seem to matter.

到 1970 年，早期的結果顯示，似乎跟總脂肪的攝取沒有關係。

But the groups of men with the highest average saturated fat intake tended to die more often from heart attacks,

但是，平均飽和脂肪攝取量最高的人群有更高的機率死於心臟病發，

and across the globe, blood cholesterol levels correlated with saturated fat consumption.

在世界各地，血液中的膽固醇水平與飽和脂肪的攝取量之間是有關聯性的，

Another large epidemiological study, the Framingham Heart Study, further supported a link between blood cholesterol and the risk of heart disease.

在另一項大型流行病學的研究「佛雷明罕心臟研究」，也進一步証實血液中的膽固醇與心髒病風險之間的聯繫。

These studies showed robust correlations, but they still were just that “correlations”.

這些研究顯示出穩健的相關性，但它們仍然僅僅是個「相關性」。

Many people, though, assumed that these results meant that reducing fat intake would protect people against coronary artery disease—

但是，許多人認為這些結果意味著減少脂肪攝取量可以預防冠狀動脈疾病，

which is not something a correlational study can actually show.

但關連性研究無法真正顯示這一點。

A handful of researchers did try to do randomised controlled trials — the gold standard for testing medical interventions —

很多研究員有嘗試過「隨機對照試驗」(用來測試新型藥物的黃金標準)

to see if low saturated fat or low cholesterol diets actually helped prevent heart attacks and deaths, as the hypothesis predicted.

看看低飽和脂肪或低膽固醇飲食是不是像之前預測的一樣，可以預防心髒病發作和死亡。

But nutrition trials are notoriously difficult.

但是營養方面的測試是非常困難的。

Some of the results suggested lowering saturated fat could help, but most were small studies and they were hard to interpret.

有一些結果表示，降低飽和脂肪可能會有所幫助，但大多數的研究規模都還蠻小的，而且難以解釋。

And each one used a slightly different diet, replacing in the saturated fat calories with different things.

每個研究都使用了略微不同的的飲食方法，以及用不同的食物來取代飽和脂肪。

So, by the late '70s, there was still no conclusive proof that reducing saturated fats could actually protect hearts.

因此，到 70 年代後期，仍然沒有確鑿的證據表是減少飽和脂肪的攝取可以確實保護心臟。

But that hadn't stopped the diet-heart hypothesis from becoming mainstream —

但這並沒有阻止「飲食 - 心臟假說」成為主流 ，

it seemed to fit most of the available data.

它似乎還是適用於大多數的可用數據。

And many experts felt the danger of cardiovascular disease was too high not to recommend some change in what Americans were eating.

而且許多專家認為，因為心血管疾病的危險性太高，因此不建議美國人改變飲食。

So in 1977, the US Senate Select Committee on Nutrition and Human Needs released its new dietary goals, telling Americans to get just 30% of their calories from fat — down from 40% —

因此，在 1977 年，美國聯邦參議院營養與人類需求特別委員會發布了新的飲食指標，表示美國人脂肪的攝取量只需總卡路里的 30％ (以往是 40％)

and to limit the saturated fat to 10% of the total.

，飽和脂肪的攝取則限制為全部的 10％。

The guidelines also suggested reducing dietary cholesterol and refined sugar, and increasing complex carbohydrates, but those weren't really talked about as much.

該指南還建議降低飲食中的膽固醇和精製糖，並增加複合型碳水化合物，但是這些並沒有真正的被拿來探討。

Other countries followed suit, so soon, pretty much everyone was told to shun butter for margarine, and supermarket shelves were quickly stocked with “low fat” options.

其他國家也緊隨其後，所以很快的，幾乎所有人都會被告知要用人造黃油來代替黃油的使用，超市也很快的充滿了「低脂」食品。

But from the beginning, critics questioned those recommendations, pointing out that the specific diet now being championed had never been tested in a trial.

但從一開始，評論家就對這些建議提出了質疑，指出目前倡導的特定飲食從未在試驗中進行過測試。

And some suspected refined sugar was a bigger problem.

還有一些人質疑精製糖存在著更大的問題。

In fact, the Seven Countries Study also showed a strong correlation between the consumption of sugar and heart attacks,

實際上，在「七國研究」也指出，糖攝取與心髒病發作之間存有很強的相關性，

but this finding wasn't given much additional study because it looked like saturated fat was the better predictor.

但是這項發現並沒有得到更多研究的支持，因為飽和脂肪看似個更好的預測指標。

And it wasn't until this century that we learned the sugar industry helped ensure its product was overlooked.

直到這個世紀，我們才知道製糖業用其他方法來確保他們所生產的產品是被忽略的。

For example, in 1967, they paid three Harvard public health researchers what would now be about $50,000 to write a review article in The New England Journal of Medicine a highly influential journal that highlighted the role of fat and downplayed any involvement of sugar.

舉例來說，在 1967 年，他們支付了約 50,000 美元給三名哈佛大學公共衛生的研究員，並請他們在一個具有影響力的雜誌「新英格蘭醫學雜誌」上撰寫評論文章 ，讓他們強調脂肪的作用，並淡化了任何糖帶來的影響。

But twenty years later, after a half century of fat-hating, the tide began to slowly turn toward against them, both in the lab and at home.

但二十年後， 經過半個多世紀，無論在實驗室還是在家裡，大家對脂肪的厭惡的潮流逐漸轉向它們。

Not only had research not found conclusive proof that saturated fats were the problem,

不僅沒有找到確鑿的證據表示飽和脂肪是個問題，

new analyses of the collective past studies showed that the link between saturated fats and heart disease was much weaker than previously assumed.

對於過去研究的新分析還表示，飽和脂肪與心髒病之間的聯繫比以前設想的還來得弱許多。

And new observational studies were finding that quickly digestible carbohydrates and added sugars were independently associated with an increased risk of heart disease.

新的觀察性研究發現，可以被快速消化的碳水化合物和添加糖都有提高罹患心髒病風險的可能。

Also, the whole idea that “cholesterol” was bad turned out to be much more complicated,

同樣的，對於「膽固醇」是不好的想法也變得更加複雜，

undermining part of the premise for why fat was supposed to be so evil.

先前人們對於脂肪不好的想法也逐漸削弱。

To their credit, researchers in the '60s and '70s had a vague sense that the type of cholesterol mattered.

多虧他們，60 年代和 70 年代的研究員仍不清楚不同的膽固醇類型會帶來不同的影響。

But they didn't fully understand how cholesterol moves in our blood, including the roles of the different lipoproteins that ferry it around.

但他們並不完全了解膽固醇在我們血液中是如何流動的，包括幫忙運送膽固醇的各種「脂蛋白」的作用。

When doctors look for “cholesterol” levels in blood now, they tend to look at triglycerides—the total amount of fat—as well as the total amount of cholesterol.

現在當醫生在測量血液中的膽固醇水平時，他們傾向於查看甘油三酸酯 (脂肪的總量) 以及膽固醇的總量。

他們也會測試究竟膽固醇是被低密度脂蛋白或 LDL (所謂的「不好的」膽固醇) 和高密度脂蛋白或者 HDL (好膽固醇) 運送。

他們也會測試究竟膽固醇是被低密度脂蛋白或 LDL（所謂的「不好的」膽固醇）和高密度脂蛋白或者HDL（好膽固醇）運送。

High LDL is a risk factor for heart disease, but having more HDL is usually considered good,

高低密度脂蛋白是心髒病的危險因素，但高高密度脂蛋白通常被認為是好的，

though researchers are still trying to understand the different sizes and subtypes of each and how they help or harm.

儘管研究員仍在嘗試了解每種化合物的大小和次類型以及它們是如何幫助或又是造成傷害的。

The problem is, foods that are high in saturated fat can raise both HDL and LDL, so they might seem more harmful if you just focus on total cholesterol or LDL.

問題是，飽和脂肪含量高的食物會同時增加高密度脂蛋白和低密度脂蛋白，因此，如果只單單關注在總膽固醇或 LDL，它們似乎會更加有害。

So as a new century began, people started rethinking the war on fat,

所以當一個新的世紀開始，人們開始重新思考對脂肪的爭議，

especially since the advice to lower fat intake wasn't helping people stay healthy.

特別是對於減少脂肪攝取可以維持健康的建議。

By the early 2000s, low-fat diets didn't seem to be doing squat for most people.

到 2000 年代初，低脂飲食似乎對大多數人沒有作用。

Obesity and diabetes — both of which are risk factors for heart disease — had skyrocketed.

肥胖和糖尿病都是心髒病的危險因素並且都在急劇上升。

And that might be because, while lots of people embraced low-fat foods,

這可能是因為當很多人接受低脂飲食，

they had opted for reduced fat snack cakes or cereal loaded with sugar or other carbs instead of healthier things like fresh fruits and veggies.

他們選擇了低脂的蛋糕或加了一大堆糖的麥片或其他碳水化合物，而不是新鮮水果和蔬菜等健康食品。

So a different diet—the low-carb, high-fat Atkins diet—became all the rage, and it did seem to help people lose weight.

因此，不同的飲食像是低碳水化合物、高脂肪的阿特金斯飲食法，變得風靡一時，它似乎也確實可以幫助人們減肥。

Scientists started to pay attention to it, too, and their initial results were promising.

科學家也開始關注它，他們的初步結果看起來是有希望的。

In short-term trials of 6 months or so, people lost a modest amount of weight and tended to slightly lower triglycerides while boosting HDL.

在 6 個月左右的短期試驗中，人們減了適量的體重，甘油三酸酯也在高密度脂蛋白提升的情況下逐漸減低。

Diets high in sugar and refined carbs, on the other hand, tended to do the opposite,

相反的，高糖和精製碳水化合物的飲食則有了相反結果，

raising triglyceride levels and bad LDL cholesterol, while lowering good HDL.

在甘油三酸酯水平和不好的低密度脂蛋白膽固醇增加的情況下，好的高密度脂蛋白也同時在降低。

And in both animals and people, excess sugar was linked to elevated blood pressure—another risk factor for heart disease.

動物和人類攝取過量的糖與高血壓是有關聯的 (高血壓也是心髒病的另一個危險因素)。

The weight of the evidence against sugar over the past twenty years in particular has tipped the scales, and now, you've probably heard all about how sugar is the worst thing ever.

尤其是在過去的 20 年中，反對糖的證據已經打破平衡的局面成為大多數，現在你聽到有關於糖的事情可能都是他們對人體帶來的負面影響。

It sure is an easy target; since sugar provides no nutrients other than calories, it's hard to defend.

由於糖除了卡路里以外不提供其他營養素，所以它很容易成為大家的目標並且很難被辯護。

You certainly don't need refined sugar to stay alive.

顯然地，你不需要精製糖來維持生命。

And that's led a lot of people to call it 'toxic' and blame almost anything on it, even diseases with strong genetic links, like inflammatory bowel disease or cancer.

這導致很多人說糖是 「有毒的」，且把所有事情都怪罪到糖身上，甚至包括遺傳力強的疾病，像是發炎性腸道疾病或者是癌症。

But careful review of the science suggests that's taking the backlash a little too far.

但是，經過仔細的科學審查後表示，這種對於糖的強烈抵制是有點過頭的。

While most of us are likely eating too much added sugar, no one really knows how much is too much.

雖然我們大多數人可能都攝取了過量的添加糖，但沒人真正知道多少是過量。

And connections to diseases, even ones that seem clear-cut, are not always so straightforward.

有些疾病即使看起來很明確是與糖有關聯的，但也並不總是僅僅那麼簡單。

Scientists don't actually know whether eating sugar can cause diabetes, for example.

舉例來說，科學家並不知道吃了糖是否真的會引起糖尿病。

Eating too much sugar can certainly lead to weight gain and obesity, which is one of the biggest risk factors for the disease.

但吃太多的糖肯定會導致體重增加和肥胖，因為糖就是導致這種疾病的最大危險因素之一。

But different people break down and use sugars differently, and so right now many experts think sugar consumption itself isn't causing diabetes—complications from being overweight are.

但是，不同的人，體內分解糖和使用糖的方式也會是不同的，因此現在許多專家認為攝取糖本身並不會引起糖尿病，體重過重的並發症則會導致人們罹患糖尿病。

Which is also likely the case for heart disease and other aspects of health.

心髒病和其他健康方面的問題也可能如此。

We know that high cholesterol in the blood, specifically LDL, is a risk factor for heart disease, but so is high blood pressure and obesity.

我們知道，高膽固醇在血液中，特別是低密度脂蛋白是心髒病的危險因素，高血壓和肥胖症也是如此。

How food fits into all of that isn't simple, since dietary fat and sugar both affect some risk factors.

我們所攝取的食物會帶來的影響並非這麼簡單，因為飲食中的脂肪和糖都會影響某些疾病的危險因素。

Other habits matter, too, like whether you exercise or smoke.

其他習慣也有關係，例如運動或吸煙。

And researchers are still trying to understand what sugar actually does to the body.

而且研究員仍在嘗試了解糖對人體帶來的實際影響。

Quote “sugar” comes in various forms, the relative merits or demerits of which scientists are still debating.

「糖」這種東西是多樣化的，科學家們仍在爭論它們的優缺點。

And the same can be said of quote “fat.”

「脂肪」也是如此。

If you ask a cardiologist today about whether saturated fat is bad for you, you may get a surprising answer: it depends.

如果你今天去問一個心臟病學家，飽和脂肪是否對人體有害，你可能會得到一個令人驚訝的答案：「不一定」。

That's because whether or not saturated fat increases cardiovascular disease in any given study seems to change depending on the exact type of fat being studied, what the source is, and what it's replaced with if it's removed from the diet.

這是因為在之前的研究中，飽和脂肪是否會增加心血管疾病似乎是取決於在研究中使用的脂肪類型，以及在研究中該脂肪是否有在飲食中被移除或是被其他東西取代。

The extent to which sugar and saturated fat are to blame for heart disease, or pretty much any disease, is still being heavily debated by researchers.

研究員至今仍在激烈爭論著，到底是糖還是飽和脂肪導致心髒病以及幾乎所有其他的疾病。

At the end of the day, though, you still have to eat, and all of this doesn't really give us a satisfying answer as to what your diet should look like.

然而到最後，你仍然必須吃東西，而且所有這些研究並不能給我們一個滿意的答案，因為他們沒有辦法告訴你，我們到底該吃什麼。

And I hate to tell you this, but head-to-head tests of low-fat and low-carb diets haven't identified a clear winner.

我不願意告訴你的是，在低脂和低碳水化合物飲食的測試中並沒有確切的贏家。

While low-carb diets seem to be a teensy bit better in the short term, when scientists study people for longer, the difference declines.

雖然短期內低碳水化合物飲食似乎比較好，但是當科學家把研究時間拉長，兩者之間的差異越來越小。

Low-carb diets seem to lead to slightly higher increases in good cholesterol and bigger drops in triglycerides, but the two diets perform about the same for other heart disease markers.

低碳水化合物飲食似乎會導致膽固醇些微升高以及大幅減低體內的三酸甘油酯，但兩種飲食對於其他心髒疾病帶來的影響大致相同。

And neither is terribly effective for people trying to lose weight.

對於要減肥的人來說，這兩者都不是非常有效的。

Typical weight loss after a year is barely over 5 kg.

大多人在一年後體重只減輕僅超過 5 公斤。

But you can always find individuals who respond really well, dropping like 30 kg, and those who gain weight while on the diet.

但是，有些人反應的效果非常好，像是體重下降 30 公斤，有些人則在實施這種飲食的過程中體重增加。

This has led some researchers to think that maybe certain people, either because of genetics or metabolic reasons, do better on a low-carb diet, while others benefit more from a low-fat regimen.

這讓一些研究員認為，也許一些人因為遺傳或代謝的關係，所以低碳水化合物飲食帶給他們更好的效果，而其他人則從低脂飲食中受益更多。

One especially attractive idea is that people who already are a little insulin resistant—a huge risk factor for type two diabetes—would probably fare better with fewer carbs and more fat.

有一個特別吸引人的想法是，這些已經有些許胰島素抗性的人 (患有第二型糖尿病的巨大危險因素) 可能會減少碳水化合物和增加脂肪的攝取來改善身體狀況。

But even this more nuanced approach doesn't seem to hold water.

但是，即使這種更加細微的方法似乎也無法解決問題。

In a 2018 study of about 600 people, assigning diets based on genes or insulin levels didn't help.

在一個 2018 年對約 600 人的研究中，根據基因或胰島素水平來分配飲食並沒有達到任何的幫助。

Everybody did about the same after one year, regardless of whether they went low-fat or low-carb.

不管是低脂還是低碳水化合物飲食，一年後每個人達到的效果都差不多。

Scientists are still hoping to find other markers, like those related to the microbiome, or how much certain genes are expressed, that could determine what diet is best for you.

科學家仍希望找到其他能決定哪種飲食最適合人們的因素，像是與微生物有關的因素，或者特定基因是怎麼反應的，

But for now, what we're left with is a bit of a draw.

但是現在，我們只能靠運氣了。

There are some things that can be gleaned from this big, nutritional mess, though.

在這巨大的營養混亂之中我們還是可以取得一些東西的。

In general, doctors still recommend cutting down on saturated fats, but it's important to pay attention to what you eat instead.

整體來講，醫生依然建議減少飽和脂肪的攝取，但還是要注意你吃的東西。

Swapping out saturated fats for unsaturated ones, like those found in nuts, is usually beneficial.

將飽和脂肪的攝取換成不飽和脂肪 (如堅果中的脂肪)，通常會帶來有益的影響。

That is also often true if you exchange the fat for whole grains, but not if you sub in other carbs, like sugar.

用穀物中的脂肪來取代也會帶來有益的影響，但是如果用其他碳水化合物像是糖來取代脂肪的攝取，那就不行了。

And it probably wouldn't hurt to cut down on refined sugar in general, too.

減少精緻糖的攝取應該也不會帶給你的生活不好的影響。

But if we've learned anything from nutrition history, it's that a blanket prohibition on any one thing isn't likely to be the answer.

但是，如果我們說，我們從營養歷史中學到了什麼，那就是如果結果表示要我們一味地杜絕任何一樣東西 (的攝取)，那這應該不是你要找的答案。

Sugar vs. fat is a false dichotomy, and when you think about it, that makes complete sense.

糖與脂肪是個錯誤的二分法，當你想想看，這是完全有道理的。

Of course too much fat is a bad idea.

但是攝取太多脂肪還是不好的。

And so is too much sugar.

太多糖也是。

But just as eating the occasional sweet is not going to give you cancer, and the occasional steak isn't going to give you a heart attack.

但是就像偶爾吃甜食不會使你罹患癌症一樣，偶爾吃牛排也不會使你得心髒病。

Thanks for watching this episode of SciShow, which is produced by Complexly.

謝謝收看這集的 Complexly 出版的 SciShow。

If you want to watch other awesome Complexly videos about nutrition and health research,

如果你要觀看其他關於營養以及健康研究的 Complexly 的精彩影片，

you might want to go check out Dr. Aaron Carroll over at Healthcare Triage.

你可以去 Healthcare Triage 頻道看看 Aaron Carroll 醫生的影片。