Why I love the 2015 Dietary Guidelines Advisory Committee

For those of you who don’t know, every five years the U.S. government produces a document called the Dietary Guidelines for Americans, which is created through a collaboration between the US Department of Agriculture the Department of Health and Human Services. These guidelines are the basis for nutrition recommendations made to consumers, like MyPyramid and the current MyPlate system, as well as the basis for food and nutrition policy, like what is served for lunch in public schools. The last Dietary Guidelines were published in 2010, and the 2015 batch is due to be published late this year. Though the Guidelines are actually written by members of the two aforementioned agencies, they are informed by the research of an appointed panel of scientific experts, the Dietary Guidelines Advisory Committee. The Committee is supposed to do a rigorous review of the current research in nutrition and write a report on their findings. The Guidelines themselves usually closely mirror the Committee’s recommendations.

I have to say that I take issue with some of the current Dietary Guidelines, and more so with what they do not say than what they say. And this makes sense after reading Marion Nestle’s Food Politics, which has made it clear to me how industry-biased the Guidelines have typically been, namely in favor of the meat, dairy, and sugar industries. I have been concerned that this year’s Guidelines would follow the same trend, but the DGAC’s report has me singing a happier tune! Here are some of their recommendations:

  • A healthier diet is higher in plant-based foods, seafood, and low or non-fat dairy, lower in red and processed meat, and low in sugar-sweetened foods and drinks and refined grains
  • A diet higher in plant-based foods and lower in animal based foods is more health promoting and associated with less environmental impact than the typical U.S. diet
  • Continue to replace saturated fats (from animal products) with unsaturated fats (from plants and fish)
  • Reducing intake of added sugars below 10% of caloric intake will reduce one’s risk of chronic disease
  • Make food labels easier to understand
  • Soda taxes are definitely worth trying
  • Change SNAP (food stamp) policies to promote consumption of healthier foods

YES, YES, AND EVEN MORE YES!! I’m trying not to get too excited, because the beef and sugar industries are already loading their weapons to fight back. I hope their influence on Congress doesn’t prevent these recommendations from becoming policy. But whether or not my wishes come to fruition, it is clear from these controversial and courageous recommendations that the tide is beginning to turn–public health might be starting to outweigh corporate interests a teensy little bit, and that is great cause to celebrate.

Are there “good” or “bad” foods?

A controversial topic among nutrition professionals is whether, for public health purposes, some foods should be labeled “good” or “bad,” or “better” or “worse” for you. Foods that might be labeled bad are soda, pizza, donuts, etc. People who argue that no foods are good or bad say that any food, in moderation, can be part of a healthy diet.

That may very well be true, but that doesn’t mean we should encourage people to consume more soft drinks and fried potatoes when they won’t do so in moderation. Highly refined food products that are high in fat, salt, and sugar by their very nature discourage moderation. I’m no saint in this regard–those of you who frequent my blog know that I binge on indulgent food from time to time; however, I see these occasions as exceptions to my healthy diet, not part of it.

I might add that the people who say that any food can be part of a healthy diet are working for the industry either directly or indirectly. Industry representatives are known for saying that as long as you balance calories you can eat anything. (Read this post of mine to remind you why that’s false.) Those who indirectly represent the industry are certain government officials and agencies and associations of health professionals (such as the Academy of Nutrition and Dietetics) whose activities are effectively and often explicitly sponsored by major food companies. Of course Coca-Cola is going to say there are no good or bad foods, and if the organization of nutritionists wants to continue to be sponsored by Coca-Cola, they are going to say that too.

Here’s my view on this–public health professionals should absolutely encourage consumption of certain foods (whole grains, fresh fruits and vegetables) and discourage consumption of others (soft drinks, fast food pizza, most highly processed snack foods/desserts). The jury is obviously still out on certain foods, but I’d put money on soda being bad for you. I’m not saying you never drink a soda without completely risking your health (although I personally feel that there are other sweets that are a lot more satisfying that are made of real food), but there is no reason to shove soda ads down children’s throats when statistics show that kids today already drink way more soda than is acceptably risky.

Eating a bad food doesn’t make you bad; I’m not trying to encourage social stigma against people who eat unhealthy foods, I’m just trying to shatter this illusion that the food industry is trying to create. We as a country, and increasingly, as a planet, have a problem: we’re eating too much of the wrong foods and too little of the right ones. The people responsible for telling us how to eat should not have their hands tied about this!

Maybe possibly understanding science a little bit

Determining validity of scientific evidence has come up in TWO of my courses in the last week, and there’s been a lot of attention on this measles outbreak because people are ignoring the “science” and refusing to have their children vaccinated. I can imagine that a lot of my readers who aren’t versed in research methods don’t realize that any time the media presents a single new ground-breaking study about our health or happiness or environment, it should be taken with a grain of salt.

Just to be clear, this is quite relevant to my areas of interest, as all nutrition and health advice given by the government and health practitioners is supposed to be based on sound scientific evidence, according to established scientific methods.

There are a lot of directions I could go with this, but I think one of the most important lessons for the scientifically illiterate is correlation vs. causation. A very popular research method in public health and many other disciplines is an observational survey. This means that the researchers don’t control or manipulate any variables, as opposed to in an experimental study, where researchers would manipulate one or more variables. For example, some researcher decades ago said “Hey, maybe this cigarette smoking thing is related to lung cancer–let’s see if we can recruit a group of people, some with and some without lung cancer, and see if and how much they smoke.” I’m guessing that that researcher found that the people who had lung cancer smoked a lot more than the people who didn’t, on average. That is what we call a correlation: smoking in this case was positively correlated with having lung cancer. Even though now we are quite certain with very little doubt that smoking causes lung cancer, such an observational study can’t infer causation, because there are too many of what we call confounding factors.

A confounding factor would be something else that’s correlated with both smoking and lung cancer, and as a result you can’t distinguish which caused which. For instance, one of the studies brought up in my classes showed that women who took supplemental estrogen around the time of menopause had fewer heart attacks than those women who didn’t take estrogen. When this result got out to the public, post-menopausal women everywhere started taking estrogen. Then researchers did a controlled experiment, where they randomly assigned some women to take an estrogen tablet regularly and some to take a placebo (something that resembles the treatment but has no active ingredients; in theory, it should have no effect). That study found that the women taking the estrogen actually had more heart attacks than the women who took the placebo. The only way to reconcile this finding with the original observational finding is to acknowledge one or more confounding factors. In this case, experts have suggested that women who voluntarily took estrogen were probably more health conscious than those who didn’t, and more likely to take care of themselves in other ways like diet, exercise, and following their doctors’ instructions. This fundamental difference between the women who took estrogen and those who didn’t would be said to have confounded the results of the study.

In the case of nutritional science, theories based on observational studies are more complex, more confusing, and can be more misleading. For example, survey after survey has shown that people who consume more foods containing Vitamin A have less cancer than those who consume less Vitamin-A containing foods. In other words, Vitamin A consumption is negatively correlated with cancer incidence. Consequently, a lot of people take Vitamin A supplements. However, as far as I’m aware no study has been able to show that people who are randomly assigned to take Vitamin A supplements have any better health outcomes than those randomly assigned to a placebo. Therefore, we cannot say with any confidence that taking Vitamin A supplements alone will reduce your risk of cancer.

Another huge problem is that the research that tends to get the most public attention is that that shows novel findings, on which there is not a broad academic consensus as to its validity. So when one study observes that people who have gluten-free diets are thinner than people who consume gluten, someone might start cutting out gluten when there are so many other explanations for this finding that haven’t been ruled out yet by other studies.

So how do we prove (or rather infer or confidently conclude, as nothing can really be proven) causation, especially when it comes to food and health? To me, there are three important criteria. One is amount of evidence. I base my plant-based diet health claims mostly on this one. It would be almost impossible to test in a controlled, experimental way whether increasing the proportion of your diet that comes from whole, plant-based foods (as opposed to heavily processed foods and animal products) universally improves human health outcomes. However, the fact that researchers have shown in countless studies that among and between practically every population, that people who eat relatively more whole grains, fruits, and vegetables, and relatively less highly processed food and meat have better health outcomes is enough for me to be very confident in my current dietary pattern.

The second criterion is scientific plausibility. There should be an explanation, a pathway, something that can tell you why variable A is causing variable B. For example, smoking very plausibly releases carcinogens into one’s lungs that facilitate the development of cancer. Vitamin A (when in food, not supplements) may prevent cancer by acting as an anti-oxidant. There is not, I would argue, a plausible scientific explanation for why ice cream consumption is correlated with murder, or why living in a poor country is associated with larger penis size (both true correlations).

The third criterion, which I alluded to above, is experimental evidence. In an ideal experiment according to accepted scientific methods, you assemble a large sample of subjects, you assign each of them randomly to one of two or more conditions (e.g. Vitamin A supplement vs. placebo), and you try to control for any other factors that might affect the results. Like you’d want to make sure that everyone took their vitamin every day throughout the course of the study. Or if you were trying to study the benefits of eating breakfast, you’d want to control for the time at which breakfast is eaten and possibly the size and composition of the meal, as well as the size and composition of other meals throughout the day.

So if you don’t eat breakfast but are perfectly healthy, I wouldn’t really worry about the next scientific study that implies that you must eat breakfast to be healthy. There is plenty of evidence, strong and weak, on both sides of the debate. Same goes for eating dairy and gluten and soy and low-carb diets.

Ah, controversy. Anyway, that’s my spiel on science. And I could have gone on for longer. In summary, I think that we can get pretty close to the truth in a lot of cases. But don’t base the “truth” on any one study, especially any one observational study.

Thoughts?

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