Small dietary changes can improve human and environmental health

• Researchers have created a “traffic-light system” to organize foods according to their health and environmental impact.
• Their results suggest that small, targeted dietary substitutions offer significant health and environmental benefits.
• The researchers hope their new approach will empower individuals to make dietary changes that lead to healthier and more sustainable lifestyles.

Dietary choices affect both the environment and human health.

Consuming too many unhealthy foods and too few healthy foods are leading causes of health burden in the United States. One study found that in 2017, dietary factors contributed to 11 million deaths and 255 million disability-adjusted life years globally.

What we eat also impacts the environment by influencing food production, which affects land use and greenhouse gas emissions.

Research has suggested that food systems have environmental limitations. One study found that, under current conditions, the planet’s food system can only provide 43% of the world’s population, or 3.4 billion people, with a balanced diet.

Another study found that if we do not adopt technological changes and prevention strategies, our food system will exceed planetary boundaries safe for humanity by 2050.

Simultaneously quantifying the health and environmental risk factors of different foods could help policymakers, food producers, and consumers make dietary choices that benefit both human health and the environment.

In a recent study, researchers from the University of Michigan and Victor L Fulgoni from Nutrition Impact, LLC, created a scale that combines the environmental impact of foods alongside their health effects to help consumers improve their dietary health while protecting the environment.

Among their findings, they discovered that just 10% of the average calorie intake is responsible for over a third of the average dietary footprint. By substituting this and the most harmful dietary items, people could benefit their health and the environment.

“The population know some of the general tendencies, [such as] carrots are better than red meat for both health and the environment,” Olivier Jolliet, Ph.D., senior author of the paper and professor of environmental health sciences at University of Michigan’s School of Public Health, told Medical News Today, “Putting numbers and quantifying these differences is important and informative in two directions.”

“First: numbers have the power to [make] future effects […] more realistic and bring them to our present consciousness, i.e., ‘Oh 36 minutes lost per hot dog, this is substantial… like two cigarettes, do I really want this?”, he added.

“Second: these results help identify what really matters and differentiate […] between the foods we need to avoid like beef and processed meat, [and] food like dairy or poultry products, that are perhaps not ideal but have [a] 4 times [the] lower carbon footprint and are close to neutral, or even slightly beneficial for health,” he concluded.

The new research appears in Nature Food.

Data analysis 

The researchers identified 5,853 foods U.S. adults consumed from the What We Eat in America 2011–2016 database. They then used the Health Nutritional Index (HENI) to calculate how healthy each food was.

HENI quantifies the healthiness of food by indicating minutes of healthy life gained or lost by consumption. The model calculates minutes of lost or gained life from correlations between certain foods and negative health outcomes.

“Some of the dietary risks we considered in HENI are mediated by other lifestyle lists, and we did take that into consideration,” first author Dr. Katerina Stylianou, who did the research as a postdoctoral fellow in the Department of Environmental Health Sciences at the University of Michigan’s School of Public Health, told MNT.

“For example, the risk of polyunsaturated fatty acids and trans-fatty acids is measured by[daily calorie intake as a percentage], so we considered physical activity as an adjusting factor for the dietary risk factor. For sugar-sweetened beverages, the risk is mediated via [body mass index]. Similarly, the effect of sodium on health is stratified by race and hypertension status,” she added.

The researchers split the foods into 48 different categories and selected the most popular among them that were closest to each group’s median HENI scores for further analysis. They also considered seven additional foods representing different dishes.

Altogether, the researchers selected 167 foods for further analysis, roughly equal to 27% of the average American’s daily caloric intake.

They then used IMPACT World+, a method to assess the life cycle impact of foods, alongside assessments on water use and human health damages, to calculate each food’s environmental footprint.

Traffic light system 

As correlations between nutritional and environmental impacts were generally weak, the researchers organized the foods into a traffic light system according to their effect on either factor.

Green indicates foods that are both nutritionally and environmentally beneficial, which included:

• nuts
• fruits
• some seafood
• whole grains
• vegetables
• legumes

Amber indicates either slightly nutritionally or environmentally detrimental foods, such as:

• most poultry
• dairy, including milk and yogurt
• cooked grains
• egg-based foods
• cooked grains
• vegetables from greenhouses

Red indicates foods that have either significant adverse environmental or nutritional impacts, such as:

• processed meat
• beef
• pork
• lamb
• sugar-sweetened beverages
• cheese-based foods
• some salmon dishes

The researchers found that plant-based foods generally outperform animal products environmentally and health-wise. However, factors, such as water use, might necessitate tradeoffs between healthy foods and those that do not damage the environment.

The researchers note their traffic light system derives from statistical risks on life expectancy according to the average diet, and therefore, by itself, may not reflect individual dietary needs.

“The relative tendencies are likely to be similar across individuals and point at the right decisions,” said Jolliet, ‘But we, of course, cannot predict what will happen for a single individual, considering that these increases in life expectancy are statistical risks that are valid for a large number of persons.”

Personalized diet plans

In the future, the researchers are considering using their results to create personalized diet plans, both according to personal preferences and budget, as well as disease risk or underlying health conditions.

“We are considering creating a series of optimal food baskets [or] diets that […] let individuals choose […] their own personalized diet according to their taste, preferences, budget,” said Jolliet. “This is the beauty — that there is not one healthy and sustainable diet, but [there are] still a lot of choices, preferences, and freedom. For this, we would be highly interested to partner with […] food distributors to inform their customers, possibly via a customized app.”

“We could also further target foods related to specific diseases [for at-risk individuals], or on the contrary, disregard [some factors based on individual needs such as] sodium if [high blood pressure] is not an issue for a given person,” he added.

The researchers conclude that small, targeted dietary substitutions offer significant health and environmental benefits.

However, one limitation to their research is that, although HENI does include risk-outcome associations, it is not exhaustive and, therefore, the model should evolve as new epidemiological research emerges.

The researchers also note that dietary risk factors per gram of food may vary across different countries, age groups, and genders. For example, they found that dietary risk factors, such as minutes of life lost per gram of fruit or sodium, are twice as high in the U.S. than in Switzerland.

“While HENI is a nutrition evaluation model with multiple factors considered, the final food score is measured in minutes, […] an easy-to-understand metric,” said Stylianou. “Additionally, classifying foods into a traffic-like system (red, amber, green) based on both their nutritional and environmental performance makes recommendations more simple and easy to follow.”

“We hope that these approaches can make this information more accessible and empower individuals to make small or even big changes to their diet that can lead to a healthier and more sustainable lifestyle,” she concluded.

“This research underscores the complexity of considering nutrition and environment at the same time,” Timothy Griffin, Ph.D., Associate Professor and Division Chair of the Agriculture, Food and Environment Friedman School of Nutrition Science and Policy at Tufts University, who was not involved in the study, told MNT.

“For example, they note that ‘correlations between nutritional and environmental impacts are weak.’ They provide some additional nuance just focusing on environmental impacts — substituting one food for another might be climate-beneficial but use more water (this is the case with some vegetables and fruit, for example),” he continued.

“It is important to continue to factor in how we choose foods, including substituting one food for another in our diets. They illustrated this by examples of how even modest changes can benefit both nutrition and [the environment],” Dr. Griffin concluded.

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