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It seems like every other week a new study comes out questioning long-held wisdom about food and nutrition. First fat was vilified; now it’s considered a part of a healthy diet. Eggs used to be off-limits for people with heart problems due to the high amount of cholesterol, but that’s no longer the case.
似乎每隔一周都会有一项新研究问世,质疑人们的食物和营养。开始是脂肪被轻视,现在它却被认为是健康饮食的一部分。由于胆固醇含量高,鸡蛋曾是心脏病患者的禁忌食品,但现在情况已不再如此。

Dr. David Ludwig is a professor of nutrition at the Harvard School of Public Health and author of the number one New York Times bestseller Always Hungry?, a book that explores the dietary drivers of hunger, obesity, and metabolic disease. In a new “Viewpoint” paper published in August in the Journal of the American Medical Association (JAMA), Ludwig and his co-authors explain the problems with current approaches to dietary research and why this leads to so much nutrition confusion.
David Ludwig博士是哈佛大学公共卫生院的营养学教授,也是《纽约时报》畅销书《永远饿吗》的作者。该书探讨了饥饿,肥胖和代谢疾病的饮食因素。在8月美国医学协会(JAMA)发布的一个“新观点”里,Ludwig和他的合作者解释了目前饮食研究调查存在的问题和是什么原因导致了这么多饮食混乱情况的发生。

Elemental: What was the impetus for the JAMA viewpoint you co-authored?
你撰写JAMA的主要推动力是什么?

Dr. David Ludwig: In the course of a week, almost every person will see headlines on diet and health that come to opposing conclusions. And we’ve seen through the years how what is believed to be an established fact in nutrition is later questioned or reversed. We wanted to address the causes of this confusion and the challenges facing nutrition research in comparison to other fields that have more established track records of assuring research quality.
David Ludwig:在一周的时间里,几乎每个人都会看到饮食和健康的头条新闻得出了相反的结论。多年来,我们已经看到因为人们的质疑,许多关于营养方面的既定事实在后来都被逆转和翻转。与其他为确保研究质量而有可靠记录的领域相比,我们想解决这种困惑的成因和营养研究所面临的挑战。

You compare nutrition research to drug research. What do you view as the key differences?
你把营养研究和药物研究进行比较。你认为主要差异是什么?

Pharmaceutical research receives lots of financial support, because drugs can be highly profitable. A major clinical trial might cost several hundreds of millions of dollars, but a successful drug can earn many billions in profits. So the pharmaceutical industry is motivated to do these studies right — to design them properly, to make sure they have the strength and statistical power to get the right answers. The last thing a trial sponsor wants is an inconclusive result. If an experimental drug doesn’t work, they want to know it as quickly as possible to avoid wasting additional time and money. Consequently, a large infrastructure has grown in recent years to support pharmaceutical research, including clinical research organizations hired to oversee trials. These CROs have the expert staff and know-how to conduct rigorous trials and ensure that all scientific and regulatory standards are properly followed.
因为药物可以带来巨大利润,药物研究会获得大量的财务支持。一项大型的临床试验可能需要花费数亿美元,但成功的药物却可以带来数十亿美元的利润。因此,制药行业有动力正确地开展这些研究,并进行适当设计,以确保它们具有获得它们能得到正确结果和数据。试验申办者需要的最后一件事是还没有定论的结果。如果实验药物无效,他们希望尽快知道原因,以避免浪费更多的时间和金钱。因此,近年来,已经建立了庞大的基础设施来支持药物研究,包括雇用来监督试验的临床研究组织。这些 CRO 拥有专业的工作人员,能够进行严格的试验,并确保正确遵循了所有的科学和监管标准。

Compare this situation to a standard dietary trial. Researchers lucky enough to win a government grant from the National Institutes of Health (typically 10% of all applications) will have at most $500,000 a year for four or five years. While $2 million may sound like a lot, that’s a tiny fraction of the budget for a standard drug trial. More typically, nutrition research must make do with shoestring budgets cobbled together from small grants provided by universities, philanthropies, or the food industry.
将此情况与标准饮食试验进行比较。研究人员幸运地赢得了美国国立卫生研究院的政府资助(通常所有申请者的10%才能获得),在四到五年内每年最多可获得500,000美元。虽然200万美元听起来可能很多,但这只是标准药物试验预算的小部分。更典型地说,营养研究必须与大学、慈善机构或食品行业一起提供的小额赠款拼凑在一起的预算有关。

Even as nutrition is less well-funded, it’s more complicated. Changing a person’s diet is much more difficult than taking a pill or a placebo, and it’s virtually impossible to do a double-blind study with food. Diet is personal, involving deeply entrenched behavior related to family, community, culture, pleasure, and even values.
即使营养学缺乏足够的资金,它也更加复杂。改变一个人的饮食习惯比让他吃药难得多,而且对食物进行双盲研究几乎是不可能的。饮食习惯是私密的,它的行为深深受家庭、社区,文化、喜悦乃至价值观的影响。

To make matters even more challenging, changing one aspect of a diet inevitably affects many others as well. If you eat more of one food, you’ll probably eat less of another. In a study examining the effects of consuming 10 servings of vegetables and fruits a day, participants may naturally tend to eat less processed foods, because they’re less hungry. So it can be hard to tell whether any health benefits seen in the study are due to eating more veggies and fruits or less of the other stuff. At the same time, nutrition trials have difficulty determining whether and how diet actually changes. You can’t just measure blood levels of a drug to assess compliance with the protocol. The challenge of producing significant diet change over the long term and the inability to accurately measure these changes create enormous uncertainties.
为了使事情更具挑战性,改变饮食的一个方面不可避免地也会影响许多生活的其他方面。如果你多吃一种食物,那么你可能就要少吃另一种食物。在一项研究中,每天食用10份蔬菜和水果,参与者自然会少吃加工食品,因为他们不饿。因此,很难确认身体健康是因为多吃了蔬菜和水果而少吃了其他食物而导致。同时,营养试验很难确定饮食是否变化和如何变化,你不能只测量药物的血液水平来评估对方案的遵守情况。长期来看,饮食结构发生重大变化的挑战以及无法准确衡量这些变化的情况带来了巨大的不确定性。

Apart from funding challenges, there’s the question of whether the people in these diet studies are actually following instructions.
除了资金压力外,还有个问题是,这些饮食研究中的人是否真正遵循了指示去做?

This is the elephant in the living room. In most clinical trials, people are told to follow one diet or another, and they are given a very modest amount of support — maybe a meeting with a dietitian once or twice a month. They are then expected to make this major change to their lifestyle on their own. This study design is especially common because of the poor funding and infrastructure in place for nutrition research. Inexpensive, low-intensity interventions are chosen by necessity. But you don’t really know if people follow them.
这是重要的问题,在多数临床实验中,人们会被要求遵循一种饮食习惯,并且他们会被给予少量的支持——也许是每月与营养师会面一到两次。然后,他们被期望自己会对生活方式做出重大改变。由于营养研究的资金和基础设施都很薄弱,这种研究设计非常普遍——根据需求选择廉价,低强度的干预。但你确实不知道是否有人在追踪他们的研究。

People can make changes for a few months, but without adequate support, they resort back to their habitual ways of eating. Because of this, we often see short-term weight loss in obesity trials followed by weight regain after a few months. These sorts of findings have been misinterpreted to mean the type of diet doesn’t matter. But that conclusion does not logically follow. Instead, it really means the intervention failed.
人们可以坚持几个月更改饮食习惯,但如果没有足够的支持,他们就会恢复到习惯性的饮食方式。因此,我们经常在肥胖试验中看到短期的体重减轻,几个月后又复胖了。这些发现被误解为饮食习惯无关紧要,但这一结论在逻辑上并不成立。不过,这确实意味着干预失败了。

Imagine there’s a promising new drug that might cure childhood leukemia. You conduct a clinical trial with one group of people assigned to take the new drug and another group receiving a placebo. But it turns out the group assigned to the drug didn’t take it as directed. In this scenario, there might be no significant change in cancer treatment success. But we wouldn’t interpret that result to mean the drug is ineffective. We would conclude that the study was flawed. Unfortunately, the conduct of diet trials isn’t always held to this standard.
想象有一种有望治愈儿童白血病的新药。你开展了临床实验,一组接受药物治疗,一组接受的是安慰剂。但结果证明,要吃药的小组没有按照指示服用该药物,这种情况下,癌症治愈的成功率可能不会发生大变化。但我们不会将结果解释为药物无效,我们可能会得出研究有缺陷的结论。不幸的是,饮食试验的执行并不总是符合此标准。

You address the importance of understanding biology and behavior. Is one more important than the other in diet trials?
你强调了理解生物学和行为学的重要性,在饮食实验中,一个比另一个更重要吗?

Both are critical, but it’s important to keep in mind which one you want to study in designing a diet trial. Many people can cut back on calories and lose weight on any diet temporarily. But after a few days or weeks, hunger increases and their metabolism slows down, which is a recipe for weight regain. That’s why we need longer-term studies to see how the type of food we eat, beyond calories, might alter biology and the success of weight-loss maintenance. But the best diet in the world won’t work if people aren’t motivated to follow it. That’s why we also need studies of behavior and environment to make the challenges of lifestyle change easier and more sustainable.
两者都是重要的,但在设计饮食试验时要牢记你想研究的是哪个。许多人可以暂时性地减少热量并通过饮食来减肥。但在几天或几周后,饥饿感会增加,并且他们的新陈代谢会减慢,而这就是会复胖的原因。这也是为什么我们需要长期的研究,看看我们吃的食物类型,除了卡路里,还可能会改变生物学、知道如何维持减肥不复胖。但是,如果人们没有动力遵循它,世界上最好的饮食习惯也不会起作用。这就是为什么我们还需要对行为和环境进行研究,以使改变生活方式的挑战变得更容易,更可持续。

How do we fix this problem?
我们如何解决这个问题?

Diet-related diseases — including obesity, diabetes, and cardiovascular disease — are the leading public health problems today. Whether or not you have one of these conditions, you’re paying for them through higher taxes, the cost of Medicare and Medicaid, and higher insurance rates. These costs are borne by everybody. And for people with a condition like Type 2 diabetes, the personal toll can be huge, including limb amputation, kidney failure, blindness, and shortened life expectancy. So it’s in everybody’s interest that research into nutrition and disease prevention be well funded and done properly.
包括肥胖,糖尿病和心血管疾病在内的与饮食相关的疾病,是当今主要的公共卫生问题。无论你是否患有这些疾病,你都会通过支付更高的税费、医疗保险、医疗补助和保险率来为这些疾病买单。这些费用会由每个人承担。对于患有2型糖尿病的病人而言,个人伤亡可能是巨大的,包括了肢体截肢,肾衰竭,失明和寿命缩短。因此,对营养和疾病预防的研究会得到充分的资金和恰当开展,因为这会符合每个人的利益。

Some say we can’t afford new government programs [to deal with this]. But today, the economic cost of Type 2 diabetes — just one diet-related disease — approaches $500 billion annually. The total medical costs and lost worker productivity of diet-related disease may already exceed $1 trillion annually. Without action, these figures will only increase, contributing to the national budget deficit and threatening the international competitiveness of the U.S. economy. A sort of Manhattan Project for diet-related disease would cost pennies on the dollar now being spent. What’s lacking is a clear national vision to align public health priorities with investment.
有人说我们负担不起新的政府计划来解决这个问题。但如今,2型糖尿病(一种与饮食有关的疾病)的经济成本每年接近5000亿美元。与饮食有关疾病的总医疗成本和工人生产力的损失每年可能已超过1万亿美元。如果不采取行动应对,这些数字只会增加,从而导致国家预算的赤字并威胁到美国经济的国际竞争力。一种为饮食相关疾病制定的曼哈顿计划(过去要花几美元现在只要几美分)正在被执行。现在缺乏的是让公共卫生优先事项和投资保持一致的清晰国家愿景。

We know humans aren’t programmed to gain more weight generation after generation. Something has changed in our environment, driving even highly disciplined people to gain weight. We have to understand what that’s about. One likely culprit is all the processed carbohydrates that crept into our diet during the low-fat diet years. But that’s not the whole story, and many other factors are undoubtedly contributing. We’ll need long-term, adequately powered studies to sort this out once and for all.
我们知道人类没有被编程设定以一代又一代地增加体重。我们的环境已发生了某些变化,甚至会让自律的人也会变胖。我们必须了解那是什么原因,罪魁祸首可能是在低脂时代所有加工食物中添加的碳水。但这还不是全部,其他许多因素也在起作用。我们需要长期的,强有力的研究来一劳永逸地解决这个问题。

We need to build the capacity to conduct effective nutrition research, and this will require sustained investment from Washington, including cultivation of a new generation of appropriately trained researchers at academic centers around the country.
我们需要建立能进行有效营养研究的能力,这需要华盛顿的持续投资,包括在全国各地的学术中心培养新一代经过培训的研究人员。

“We know humans aren’t programmed to gain more weight generation after generation. Something has changed in our environment... We have to understand what that’s about.”
“我们知道人类没有被编程以一代又一代地增加体重。我们的环境已经发生了某些变化……我们必须了解发生了什么。”

What advice can you offer the general public for reading and consuming news stories about nutrition research?
你可以向公众提供什么建议以阅读和使用有关营养研究的新闻报道?

Ideally, medical journalists need better training to identify basic design flaws in clinical trials
so they can convey a more balanced view of study strengths and limitations. We don’t want the public dragged back and forth with every weak new research finding. As a general rule, if a clinical trial on obesity has a small number of participants (fewer than 20 people), if it’s very short term, or if it doesn’t clearly demonstrate that meaningful dietary changes were made, the results can be considered weak.
理想情况下,医学记者需要接受更好的培训,以识别临床试验中的基本设计缺陷,以便他们可以更平衡地了解研究的优势和局限性。我们不希望公众因还没确定的研究而左右。一般而言,如果肥胖症的临床试验参与者人数少(少于20人)、时间很短、或者不能清楚地表明进行了有意义的饮食改变,就可以考虑它的结果弱。

Many people are confused about healthy eating. What’s your advice on how to eat healthy?
许多人对健康饮食感到困惑。你对如何健康饮食有什么建议吗?

I advocate a “low glycemic load” diet — one that controls the surge in blood glucose and insulin after the meal. The way to achieve this is by cutting back on processed carbohydrates (refined grains, potato products, and sugar); increasing healthy fats, like nuts and nut butters, avocado, olive oil, and even dark chocolate; and having an adequate amount of protein, which can come from animal or plant-based sources. This approach involves a moderate reduction in total carbohydrates but still offers lots of flexibility in food choice. For people with diabetes, more severe restriction of carbohydrates may have additional benefits.
我提倡一种“低血糖负荷”的饮食习惯,这种饮食习惯可以控制饭后血糖和胰岛素的激增。实现这一目标的方法是减少加工后的碳水化合物(精制谷物,马铃薯产品和糖)的摄入;增加健康的脂肪,例如坚果、坚果黄油、鳄梨、橄榄油,甚至黑巧克力;并且补充足够的蛋白质,这些蛋白质可以来自动物或植物。这种方法可以适度减少碳水化合物的总量,但在食物选择上仍具有很大的灵活性。对糖尿病患者来说,严格控制碳水化合物的摄入还会带来其他的好处。

Not all researchers or clinicians, of course, will agree with this recommendation. That’s why we need the definitive research.
当然,并非所有研究人员或临床医生都会同意该建议。这就是为什么我们需要确定的研究成果。