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“兔子饥饿症”:高蛋白饮食对人体有何影响

更新时间:2018-6-6 20:27:42 来源:纽约时报中文网 作者:佚名

We don't need nearly as much protein as we consume
“兔子饥饿症”:高蛋白饮食对人体有何影响

In the early 20th Century, Arctic explorer Vilhjalmur Stefansson spent a collective five years eating just meat. This meant that his diet consisted of around 80% fat and 20% protein. Twenty years later, he did the same as part of a year-long experiment at the New York City’s Bellevue Hospital in 1928.

20世纪初,北极探险家斯蒂芬森(Vilhjalmur Stefansson)曾连续五年内只吃肉食,这意味着他的饮食由约80%的脂肪和20%的蛋白质组成。二十年后的1928年,他在纽约市贝尔维尤医院再做了一次为期一年的只吃肉食的实验。

Stefansson wanted to disprove those who argued that humans cannot survive if they only eat meat. But unfortunately for him, in both settings he very quickly became ill when he was eating lean meats without any fat. He developed "protein poisoning”, nicknamed “rabbit starvation”. His symptoms disappeared after he lowered his protein intake and he raised his fat intake. In fact, after returning to New York City and to a typical US diet with more normal levels of protein, he reportedly found his health deteriorating and returned to a low-carb, high fat, and high protein diet until his death aged 83.

斯蒂芬森想反驳那些认为如果人类只吃肉就无法生存的人。但不幸的是,无论是在北极还是纽约,当他只吃瘦肉,不要脂肪,他很快就生了病。借此,他提出了“蛋白质中毒”这一病症,绰号为“兔子饥饿症”。不过,当他降低蛋白质摄入量并且增加了脂肪的摄入后,症状也就消失了。事实上,他从北极回到纽约,恢复美国典型的高蛋白饮食生活时,就发现自己的健康状况恶化,因此他选择了继续其低碳水化合物,高脂肪和高蛋白的饮食习惯,直至他83岁逝世。

His early experiments are some of the few recorded cases of high protein intake having extreme adverse effects – but despite soaring sales of protein supplements, many of us are still unsure how much protein we need, how best to consume it, and if too much, or too little, is dangerous.

他的早期实验是为数不多记录了蛋白高摄入量会带来极端不良反应的案例——尽管现今蛋白补充剂的销售量节节飙升,许多人仍然不确定我们究竟需要多少蛋白质,不知哪一种摄入方法最好,以及是否摄入太多或是太少,都会对人体有害。

Despite obesity rates doubling over the past two decades, we’re becoming increasingly conscious of what we’re eating. In recent years many of us have swapped white bread for brown and wholemeal bread and full-fat milk for skimmed. Taking centre stage in our health kick is protein, with protein balls, bars and enhanced protein versions of staple products, from cereals to soup, dominating supermarket shelves. And with the global protein supplements market valued at $12.4bn (£9.2bn) in 2016, it’s clear we’re buying into the idea that we need as much protein as possible.

尽管过去二十年肥胖率翻了一番,但我们实际已越来越注意我们的饮食。近年来,许多人改变自己的饮食习惯,如将白面包换成黑面包和全麦面包以及将全脂牛奶换成脱脂牛奶之类。在健康养生中占主要位置的便是蛋白质。蛋白球,蛋白棒,以及从谷物到汤饮等增加了蛋白质含量的主食类产品,这些产品大比例占据了市场。2016年,全球蛋白质补充剂市场价值达124亿美元(合92亿英镑),显然我们认为我们需要摄入尽可能多的蛋白质。

But some experts now argue that foods with inflated protein (and prices) are a waste of money.

但一些专家现在认为,富含蛋白质的食物是浪费金钱。

Protein is essential for the body to grow and repair. Protein-rich food such as dairy, meat, eggs, fish and beans are broken down into amino acids in the stomach and absorbed in the small intestine, then the liver sorts out which amino acids the body needs. The rest is flushed out in our urine.

蛋白质对人体的生长和修复至关重要。富含蛋白质的食物,如乳制品、肉类、蛋类、鱼类和豆类在胃中被分解成氨基酸并被小肠吸收,然后肝脏分辨出人体需要的氨基酸,剩下的废物会通过尿液排出体外。

Adults who aren’t especially active are advised to eat roughly 0.75g of protein per day for each kilogram they weigh. On average, this is 55g for men and 45g for women – or two palm-sized portions of meat, fish, tofu, nuts or pulses.

不常运动的成年人被建议每公斤体重每天吃约0.75克蛋白质。平均来说,男性为55克,女性为45克——即两个手掌大小的肉、鱼、豆腐、坚果或豆类。

Not getting enough protein can lead to hair loss, skin breakouts and weight loss as muscle mass decreases. But these side effects are very rare, and largely only occur in those with eating disorders.

如果没有摄入足够的蛋白质会导致肌肉流失、脱发、皮肤爆痘和体重减轻等健康问题。但这些副作用非常少见,主要发生在进食障碍患者身上。

Despite that, most of us have long associated protein with building muscle. This is accurate. Strength-based exercise causes a breakdown of protein in the muscle. For muscles to grow stronger, the proteins need to rebuild. A type of amino acid called leucine plays a particularly big part in triggering protein synthesis.

尽管如此,大多数人长期摄入蛋白质是为了增强肌肉。这是正确的做法。因为力量运动会导致肌肉中的蛋白质分解。为了强壮肌肉,必须重建破裂分解的蛋白质。称为亮氨酸的氨基酸类型在触发蛋白质合成重建中起着特别重要的作用。

Some experts even argue that not consuming protein post-workout could cause the breakdown of muscle to be higher than the synthesis – meaning there’s no net gain in muscle mass. Supplement brands advise drinking protein shakes after a workout to help the growth and repair of muscle tissue, usually in the form of leucine-rich whey protein, a by-product of making cheese.

一些专家甚至认为,为增强肌肉而锻炼,但事后不补充蛋白质可能会导致肌肉流失得多,而蛋白质合成重建得少 - 这意味着肌肉不增反减。蛋白补充剂品牌建议在健身锻炼后喝蛋白质饮料奶昔(shakes),以帮助肌肉组织的生长和修复,这种饮料为富含亮氨酸的乳清蛋白(一种制作奶酪的副产品)。

Many consumers agree. Research company Mintel’s 2017 Report found that 27% of Brits use sport nutrition products such as protein bars and shakes. This figure rises to 39% for those who exercise more than once a week. But more than half of the individuals who use the products (63%) find it difficult to tell whether they’re having any effect.

许多消费者也同意锻炼后需要补充蛋白。市场研究咨询公司英敏特(Mintel)的2017年报告发现,27%的英国人食用运动营养产品,如蛋白棒和奶昔。对于每周锻炼超过一次的人来说,这个数字上升到39%。但是,食用这些产品的人超过一半以上(63%)无法判断补充蛋白食品是否有任何效果。

Indeed, research on the muscle-building power of protein supplements is varied. A 2014 analysis of 36 papers found that protein supplements have no impact on lean mass and muscle strength during the first few weeks of resistance training in untrained individuals.

事实上,关于补充蛋白质与增强肌肉力量的研究有不同的结论。2014年通过对36篇论文的一项分析发现,从未受过力量运动培训的个体在进行抗阻训练的前几周,蛋白质补充对瘦身和强化肌肉力量没有任何影响。

Over time and if the training becomes harder, supplements can promote muscle growth. However, the paper also concludes that these changes have not been proven over the long term. A 2012 review paper further says that protein “increases physical performance, training recovery and lean body mass”… but for the benefit to be optimal, it should be in combination with a fast-acting carbohydrate.

但如果坚持下去,训练强度加大,补充蛋白质确实可以促进肌肉生长。但是,该论文也得出结论认为这些变化未被长期实践证实。2012年的一篇评论文章进一步指出,蛋白质能“增加体能,促进训练后的肌肉恢复,以及瘦身减肥”...…但为了获得最佳效果,它应该与速效碳水化合物结合使用。

But even if athletes and gym goers may benefit from a post-workout protein boost, that doesn’t mean they should reach for the supplements and smoothies. Most people get more than their daily recommended allowance from food, says Kevin Tipton, a sport professor of the University of Stirling. “There’s no need for anyone to have supplements. They’re a convenient way to get protein, but there’s nothing in supplements you can’t get in food. Protein bars are really just candy bars with a bit of extra protein.”

但即使运动员和健身爱好者可能从运动后蛋白质补充中受益,这并不意味着他们应该食用蛋白补充剂和冰沙(smoothies,水果、碎冰和酸奶搅拌而成的健康饮料,也译为果昔)。斯特林大学体育教授蒂普顿(Kevin Tipton)说:“大多数人通过食物摄入的蛋白含量已高过每日所需,没有必要再服用补充剂。虽然补充剂是获得蛋白质的便捷方式,但任何补充剂内的要素都已经包含在食品内。蛋白棒实际上只是多一点额外蛋白质的糖块。”

Tipton adds that even among bodybuilders, products like whey protein aren’t as critical as they are hyped up to be. “There’s too much focus on which supplements to take, as opposed to getting in the gym and working harder. There are so many other variables, such as sleep, stress and diet,” he says.

蒂普顿补充说,即使在健美运动员中,乳清蛋白等产品也不像被炒作的那么重要。他说:“现在许多健美运动员过多关注要摄入哪些补充剂,而不是进入健身房努力锻炼。运动员锻炼还有很多其他变量,如睡眠,压力和饮食等。”

Most experts agree with Tipton that protein is best consumed in food instead of supplements. But there are some exceptions, such as athletes who find it difficult to hit their daily protein targets, points out Graeme Close, professor of human physiology at Liverpool John Moores University. “I believe most need more than the recommended daily allowance, and there’s good evidence to support this,” he says. In this case, he says, a shake can be useful.

大多数专家都同意蒂普顿的观点,即蛋白质最好通过食物摄入,而不是补充剂。但也有一些例外,如有的运动员发现仅靠饮食很难达到每日蛋白质摄入目标量。利物浦约翰摩尔大学人体生理学教授克洛斯(Graeme Close)指出,“我相信大多数人身体对蛋白的需要应该比推荐的每日摄取量要高,而且有很好的证据支持这一点”,在这种情况下,饮一杯奶昔是有益的。

Another demographic who can benefit from extra protein? The elderly. That’s because as we age, we need more protein to retain muscle mass. But we also tend to eat less protein as we get older because our taste-buds begin to prefer sweet over savoury.

另一类可以因摄入额外蛋白质量而受益的人群就是老人。因为随着年龄的增长,人类需要更多的蛋白质来保持肌肉质量,但我们却偏偏倾向于少吃蛋白质食物,因为我们的味蕾开始偏爱甜味而非咸味。

Emma Stevenson, professor of sport and exercise science at Newcastle University, is working with food companies to get more protein into snacks that the elderly  are known to regularly buy, such as biscuits. “We need to maintain our muscle mass as we age, because we become less active and frail,” she says.

纽卡斯尔大学体育与运动科学教授史蒂文森(Emma Stevenson)正在与食品公司合作,将更多的蛋白质加入老人常吃的零食中,例如饼干。她说:“随着年龄的增长,我们需要摄入蛋白质以保持肌肉质量,因为我们的活力下降,躯体渐趋孱弱。"

Close says the elderly should increase protein intake to around 1.2g per kg body weight.

克洛斯认为老人应该增加蛋白质摄入量到每公斤体重约1.2克。

Fortunately, it’s difficult to have too much protein. While we do have an upper limit of protein intake, it’s “virtually impossible” to reach, says Tipton. “There are concerns among some dieticians that a high protein diet can hurt the kidneys and bones, but evidence in otherwise healthy people is minimal. It is possible there could be a problem if someone with an underlying kidney [issue] eats high amounts of protein, but the odds of any adverse effects are very low.”

幸运的是,人体实际很难摄入过量蛋白质。蒂普顿提到,虽然我们确实有蛋白质摄入量的上限,但"实际上不可能"达到。他说:“有些营养师担心高蛋白饮食会伤害肾脏和骨骼,但实际在健康人群中的影响非常小。如果有肾脏问题的人吃大量的蛋白质,可能会有问题,但是任何不良反应的几率都很低。”

But while protein itself isn’t harmful, many protein supplements are high in carbohydrates called FODMAPs that trigger digestive symptoms like bloating, gas and stomach pain. Stevenson advises reading labels carefully on supplements, bars and balls. “Often, they’re very high in calories and contain huge amounts of carbs, often in form of sugar. You shouldn’t necessarily think that because it says it’s high protein that its healthy,” she says.

虽然蛋白质本身是无害的,但许多蛋白质补充剂都有含量很高的短链碳水化合物(FODMAPs),会引发消化系统症状,如胃胀气,胃痛。史蒂文森建议仔细阅读在蛋白补充剂,蛋白棒和蛋白球上的标签。她说道:“通常它们的卡路里含量非常高,含有大量的碳水化合物,通常以糖的形式存在。你不要以为但凡产品标明高蛋白就一定是健康食物。”

Weight loss

减肥

Protein has long been linked to weight loss, with low-carb, high-protein diets such as Paleo and Atkins promising to prolong the feeling of fullness. People fail to lose weight often because they feel hungry, and MRI studies have shown that a high-protein breakfast can help stop cravings later in the day.

蛋白质长期以来一直与减肥有关,低碳水化合物和高蛋白的饮食如原始饮食法(Paleo)和阿特金斯饮食法(Atkins)承诺延长饱腹感。人们常常因为感到饥饿而无法减少体重,而核磁共振研究表明,高蛋白质早餐有助于减少饥饿感。

There is sufficient evidence that protein is satiating, says Alex Johnstone of the University of Aberdeen. If you’re trying to lose weight, it’s therefore more important to have a high-protein breakfast, such as beans on toast or a dairy smoothie, rather than to have supplements.

阿伯丁大学的约翰斯通(Alex Johnstone)认为,有足够的证据表明蛋白质能带来饱腹感。如果你想减肥,你需要拥有高蛋白质的早餐,比如说烤面包上的豆子,或者牛奶冰沙,而不是摄入补充剂。

But she doesn’t advocate “Atkins-type” diets and has found that cutting out carbohydrates has adverse affects on gut health (and we now know that maintaining a healthy gut is crucial to many aspects of our health and well-being).

但她并不提倡”阿特金斯型“饮食,并且发现断绝碳水化合物会对肠道健康产生不利影响。我们现在也知道肠道健康对于保持我们健康和幸福的许多方面都至关重要。

Instead, Johnstone recommends that overweight people eat a high-protein and moderate-carb diet, consisting of 30% protein, 40% carbs and 30% fat – compared to the average diet of around 15% protein, 55% carbs and 35% fat.

相反,约翰斯通建议超重的人吃一种高蛋白和中等碳水化合物的饮食,由30%的蛋白质,40%的碳水化合物和30%的脂肪组成。而普通均衡饮食中约15%是蛋白质,55%是碳水化合物,脂肪为35%。

But, of course, upping protein intake alone won’t help you lose weight. Choosing lean meat such as chicken or fish is key. Studies also show that eating large amounts of animal protein is linked to weight gain and red meat in particular is linked to an increased risk of cancer as well as heart disease.

但,可想而知,单单增加蛋白质摄入量并不能帮助你减肥。选择瘦肉如鸡肉或鱼肉是减肥关键。还有研究表明,吃大量的动物蛋白会导致体重增加,特别是红肉会增加患癌症和心脏病的风险。

There are, though, healthy proteins which are not meat like mycoprotein, a plant-based protein derived from fungi. Mycoproteins like Quorn are high in fibre as well as protein.

尽管如此,健康的蛋白质并不一定来源于肉,菌蛋白是一种来自真菌的健康植物蛋白质。像植物素肉这样的菌蛋白在纤维和蛋白质两方面含量都很高。

Researchers now are looking into how this unique composition (of both protein and fibre) can affect satiety and insulin levels, which are linked to type two diabetes. One team compared a mycoprotein diet to a chicken diet and found that the insulin levels in those who ate quorn achieved the same sugar control, but needed less insulin to be produced by the pancreas.

研究人员现在正在研究这种独特的蛋白质和纤维组合食物如何影响与二型糖尿病有关的饱腹感和胰岛素水平。一个研究小组将菌蛋白饮食和鸡肉饮食进行了比较,发现那些吃植物素肉者的胰岛素水平达到了控制糖分的相同作用,但需要胰腺所分泌的胰岛素则较低。

The risk of consuming too much protein is small, but the bigger risk might just be falling for overpriced products offering us more protein than we need. “Some products labelled as high protein aren’t, and they’re quite expensive. Anyway, consuming more protein than need is wasteful in terms of money, and it’s paid down the toilet,” says Johnstone.

消耗过多蛋白质的风险很小,但是使用高价产品从而获得比人体所需更多的蛋白质反而会带来更大的危害。约翰斯通说道:“有些标记为高蛋白的产品实际上并不是高蛋白,而且它们非常昂贵。无论如何,摄入比所需更多的蛋白就是浪费金钱,等于倒钱入马桶。”

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