Humanity's Future

I interview Dr. Gil Carvalho about nutrition—I ask him where we want to go and what policies can help us get there.

Image source here.

Gil Carvalho (MD, PhD) is a research scientist and science communicator. He’s published research in various fields—genetics, molecular biology, nutrition, aging, neuroscience. He started the “Nutrition Made Simple!” YouTube channel—which I highly recommend—in 2018.

I was honored and thrilled to be able to ask Dr. Carvalho about nutrition—see below my interview with him that I edited for flow and organized by topic. He and I both contributed hyperlinks.

Nutrition Science

1) What are nutrition science’s most striking points of consensus?

It’s essentially unanimous that the following are the pillars of a health-promoting dietary pattern: 

• (A) mostly unprocessed—or lightly processed—foods

• (B) plant-rich

• (C) low—or moderate—in added sugar, salt, and alcohol

Those are the pillars. And for a visual of this basic foundation, see the now-famous picture of the latest version of Canada’s Food Guide: 

That image tells you everything you need to know. 

2) What are nutrition science’s most striking points of uncertainty?

The details are less clear—how much and what type of processed food is it OK to include? What percentage of the diet should be plants? Is there a specific macronutrient composition that’s ideal? Does this ideal vary from person to person?

Individual variability is an area of particular uncertainty—we know that some people can get away with more than others can, but we have a limited understanding of the underlying mechanisms. 

There are immense challenges regarding appetite and obesity—we need practical solutions that we can successfully apply to a general population. We’ve recently seen some exciting pharmacological developments, but we have a long way to go. And when it comes to insulin resistance and diabetes, you can read extensive overviews of the field and you’ll find staggering complexity and lots of uncertainty. 

3) What’s the most exciting research in nutrition science? 

Some fascinating emerging fields include the microbiome; how food affects brain function and mood; lab-cultured meats, which have important nutritional and—especially—environmental promise; and food production’s environmental impact. 

The stakes are genuinely existential when it comes to research related to the environment—there’s no healthy diet on a wrecked planet.

There’s also exciting research on the topic of how artery walls retain lipoproteins—understanding this process might allow us to directly target this retention, protect the population at large against the number-one cause of death in the world, and particularly help individuals with familial hypercholesterolemia.

4) How would you respond to my impression that nutrition science is in the dark, that there’s no consensus on anything, and that one expert’s advice will conflict with another’s?

Professional scientific organizations—across countries, cultures, and medical fields—overwhelmingly agree on the fundamentals. 

It’s been that way for decades. The first edition of the Dietary Guidelines for Americans came out in 1980 and offered seven key recommendations—six remain unchanged and one has been honed. None have been invalidated.

The media sometimes contributes to the perception that “experts can’t agree”—science is an incremental process where new studies add nuance and detail to a vast amount of existing data, but old news doesn’t get clicks, so news pieces have to emphasize what appears “revolutionary”. You get lots of attention with exciting headlines—like “New Study Shows Everything You Thought You Knew About Nutrition Is Wrong!”—that often don’t reflect the science accurately. 

5) Shouldn’t we be excited if nutrition science is in its infancy, since that means that we can expect many enormous benefits as the field matures? 

We already know a lot. 

But many mysteries remain—nutritional understanding and technological innovation will likely make great advances when it comes to our health and protecting our environment. 

6) Imagine that a doctor from the year 3000 appeared and started to talk to you about medicine and nutrition—what studies might they show you that would make your jaw drop? 

Meeting someone from the year 3000 would be fantastic news, since it would mean humanity had survived!

I’d be interested to see what advances had occurred in precision medicine, which is the next frontier in public health. Many smokers never get cancer—we see that same variability with most risk factors. How can we identify the vulnerable—and focus prevention on them—while reassuring the less susceptible that they have more leeway?

I’d also be curious to see if they’d developed any artificial foods designed to optimize specific aspects of health—I imagine that would be possible with more knowledge and technology.

Diagnosis will advance enormously. It would be a boon to public health if biomarkers and imaging techniques got to the point where you could diagnose cancer when the first cancerous cell appeared or diagnose heart disease when atheromatous plaque first started to accumulate—early detection would facilitate prevention and early intervention.

Treatment will probably evolve concurrently. Highly specific therapies could target tumor cells, spare healthy ones, and—together with early detection—obviate the need for surgery, chemotherapy, and radiotherapy. 

Where We Want to Go 

1) Health-wise, where do we want humanity’s diet to be? And which key papers and studies support this view?

Optimal health will—for most people—result from eating a diet that’s based on the aforementioned three pillars. But there’s substantial room for personal preference as well as individual needs and sensitivities. 

The best diet is—ultimately—the one you can actually sustain. Good sustained habits produce weight loss and long-term benefits. 

It’s difficult to single out just a few studies, but here are some influential ones: 

• “A Clinical Trial of the Effects of Dietary Patterns on Blood Pressure” (17 April 1997) 

• “Mediterranean Diet, Traditional Risk Factors, and the Rate of Cardiovascular Complications After Myocardial Infarction” (16 February 1999) 

• “Food Groups and Risk of All-Cause Mortality: A Systematic Review and Meta-Analysis of Prospective Studies” (26 April 2017) 

• “Primary Prevention of Cardiovascular Disease With a Mediterranean Diet Supplemented With Extra-Virgin Olive Oil or Nuts” (21 June 2018)

• “Carbohydrate Quality and Human Health: A Series of Systematic Reviews and Meta-Analyses” (10 January 2019)

• “Long-Term Secondary Prevention of Cardiovascular Disease With a Mediterranean Diet and a Low-Fat Diet (CORDIOPREV): A Randomised Controlled Trial” (May 2022)

These studies will give you a sense of why there’s essential unanimity when it comes to those three pillars. 

2) Environment-wise, where do we want humanity’s diet to be? And which key papers and studies support this view?

Interestingly, most foods that are good for our body are also good for the planet! A very fortunate confluence, since we don’t have to choose between health and the environment. A 2019 study shows that foods associated with improved health outcomes—whole grains, fruits, vegetables, legumes, nuts, olive oil, and fish—tend to have lower environmental impacts than many of the alternatives.

Another important realization comes from a 2008 analysis, which reports that the type of food you eat matters more than whether it’s imported or locally produced. Beef has—as discussed in a 2017 study and also in a 2018 study—a disproportionate climate impact. And the startling emerging conclusion is that plant foods—lentils, fruit, and so on—shipped from across the globe can actually have a smaller environmental impact than locally raised beef.

3) In terms of animal rights, where do we want humanity’s diet to be? And which key papers and studies support this view?

My professional focus is nutrition science, so I’m not as familiar with the literature on this topic. 

But one surprising—and unfortunate—finding is that carbon efficiency tends to correlate inversely with animal welfare. A 2012 study finds that factory farms—which are absolutely horrific for the animals—can be less polluting than the ethically preferable option of grass-fed beef. 

It’s environmentally preferable to favor small animals—like poultry or fish—over cattle, but that requires killing a larger number of animals to obtain the same amount of food. There’s also another tradeoff, since the conditions involved in raising, transporting, and killing poultry and fish are even worse than those involved in raising cattle. 

The intuitive answer is to minimize animal products—that would be ethically preferable, although we’d have to weigh the indirect damage to animals from producing, processing, and transporting the substituted plant foods.

4) Suppose that we managed to implement our best science on what humanity’s diet should be—what changes would we see in terms of health?

Estimates indicate that lifestyle accounts for a large chunk of chronic disease burden in the West.

A healthy diet largely eliminates risk factors like BMI, high blood pressure, type 2 diabetes, and high cholesterol. So the potential is absolutely enormous when it comes to reducing chronic disease. 

Observational studies—like EPIC—indicate that we might cut the risk of chronic disease in half if we got everyone to implement a single major healthy behavior like quitting smoking, getting regular exercise, or adhering to a health-promoting diet.

The effect on society would be profound. So there are absolutely enormous potential gains. 

5) In terms of the environment?

I’m not trained in sustainability science and estimates vary widely. But as far as I can tell, there’s overwhelming agreement that dietary choices impact the climate in a decisive way—I’ve seen some startling numbers in the specialized literature. 

A 2017 analysis reports that replacing beef with beans “could achieve approximately 46 to 74% of the reductions needed to meet the 2020 GHG target for the US”—the analysis also reports that this replacement “would free up 42% of US cropland”. 

A 2018 Nature report concludes that we can’t sufficiently mitigate GHG emissions if we don’t implement substantial dietary changes. 

High-income nations bear the brunt of the responsibility, since we have—due to type and amount of food eaten and the scale of food waste—much more carbon-intensive dietary habits. A 2022 Nature study simulates what would happen if 54 high-income nations—representing only 17% of the global population—implemented some dietary shifts. The results show a huge reduction in emissions that “could potentially fulfill high-income nations’ future sum of carbon dioxide removal (CDR) obligations”. Keep in mind this study didn’t even look at drastic dietary changes—only at a prudent plant-rich diet that’s also predicted to greatly enhance health outcomes. 

As is often the case, the facts are clear but implementation is the hurdle. 

6) In terms of animal rights? 

My intuition is that technological innovation will have a big impact on animal rights. I expect that meat alternatives—for example, cultured meat—will gradually displace traditional meat as long as the alternatives have comparable taste and similar or lower price. This displacement will take decades and will proceed at vastly different paces in different parts of the world—Western beef consumption is projected to decline over the next few decades but global beef consumption is expected to increase.

The natural course is that we will—eventually—scale down factory farming. The sooner this happens, the better.

Policies

1) What are the best policies that could move the needle on humanity’s diet?

Education is key, albeit an extremely slow process. 

There’s a well-documented lack of proper nutrition training among health professionals. It’s essential to improve this aspect of medical education and make registered dieticians—generally underused—an integral part of medical teams. 

At the societal level, nutrition should be emphasized—and improved—throughout basic education. What we eat is one of the most important decisions we have to make.

Finally, financial incentives have demonstrated promise—research shows that subsidies can be effective and that sugar taxes can successfully lower consumption. 

2) How can the various food lobbies’ influence be overcome?

This is a great question that goes far beyond just food—industry lobbies strongly influence the government in many areas, often in a way that counters popular interests. 

The USDA and the HHS issue the Dietary Guidelines for Americans, but one of the USDA’s institutional missions is to promote consumption of agricultural products, which has led to a common grievance that there’s a conflict of interest. I’m in favor of an independent scientific organization—like the National Academy of Medicine—issuing dietary recommendations for the population.

3) It looks like Canada has—when it comes to developing a national food guide—overcome the food lobbies. How did Canada achieve this? And how can other countries replicate Canada’s success on this front? 

Health Canada set out to develop—with scientists’ input and without industry influence—a new evidence-based food guide. 

The result was an excellent set of recommendations that nutrition professionals have universally praised—it’s proof of principle that it can be done.

4) Regarding food, what are the best books to read on corporate interference?

Marion Nestle’s books are the best I’ve encountered. 

Her 2002 book Food Politics is a great introduction to the topic.

Talking to People About Diet

1) What are some instances where popular documentaries distort nutrition science?

Popular documentaries can be fun to watch. But they’re not ideal sources of information. 

They usually contain at least some degree of distortion. They tend to shoehorn findings to fit a specific—often predetermined—narrative. 

It’s a movie at the end of the day—infotainment. Ask yourself if the story reflects the totality of what we know scientifically. 

2) What’s a good example of a popular documentary distorting nutrition science in an egregious way?

We made a video fact-checking some of the claims in Seaspiracy. It’s a pretty good movie—despite some inaccuracies—until you get to the last segment where they suggest it’s unhealthy to eat fish. The scientific evidence mainly shows health benefits of including some low-mercury fatty fish in your diet—the movie completely misrepresents the evidence on this particular front.

I avoid fish myself, mainly for environmental reasons. But distorting the science is a disservice to the viewer. It’s also counterproductive—credibility is tarnished when people find out about the inaccuracies. 

It’s critical to give people the facts, let them make their own decisions, and not infantilize the public.

3) What does research show is the best way to talk to people about diet? There are different values—health, the environment, animal rights—that one could prioritize. 

It really depends on the individual. 

Some people are focused on health, others on the environment, and others on animal rights—fortunately, there are communicators with different areas of expertise who can cater to different interests. 

Our channel focuses primarily on health and medicine, with some content on environmental science.

4) Should people read popular nutrition books?

It’s fine to read them.

But take them with a big grain of salt—popular books aren’t peer-reviewed. Some have scholarly substance, others are essentially fiction. Commercial success tends—unfortunately—to correlate inversely with scientific understanding. 

Be particularly skeptical of wild claims.

Sample different authors—try to get a broader view. It’s tempting to pick content that reinforces our prior beliefs. 

Red Pen Reviews is a great—and completely free!—resource that reviews popular nutrition books with a lot of scientific rigor.