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Your individual diet choices can add or remove years of your life

A new study puts numbers to the health and environmental benefits of eating foods, and shows how small changes can make a significant difference.

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The American diet has evolved to include vegetarian and vegan options at both luxury dining establishments and national fast-food companies. And a lot of individuals are aware that the dietary choices they make have an impact on both the planet’s and their own health.

However, it can be difficult to predict how daily decisions—like picking up mixed greens at the grocery store or ordering chicken wings at a sports bar—might affect one’s overall physical and emotional well-being. With this study, we intend to close that gap.

We are a member of a group of scientists with backgrounds in epidemiology, environmental health, and nutrition as well as food sustainability and life cycle evaluation. We are aiming to uncover environmentally sustainable foods that both boost human health in order to obtain a deeper understanding beyond the frequently overly simplified animal versus plant diet dispute.

Using this multidisciplinary knowledge as a foundation, we evaluated, categorized, and ranked more than 5,800 different foods. We did this by combining 15 nutritional health-based dietary risk factors with 18 environmental variables.

In the end, we sought to understand: Are significant dietary changes necessary to increase personal health and lessen environmental effects? Does going vegan require the entire population in order to significantly improve both human and environmental health?

Putting specific figures on food options

Some of the first actual figures for the health cost of various dietary options are included in our 2021 study, which was published in the academic journal Nature Food. To determine the relative advantages or disadvantages of each food, we examined each one separately depending on its composition.

We converted this data into minutes of life lost or gained per serving size of each food item ingested using the Health Nutritional Index that we created. For instance, we discovered that consuming one hot dog takes 36 minutes away from a person’s “healthy” life. Comparatively, we discovered that consuming 30 grams of nuts and seeds each serving results in an additional 25 minutes of healthy life, or an extension of good health and disease-free life expectancy.

Our research also demonstrated that a U.S. consumer’s dietary carbon footprint could be reduced by one-third on average and that they could add 48 healthy minutes to their daily lives by replacing just 10% of their daily caloric intake of beef and processed meats with a variety of whole grains, fruits, vegetables, nuts, legumes, and select seafood. For such a small dietary adjustment, this is a significant improvement.

How were the numbers computed?

Our Health Nutritional Index was created using data from the Global Burden of Disease, an extensive epidemiological study that involved more than 7,000 academics from around the world. 15 dietary risk factors are among the environmental, metabolic, and behavioral components that the Global Burden of Disease assesses for risks and benefits.

Our group modified that epidemiological information at the population level to the level of specific foods. We computed the health burden associated with ingesting one gram of food for each of the dietary risk variables, taking into account more than 6,000 risk estimates specific to each age, gender, disease, and risk as well as the fact that there are approximately 500,000 minutes in a year.

For instance, we discovered that each gram of processed beef consumed in the United States results in an average time loss of 0.45 minutes. The relevant dietary profiles that we had previously created were then multiplied by this number. Going back to the hot dog as an example, the 61 grams of processed meat in a hot dog sandwich results in the loss of 27 minutes of healthy life. We then arrived at the final estimate of 36 minutes of healthy life lost per hot dog after accounting for other risk variables such as sodium and trans fatty acids in the hot dog, which were balanced by the benefit of its polyunsaturated fat and fibers.

More than 5,800 different foods and mixed dishes were used in this calculation. The results of the health indices were then compared to 18 various environmental indicators, such as the carbon footprint, water use, and effects of air pollution on human health. Finally, we assigned each food item a color—green, yellow, or red—based on the relationship between health and the environment. Similar to a traffic light, green foods should be increased in the diet while red foods should be decreased because they have positive health effects and less environmental impact.

What’s the next step for us?

We were able to pinpoint a few high-priority steps that people can take to both enhance their health and lessen their environmental impact thanks to our study.

We discovered considerable differences in environmental sustainability both within and between diets based on animals and those based on plants. Beef, which has a carbon footprint that is twice as high as that of hog or lamb and four times that of poultry and dairy, has the highest carbon footprint of all the “red” foods. When compared to other food groups, cutting out processed meat and lowering overall sodium intake had the biggest positive impact on health.

As a result, consumers might think about consuming less beef, hog, and lamb, followed by processed meat-heavy items. Notably, greenhouse-grown vegetables had the worst environmental impacts of all plant-based diets because of the combustion emissions during heating.

Foods with great health benefits and minimal environmental impact are ones that people may want to increase their intake of. We saw a lot of variety among these “green” options, which also included whole grains, fruits, vegetables, nuts, legumes, fish and shellfish with minimal environmental impact. These products provide possibilities for people of diverse socioeconomic backgrounds, preferences, and cultures.

Our analysis also demonstrates that it is not sufficient to merely take into account the quantity of greenhouse gases emitted, or the so-called carbon footprint, when it comes to food sustainability. The use of water-saving strategies like drip irrigation and the recycling of residential effluent from sinks and showers can also significantly reduce the water footprint of food production.

The epidemiological data prevents us from making distinctions within the same food group, such as the health advantages of a watermelon vs an apple, which is a shortcoming of our study. Additionally, each food must always be seen in the context of the individual’s diet, taking into account the point at which a meal’s benefits stop increasing. For example, one cannot live indefinitely by just consuming more fruit.

Our Health Nutrient Index has the ability to be regularly modified in order to take into account new information as it becomes available. Additionally, it is completely customizable and has already been done in Switzerland.

It was energizing to observe how modest, focused adjustments could have such a significant impact on environmental sustainability and human health, one meal at a time.

This story was first posted on The Conversation, a non-profit news outlet that shares viewpoints from academic authorities.

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The National Dairy Council and the University of Michigan Dow Sustainability Fellowship provided funding for this study. Olivier Jolliet has received funding for unrelated projects from the US EPA, USDA, American Chemistry Council Long-Range Research Initiative, and Unilever. He also joined the Sustainable Nutrition Scientific Board, which was established with the unrestricted support of Nutella, following submission of the current manuscript. The financing organizations played no part in the creation of the work.

The National Dairy Council and the University of Michigan Dow Sustainability Fellowship provided funding for this study.