Personal and Planetary Health—The Connection With Dietary Choices

Globally, humanity is confronting the chronic disease burden of poor nutrition while also experiencing the loss of life and property because of climate change. Now is the time to focus on the health benefits of dietary changes.

Increasing consumption of animal protein is driving animal agriculture growth. The world now produces more than 3 times the meat and more than double the milk as it did 50 years ago.¹ This has well-established negative effects on the environment, including the destruction of native ecosystems to support livestock grazing and increased cultivation of animal feedstocks. Livestock and its supply chain also contribute to greenhouse gas emissions, such as carbon dioxide, methane, and nitrous oxide.² Livestock farming accounts for 50% of methane and 60% of nitrous oxide emissions, which respectively have 25 and 298 times the global warming potential of carbon dioxide on a mass basis.³ Additionally, most nitrogen pollution in waste-water is due to animal-based protein sources and inefficient agricultural practices,⁴ which lead to acid rain and toxic algal blooms that cause dead zones of aquatic life.

Humanity’s window for climate action is closing rapidly. In 2016, the Paris Agreement, a legally binding international treaty on climate change, set a goal of limiting the increase in global temperatures to well below 2 °C (preferably 1.5 °C) of preindustrial levels. Furthermore, the United Nations Climate Change Conference recognized climate change as a global emergency, and the American Medical Association (AMA) announced climate change a public health crisis.

According to the EAT-Lancet Commission,⁵ transformation to healthful sustainable diets by 2050 will require a greater than 50% reduction in global consumption of red meat and greater than 100% increase in consumption of nuts, fruits, vegetables, and legumes. This reduction in animal agriculture’s significant contribution to greenhouse gas emissions is an important step to meet the goals of limiting global temperature increases. Even if fossil fuel emissions were eliminated, emissions from the global food system alone would make it impossible to meet the targets of the Paris Agreement.⁵ Accordingly, the Intergovernmental Panel on Climate Change recommends major changes in food consumption (and production) toward energy-balanced sustainable plant-based diets to meet these goals.^5,6

Physicians have historically focused on patient health and relegated planetary health to environmentalists and lawmakers. However, dietary choices are the largest driver of chronic diseases.^5,7 National surveys indicate less than 5% of the US population meets dietary fiber recommendations due to inadequate plant-based food intake.⁸ Plant-based diets are also associated with reduced incidence of chronic diseases such as obesity, cardiovascular disease, diabetes, chronic kidney disease, and cancer in multiple studies.⁷ They have been associated with lower risk and severity of COVID-19 as well.⁹ Historical evidence also suggests that continued industrial animal agriculture practices could facilitate the emergence of future pandemics.

As physicians, providing dietary guidance for overall health may be a worthy consideration. This impact is no longer limited to the personal health of their patients—but rather, broadly impacts the health of the planet (and everyone on it). Increasing consumption of plant-based foods would augment personal health while simultaneously lessening worldwide food scarcity, pollution, and climate change, thereby improving planetary health as an indirect consequence.⁵ By treating individual trees (ie, patients), physicians may also positively impact the metaphorical forest (ie, planet). Indeed, some patients are encouraged by the knowledge that a plant-based diet reduces the adverse effects of climate change and antibiotic resistance (Figure).¹⁰

Figure.

Personal and Planetary Health and Food Choices

Carbon dioxide equivalents (CO₂eq) measure an entity’s global-warming potential based on environmental gases. Plant-based proteins such as legumes and soybeans represent less than 1 CO₂eq per 28-g dry serving whereas on average an equivalent amount of animal-based proteins such as ruminant meat (beef) are 1200 CO₂eq and pork is 200 CO₂eq.⁵ As a result, global greenhouse gas emissions from animal-based foods are twice those of plant-based foods and animal-based food production (including livestock feed) contributes 57% of food production-related greenhouse gas emissions (vs only 29% contributed from plant-based foods).¹¹ Accordingly, transitioning to more plant-based diets that align with standard dietary guidelines could reduce global mortality by 6% to 10% and food-related greenhouse gas emissions by 29% to 70% in 2050. The economic benefits of improving diets are estimated to be up to 13% of global gross domestic product in 2050.⁶

National guidelines could also incorporate the environmental impact of food choices into their recommendations.⁵ A recent study evaluated national dietary guidelines from 83 countries and found that only 45% of these guidelines (representing 17% of the world’s population) mentioned environmental sustainability. The principles most addressed in these guidelines were respecting local culture, followed by increasing plant-based and reducing animal-based foods consumption.¹² New York City (NYC) provides plant-powered meals for school lunches every Friday and has instituted “Meatless Mondays” in hospitals, both serving as effective awareness programs that have encouraged individuals to reduce meat consumption. Furthermore, NYC Health + Hospitals, which operates the city’s public hospitals, appointed a director of nutrition and lifestyle medicine and now serves culturally diverse plant-based meals as the primary option for inpatients at its 11 hospitals. Incorporating plant-based nutrition into medical education can also be a part of the solution. As an example, NYC and the American College of Lifestyle Medicine announced a partnership to provide every NYC health care practitioner with free nutrition training. New York University Grossman School of Medicine has added a culinary medicine elective course, which could be adopted by medical schools. Additionally, medical organizations such as the World Health Organization, AMA, and American College of Physicians can provide sustainable dietary guidance.

A dopting evidence-based, energy-balanced, low-meat dietary patterns may lead to large reductions in premature mortality (reduction of 19%; 95% CI, 18%-20% for the flexitarian diet to 22%; 95% CI, 18%-24% for the vegan diet).⁶ It may also markedly reduce environmental impacts globally (reducing greenhouse gas emissions by 54%-87%).⁶ This evidence makes a compelling case for increased public and private spending on programs aimed at more healthful and environmentally sustainable diets.

Medical professionals have the unique opportunity to positively influence patients, family members, the wider population, and the planet. Stakeholders of animal agriculture and the food or pharmaceutical industries are not likely to recommend healthful dietary changes because their incentives may not align. Currently, messaging is confusing with multiple opposing dietary patterns being recommended: low-carbohydrate, ketogenic, paleolithic vs plant-based patterns such as vegan, vegetarian, flexitarian, and Mediterranean diets. Ultimately, the greatest benefit lies in incremental changes toward increasing unprocessed plant-based food consumption for personal health reasons with the simultaneous benefits to planetary health. The medical community cannot miss the forest for the trees and owes this to patients, future generations, and the planet to counsel, educate, and empower. Physicians can play an important role as advocates for such change.