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Recent research has painted a pretty bleak picture for sugar-lovers, linking excessive sugar consumption to obesity, diabetes, and heart disease.
近期研究已经为喜欢糖的人描绘出了一幅凄凉黯淡的画面，将过度食用糖和肥胖、糖尿病以及心脏病相联系。
So you might be tempted to switch to artificial sweeteners or any of the myriad of high-intensity sweeteners available today.
所以你或许想要转食人工合成甜味剂或是如今各种可得的高强度甜味剂。
At first glance, that seems like it would let you have your cake and eat it too, giving you the sweetness of sugar without so many calories.
起初，这些甜味剂似乎可以让你享用你的蛋糕，给你糖的美味而无需担心大量的卡路里。
And that's about where things were in 2013, when we talked about sweeteners in our episode on "The Science of Sweetness."
事情从2013年开始，当时我们在《糖的科学》这一期视频中谈到了甜味剂。
But since then, scientists have been hard at work studying the potential impacts of switching from sugar to things like Sweet'n Low or Splenda
但自那时起，科学家们一直在苦苦研究Sweet'n Low或善品糖的潜在影响
and a fierce debate about the effects of sweeteners has emerged.
并且一场关于甜味剂影响的激烈争论由此出现。
One thing seems certain, though: they aren't going to fix all the things sugar broke.
但有一件事似乎是确定的：它们无法解决所有糖破坏的事情。
Several large epidemiological studies in humans—some containing nearly half a million participants—
针对人类的几个大型流行病学研究—一些研究的参与者有近50万人—
have basically eliminated fears raised in the 1970s that artificial sweeteners like saccharin cause cancer.
基本消除了20世纪70年代产生的恐惧—人工合成甜味剂，如糖精，致癌。
But in the past couple decades, studies have started to suggest that they and other high-intensity sweeteners might still have negative effects on the body.
但在过去几十年中，研究开始表明它们和其他高强度甜味剂仍对身体有消极影响。
Some of the strongest evidence against these sweeteners centers around the idea that they help with weight loss.
一些反驳这些甜味剂最强有力的证据都集中于这样的想法—它们可以帮助减肥。
They're used in things like diet sodas or low-calorie snacks because they can replace sugar's sweetness with way fewer calories.
很多东西中都用到了它们，比如低糖汽水或低卡路里零食，因为它们可以用低量卡路里代替糖的甜味。
Some, like the steviol glycosides found in the natural sweetener Stevia, aren't processed in our guts the same way as sugars, so they don't have any calories of their own.
一些，比如天然甜剂甜菊中的甜菊醇糖苷，是无法像糖一样被肠道消化的，所以它们本身没有任何卡路里。
And even those that do are tens to thousands of times sweeter than sugar, so they can be used to make low-calorie substitutes for our favorite sweets.
即使是那些比糖甜千百倍的甜味剂也可被用来制成甜食的低卡路里替代版。
But in 2014, a large meta-analysis of randomized controlled trials—the gold standard for health research—
但在2014年，一项随机对照试验的元分析—健康研究的黄金标准—
found that using artificial sweeteners instead of sugar resulted in weight loss of just 0.8 kg on average.
发现使用人工合成甜味剂代替糖会导致平均体重减少仅0.8千克。
And individual results in studies vary from tons of weight loss to weight gain.
研究的个体结果从减重和增重各不相同。
The lack of a clear weight-loss benefit might come down to what sweetness does to mammal brains.
明确减肥益处的缺乏或许是因为甜味对哺乳动物大脑的影响。
Normally, a sweet taste means that the body receives a bunch of calories—the food energy we need to survive.
通常，甜味意味着身体接收了大量的卡路里—我们生存所需的食品能量。
So some scientists think tasting sweetness without getting an energy boost confuses the parts of the brain that regulate hunger and fullness.
所以一些科学家认为品尝无法获取能量增强剂的甜味会扰乱大脑管控饥饿和饱腹的部分。
This confusion could mean we don't know when to stop eating, so we actually end up eating more overall.
这种混乱可以意味着我们不知道何时停止进食，所以结果我们会吃的更多。
Though this phenomenon hasn't been conclusively demonstrated in people, studies in animals suggest it can happen.
虽然这种现象没有在人类身上进行结论性演示，但对动物的研究表明这是可以发生的。
In one study, rats fed sugary food ate much less of a sweet yogurt when offered it than rats only fed saccharin-sweetened food before.
在一项研究中，食用甜食的老鼠吃的舔酸奶更少，而只食用含有大量糖精食物的老鼠吃的更多。
And there might be other factors at play as well that explain why lowering sweet calories doesn't translate into weight loss.
或许有另一些起作用的原因可以很好的解释为什么低甜味卡路里无法转化成体重的下降。
We used to think that because high-intensity sweeteners aren't digested like sugars, they just pass through our guts unnoticed.
我们过去常认为这是因为高强度甜味剂是不能像糖一样被消化的，它们只能悄无声息的流过我们的肠胃。
But several recent studies in rodent models have suggested that they can affect intestinal bacteria, which play a big role in how we process food.
但一些对啮齿类动物模型的近期研究表明它们可以影响肠道细菌，这些肠道细菌在我们消化食物中起到重要作用。
For example, a paper published in Nature in 2014 found that mice fed saccharin developed changes in their gut microbiome and symptoms of prediabetes.
例如，2014年发表于《自然》上的一篇论文发现喂食糖精的老鼠，它们的消化系菌群和前驱糖尿病症状出现了变化。
Scientists then transferred gut bacteria from these mice into germ-free mice—animals that are born by Caesarean section and raised in totally sterile conditions.
科学家们将这些老鼠体内的肠道细菌转移到了无菌老鼠体内 — 这种老鼠是剖腹产出生，并在完全无菌环境中生长。
And those mice also developed prediabetes symptoms, which is strong evidence that sweetener-induced changes to the microbes were to blame.
那些老鼠还出现了前驱糖尿病症状，这强有力的表明由甜味剂导致了细菌的变化。
But similar studies haven't been conducted on people, and I know we say this a lot, but it's worth repeating: rats aren't people.
但并没有对人类进行类似研究，并且我知道我们说过很多次，但是还是值得重复一遍：老鼠并非人类。
In fact, that's a common theme in sweetener research.
事实上，这是甜味剂研究中的一个常用主题。
Since, for ethical reasons, most studies on humans are observational, it's difficult to determine cause and effect.
由于伦理原因，大部分对人类的研究都是观察性的，很难决定其因果关系。
And studies finding strong negative effects on sweeteners in animal models have created a rift of sorts in the scientific community.
发现甜味剂对动物模型消极影响的研究已经在科学界引起了各种分歧。
One camp thinks that sweeteners actually cause harm, and that the animal studies show us what's really going on.
一阵营认为甜味剂可以造成伤害，其过程正如对动物的研究一样。
They point to observational studies in humans as further proof—
他们将对人类的观察性研究作为进一步证据—
like a 2017 study of over 64,000 women which found that heavy consumers of any type of artificial sweetener were about 21% more likely to develop type 2 diabetes.
比如2017年对64,000多名女性的研究发现任何人工甜味剂的重度食用者患2型糖尿病的几率高约21%。
The other camp says the the rodent studies aren't realistic—the rodents are fed way too much of a sweetener, for example
其他阵营表示啮齿动物的研究并非实事求是—比如，给啮齿动物喂食的甜味剂过多
and so those researchers think something else explains human study findings: reverse causation.
因此那些研究人员认为有其他的理论可以解释人类研究的发现：逆因果关系。
As the name implies, that's when two observed things are indeed correlated, but the cause and effect are flipped from what you think.
正如其名字所示，这是指两种被观察物确实相关，但因果关系和人们所想颠倒。
In other words: yes, sweetener consumption is linked to diabetes, but not because the sweeteners are causing diabetes.
换句话说：没错，食用甜味剂和糖尿病相关，但这并不是因为甜味剂引起了糖尿病。
Instead, it could be people knowing they have a higher risk for diabetes that drives their sweetener use.
相反，它可以是因为知道自己是糖尿病的高风险人群而驱使了他们食用甜味剂。
And that's what scientists in a 2011 study of more than 40,000 men concluded.
并且2011年科学家在对超过4万人的研究中得出了这个结论。
While there was an irrefutable link between sugary drinks and type 2 diabetes in their data,
而在他们的数据中，含糖饮料和2型糖尿病有着无可辩驳的联系，
the link between diet drinks and diabetes disappeared when they corrected for other potential factors like the participants' starting weight.
当为其他潜在因素（如参与者的起始重量）作出修正时，低糖饮料和糖尿病之间的联系会消失。
The scientists in the 2017 study of women did similar statistical analyses to control for BMI and several other major risk factors for diabetes
在2017年针对女性的研究中，为了控制BMI和其他糖尿病主要风险因素，科学家们做了类似的数据分析
and the connection between sweeteners and diabetes remained significant.
并且甜味剂和糖尿病之间的联系仍然显著。
But the statistics are very complicated, and many scientists, including those involved in the 2017 study,
但是数据非常复杂，很多科学家，包括参与2017年研究的科学家
argue the math isn't always able to completely remove the influence of other risk factors, a concept known as residual confounding.
争论称，数学并非总能够完全消除其他风险因素的影响，这一概念被称为残余混杂。
For example, it's possible the significant increase in diabetes risk from sweetened drinks in the 2017 study
例如，在2017年研究中，甜味饮料中糖尿病风险的显著增加
was driven by participants that were obese at the beginning of the study.
是由起始体重超标的参与者所导致的。
Because of the difficulties of conducting nutritional science in people,
由于对人类实施营养科学的困难，
the scientific debate about high-intensity sweeteners isn't going to be resolved any time soon.
关于高强度甜味剂的科学辩论无法马上得到解决。
But there is something everyone seems to agree on, and that's that high-intensity sweeteners aren't a magic bullet.
但是有一点是每个人都同意的：高强度甜味剂并非灵丹妙药。
So if you really want to improve your overall health, you might want to limit both sugar and sweeteners in your diet.
所以如果你想改善整体健康，那么你可能既要控糖又要控制甜味剂了。
Thanks for watching this episode of SciShow.
感谢收看本期《科学秀》。
If you want to learn more about why people like sugar and how all these different sweeteners work,
如果你想了解更多关于为什么人们喜欢糖以及这些不同甜味剂如何工作的知识，
you might want to check out that video I mentioned called The Science of Sweetness.
你或许想要看看我之前提到的视频《糖的科学》。
