The food choices we make every day have a profound impact on our health, influencing our risk of developing chronic diseases and even affecting the planet. Unhealthy eating habits are a major lifestyle factor that increases the risk of death associated with heart disease, stroke, and type 2 diabetes. Numerous studies highlight the strong connection between diet and mortality, emphasizing that the battle against these leading causes of death may be won or lost based on our grocery lists.
The Impact of Dietary Choices on Mortality
Several studies underscore the significant role of diet in overall health and longevity. For instance, a study revealed that more than two-thirds of heart disease-related deaths worldwide could be linked to food choices, estimating that 6 million deaths could have been avoided through better diets. Another study concluded that healthy lifestyle choices could reduce the risk of stroke by 80%, with diet identified as the leading factor. Furthermore, poor dietary habits contributed to almost half of over 700,000 deaths reviewed in a study focusing on heart disease, stroke, and type 2 diabetes.
These findings highlight the profound impact of food choices on health. Registered dietitian Kate Patton emphasizes the importance of viewing food as medicine, stating that "The right food can really improve your health and decrease your risk of developing these chronic diseases."
Foods to Limit for a Healthier Diet
Certain foods have been consistently identified as detrimental to heart health and metabolism. Excessive sodium intake is a primary concern, as too much sodium can lead to high blood pressure and damaged arteries, straining the heart. The federal Dietary Guidelines for Americans 2020-2025 recommend limiting sodium intake to less than 2,300 mg per day.
However, it's not just about reducing salt intake. Sugary beverages, processed foods (especially meat), and foods high in saturated fats also pose significant risks. The studies reviewed consistently flagged these items as major contributors to poor diets.
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Building a Healthier Diet
The journey to healthier eating begins with incorporating more fruits and vegetables into your diet. These foods are packed with essential nutrients and antioxidants that protect against disease.
For the Global Burden of Disease study, researchers estimate the burden of disease for adults 25 and older associated with 15 dietary risk factors: fruits, vegetables, legumes, whole grains, nuts and seeds, fiber, seafood omega-3 fatty acids, omega-6 polyunsaturated fatty acids, calcium, milk, sodium, red meat, processed meat, sugar-sweetened beverages, and trans fats.
These dietary risk factors can be harmful (like sugar-sweetened beverages), meaning they increase the risk of disease; protective (like vegetables); or have mixed effects depending on the amount consumed and the disease outcome in question.
The Importance of Evidence-Based Dietary Recommendations
Measuring the effect of diet on health outcomes can be complicated by lack of available evidence. For this reason, it is important to understand two factors: The strength of the relationship between a certain health risk (like eating too much sodium) and a health outcome (like heart disease) and the strength of the evidence for the risk-outcome relationship. While some risk-outcome pairs have clear evidence of association - for example, low vegetable consumption and elevated risk of ischemic stroke - others are less clear, like red meat and ischemic stroke.
Global Dietary Trends and Their Implications
The previous decade has seen little progress in improving diets, and a quarter of all deaths among adults are attributable to poor diets - those low in fruits, vegetables, nuts/seeds and whole grains, and high in red and processed meat and sugary drinks.
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Current dietary patterns globally and in most regions are neither healthy nor sustainable. Our diets affect both our own health and the health of the planet. Imbalanced diets low in fruits, vegetables, legumes, nuts/seeds and whole grains, and high in red and processed meat are responsible for one of the greatest health burdens globally and in most regions. At the same time, our diets and the food system underpinning them are major drivers of environmental pollution and resource demand, which is contributing to the crossing of key planetary boundaries that attempt to define a safe operating space for humanity on a stable Earth system. Preserving the integrity of our environment and the health of populations will require substantial changes in the foods we produce and eat.
A healthy diet consists of plenty of fruits, vegetables, legumes, nuts/seeds, whole grains and oils high in unsaturated fats, and little to no red and processed meat, sugar-sweetened beverages, refined grains and oils high in saturated fats. Nutritional epidemiology has identified many of those aspects as key risk factors for or against leading causes of overall illness and death, including coronary heart disease, stroke, type-2 diabetes and several cancers. Between 20% and 25% of all deaths in adults have been associated with imbalanced diets.
Advances in nutritional science in the last two decades now provide a substantial body of evidence to identify key dietary priorities for action. The evidence linking diets to intermediate risk factors (e.g. raised blood pressure) and final health (disease) outcomes (e.g. heart disease) comes from various lines of evidence. These include studies of biological processes, clinical trials of risk factors, long-term observational studies of health outcomes, and clinical trials of health outcomes. The different study designs have complementary strengths and weaknesses, and their similar conclusions from different approaches provide increasingly robust evidence.
Methodology for Analyzing Dietary Factors
For the analysis, researchers followed several steps to ensure that the selection of diet factors reflects the current evidence on healthy eating. First, they focused on evidence from meta-analyses that have pooled all available studies linking diets to health outcomes, to minimise bias from any one study. Second, they only used diet-disease associations whose strength of evidence in meta-analyses was graded as moderate or high, or as probable and convincing. Third, they did not include diet-disease associations, e.g. for dairy products and fish, which became statistically non-significant when adjusted for potential confounding factors, such as co-consumption with other foods. Fourth, they focused on foods and not nutrients, to reduce the risk of double-counting as foods often include several nutrients. Further details are provided in the forthcoming methodology (see the section called Data for comparative risk assessment). They focused on foods with impacts on coronary heart disease, stroke, diabetes, cancers and respiratory disease.
Environmental Impact of Food Choices
When it comes to the environmental impacts of foods, it is generally recognised that animal-based foods have greater environmental impacts than plant-based foods. For example, for greenhouse gas emissions, beef and lamb have about ten times the emissions per serving as pork, poultry and dairy products, and those have about ten times the emissions of plant-based foods, including grains, fruits and vegetables, and legumes. Similarly for water, the average fresh-water footprint per tonne of animal-based product is greater than that of plant-based products, with the exception of milk, which has a relatively low water footprint, and nuts, which have a relatively high water footprint when measured on a per-tonne basis, but not on a per-calorie or per-protein basis.
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Much of the evidence linking environmental impacts to foods comes from life-cycle analyses that record the various impacts across all stages of the food chain, including production, transport, processing and consumption. The strength of life-cycle analysis is that both direct and indirect impacts are accounted for, something that explains the differentiated impacts of foods. Animal-based foods tend to have greater footprints of greenhouse gas emissions than plant-based foods because, in addition to direct emissions from manure and, for ruminant animals, their digestion, animals also generate indirect emissions from their feed whose production generates emissions and requires large amounts of environmental resources, including land, water and fertilisers.
For analysis, researchers used the most recent and comprehensive set of life-cycle assessments to estimate the environmental impacts of diets (see the section called Environmental analysis in the forthcoming methodology). They included in the assessment the impacts of foods on greenhouse gas emissions, cropland use, fresh-water use and nitrogen and phosphorus application related to fertilisers. Dietary changes towards more plant-based diets have been identified as the most efficient way of reducing the greenhouse gas emissions of the food system. Several technological and management options exist for reducing other environmental impacts. However, when it comes to greenhouse gas emissions, those are relatively ineffective because most emissions are associated with the characteristics of animals, such as feed requirements and digestion-related gases, that cannot be altered substantially.
Trends in Dietary Intake
The last decade, based on data for 2010 and 2018, has seen little progress in improving diets Based on analyses of the latest data on average per-person dietary intakes from the Global Dietary Database, intakes of whole grains, and of fruit and vegetables, both critical components of healthy diets, have increased by a mere 2% globally, fish intake remained unchanged, while legume consumption has decreased on average (−4%) and the consumption of sugary drinks has increased (+4%). Among the health-promoting foods, only nut/seed intake showed more substantial increases (+17%), albeit from a very low baseline. Global dairy intake (measured in milk equivalent in grams per day, g/d) has decreased (−7%), but the intake of other foods associated with high environmental and health impacts, in particular red meat and processed meat, has increased (+2-3%). In addition, overeating and, associated with that, the proportion of overweight and obesity, have increased almost five times more (+0.70%) than levels of underweight have decreased (−0.15%).
Both positive and negative dietary changes were often confined to high- and upper-middle-income countries, with least progress in low-income countries. For example, the average fruit and vegetable intake per person increased in Latin America and the Caribbean (+8%), Europe (+5%), Asia (+4%); it stayed unchanged in Northern America; and it decreased in Africa (−4%) and Oceania (−13%). Likewise, red and processed meat intake increased in Oceania (+59%), Latin America and the Caribbean (+7%), Asia (+6%) and Europe (+4%); it changed little in Northern America (+1%); and it decreased in Africa (−10%).
Comparing Current Diets to Recommendations
Current dietary patterns are neither healthy, nor sustainable. Compared to recommendations for healthy and sustainable diets developed by the EAT-Lancet Commission on Healthy Diets from Sustainable Food Systems (Box 2.1), the intake of health-promoting foods in 2018 remains too low and that of foods with high health and environmental impacts remains too high. Global vegetable intake is 40% below the recommended three servings per day, fruit intake 60% below the recommended two servings per day and legume and nuts intake 68-74% below the one to two recommended servings. Red and processed meat intake is almost five times above recommendations. Only milk and fish intakes are within recommended ranges.
The EAT-Lancet Commission
The EAT-Lancet Commission on Healthy Diets from Sustainable Food Systems was a scientific commission on how to achieve a sustainable food system that can deliver healthy diets for a growing population. Convened between 2017 and 2019, it consisted of 19 commissioners and 18 co-authors from 16 countries and various fields, including human health, agriculture, political science and environmental sustainability. Its report was published in the medical science journal The Lancet in 2019.
The Commission’s work included the development of: new recommendations for healthy diets based on a comprehensive review of the literature on healthy eating; science-based targets for sustainable food production that included the definition of planetary boundaries of the food system; analyses of the health, nutritional and environmental impacts of dietary and food-system changes that would be needed to stay within planetary boundaries; and strategies for a ‘great food transformation’ towards healthy diets from sustainable food systems by 2050.
In this chapter, we use the EAT-Lancet Commission’s dietary recommendations and the science-based targets for sustainable food production to compare current dietary patterns with the current scientific understanding of healthy eating and sustainable diets. Despite variation, no region met the recommendations for healthy and sustainable diets. Lower-income countries continue to have the lowest intake levels of health-promoting foods and the highest levels of underweight, while higher-income countries have the highest intake levels of foods with high environmental and health impacts, and the highest levels of overweight and obesity. For example, fruit and vegetable consumption in 2018 was 59% below recommended intake in Africa, but also 41% and 56% below recommendations in Europe and Northern America, respectively.
Health Burden of Poor Diets
The current level of dietary imbalance can have serious implications for human and planetary health. For this report, researchers produced new estimates of the health burden of poor diets by using a global comparative assessment of dietary risks with country-level detail (see the sections called Comparative risk assessment and Data for comparative risk assessment in the forthcoming methodology). The assessment combines estimates of food intake with cause-specific mortality rates via a comprehensive set of diet-disease relationships, each accounting for physiological (age, sex) and geographic (country-level) variation. In this framework, researchers accounted for risks for diet-related, non-communicable diseases (NCDs) associated with imbalanced diets, such as those low in fruits and vegetables, as well as for risk associated with imbalanced energy intake related to underweight, overweight and obesity. Because risks for NCDs primarily affect adults, they focused on risks to those aged 20 and above. In this chapter, they report the mean values of our estimates for ease of presentation. The low and high values of 95% confidence intervals are provided in the forthcoming dataset that will be online.
According to estimates, today’s diets are associated with a large and increasing health burden. Overall, poor diets were responsible for more than 12 million avoidable deaths in 2018, which represents 26% of all deaths among adults. Compared to 2010, the number of avoidable deaths due to diet grew by 15%, more rapidly than the population (10%). Almost half of the avoidable deaths were from coronary heart disease (5.9 million, 47%), about a fifth each from cancers (2.8 million, 22%) and stroke (2.4 million, 19%) and around 5% each from type-2 diabetes (690,000) and respiratory diseases (760,000). The estimate of attributable deaths is comparable to the combination of diet- and weight-related risk estimates of the Global Burden of Disease project (7.8 and 4.8 million attributable deaths, respectively).
About two-thirds of the avoidable deaths in the analysis (9.3 million, 65%) were due to risks related to dietary composition, including low intake of fruits (2.8 million, 25% of the avoidable composition-related risks), whole grains (2.3 million, 20%), vegetables (1.7 million, 14%), legumes (1.5 million, 13%), nuts and seeds (1.0 million, 9%), and high intake of red meat (980,000, 9%), processed meat (880,000, 8%) and sugar-sweetened beverages (290,000, 3%). The proportion of premature death attributed to dietary risks differs markedly by region, reflecting regional differences in diets as well as the contribution of NCDs. It is highest in higher-income regions, including Northern America (31%) and Europe (31%), and lowest in lower-income regions such as Africa (17%). Among the dietary risks evaluated, the leading causes of dietary ill health were similar in each region and included low intake of fruits and vegetables (5-8% of premature mortality).
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