美国好消息:奶酪对您而言并不坏

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奶酪是极有罪的享乐之一。黏糊糊的好肥这很美味。大量的研究表明,奶酪作为一种令人发胖的,令人讨厌的食品而享有盛誉。谈到体重和其他关键健康结果时,奶酪充其量是中性的,甚至可能对您有益。然而,这项研究似乎并未突破常识。奶酪恰好位于中间:平均而言,多吃或少吃奶酪对体重基本上没有影响。但是,如果美国人的奶酪消费量上存令人困惑的变量,那么他们应该使它的效果看起来更糟,而不是更好。

奶酪是极有罪的享乐之一。黏糊糊的好肥这很美味。只是对你有害,对吧?

错误的。大量的研究表明,奶酪作为一种令人发胖的,令人讨厌的食品而享有盛誉。谈到体重和其他关键健康结果(不考虑乳糖不耐症和道歉问题)时,奶酪充其量是中性的,甚至可能对您有益。然而,这项研究似乎并未突破常识。如果您使用Google“奶酪”,则“人们还会问”下的最高结果是不合语法的查询“为什么奶酪对您有害?”现,如果您是正思考的人,“有什么大不了的?我适度地吃着自己喜欢的东西,而不必担心卡路里。”-恭喜,我为您感到高兴,我们有很多关于科学和技术的精彩文章,您可能会喜欢。另一方面,如果您像我一样,担心自己的饮食逐渐使您变胖,请继续阅读。

奶酪有益影响的最好证据来自长期的队列研究,该研究追踪了成千上万的人的健康和饮食习惯。 2011年发表《新英格兰医学杂志》上的一篇论文分析了三个队列,过去的几十年中共追踪了120877名美国成年人。作者发现,土豆,加工肉和精制谷物等食物与体重增加有关,而酸奶,水果和坚果与体重减轻有关。奶酪恰好位于中间:平均而言,多吃或少吃奶酪对体重基本上没有影响。

这一发现最近的研究中得到了保留。例如,2018年对爱尔兰2,512名男性进行的一项研究分析显示,五年后奶酪的摄入量与体重之间存轻微的反比关系,这意味着吃奶酪与减肥相关,尽管这种影响10年后逐渐消失。对37项随机临床试验的荟萃分析发现,增加牛奶消费量总体上会导致瘦肌肉数量增加和体脂减少。

“几乎没有证据表明奶酪会导致体重增加-实际上,有证据表明奶酪最坏的情况下是中性的,”塔夫茨·弗里德曼营养科学与政策学院院长,2011年论文的主要作者达里什·莫扎法里安说。 “没有证据表明奶酪与心血管疾病有关,某些研究中,奶酪甚至与较低的风险有关。然后,对于糖尿病来说,它再次处于最坏的中性状态,甚至可以起到保护作用。”

的确,观察研究只能揭示相关性。但是,如果美国人的奶酪消费量上存令人困惑的变量,那么他们应该使它的效果看起来更糟,而不是更好。美国人吃奶酪的方式,尤其是1980年代和90年代吃奶酪的方式,当时已经收集了许多数据,往往将其与不健康的食物搭配使用:想象一下意大利辣香肠比萨饼或白色火腿和奶酪三明治面包与芯片的一面。莫扎法里安说:“不是人们核桃和葡萄切菜板上吃奶酪。” “如果有混淆的[因素],那就是体重增加。”

因此,到目前为止,我们只需要回顾一下:证据倾向于表明奶酪不会使您变胖。为什么这个惊人的消息没有更广泛地传播?毕竟,过去的一两年中,我们已经重新考虑了许多有关食物,体重增加和健康的传统观念。某种程度上,要归功于迈克尔·波伦(Michael Pollan)和加里·陶伯斯(Gary Taubes)等作家的作品,二十世纪后期的低脂饮食口号已声名狼藉,取而代之的是人们认识到加糖,精制碳水化合物和加工食品是美国最有可能的罪魁祸首肥胖流行。

尽管如此,许多营养学家和普通百姓仍然坚持这样一个古老的观念:体重增加或减少是“卡路里增加,卡路里减少”的纯粹功能,也就是说,无论食物来源如何,您消耗多少卡路里减去燃烧多少卡路里。这种思想下,应避免食用高脂食品,因为一克脂肪具有9卡路里的热量,而一克蛋白质或碳水化合物仅具有4卡路里的热量。卡路里高的食物会使您发胖,”莫扎法里安说。

值得注意的是,即使根据净卡路里理论,将奶酪视为一种特别发胖的食物也没有多大意义,原因很简单,因为奶酪实际上并不是那么热量。我的冰箱里有一盒切达干酪,每盎司包含110卡路里的热量。同时,我的厨房中,一包全麦饼干包含…110卡路里/盎司。奶酪中除了脂肪以外还有其他东西,当您将食物作为一个整体时,事实证明,奶酪的热量消耗并不比许多日常碳水化合物食品高。

而且只有您仍然坚持纯卡路里的配方(只有越来越少的营养专家这样做)时,这才有意义。实验研究表明,动物和人类从不同的食物来源摄取相同数量的卡路里后,体重会有所不同。其他研究表明,卡路里的摄入和消耗不是独立的。减少卡路里可以降低身体燃烧卡路里的速度,从而阻止体重减轻。像我上面提到的那样,队列分析表明,坚果等超高热量食物与长期减肥相关。 (一盎司干烤杏仁:168卡路里。)食物很复杂,身体也很复杂。我们似乎没有像一块蛋糕中那样处理一条鱼中的卡路里。

以奶酪为例,尽管需要更多的研究,但可能有几个原因导致其对体重的影响不足。奶酪经过发酵,这意味着它具有活菌培养。这可能会对肠道微生物组产生积极影响,肠道微生物组似乎体重调节中发挥作用。发酵过程还产生维生素K2或甲萘醌,实验研究表明该维生素K2与改善的胰岛素功能有关。胰岛素调节血糖水平,饥饿,卡路里消耗和脂肪存储。 (结果是,经过发酵的坚硬,老化的奶酪可能比未经发酵的软奶酪提供的好处更多。)关于被称为牛奶脂肪球状膜的化合物的益处,还有一些很有希望的研究。奶酪,但不加牛奶或黄油。

鳄梨等其他高脂肪食品最近享有声誉恢复。奶酪,不是很多。一个原因可能是这样的事实,即奶酪不仅包含大量脂肪,而且包含大量饱和脂肪,这是与较高的胆固醇和心血管疾病发生率相关的主要饮食习惯。但是这里,科学界也说奶酪不应该受到歧视。奶酪的确具有很高的饱和脂肪,但这似乎与心脏病的高发无关。 2012年发表的一项针对5,209名美国成年人的研究发现,来自肉类的饱和脂肪与心血管疾病的发病率较高相关,而来自乳制品的饱和脂肪与较低的发病率相关,这是Mozaffarian的合著者。两项队列研究的荟萃分析对成千上万的总受试者同样得出结论,特别是奶酪的消费与较低的风险相关。 (对于糖尿病也有类似的发现。对一个26,930人的瑞典队列进行的分析发现,食用奶酪与女性患糖尿病的风险较低有关。发酵过程中生产甲萘醌可能与此有关。)

UCSF医学院教授,​​饮食专家罗纳德·克劳斯(Ronald Krauss)表示:“最重要的是,奶酪其对胆固醇(进而对心脏病)的不利影响方面声誉欠佳,这很大程度上是不应该的”。和胆固醇。 “饱和脂肪实际上是由饱和脂肪酸组成的,构成脂肪。那些饱和脂肪酸有许多不同的形式,它们具有不同的生化作用。他们中的大多数可以提高血液中的胆固醇,但并非所有人都能。”

克劳斯(Krauss)和莫扎法里安(Mozaffarian)都说,尽管这项研究令人鼓舞,但仍然没有足够好的数据来确切地说奶酪能预防心脏病或肥胖。但是,很明显,平均而言,至少吃正常量的奶酪似乎并没有增加风险。克劳斯说:“我花了很多时间与患者进行饮食建议,我告诉他们,'不用担心奶酪。' “他们喜欢它。”

当然,有些人有理由避免吃奶酪。克劳斯(Krauss)警告说,每个人的身体都不一样,胆固醇高居不下的人可能仍会从切奶酪中受益。高度加工的品种,尤其是钠和其他人们可能试图限制的成分可能很高。如果您是素食主义者,无论是由于动物残忍还是气候变化,我都不会改变主意。 (根据哈佛大学法学院研究员Helen Harwatt的分析,全球乳制品产量约占温室气体排放量的3.6%。)重点仅于,许多人喜欢吃年迈的Gouda,切达干酪和的确是他们的时髦戈贡佐拉(Gorgonzola),就健康而言,他们不需要为此感到内。

好消息尚未广为流传的真正原因可能是,迄今为止的证据表明,奶酪既不是酸奶等超级食品,也不是糖味苏打等杀手。 (如果更多的研究证实了2020年的一项研究发现奶酪可以防止与年龄有关的认知能力下降,那么情况可能会改变。)这使得人们更难知道该如何正确使用这些信息。

莫扎法里安将奶酪放他的个人三层食物金字塔中间。最重要的是“保护性”食品,其中包括水果,豆类,坚果,鱼,酸奶和最低加工的全谷类,莫扎法里安建议大量食用。底部是他避免食用的食物,例如精制碳水化合物和加工过的红肉。中性食品,如奶酪,介于两者之间。

他说:“我们不能总是吃最健康的食物。” “我们需要中性食品以实现多样性,娱乐性,适口性,所以奶酪我的清单上。如果我不吃绝对最好的水果,坚果,种子,鱼,奶酪很棒。如果将它添加到其他食物中,那就太棒了。”


英文译文:

Cheese is among the ultimate guilty pleasures. It’s gooey. It’s fatty. It’s delicious. It just has to be bad for you, right?

Wrong. A large body of research suggests that cheese’s reputation as a fattening, heart-imperiling food is undeserved. When it comes to weight and other key health outcomes (and setting aside the issue of lactose intolerance, with apologies), cheese is neutral at best, and possibly even good for you. And yet that research doesn’t seem to have broken through into common knowledge. If you Google “cheese,” the top result under “people also ask” is the ungrammatical query “Why cheese is bad for you?” Now, if you’re the type of person who’s thinking, “What’s the big deal? I eat what I like, in moderation, and don’t worry about calories”—congratulations, I’m happy for you, we have lots of great articles about science and tech you might enjoy. If, on the other hand, you’re like me and worry that your diet is making you gradually fatter, keep reading.

The best evidence for the benign impact of cheese comes from long-term cohort studies that tracked the health and eating habits of tens or hundreds of thousands of people. A 2011 paper published in the New England Journal of Medicine analyzed three cohorts that together tracked 120,877 US adults over several decades. The authors found that foods like potatoes, processed meats, and refined grains were associated with weight gain over time, while yogurt, fruit, and nuts were associated with weight loss. Cheese was right in the middle: On average, eating more or less of it had essentially no effect on weight.

That finding has held up in more recent research. A 2018 analysis of a study of 2,512 men in Ireland, for example, showed a mild inverse relationship between cheese consumption and body mass after five years, meaning eating cheese was associated with weight loss, though that effect faded at the 10-year mark. A meta-analysis of 37 randomized clinical trials found that increased dairy consumption overall led to increased lean muscle mass and decreased body fat.

“There’s almost no evidence that cheese causes weight gain—and in fact, there’s evidence that it’s neutral at worst,” says Dariush Mozaffarian, the lead author of the 2011 paper and dean of the Tufts Friedman School of Nutrition Science and Policy. “There’s no evidence that cheese is linked to cardiovascular disease, and in some studies, it’s even a little bit associated with lower risk. And then, for diabetes, again, it’s at worst neutral, and maybe protective.”

It’s true that observational studies can only reveal correlations. But if there are confounding variables when it comes to Americans’ cheese consumption, they should make its effects look worse, not better. The way Americans eat cheese, and especially the way they were eating it in the 1980s and ’90s, when much of the data was gathered, tends to pair it with unhealthy foods: Imagine a pepperoni pizza, or a ham and cheese sandwich on white bread with a side of chips. “It wasn’t people eating cheese on cutting boards with walnuts and grapes,” Mozaffarian says. “If there were confounding [factors], it would be toward weight gain.”

So just to recap so far: The evidence tends to show that cheese does not make you gain weight. Why hasn’t this amazing news spread more widely? After all, we’ve seen many conventional ideas about food, weight gain, and health be reconsidered over the past decade or two. Thanks in part to the work of authors like Michael Pollan and Gary Taubes, the low-fat diet mantra of the late 20th century has been discredited, replaced by an awareness that added sugars, refined carbohydrates, and processed foods are the likelier culprits in America’s obesity epidemic.

Still, many nutritionists and ordinary people adhere to the old notion that weight gain or loss is a pure function of “calories in, calories out”—that is, how many calories you consume, regardless of the food source, minus how many you burn. Under this thinking, fatty foods are to be avoided because a gram of fat has 9 calories compared to a gram of protein or carbohydrate, which only has 4. “There still is this long-standing perception bias that fatty foods make you fat, or calorie-dense foods make you fat,” says Mozaffarian.

It’s worth noting, however, that even under the net calorie theory, it doesn’t make much sense to think of cheese as a particularly fattening food, for the simple reason that it isn’t actually all that caloric. I have in my refrigerator a package of cheddar cheese that contains 110 calories per ounce. Meanwhile, a package of whole-grain crackers in my pantry contains … 110 calories per ounce. There is stuff in cheese other than fat, and when you take the food as a whole, cheese turns out to be no more calorie-dense than lots of everyday carb-based foods.

And that’s only relevant if you still cling to the net calories formula, which fewer and fewer nutrition experts do. Experimental studies have shown that animals and humans fed identical numbers of calories, from different food sources, gain different amounts of weight. Other research shows that calorie intake and expenditure are not independent; cutting back on calories can lower the rate at which the body burns them, thwarting weight loss. Cohort analyses like the ones I mentioned above show that super-high-calorie foods like nuts are correlated with long-term weight loss. (One ounce of dry-roasted almonds: 168 calories.) Food is complex, and so are bodies; we don’t seem to process a calorie in a piece of fish the same way we do in a piece of cake.

In the case of cheese, there could be several reasons for the surprising lack of impact on weight, though more research is needed. Cheese is fermented, meaning it has live bacterial cultures. That could have a positive effect on the gut microbiome, which appears to play a role in weight regulation. The fermentation process also creates vitamin K2, or menaquinone, which experimental studies have linked to improved insulin function. Insulin regulates blood sugar levels, hunger, calorie expenditure, and fat storage. (One upshot is that hard, aged cheeses, which are more fermented, probably provide more benefit than soft, less fermented ones.) There’s also some promising research about the benefits of a compound called the milk-fat globule membrane, which is intact in cheese but not in milk or butter.

Other high-fat foods, like avocados, have lately enjoyed a reputational rehabilitation. Cheese, not so much. One reason may be the fact that cheese contains not just a lot of fat but a lot of saturated fat, a major dietary scofflaw linked to higher blood cholesterol and rates of cardiovascular disease. But here, too, the science says cheese doesn’t deserve its stigma. While cheese does have high saturated fat, that doesn’t appear to correlate with higher risk of heart disease. A study of 5,209 US adults published in 2012, of which Mozaffarian was a coauthor, found that saturated fat from meat was associated with higher rates of cardiovascular disease, but that saturated fat from dairy was associated with lower rates. Two meta-analyses of cohort studies with hundreds of thousands of total subjects likewise concluded that cheese consumption, specifically, was correlated with lower risk. (There have been similar findings for diabetes. An analysis of a 26,930-person Swedish cohort found that consumption of cheese was associated with lower risk of diabetes in women. The production of menaquinone in the fermentation process could have something to do with that.)

“The bottom line is that the bad reputation that cheese has regarding its adverse effects on cholesterol, and hence on heart disease, is undeserved for the most part,” says Ronald Krauss, a professor at the UCSF School of Medicine and an expert on diet and cholesterol. “The saturated fat is really composed of saturated fatty acids in a structure that forms a fat. Those saturated fatty acids come in many different forms, and they can have very different biochemical effects. And most of them can raise blood cholesterol, but not all of them do.”

Both Krauss and Mozaffarian say that, despite the promising research, there still isn’t enough good data to say conclusively that cheese prevents heart disease or obesity. What is clear, however, is that eating normal amounts of cheese at least doesn’t appear to raise the risk, on average. “I spend a lot of my time with patients giving dietary advice, and I tell them, ‘Don’t worry about cheese,’” Krauss says. “They love it.”

Of course, there are reasons for some people to avoid cheese. Krauss cautions that everyone’s body is different, and people with stubbornly high cholesterol might still benefit from cutting out cheese. Highly processed varieties, in particular, can be high in sodium and other ingredients people might be trying to limit. If you’re vegan, whether it’s because of animal cruelty or climate change, I’m not trying to change your mind. (According to an analysis by Helen Harwatt, a fellow at Harvard Law School, global dairy production accounts for about 3.6 percent of greenhouse gas emissions.) The point is merely that a lot of people love eating their aged Gouda, their sharp cheddar, and indeed their funky Gorgonzola, and as far as health is concerned, they don’t need to feel guilty about it.

Perhaps the real reason the good news hasn’t caught on widely is that the evidence so far reveals cheese to be neither a superfood, like yogurt, nor a mass killer, like sugary soda. (That might change if more research confirms a 2020 study that found that cheese protected against age-related cognitive decline.) This makes it harder to know what exactly to do with the information.

Mozaffarian puts cheese in the middle of his personal three-tier food pyramid. At the top are “protective” foods, which include fruits, beans, nuts, fish, yogurt, and minimally processed whole grains, of which Mozaffarian advises eating a lot. At the bottom are foods that he avoids, like refined carbohydrates and processed red meat. Neutral foods, like cheese, go in between.

“We can’t always eat the healthiest possible thing,” he says. “We need neutral foods for variety, fun, palatability, so cheese is up there on my list. If I’m not going to have the absolute best—fruits, nuts, seeds, fish—cheese is great. And if you add it to those other foods, it’s fantastic.”


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