What science says about the best way to eat (and what we’re still figuring out)

Eggs are good for you. Eggs are bad for you. Avoid red meat. Enjoy red meat in moderation. Butter is out. Butter is back. If your head is spinning, you’re not alone. According to a recent International Food Information Council Foundation survey, 80 percent of people feel confused about nutrition. Of course, headlines are partly to blame, but disinformation on social networks — along with food marketing — makes matters worse.

Yet despite the seemingly always changing nutrition landscape and turnabouts in opinion — and setting aside tribalistic views — there’s actually a lot of agreement in the nutrition world. In other words, these headline shifts are actually at odds with what we know. Here’s a look at where there is consensus, along with a look at some areas where even the scientists are still a bit unclear.

What We Agree On

Emphasize plant foods

Research consistently shows that when you eat mostly plant foods, markers of health improve. Benefits include lower blood pressure, triglyceride levels, glucose and waist circumference, which can translate to a lower risk of a number of different diseases, including heart disease and diabetes.

An interesting, recent study looked at different patterns of plant-based eating, from a strict vegan diet to a more flexible semi-vegetarian approach to a non-vegetarian diet, examining how each dietary pattern impacts different predictors of health. What was notable about this study is it investigated a spectrum of plant-based eating styles. It turns out, a strict vegan diet produced the highest levels of healthy biomarkers and the lowest levels of unhealthy markers. Vegetarians who include eggs, dairy and/or fish scored next best. The non-vegetarian group had the least favorable health markers in their blood, urine and tissue samples.

Plant-based eating isn’t a new concept. It’s been studied for decades and research repeatedly shows that a plant-focused plan can help offset a lot of the health challenges that develop over time. No matter what type of dietary pattern you follow, you should be eating mostly plant-based foots. That means 75 percent of your plate should include some mix of veggies, fruits, nuts, seeds, pulse and whole grains.

Reduce red and processed meats

Though headlines this fall claimed otherwise, the majority of scientific evidence is on the side of limiting or avoiding these foods. In fact, the study from which these headlines arose was massively criticized and disputed. If you like red meat, but you also want to reduce your chances of dying prematurely from any number of causes, including heart disease and cancer, consider how you might cut back. Maybe that means eating a smaller portion of red meat on the occasions you’re enjoying it, or maybe it means having it a little less often. Also consider what else you’re eating alongside your steak dinner or at other eating occasions. A little red meat can be fine if your diet is rich in plant foods (see above).

The case against processed meat is a little more concerning. Earlier this year, Frank B. Hu, MD, Professor and Chair, Department of Nutrition, Harvard T.H. Chan School of Public Health, told me, “The current evidence suggests the higher intake of processed meat, the higher the risk of chronic diseases and mortality.” When pressed on what amount might be safe, he explained that we don’t have evidence to suggest a safe amount, but that eating a small amount of processed meat on occasion (which he defined as once or twice a month) is unlikely to have a considerable impact on your health. If you’re currently eating above this amount, it makes good health sense to cut back.

Focus on healthy fats and carbs

In the fat vs. carbs war, healthy wins. In other words, you can eat a low-fat, high-carb diet healthfully just as you can eat a high-fat, low-carb diet healthfully. The main thing is choosing your fat or carb options wisely. We’re crystal clear on the fact that carbs from foods like veggies, starchy veggies (such as potatoes), fruits and pulses, all of which supply antioxidants, vitamins, minerals and fiber, are quite different from overly processed carbs, which supply few, if any, whole food nutrition.

There is also considerable agreement that fat is not the enemy and that fats from plant and fish sources provide anti-inflammatory health benefits. Inflammation within the body may not cause obvious symptoms, but when it persists, it’s thought to be involved in a number of disease processes, from mood disorders like depression, to heart disease, diabetes and Alzheimer’s disease. Though butter and other saturated fats may not be as unfavorable as we once thought, anti-inflammatory fats — when eaten along with other foods that lower the inflammatory process — may help you live and age more healthfully. In fact, even if you’re following a high-fat keto diet, health experts recommend focusing on these fats over others.

Eat mostly whole or minimally processed foods

I struggle to think of any dietary advice that has more unanimous agreement than to reduce your intake of hyper-processed foods and to favor whole or minimally processed foods instead. We’ve discovered that heavily processed foods, which include processed meats, refined grains and many snacks and sweets, drive the inflammatory process that promotes disease, and diets high in heavily processed foods are associated with higher body weights and poorer health.

For the most part, choose whole or minimally processed foods whenever you can. That means looking at ingredient lists and trying to make healthier swaps for foods that are high in sodium, sugar, artificial sweeteners, colors and preservatives, which often signal that a product is heavily processed. This doesn’t mean giving up convenience, though. There’s a wide range of minimally processed foods that make meal prep saner and get the green light from nutritionists.

You do you: A healthy diet doesn’t look the same for everyone

Any one person can benefit from any number of eating patterns if focused on the above factors. Eating is a highly personal experience and it involves more than just fueling your body or sitting down to nutrients on a plate. Food can be nostalgic, part of social and religious events, and it can elicit an emotional response, providing a sense of comfort, stress reduction or joy. A meal is hardly ever just one thing and understanding all of the things it is to you, along with your personal non-negotiables (what you won’t give up), can help guide you toward a dietary approach that you can live with.

Your neighbor might be successful on a keto plan and your co-worker may love being a pescatarian, but if you’re a kosher vegetarian, these plans pose too many challenges. This may be an extreme example, but it’s meant to illustrate how important it is to understand your unique needs and then identify an eating pattern that suits you best. It’s now widely recognized that different eating patterns can be appropriate for different situations, but that’s only if you can stick with the advice. There are people who thrive on an intermittent fasting protocol while others can’t put up with the hunger or limitations of restricting eating to certain time windows each day. Nourishing your body is a commitment — not a passing fling — so determine what type of eating pattern sounds most doable to you and then try to adhere to it in the healthiest way possible. That means something different to everyone, so just do you.

Where We’ve Missed the Mark

Nutrition isn’t a perfect science — in fact, far from it — and we don’t have everything sorted out. Here’s where we’re not as buttoned up.

Focusing on individual nutrients

Many of our health recommendations boil down to reducing certain nutrients and emphasizing others but you don’t eat a nutrient — say fiber — in isolation. Health recommendations based on these reductionist principles can be very misleading. Sticking with the fiber example, there’s a tremendous difference between a fiber-rich quinoa and vegetable nourish bowl and a fiber-enhanced powdered supplement drink taken with a fast-food meal. Both meals might provide the same amount of an individual nutrient (fiber), but other than that, these two meals aren’t comparable.

In 2015, our Dietary Guidelines started talking about eating patterns, but it still called out individual nutrients, including saturated fat and sodium. And the following example highlights why this approach needs to be reassessed.

Under the suggestion to limit saturated fat, which has been linked to an increased risk of heart disease, you might cut full-fat milk, yogurt and cheese (all notoriously high in saturated fat) from your diet. But studies have shown that the saturated fats from these foods don’t deserve the bad rap.

A recent, large meta-analysis involving 29 studies and more than 900,000 participants found that neither total dairy consumption nor milk consumption was linked with an increased risk of death and more notably, death from heart disease. To the contrary, in fact. Cheese, which is especially high in saturated fat (and also high in sodium), was associated with a slightly lower risk of stroke and coronary artery disease. An earlier study involving more than 5,000 participants reached similar conclusions — that high-fat dairy foods aren’t as risky as we once thought.

There are many theories about why the saturated fats in dairy foods don’t seem to promote cardiovascular diseases, but it’s a solid example of why we can’t reduce our dietary advice to single nutrients.

Plus, the advice to remove something from your diet doesn’t clearly address what to replace it with, which is a big deal. Looking back, when we cut fat from our diet, we replaced it with high-sugar carbs (Snackwells, anyone?), which set off a cascade of health problems. In this case, replacing a bit of cheese with potato chips isn’t the same as replacing it with olives.

Instead of worrying about each individual nutrient, you can begin to make healthier shifts to your diet by following the advice described above (what we’ve gotten right), which are broader, health promoting eating patterns.

Weight loss

While Harvard researchers now predict that close to 50 percent of the population will be obese by 2030 and 25 percent will have severe obesity, we haven’t figured out how to tailor dietary advice to help people successfully lose weight for the long term. In fact, one study by Stanford University researchers attempted to determine whether people with certain genetic traits would lose weight better with either a low-fat or low-carb diet. Results were all over the map. After a year, people had lost an average of 13 pounds, but weight loss varied widely (some lost much more and others gained weight) and the study offered no clues as to which genotype might be predictive of weight loss success with either menu.

What this tells us is that neither eating pattern is superior, something we’ve seen repeatedly when pitting one diet against another. So again, do you. In this case, the study also underscores much of what I said earlier. Because eaters in both arms of the study were offered similar advice — to include more veggies, emphasize whole foods and to limit junk food — it validates that you can lose weight by following these three pillars of healthy eating.

Personalized nutrition

Marketing is way ahead of science here and while you may be able to send off a stool sample in order to reveal information about your microbiome, we don’t yet know how to reconfigure your microbiome or influence your weight based on this, your genetics or your metabolism.

In terms of your microbiome, here’s what we do know. You can alter your microbiome in response to altering your diet, but other factors, including age, sex, ethnicity, environmental factors, lifestyle factors and medications can also influence the microbiome, making it difficult to create a personalized nutrition plan. Plus, even among food patterns we know to cause favorable shifts in the microbiome, like eating a fiber-rich diet that includes diverse food sources, there are individual responses that we can’t yet predict and address. According to a recent review study, a “tailored nutritional approach is in its infancy, and more feasible, sustainable personalized nutritional strategies need to be developed to optimize one’s gut microbiome and improve host responsiveness.” A new survey among physicians finds that 53 percent of doctors think this technology needs five or ten more years before it’s standard practice.

If you’re curious about your genetics or your microbiome and you want to get tested, do so knowing that there’s a lot we still don’t know about how to personalize an eating approach based on those results.


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