全球对话|从膳食指南到大众健康——塔夫茨大学Alice Lichtenstein教授专访「Voice Of Nutrition」

Alice H. Lichtenstein

博士

The Dietary Guidelines for Americans (DGA) has been published every 5 years since 1980 by the Federal Government. The preparation of the 2015 version started from late 2012 when nominations for Dietary Guidelines Advisory Committee (DGAC) were solicited through a Federal Register notice. The committee was appointed by Secretaries of Human and Health Service (HHS) and Unite States Department of Agriculture (USDA) in May 2013. The committee then examined the 2010 DGA and determined whether new scientific evidence might inform revisions, or suggested new guidance with primary focuses on the systemic review and analyses of the evidence published since the last DGAC deliberations. The DGAC used a variety of evidence sources to develop its Advisory Reports. The Committee graded its conclusion statement using a table of strength of evidence grades (see below) adapted specifically for the use with existing reports.

自1980年以来，联邦政府每5年出版一次《美国膳食指南》(DGA)。2015年版本的起草工作从2012年底开始，当时通过联邦登记公告开始接受膳食指南顾问咨询委员会 (DGAC) 的成员提名。该委员会于2013年5月由人类和卫生服务部(HHS)和美国农业部(USDA)任命。委员会随后审查了2010年的DGA，并确定了新的科学证据是否足够进行新版修订。本次修订的重点为对自上届DGAC成立之后发表的新证据的系统审查、归纳和分析。DGAC使用了各种证据来源来制定其咨询报告。委员会根据现有报告，根据证据等级（见下表），对其研究的结论进行了评级。

In early 2015, the DGAC submitted an advisory report to Secretaries of HHS and USDA. The public is also welcomed to submit written comments to the DGAC throughout the whole process. By the end of 2015, the Secretaries of HHS and USDA and other federal staff wrote and released the 2015-2020 version of DGA to the public.

2015年初，DGAC向HHS和USDA的秘书处提交了顾问委员会咨询报告。公众也可以在整个过程中向DGAC提交书面意见。2015年底，HHS和USDA的秘书处和其他联邦工作人员撰写，并向公众发布了2015-2020版的DGA。

Alice H. Lichtenstein

博士

I think that people have different priorities in their life. For some people, health is a priority and they are aware of the current guidelines. They generally know what a healthy diet is and the importance of engaging in regular physical activity. But there are some people who don't have that health literacy or they do not prioritize health in their life. Those are actually the people that we should try to reach the most, which is usually not easy to do. I don't have a magic answer for it and probably it’s going to take a multi-pronged approach. One of the things I think in the long run to be most useful is introducing food and nutrition education into the school system starting in kindergarten straight up through high school, because then people have a sound foundation. I think if we bring people up in a way so they really understand the relationship between food and health, maybe it's more likely we'll be able to reach those people.

我认为人们在生活中有不同的重心，不同的选择。对一些人来说，健康是重中之重，所以他们会熟知当前的膳食指南，知道健康饮食是什么，以及定期进行体育活动的重要性。但也有一些人可能没有这种健康素养，或者说他们没有把健康放在首位。这部分人实际上是我们最应该尝试进行营养健康知识普及的，可这通常并不容易。我没有一个“万灵药”般的答案，但是多管齐下的方法可能会比较有效。从长远来看，我认为最好的一个办法就是把食品和营养教育引入教育系统，从幼儿园一直到高中，孩子们在学习和成长过程中对营养耳濡目染，所以等他们长大了之后则会有一个更好的基础。我认为，如果我们以某种方式让人们认识到食物和健康之间的关系，也许我们更有可能让原本对营养和健康并不关注的一些人更加关注健康。

For nutrition education, in general, I think we have to make things as easy as possible for people and the most useful thing is “food based general guidelines”, meaning we don't need to stress that blueberries are better than strawberries or that salmon is better than tilapia. We just need to provide very general broad guidelines that can be adapted to people's personal preferences, and ethnic and cultural back grounds. For example, a good diet is usually high in fruits and vegetables, but in reality, people are not eating enough. To begin with, it’s better to get people start eating more fruits and vegetables rather than telling them they need to eat specific kinds. The same thing with fish, people don't eat enough fish in the United States. So, we could not split hairs and say, salmon is much higher in omega three fatty acids than flounder and tilapia. If people aren't eating fish, just get them to eat whatever fish they're willing to eat. Then I think things like whole grains, they're ubiquitous in the market at a comparable price so it's just a matter of somehow getting people to make the change, but we need to understand that people change dietary habits slowly.

至于营养教育，总的来说，我认为我们必须尽可能地将信息简化。最有用的方式是“基于食物的简单指南”，这意味着我们可能不需要强调蓝莓比草莓好，或三文鱼比罗非鱼好。我们只需要提供非常宽泛的指导方针，以适应人们的个人喜好、种族和文化的背景的不同。例如，一个优质的膳食结构通常植物性食物应该占大多数，但实际上人们吃的量并不太够。在公共营养方面进行干预，我们首先应该让人们开始吃更多的果蔬，而不是告诉他们需要吃特定的果蔬。鱼也是类似的一个例子，美国人吃的鱼不够。所以，我们不必在细节上做过多文章，比如说三文鱼的ω-3脂肪酸要高于比目鱼和罗非鱼。如果人们不吃鱼，更好的办法是先让人们开始吃任何种类他们喜欢吃的鱼，而不是给一些太过具体的建议。然后，我认为像五谷杂粮这样的东西，它们在市场上无处不在、价格实惠，但是选择更优化的膳食是人们改变行为的一个过程，我们必须要认识到这个过程是缓慢的。

Alice H. Lichtenstein

博士

As far as the recommendation changes for carbohydrate, lipid, and cholesterol over the past decades, the changes were made on the basis of emerging science. At one point, it was thought that low fat diets were the best. There was an unanticipated consequence that people were taking fat out and substituting it with sugar and refined carbohydrate. That was unfortunate. Then the research showed that low fat diet induced hypertriglyceridemia, so the recommendation was changed from low fat to moderate fat. As far as cholesterol, the very first studies were done with very high cholesterol diets in rabbits, which can handle high cholesterol intake, and it just seemed logical. High cholesterol diet would raise cholesterol levels in plasma, but then science showed that the effect was stronger for saturated fat rather than dietary cholesterol, so we have to modify recommendation on the basis of what the most recent science shows: the quality of dietary fat is very important.

在过去的几十年里，对于碳水化合物、脂肪和胆固醇膳食建议是以不停更新的科学证据为基础而做出改变的。人们一度认为低脂肪饮食是最好的，可没有预料到的结果是，人们把脂肪拿走之后，用糖和精制碳水化合物来代替，这非常不幸。大量研究表明，低脂饮食会诱导高甘油三酯血症，因此膳食建议转变为适度的脂肪摄入，而不是之前推崇的低脂饮食。就胆固醇而言，最初的研究都是用高胆固醇饮食，在用耐高胆固醇摄入的兔子为模型来做的，这似乎符合逻辑。诚然，高胆固醇饮食会提高血浆中的胆固醇水平，但后来的科学表明，饱和脂肪对健康的影响比膳食中的胆固醇更强，所以我们必须根据最新的科学证据修改建议：膳食脂肪的质量是非常重要的。

Alice H. Lichtenstein

博士

There's an article that just came out in JAMA recently (title: Disclosure in Nutrition Research. Why It Is Different?). The article raised some important issues regarding conflict of interest. However, it is important to understand that now, for industry sponsored research, there are safeguards in place so the sponsors cannot influence the results of the study. It is not uncommon for there to be different findings on a topic among studies. What is important to do is understand whether there are just different results or there were design issues that could explain the differences. I don't think there are many people who really just fabricate or misinterpreted data for their own benefit. Sometimes studies can be designed with a certain outcome in mind, but hopefully the peer review process will take care of that. When there are conflicting studies it's just a matter of reading them very carefully, and trying to understand where there might be study design issues that cause the difference in results.

最近有一篇文章在《美国医学会刊》上发表 (标题：Disclosure in Nutrition Research. Why It Is Different?)。这篇文章提出了一些重要的和“利益冲突”有关的问题。然而，值得指出的是， 现在对于那些由工业界赞助的研究，是有一系列安全措施来保证科学证据的正直性的，因此赞助商一般不能影响研究的结果。而在研究中，一个显而易见的现实是，对于同样的话题，不同的结论并不少见。对我们来说，最重要的是去区分是否在事实上这些结论是相悖的，还是有可能是因为实验设计的不同而导致的结果的不同。我不认为大部分人只是为了自己的利益而编造或曲解数据。虽然有时候实验设计可以人为地使结论偏向某个方向，但是成熟的同行评审系统能够很好避免这个问题。每当我们碰见结论相互冲突的研究时，应该要很小心地理解其中的差别，并看看是否是因为研究的设计导致了结论的不同。

Alice H. Lichtenstein

博士

I think it's important to keep the media on message rather than letting them determine what we say. We should decide what point we're going to make. No matter how many times they ask the question in different ways we should make our points clearly and consistently. If I have the option to respond via e-mail usually do, then they'll more likely use that quote. Sometimes I will not talk to a reporter if I think they are very biased going into the interview, so anything I say will be misinterpreted. Most of the time, we just have to be very firm and clear, yet not get too much in the details. They don't want the details. They want a clear message. Sometimes the reporter’s background knowledge can be an issue. If they have no science training, they may not understand how things need to be kept in context. Certainly, we have to do a little more. Keeping things very simple is the key.

我认为重要的是给媒体非常确定的、我们明确想要表达的信息，而不是由他们去决定我们传递什么信息。 不管他们如何用不同的方式提出问题，我们都应该清晰而一致地阐述我们的观点。如果我可以选择通过电子邮件来回复，那么媒体就更有可能直接引用我在邮件中的原文，这样一来传递的信息就会有更少的偏移。有时，如果我觉得媒体对信息是有明显偏见的，我就不会选择和记者交谈，因为我说的任何话都有可能会被曲解。大多数时候我们必须非常坚定和清晰，但不用给太多的细节。媒体不想要细节，他们想要的是非常明确的信息。有时，记者可能不会有充足的背景知识来对我们传递的信息进行系统性的理解。另外如果他们没有足够的科学训练，他们可能不明白语境和前提条件的重要性，所以我们可能要花更多精力去思考如何给他们传递正确的信息。总之一句话，保持信息简单、清晰、一致是关键。

Alice H. Lichtenstein

博士

I think we're still learning about personalized nutrition and I suspect that different people do have different requirements for different nutrients. However, most of the time within the context of human consumption, we consume more than we need. We don't consume many nutrients at minimum amount. For example, even if two people have a different requirement for protein, because it’s very likely that they both consume protein in excess of their minimum requirement, it's probably not going to matter. I think the only time it really matters is if there's some kind of genetic inborn error of metabolism or whether there's a period of deprivation where there is not enough of certain types of food, which are extreme cases. Under normal circumstances, when we think about food, it is in the context of eating with other people. If we go more towards personalized nutrition we can make up some kind of bar that's perfect for each individual, but we could lose that whole social aspect of food. That would be unfortunate. I think we need to find out a little bit more about how much variability there is among individuals and then whether individualized requirements are really necessary, or whether we just have enough of all essential nutrients because our food supply is fortified with most things and we have an abundant amount of food.

我认为在个性化营养上我们还有很长的路要走，我也相信不同的人对不同的营养素会有不同的要求。然而在大多数情况下，我们的膳食摄入量比我们身体需要的量要多了许多。例如，即使两个人对蛋白质有不同的要求，因为很有可能他们的蛋白质摄入量远超过了他们需要的量，所以导致了这个“个性化的蛋白质需求”可能并不重要。我认为个性化营养在某些情况下是十分重要的，包括某种天生的基因缺陷导致的代谢失常，或是某段时间缺乏某类食物的摄入，然而这些都是极端的情况。在正常情况下，当我们谈及食物的时候，通常是和他人一起进食的，具有社会属性。如果我们更倾向于个性化营养，那么虽然我们可以为每个人建立一个完美的营养需求列表，但是我们可能会失去膳食的社会属性，由此一来将非常遗憾。我认为我们需要花更多精力去了解个体之间的差异有多大，然后才能去更好判断个性化营养是否真的有必要。由于我们的食品体系已经供给了足够的食物，对一些营养素也进行了人工加强，在正常膳食情况下我们是否就已经满足了大量营养素的需求了呢？这是一个值得思考的问题。

Alice H. Lichtenstein

博士

Conducting large-scale studies. We can conduct well-controlled feeding interventional studies and it'll answer a certain question, but it will have relatively low generalizability. We can do lots of analytical work on those studies and generate lots of data but it's still not going to make it more generalizable. I think the most impactful studies we've had in the field of nutrition have been large-scale intervention studies. A lot of people are doing a lot of work, trying to figure out creative ways of conducting those in a cost-effective manner so that we can really have highly generalizable results.

进行大规模的研究。我们可以进行严格控制的饮食干预研究来回答一个特定的问题，可是它具有相对较低的普适性。虽然我们可以对这些研究做大量的数据分析，然而这个过程仍然不能使研究具有更大的普适性意义。我认为我们在营养学领域最具影响力的研究是“大规模”的干预研究。现在很多人都在做大量的工作，试图找出创造性的方法在控制好成本收益的情况下，做出具有更大普适性的研究结论。

Alice H. Lichtenstein

博士

To gain as broad knowledge base as possible. You don't know what you're going to be doing in 5 years, 10 years or 20 years from now. I wouldn't have anticipated I was doing what I'm doing. I think the broader your knowledge base, the more flexibility you'll have later on, even though it entails more work. It may not make you more productive in the short term but it may impact future tremendously.

尽可能地拓宽知识面，因为你不知道你将在5年、10年或20年后会做什么。我在年轻的时候不会预料到我现在正在做的事情。我认为一个人的知识面越广，那这个人以后事业的灵活性、可能性就越大。尽管这个过程会耗费额外的精力，也可能不会让你在短期内见到收益，但它可能会对未来产生巨大的影响。