October 2018 Issue
The Power of Plant-Based Diets — An Interview With Joan Sabaté
By Sharon Palmer, RDN
Vol. 20, No. 10, P. 20
TD talks study findings, the Blue Zones, and the pros of plant-based eating patterns with a leader in vegetarian nutrition and research.
Fresh off the success of the seventh International Congress on Vegetarian Nutrition (ICVN), held at the Loma Linda University School of Public Health in Loma Linda, California, in February 2018, I sat down with one of the leading plant-based diet and health researchers of our time: Joan Sabaté, MD, DrPH. Sabaté, a board-certified physician with his Doctor of Public Health in Nutrition from Loma Linda University, has served as chair of the department of nutrition there since 1998 and as chair of ICVN since 1997. He's also editor of the 2001 book Vegetarian Nutrition and the principal architect of the Vegetarian Food Guide Pyramid, redesigned in 2008.
ICVN, a premium international scientific conference with researchers and experts from around the world presenting on the latest advances in plant-based nutrition, takes place about every five years to capture the body of cutting-edge evidence in the field of vegetarian nutrition. This year, ICVN's theme was "Plant-Based Nutrition for Personal, Population, and Planetary Health," with speakers including Frank Hu, MD, PhD, from Harvard School of Public Health; Tim Key, PhD, from the University of Oxford in the United Kingdom; Tina Chiu, PhD, RD, from the Tzu Chi Medical Foundation in Taiwan; and Preet K. Dhillon, PhD, of the Public Health Foundation of India. Presentations included the following:
- epidemiological findings of four cohort studies from around the world investigating health outcomes of populations on vegetarian diets;
- the latest findings on maternal health for people eating plant-based diets;
- science on plants and their impact on the gut microbiome;
- evidence on reversing chronic diseases with plant-based diets;
- findings on the nutrition status of vegetarians;
- nutrition science on plant protein quality;
- research on plant-based diets' impact on the environment; and
- strategies for professionals to apply plant-based diets.
More than 750 people—including physicians, dietitians, and other health professionals—from 36 countries attended the conference. Look for the proceedings of ICVN to be published as a supplement to the journal Advances in Nutrition in the future.
What were the main findings from ICVN this year? The analyses of multiple large cohorts of people eating vegan and vegetarian diets from around the world—the United States, United Kingdom, Taiwan, and India—showed that, in comparison with nonvegetarian diets, plant-based diets are linked with higher nutrient intake, lower blood pressure, lower LDL cholesterol, lower BMI, lower fasting blood sugar, and lower risk of type 2 diabetes, cataracts, kidney stones, gout, and certain cancers.
In addition, plant-based diet patterns are linked with significantly lower greenhouse gas emissions compared with nonvegetarian diets. Another important finding presented at ICVN is that the quality of plant-based diets really does make a difference; a plant-based diet filled with whole plant foods results in greater benefits than a plant-based diet filled with refined, sugary foods.
The Adventist Health Studies
ICVN showcased the Adventist Health Studies (AHS), cohort studies that began in the 1950s. There's significant interest in studying this population due to its homogenous lifestyle choices (eg, avoidance of cigarettes and alcohol) and heterogeneous diet habits, which include a wide range of diets ranging from veganism to a typical Western diet.
The Adventist Mortality Study was conducted from 1958–1966, comparing causes of death between populations. AHS-1 took place in 1974–1988, exploring which components of the Adventist lifestyle helped protect against disease. AHS-2, which started in 2002 and is still ongoing, is one of the largest and most comprehensive studies of diet in the world, exploring cancer and risk of cancer and heart disease among African Americans, as well as other conditions and populations.
Sitting Down With Sabaté
I studied dietetics at Loma Linda University long before Sabaté helped lead the internationally renowned research on vegetarian nutrition through the AHS and the first ICVN was scheduled on campus. This was also before Dan Buettner, a National Geographic Fellow, identified Loma Linda as one of the world's five Blue Zones—locations with the largest number of centenarians—and the only Blue Zone in the United States.
Little did I know at the time that Loma Linda University would go on to become a leader in the field of plant-based food and nutrition and that I would end up speaking about how to apply plant-based diet strategies at ICVN in 2018. As a result, it was a true honor to sit down with Sabaté to learn more about the key takeaways related to plant-based diets and health—for people and the planet.
Today's Dietitian (TD): What led you to your work on studying the effects of diet—in particular, plant-based diets—on health?
Sabaté: The inspiration for my work came from my cultural and religious backgrounds, in addition to my findings as a postdoc working with the Adventist Health Studies. I was born and raised by the Mediterranean Sea, so I had always consumed what is known as the Mediterranean diet, which is now so fashionable. I grew up in a Seventh-day Adventist home where my mother integrated the concepts of a plant-based diet and a vegetarian diet. I grew up when this diet was not so fashionable.
In my postdoc experience, I was trying to relate the foods in the questionnaire from the AHS core study, and found that three foods were consistently related to cardiovascular disease: nuts were protective, whole grains were protective, and meat intake was detrimental for heart disease. These three pillars were the inspiration to study the effects of plant foods on health.
TD: What are some of the primary conclusions about diet and health that have resulted from the AHS?
Sabaté: The AHS is a cohort study on diet and health outcomes done on Adventists with a wider spectrum of food intake. The AHS was the first to report that tomatoes prevent prostate cancer; it was the first to report that whole grains prevent cardiovascular disease; it was the first to report that the frequency of nut consumption was linked to the prevention of CVD, and that, in general, a plant-based diet helps in life expectancy and increased longevity. The AHS also found that eating meat—particularly red meat—increased heart disease risk, particularly in males. Dairy and eggs were found to have a more moderate effect and were not as detrimental as many people were thinking.
TD: How do the results of AHS compare with similar cohort studies examining the impact of diet patterns, such as vegetarian-style diets?
Sabaté: I think there are two types of studies: those that are done with the general population and those that are nongeneral, such as the Nurses' Health Study (NHS) and the Physicians' Health Study (PHS). The NHS and PHS findings overwhelmingly reproduce what AHS originally presented. Eight years after AHS, NHS found that nuts prevent heart disease, meat increases risk of heart disease, and whole grains prevent colon cancer. The study was in concordance with the findings of AHS.
Of course, there are many other studies that further deepen these results. Other cohort studies, including the Oxford study in England, compared a cohort of vegetarians and nonvegetarians. There are even newer and much smaller cohort studies in Taiwan and India. The studies in Taiwan and India are relatively new, so the results are limited.
The Oxford study—a 20-year study—found that as far as CVD and longevity, there is a high degree of concordance with AHS findings, in terms of less heart attacks and heart disease among vegetarians. However, when it comes to cancer outcomes, there is some discordance.
In the Oxford study, vegetarians do not enjoy lower risk of colon and breast cancer. There is a degree of disagreement between these studies as far as cancer outcomes. It could be due to the fact that it's only one comparison, and that the findings were random with no explanation for them. Or it could be that there were too many similarities between the two diets.
In the US, Adventists who were vegetarian and the vegetarians in Oxford both did not consume meat, but the rest of the diet could have been different. As a matter of fact, there is some evidence that diets of vegetarian Adventists are richer in whole plant foods and have more whole grains as opposed to the diets of vegetarians in England, which have more processed foods. If that is the explanation for the differences in findings, it's in agreement with NHS, which showed that plant-based diets are healthier, particularly when considering processed foods. You can have a plant-based diet full of processed foods, but it's not as healthy as a plant-based diet with unprocessed foods, which focuses on eating unrefined products and cooking from scratch.
TD: Has this knowledge built itself into a consensus on the potential health benefits of plant-based diets?
Sabaté: As a member of the scientific community, I do research and follow the literature very closely. There is a clear consensus that plant-based diets prevent many chronic diseases. However, there is still this idea among many clinicians and dietitians, who may have studied nutrition many years ago and are not current with the literature, that animal products are essential for good nutrition.
But as far as an adult population living in an abundance of food like [in] most Western societies, the general consensus is that plant-based diets are the way to go.
TD: What can we say about the environmental benefits of plant-based diets, based on the current body of science?
Sabaté: Today's research helps form a consensus based on clear evidence that the foods we produce and consume are one of the main contributors to the use of natural resources and degradation of the environment. Among all foods, animal products, in particular meat and dairy products from ruminants like cows, are the ones that have the lion's share of responsibility for the degradation of the environment.
Eliminating or dramatically decreasing meat in the diet could be the single most important thing that a person can do to prevent the degradation of the environment. A decrease in meat is much more effective than changing your car from an SUV to a regular car, or a regular car to an electric car. The lifestyle behaviors that the general population could adopt, such as changing the diet, are powerful. What we do with diet is more powerful than anything else in our control.
TD: Being located in one of the Blue Zones, how has Loma Linda University School of Public Health become a leader in the plant-based movement?
Sabaté: Dan Buettner's research for National Geographic in 2005 marked Loma Linda as the only Blue Zone in the United States. It is a concept that encompasses the geographical areas where the greatest numbers of centenarians live. Buettner identified five in the world, including Japan, Greece, Italy, and so forth. Loma Linda was portrayed as a Blue Zone, but this was not the original intent for Loma Linda. I believe it's the lifestyle of the community, not the geographic location, that makes a difference in longevity.
Loma Linda has a specific lifestyle as a religious community that is linked with health. In fact, the Loma Linda School of Public Health has been conducting the AHS study for the last 50 years. We know that Adventist vegetarians as a community live long. It's one thing to have 1%, 2%, or 3% of the population live to 100 years, but the majority of the Adventist population has shifted to a longer life, with an average life expectancy of eight to 10 years more than the general population. In addition to diet, exercise, not smoking, keeping Sabbath as a day of rest once a week, and trust and hope in God are parts of the lifestyle that have been identified in this community.
TD: What are some of the future research topics on plant-based diets that need to be explored?
Sabaté: There are a few areas of interest. One is with AHS as we try to identify the health benefits of other plant foods. We started with nuts, and we are expanding by disentangling meats vs eggs and the risk of diabetes. We thought eggs would increase diabetes as meat does, but there may be advantages of eggs for subjects that don't consume either or for those that consume both. We are unscrambling this by looking at the effect of eggs in a feeding study.
We are also doing a clinical trial to study the effect of avocados on intra-abdominal fat. In addition, we are studying the effect of soy, especially the estrogenic effect in males. Lastly, we are looking at the effects of phtyoestrogens on health due to relevant questions on these foods.
TD: What is your advice regarding micronutrient supplementation for plant-based diets?
Sabaté: I think if people eat a plant-based diet with variety that is not filled with highly refined foods, there is no need for concern. Plant foods carry all of the minerals, and all of the vitamins, except for one. In fact, they contain the important compounds phytochemicals. Plant foods are much richer in all of these micronutrients, so there is no need to supplement, except for vitamin B12.
If somebody goes all the way with a plant-based diet and becomes a strict vegan, with no animal products in the diet, then vitamin B12 becomes important to take care of. If people eat a plant-based diet that occasionally includes meat, fish, yogurt, milk, cheese, and eggs, I don't think there is any concern for vitamin B12.
— Sharon Palmer, RDN, is a plant-based food and nutrition expert, author, and blogger located in Los Angeles. She's author of the books The Plant-Powered Diet and Plant-Powered for Life and also serves as the nutrition editor for Today's Dietitian.