Although our brain accounts for just 2 percent of our body weight, the organ consumes half of our daily carbohydrate requirements—and glucose is its most important fuel. Under acute stress the brain requires some 12 percent more energy, leading many to reach for sugary snacks.
尽管我们的大脑只占体重的百分之二，可这个器官却要消耗一半的碳水化合物能量——而葡萄糖是是它最为重要的燃料。如果处在高度紧张之下，它则需要额外的百分之十二的能量，于是便有许多人去触祭含糖的点心。
Carbohydrates provide the body with the quickest source of energy. In fact, in cognitive tests subjects who were stressed performed poorly prior to eating. Their performance, however, went back to normal after consuming food.
碳水化合物为身体提供最快的能量来源。事实上，在认知测试中，有压力的受试者在进食前表现不佳。然而，在进食后，他们的表现恢复正常。
When we are hungry, a whole network of brain regions activates. At the center are the ventromedial hypothalamus (VMH) and the lateral hypothalamus. These two regions in the upper brain stem are involved in regulating metabolism, feeding behavior and digestive functions. There is, however, an upstream gatekeeper, the nucleus arcuatus (ARH) in the hypothalamus. If it registers that the brain itself lacks glucose, this gatekeeper blocks information from the rest of the body. That’s why we resort to carbohydrates as soon as the brain indicates a need for energy, even if the rest of the body is well supplied.
当我们饥饿时，整个大脑区域网络就会被激活。位于中心的是下丘脑腹内侧(VMH)和外侧下丘脑。上脑干的这两个区域参与调节新陈代谢、进食行为和消化功能。然而，在下丘脑有一个上游的看门人，即弓状核(ARH)。如果它发现大脑本身缺乏葡萄糖，这个“看门人”就会封锁身体其他部位的信息。这就是为什么当大脑显示出对能量的需求时，我们就会求助于碳水化合物，即使身体的其他部分供应充足。
To further understand the relationship between the brain and carbohydrates, we examined 40 subjects over two sessions. In one, we asked study participants to give a 10-minute speech in front of strangers. In the other session they were not required to give a speech. At the end of each session, we measured the concentrations of stress hormones cortisol and adrenaline in participants’ blood. We also provided them with a food buffet for an hour. When the participants gave a speech before the buffet, they were more stressed, and on average consumed an additional 34 grams of carbohydrates, than when they did not give a speech.
为了进一步了解大脑和碳水化合物之间的关系，我们对40名受试者进行了为期两天的研究。在一项研究中，我们要求研究参与者在陌生人面前做10分钟的演讲。在另一个阶段，他们不需要发表演讲。在每个疗程结束时，我们测量了参与者血液中应激激素皮质醇和肾上腺素的浓度。我们还为他们提供了一个小时的自助餐。当参与者在自助餐前发表演讲时，他们比不发表演讲时压力更大，平均额外消耗34克碳水化合物。
So what about that chocolate, then? If a person craves chocolate in the afternoon, I advise him or her to eat chocolate to stay fit and keep his or her spirits up. That’s because at work people are often stressed and the brain has an increased need for energy. If one doesn’t eat anything, it’s possible the brain will use glucose from the body, intended for fat and muscle cell use, and in turn secrete more stress hormones. Not only does this make one miserable, it can also increase the risk of heart attacks, stroke or depression in the long run. Alternatively, the brain can save on other functions, but that reduces concentration and performance.
可这样一来关巧克力什么事呢？要是谁希望在午后吃到巧克力，我就建议他吃巧克力是为了保持身心健康，为了振作三魂七魄。那是因为在万机忙碌之中，人们通常会绷紧神经，大脑越来越渴望能量的输入。如果谁不吃一丁点东西，大脑可能就会从体内窃取脂肪和肌肉细胞同样所需的葡萄糖，相应地会分泌更多神经紧张荷尔蒙。这一切不但会酿成悲剧，长此以往，还可能增加罹患心血管疾病、中风或抑郁的风险。倘若言之他法，大脑或许可以通过其他的机制节能，而非削弱注意力和表现力。
In order to meet the increased needs of the brain, one can either eat more of everything, as the stressed subjects did in our experiment, or make it easy for the body and just consume sweet foods. Even babies have a pronounced preference for sweets. Because their brain is extremely large compared with their tiny bodies, babies require a lot of energy. They get that energy via breast milk, which contains a lot of sugar. Over time, our preference for sweets decreases but never completely disappears, even as we become adults. The extent to which that preference is preserved varies from person to person and seems to depend, among other things, on living conditions. Studies suggest people who experience a lot of stress in childhood have a stronger preference for sweets later in life.
为了满足大脑日益增长的需求，我们可以吃更多的任何东西，就像我们实验中压力大的受试者所做的那样，或者让身体变得更容易，只吃甜食。甚至婴儿对糖果也有明显的偏好。因为他们的大脑与他们的小身体相比是非常大的，婴儿需要大量的能量。它们通过含有大量糖分的母乳获得能量。随着时间的推移，我们对甜食的喜好会减少，但绝不会完全消失，即使我们已经长大成人。保留这种偏好的程度因人而异，似乎除其他外，还取决于生活条件。研究表明，童年经历过很多压力的人在晚年更喜欢吃甜食。
For some, the brain cannot get its energy from the body’s reserves, even if there are enough fat deposits. The most important cause of this is chronic stress. To ensure their brains are not undersupplied, these people must always eat enough. Often the only way out of such eating habits is to leave a permanently stressful environment. So although many tend to be hard on themselves for eating too many sweets or carbs, the reasons behind such craving aren’t always due to a lack of self-control and might require a deeper look into lifestyle and stressful situations—past and present. Once the root cause of stress addressed, eating habits could ultimately resolve themselves.
对一些人来说，即使有足够的脂肪沉积，大脑也不能从身体的储备中获取能量。最重要的原因是长期的压力。为了确保他们的大脑不被供应不足，这些人必须经常吃足够的食物。通常，摆脱这种饮食习惯的唯一方法就是离开一个长期有压力的环境。因此，尽管许多人往往因为吃了太多的甜食或碳水化合物而对自己苛刻，但这种渴望背后的原因并不总是由于缺乏自我控制，可能需要更深入地研究生活方式和压力状况——过去和现在。一旦压力的根源得到解决，饮食习惯最终会自行解决。
