The Benefits of Plant-Based Nutrition: Diet Quality
Plant-based diets can address poor diet quality by providing essential macronutrients, micronutrients and fiber. This article reviews the essential nutrients for optimal health and the ability of plant-based diets to adequately meet recommendations.
Poor diet quality is a growing problem and driver of poor health and chronic disease. Globally, we are facing a “double burden” of undernutrition due to insufficient consumption of energy and/or nutrients, as well as poor nutrition due to overconsumption of calorie-dense, nutrient-poor foods. Plant-based diets can address poor diet quality by providing essential macronutrients and micronutrients with intact fiber that helps to regulate the consumption and absorption of food. This paper reviews the essential nutrients needed for optimal health and the ability of plant-based diets to adequately meet recommendations.
Key Points for Practitioners
- Typical dietary patterns of US adults are of poor quality, with under-consumption of calcium, magnesium, potassium, iron, vitamins A, C, D, E, choline, and fiber,14 as well as overconsumption of added sugars, saturated fat, and sodium.14
- Whole food diets that are either predominantly plant-based or entirely plant-based are naturally higher in most under-consumed nutrients and lower in overconsumed nutrients.
- A high-quality dietary pattern is more likely to be achieved by choosing primarily plant foods and paying attention to specific important details—these include supplementation with vitamin B12, vitamin D in the case of inadequate sunlight exposure, and consuming sea vegetables and/or iodized salt.
- Adequate protein intakes are easily achieved eating a whole food, entirely plant-based diet.
- If patients express interest in trying a whole food, plant-based diet of some kind, it is helpful to share educational and support resources with them.
Diet Quality in Context
Though variation exists with respect to the definition,1, 2 diet quality refers to the ability of the overall dietary pattern to supply energy and all essential nutrients from food to allow for growth, healing, physical activity, and optimal health at all stages of life, according to standardized dietary metrics.2 A new global, multidimensional definition considers nutritional, sociocultural, food safety, and sensory features.1 It is generally agreed that a diet founded on minimally processed whole foods while limiting or avoiding refined foods with added sugars, fats, and salt, and processed animal foods provide the healthiest dietary pattern for most individuals. The most frequent components of diet quality metrics include vegetables, fruits, grains, roots, tubers, as well as certain nutrients such as added sugar and saturated fat.2 Mixed dishes such as burgers, pizza, and salty or sweet snacks contain added sugars, sodium, and saturated fats, which are associated with poor health outcomes.3
Poor diet quality is a leading and preventable cause of poor health and chronic disease. Globally, we are facing a “double burden” of conventional malnutrition from insufficient calories or nutrients (both macro and micronutrients) as well as poor nutrition due to overconsumption. Modern malnutrition is marked by excess calories and consumption of sugar, fat, and salt, often leading to obesity, type 2 diabetes, cardiovascular diseases, and cancer.2, 4 In the US, poor diet quality is driving chronic disease as six in ten Americans live with at least one chronic disease.5 Globally, improved living standards and increased food availability have shifted the problem from obtaining adequate energy to eating well for health and disease prevention in an environment of excess.1
The overall dietary pattern influences human health and disease and directly affects quality of life throughout the lifespan.6 Current food trends towards a Western-style diet of animal and processed foods, including excess calories, added sweeteners, saturated fats, coupled with the underconsumption of whole grains, legumes, fruit, and vegetables, contribute to the rising levels of chronic conditions and obesity.7 Food systems to support diet quality have the potential to nurture human health and address disease conditions. Harvard’s seminal 2020 EAT-Lancet Commission on Food, Planet and Health states that “unhealthy diets pose a greater risk to morbidity and mortality than does unsafe sex, and alcohol, drug, and tobacco use combined.”7 Thus, as the U.N. Sustainable Development Goals do, public health efforts need to address the double burden of malnutrition and excess.2 Lifestyle medicine nutritional prescriptions hold the potential to steer individuals towards higher-quality dietary patterns.
Measuring Diet Quality
Assessment of diet quality is essential to developing effective strategies and public policies to address malnutrition and achieve global nutrition safety. A clear example of this can be found in the U.N. Sustainable Development Goals.2 Measuring diet quality must depend on reliable dietary metrics developed to capture diet components, such as quality, adequacy, and diversity.2 A recent systematic review has identified nineteen dietary metrics that have been validated against health outcomes and are widely used to address maternal and child health (MCH) and non-communicable diseases (NCD).2 While the dietary metrics varied significantly, the MCH metrics generally focused on a few key foods (grains, fruits, vegetables, dairy products, meat, and fish), while the NCD metrics had a more diverse mix of foods and nutrients. Only four metrics (Mediterranean Diet Score, Alternative Healthy Eating Index, Healthy Eating Index, and Dietary Approaches to Stop Hypertension) had convincing evidence of protective associations, mainly for all-cause mortality, cardiovascular diseases, type 2 diabetes, total cancer, and cancer mortality.2
Defining Nutritional Terminology in the Context of Diet Quality
A variety of terms exist that are relevant to diet quality:
Adequacy: The term “adequacy” refers to ensuring that enough of a particular food or nutrient is consumed to maintain health.
Moderation: The principle of moderation reflects the need to restrict intake to prevent harmful effects on health1 and, thus, limit selected foods that contribute to excess risk for disease.8
Dietary Reference Intakes (DRIs): The National Academies of Sciences, Engineering, and Medicine (NASEM) define the Dietary Reference Intakes (DRIs) as a set of standards and recommendations to address adequacy and moderation.9 The DRIs include the following components:
- Estimated Average Requirement (EAR): The mean required level of consumption. At this level, 50% of the population will receive more than their individual needs, and 50% will receive less than their individual needs.
- Recommended Dietary Allowance (RDA): Two standard deviations above the EAR, this recommended intake level will meet the needs of ~97–98% of individuals.
- Adequate Intake (AI) is established when evidence is insufficient to develop an RDA and is set at the population average intake, which is assumed to ensure nutritional adequacy.
- Tolerable Upper Intake Level (UL): Highest average daily nutrient intake level likely to pose no risk of adverse health effects.
- Chronic Disease Risk Reduction Level (CDRR): The lowest level of intake for which there was sufficient strength of evidence to characterize a chronic disease risk reduction (used only for sodium).10
Undernutrition denotes insufficient energy intake and nutrients to meet an individual’s needs to maintain good health, whereas malnutrition includes both undernutrition and overnutrition. Undernutrition is synonymous with malnutrition in much of the literature.11
Overnutrition: Refers to excess intake of macronutrients and micronutrients. Poor diet was previously associated with undernutrition but is now more associated with excess intake of calories, saturated fat, and sodium.
Malnutrition: Assessing malnutrition remains unclear as few widely used and validated metrics can define the double burden of MCH and NCDs.2 Traditionally, it is defined as “insufficient caloric or other nutrient intake leading to insufficient physical growth (stunting), rapid weight loss, or failure to gain weight (wasting), cognitive impairment, exacerbation of anemia and blindness, or weakening of the immune system resulting in the increased risk of infectious diseases and mortality.”12 Regarding chronic disease, malnutrition considers excess consumption of fat, sugar, salt, and calories.2, 4 Recently, both are frequently coexisting with poor diet quality within individuals and populations.2 The World Health Organization defines malnutrition to include undernutrition (wasting, stunting, underweight), inadequate vitamins or minerals, overweight, obesity, and resultant diet-related, chronic diseases.13
Underconsumed and overconsumed nutrients are nutrients or foods whereby five percent or more of Americans or a population subgroup fail to sufficiently consume to achieve recommended intakes, according to the USDA Dietary Guidelines Advisory Committee Report.14 These include calcium, magnesium, potassium, iron; vitamins A, C, D, E; and choline, and fiber.14 Four of these (calcium, potassium, vitamin D, and fiber) are considered Nutrients of Public Health Concern because their low intakes are associated with health concerns.14 Overconsumed nutrients include added sugars, saturated fat, and sodium.14 Nutrients of concern are included on U.S. food labels.
Though there is a scarcity of research on children and plant-based diets, most studies do not indicate any detrimental effects of vegetarian or vegan diets on children, with some pointing towards multiple health benefits, such as lower risk for obesity, cardiovascular disease and diabetes.15 Parents of vegetarian and vegan children are advised to pay close attention to critical nutrients, including protein, iron, calcium, vitamins D and B12, and omega 3 fatty acids.16–19
Physical development between vegetarian and omnivore children was similar, and both groups met reference values for protein and energy. Iron intakes in both groups were 60–70% of the reference intake.20, 21 The Dietary Guidelines for Americans now include children under two years old with suggestions that human milk is provided exclusively for the first six months of life and only human milk (not plant or cow’s milk) for the first 12 months. Early exposure (in the first year) to highly allergenic foods is now suggested, including peanuts, egg, cow’s milk products, tree nuts, milk, seafood, and soy.22 American children overconsume added sugar, which may be contributing to the current obesity epidemic.23
American children also regularly consume fast food, which results in higher total energy and reduces diet quality.24 Dietary patterns should include potassium-rich foods, alternatives to red and processed meat, whole grains, and avoidance of solid fats and sweetened beverages.14
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