INTRODUCTION — Poor diet is the leading cause of mortality in the United States, outpacing tobacco use, hypertension, and overweight, and it is the third leading cause for disability-adjusted life years [1].
Decades of research have revealed strong links between many dietary components and eating patterns and important health outcomes [2]. Furthermore, the majority of patients and clinicians view eating habits as important to health and an important part of healthy lifestyle counseling [3,4].
This topic will discuss the evidence on the health effects of various types of dietary patterns, dietary components, and select foods. Although the science on the larger environmental effects of food choices, and their potential impact on health, continues to advance, it is an issue that is outside the current scope of this review [5].
Dietary assessment and diets for specific populations are discussed elsewhere:
●(See "Dietary assessment in adults".)
●(See "Dietary history and recommended dietary intake in children".)
●(See "Obesity in adults: Dietary therapy".)
●(See "Nutrition in pregnancy: Assessment and counseling".)
●(See "Nutrition in pregnancy: Dietary requirements and supplements".)
●(See "Geriatric nutrition: Nutritional issues in older adults".)
●(See "Nutritional considerations in type 2 diabetes mellitus".)
●(See "Lipid management with diet or dietary supplements".)
IMPACT OF A HEALTHY DIET — While the specifics of healthy eating can vary, the overall goal of a healthy diet is to improve patients’ health and lower the risk of disease. Considerable evidence shows us that healthy food choices can extend longevity [6] and reduce the risk of cardiovascular disease, diabetes, hypertension, and cancer, among other important chronic diseases. A healthy diet can also help with weight management and improve health-related quality of life [7-10].
With such a broad impact, population-wide improvements in diet could have a substantial impact not only on population health but also on health care costs. Considering only cardiometabolic disease, a 2019 analysis using the United States National Health and Nutrition Examination Survey (NHANES) estimated the total annual costs related to poor diet to be approximately USD $50 billion [11]. Obesity-related medical costs have been estimated at $150 billion USD per year [12].
CHOOSING A HEALTHY DIET: PATIENT COUNSELING
Choosing a dietary pattern — The specific diet or dietary pattern an individual chooses is strongly influenced by a wide range of factors, including personal preference, social and cultural influences, as well as economic considerations. While maintenance of good health or prevention of disease may be important drivers of dietary choices, these will generally not be the patient’s sole considerations; taste preferences, cost and food availability issues, religious requirements, social norms, and media and marketing forces all contribute.
Clinicians should work with individuals to determine the best healthy diet pattern based upon their unique circumstances. Patient encounters provide a valuable opportunity to promote healthy food choices. In a 2017 systematic review evaluating the impact of behavioral interventions, there were multiple, though small, benefits from behavioral interventions on diet and physical activity, serum lipids, body mass index (BMI), and blood pressure at 6 to 12 months [13]. While rates of such counseling have been increasing in the United States, however, in 2016, only around one-third of patients reported receiving dietary advice from clinicians or other medical professionals [14].
Maintaining energy balance — Although weight management is not the focus of the diets in this review, any discussion of healthy diet needs to emphasize the importance of maintaining energy balance over time. Overnutrition leading to overweight and obesity is the single most important dietary factor associated with poor health outcomes. It is associated with premature mortality as well as increased incidence of cardiovascular disease, diabetes, hypertension, cancer, and other important conditions [15-17].
Whatever dietary pattern an individual follows, maintenance of energy balance is an important overall goal. Avoidance of weight gain, even if a patient is overweight or has obesity, can have important long-term health benefits.
Total energy expenditure for recommended daily caloric intake is based upon age, sex, weight, and activity level (table 1) (see "Obesity: Genetic contribution and pathophysiology", section on 'Physiological processes affecting energy balance'). Calculating a patient’s daily caloric intake can be aided by using 24-hour dietary recall, a food diary, or other assessment tools to determine intake of different foods and beverages. Assessment tools, including consumer-focused apps and online tools that can help patients readily track what they eat and drink, are discussed separately. (See "Dietary assessment in adults".)
SPECIFIC HEALTHY DIETARY PATTERNS
Dietary guidelines: Recommended dietary patterns — Specific dietary guidelines may vary, but in general, a high-quality, healthy diet emphasizes limited consumption of red and processed meats, unhealthy fats (saturated and industrial trans-fats), sugar, sodium, and alcohol, and a greater intake of fruits, vegetables, legumes, nuts, and whole grains. This pattern is consistent with that generally recommended by the World Health Organization (WHO) [18], the World Cancer Research Fund/American Institute for Cancer Research [19], the American Cancer Society [20], and the US Department of Agriculture [21], as well as other groups [22]. In addition to multiple disease-specific benefits, results of meta-analyses and individual observational studies have found consistent associations between this dietary pattern and decreased mortality [23-30].
The development of healthy eating guidelines can vary substantially, from expert panel review of existing evidence to the development and analysis of guideline-specific data [19]. While differences in methods may impact the detailed conclusions of guidelines as well as the confidence in them, there is generally consistency in messaging, both among organizations and even countries [21,31-33].
The evidence evaluating specific dietary patterns can vary substantially, and it is likely that some diets that patients inquire about have been little studied. Although long-term randomized controlled trials are often absent, observational studies support the association of health benefits with a number of dietary patterns.
Most of the dietary patterns discussed below share some similar aspects but are further defined by regional characteristics or a specific focus or restriction on dietary components or types of foods.
Mediterranean diet — There is no single definition, but a Mediterranean diet is typically high in fruits, vegetables, whole grains, beans, nuts, and seeds. A Mediterranean diet includes olive oil as an important source of monounsaturated fat and allows low to moderate wine consumption. It generally includes low to moderate amounts of fish, poultry, and dairy products, and it includes little red meat. Although the Mediterranean diet is associated with several health benefits, it remains uncertain if a single component of the Mediterranean diet is associated with the protective benefit or if the benefit results from an aggregation of effects.
●In a meta-analysis of randomized trials including the large PREDIMED trial [34], a Mediterranean diet reduced the risk of stroke compared with a low-fat diet (hazard ratio [HR] 0.60, 95% CI 0.45-0.80) but did not reduce the incidence of cardiovascular or overall mortality [35].
●In a subsequent 2022 trial including over 1000 adults with coronary heart disease conducted in Spain (CARDIOPREV), randomization to a Mediterranean diet resulted in fewer major cardiovascular events (myocardial infarction, revascularization, ischemic stroke, peripheral artery disease, cardiovascular death) compared with a low-fat diet at seven years’ follow-up [36].
●In observational studies, a Mediterranean diet has been associated with lower overall mortality and cardiovascular mortality [37-40], as well as a decreased incidence of Parkinson disease, Alzheimer disease, and cancers, including colorectal, prostate, aerodigestive, oropharyngeal, and breast cancers [37,38,41-43]. (See "Factors that modify breast cancer risk in women", section on 'Diet rich in fruits and vegetables, fish, and olive oil (eg, Mediterranean diet)'.)
The effects of the Mediterranean diet on type 2 diabetes mellitus are discussed separately. (See "Nutritional considerations in type 2 diabetes mellitus", section on 'Macronutrient composition'.)
DASH diet — The DASH (Dietary Approaches to Stop Hypertension) diet is comprised of four to five servings of fruit, four to five servings of vegetables, and two to three servings of low-fat dairy per day, with <25 percent of daily caloric intake from fat.
The DASH diet has been studied in both normotensive and hypertensive populations and has been found to lower systolic and diastolic pressure more than a diet rich in fruits and vegetables alone [44]. The combination of low-sodium and DASH diet resulted in further decreases in blood pressure, comparable with those observed with antihypertensive agents [45]. (See "Salt intake, salt restriction, and primary (essential) hypertension" and "Diet in the treatment and prevention of hypertension".)
The DASH diet has also been associated with a lower risk of colorectal cancer, cardiovascular disease, premature mortality, and gout (in men) [29,46-50]. (See "Lifestyle modification and other strategies to reduce the risk of gout flares and progression of gout", section on 'Dietary composition'.)
Plant-based and vegetarian diets — Plant-based diets, which include vegetarian (and similar) diets, focus on the consumption of cereals, fruits, vegetables, legumes, and nuts, with the restriction of animal-based foods, including meat, dairy products, and eggs [51]. The degree of animal food restriction in plant-based eating varies considerably [52]. Vegan diets exclude all animal-based foods, while less restrictive approaches can include eggs, dairy products, and some meat. Selected plant-based diets may be grouped as follows:
●Vegan – All animal products, including eggs, milk, and milk products, are excluded from the diet. Some vegans do not use honey and may refrain from using animal products such as leather or wool. They also may avoid foods that are processed or not organically grown [53].
●Lactovegetarian – Milk and milk products are included in the diet, but no eggs or meat are consumed.
●Lacto-ovovegetarian – Eggs, milk, and milk products (lacto = dairy; ovo = eggs) are included, but no meat is consumed.
●Semi-vegetarian (flexitarian) – Meat occasionally is included in the diet. Some people who follow such a diet may not eat red meat but may eat fish (pescatarian) or chicken (pollotarian). The Mediterranean diet could be considered a semi-vegetarian, plant-based diet. (See 'Mediterranean diet' above.)
●Macrobiotic – Vegetables, fruits, legumes, and seaweeds are included in the diet, while whole grains, especially brown rice, are also emphasized. Locally grown fruits are recommended. Animal foods are generally limited to white meat or fish, which may be included in the diet once or twice a week.
The long-term effects of a plant-based diets on health outcomes may be difficult to separate from lifestyle factors associated with consumption of a plant-based diet (eg, regular exercise, avoidance of tobacco and alcohol products). However, observational studies suggest that consumption of plant-based and vegetarian diets is associated with lower risk of obesity, coronary heart disease, hypertension, type 2 diabetes, certain cancers, and possibly all-cause mortality [54-62]. Results of randomized trials have found a beneficial impact of vegetarian diets on a number of cardiovascular risk factors [63].
The nutritional adequacy and quality of plant-based and vegetarian diets should be judged individually, not on the basis of what it is called but on the type, amount, and variety of nutrients that are consumed [64]. As an example, some but not all studies suggest that vegans (who exclude all animal-based products, including dairy) may be associated with lower bone mineral density and higher fracture risk due to lower intake of calcium [65,66]. In addition, individuals who eat a vegan diet may also have inadequate vitamin B12 intake and may need to take vitamin B12 supplements. (See "Vitamin intake and disease prevention", section on 'Special diets'.)
Additionally, as with other healthy eating patterns, plant-based diets should emphasize the consumption of lesser amounts of processed foods as well as foods that are low in unhealthy fats, refined grains, sugar, and sodium.
Low-fat diet — Low-fat diets focus on limiting calories from fat. Some approaches are very low-fat, with calories from fat ≤10 percent of total calories; others are more moderate, with ≤30 percent of daily caloric intake from fat.
Most evidence also points to little or no health or mortality benefit from a low-fat dietary pattern [67-69], although ongoing analyses from the Women’s Health Initiative trial suggest some possible coronary heart disease, diabetes, and breast cancer survival benefits [70].
Compared with higher-fat diets, lower-fat diets are associated with lower body adiposity [71]. Overall, however, low-fat diets have been found to be no more effective than other types of diets for weight control [72,73]. This is discussed in detail separately. (See "Obesity in adults: Dietary therapy", section on 'Low-fat diets'.)
Individuals choosing a reduced-fat diet should focus on food quality in addition to fat content. A 2020 prospective cohort study using data from the US National Health and Nutrition Examination Survey (NHANES) found that an unhealthy low-fat diet was associated with a modest increase in total mortality, while a healthy low-fat diet was associated with a modest decrease in total mortality [74]. While consuming a reduced-fat diet, the emphasis should be on whole grains, legumes, fruits, and vegetables, with limited refined grains and sugar; fat should be from healthy sources, such as fatty fish, olive oil, and canola oil.
Low-cholesterol diet — A low-cholesterol diet focuses on limiting the amount of dietary cholesterol, which can be found in higher levels in foods such as certain shellfish, full-fat dairy, and eggs.
While elevated serum levels of low-density lipoprotein (LDL) cholesterol are an established risk factor for the development of cardiovascular disease, the relationship between dietary cholesterol intake and cardiovascular disease is less certain [75,76]. Because of their cholesterol content, eggs have often been restricted in low-cholesterol diets. A 2020 systematic review and meta-analysis of egg consumption found no association between daily intake of a single egg and risk of cardiovascular disease [77]. Similar overall null results were found for type 2 diabetes, although a small increase in risk with moderate egg consumption was seen in United States study populations [78]. However, in a subsequent 2021 observational study including over 96,000 postmenopausal females without known cardiovascular disease at baseline, higher egg consumption (≥1 egg/day versus <1 egg/week) was associated with greater risk of incident cardiovascular disease and total mortality (HR 1.14, 95% CI 1.04-1.25; and HR 1.14, 95% CI 1.07-1.22, respectively) [79].
The 2020 to 2025 Dietary Guidelines for Americans recommend maintaining an overall healthy eating pattern and consuming as little dietary cholesterol as possible [21].
DIETARY COMPONENTS ASSOCIATED WITH HEALTH BENEFITS — Although we focus on overall dietary patterns, individual dietary components can play an important role in nutrition and health outcomes and can offer patients specific areas to focus their efforts at improving their diet.
Fruits and vegetables — Patients should be counseled to consume 2.5 cups of vegetables and 2 cups of fruit per day for a 2000 calorie diet (table 2) [21]. Fruits and vegetables are a rich source of fiber, essential vitamins and minerals, and other potentially beneficial compounds, as well as carbohydrates with a low glycemic index. (See 'Fiber' below and "Vitamin intake and disease prevention".)
In large, prospective cohort studies, increased consumption of fruits and vegetables is associated with decreased all-cause and coronary heart disease mortality [80-83]. Several studies suggest that fruit and vegetable consumption is associated with a lower risk of coronary heart disease and stroke [84-86]. While large prospective cohort studies have not found a substantial effect of fruits and vegetables on cancer incidence in the general population, there is evidence of impact on some specific cancers, including aerodigestive cancers [87] and estrogen receptor-negative breast cancer. Some observational studies also support an association between higher intake of tomatoes and tomato-based products with a lower risk of prostate cancer [88,89]. (See "Overview of cancer prevention", section on 'Fruits and vegetables'.)
Whole grains — Individuals should consume at least one-half of all grains as whole grains (ie, 3 ounces of whole grains for a 2000 calorie diet), as recommended by the Dietary Guidelines for Americans (table 2) [21,90], and replace refined grains with whole grains wherever possible.
Common types of food made from grain include breads, breakfast cereals, oatmeal, tortillas, and pasta. Grain products vary by level of milling or processing and can be defined as follows:
●Refined grains (eg, white rice, white bread, refined and sweetened cereals) have bran and germ removed during processing, which also removes fiber, iron, B vitamins, and other nutrients. Processing produces a finer texture and improves shelf life.
●Enriched grains are refined grains that have iron and B vitamins added back, but not fiber in most cases.
●Whole-grain foods include brown rice, whole-wheat bread, whole-grain cereal, and oatmeal. These are a good source of fiber and other nutrients and are considered carbohydrates with a lower glycemic index.
Increased consumption of whole grains is associated with a variety of health benefits, including improved weight management, reduction in cardiovascular and all-cause mortality, and decreased incidence of coronary heart disease and cancer [91-94]. Representative studies include:
●In a prospective study of over 120,000 healthy individuals, an increased intake in refined grains was associated with long-term weight gain, whereas an increased intake in whole grains was associated with weight loss [92].
●In a 2014 meta-analysis of 18 studies including over 400,000 participants, increased whole-grain intake was associated with decreased risk for coronary heart disease (relative risk [RR] 0.79, 95% CI 0.74-0.83) [93].
●In a pooled prospective cohort study including over 117,000 individuals, higher whole-grain consumption was associated with lower cardiovascular (RR 0.85, 95% CI 0.78-0.92) and total (RR 0.91, 95% CI 0.88-0.95) mortality [94].
The World Cancer Research Fund/American Institute for Cancer Research, in their Third Expert Report: Diet, Nutrition, Physical Activity and Cancer, recommends increased dietary intake of whole grains to reduce the risk of developing colorectal cancer [87].
Fiber — The recommended amount of dietary fiber is approximately 14 g per 1000 calories, which translates to approximately 25 g to 34 g per day for most adults [21].
Fiber is the portion of plants that cannot be digested by enzymes in the gastrointestinal tract. Fiber is available in a large variety of natural foods and supplements (table 3). Patients should be advised to replace refined grains (eg, white rice, white bread) with whole grains (eg, brown rice, whole-wheat bread), which have higher fiber content.
Increased fiber intake is associated with many health benefits, including a decreased risk of coronary heart disease, cardiovascular and all-cause mortality, colorectal cancer, stroke, and type 2 diabetes [87,91,95-103]. High-fiber diets may in part protect against coronary heart disease by controlling cardiovascular risk factors, including lowering insulin levels and blood pressure, and improving lipid profiles [104,105].
The benefit of increased fiber intake is also observed in people with established cardiovascular disease. For example, in a prospective cohort study following 4000 patients after a first myocardial infarction, eating a high-fiber diet (post-myocardial infarction) was associated with lower cardiovascular and all-cause mortality (RR 0.72, 95% CI 0.52-0.99; and RR 0.73, 95% 0.58-0.91, respectively) [106]. The largest benefit was seen among those with the greatest increase in fiber consumption, comparing pre- and post-myocardial infarction fiber intake.
Further details on dietary fiber in managing and preventing disease are discussed separately. (See "Type 2 diabetes mellitus: Prevalence and risk factors", section on 'Dietary patterns' and "Nutritional considerations in type 1 diabetes mellitus" and "Nutritional considerations in type 2 diabetes mellitus" and "Colorectal cancer: Epidemiology, risk factors, and protective factors", section on 'Fiber' and "Overview of cancer prevention", section on 'Fruits and vegetables'.)
Reduced-fat dairy — The United States Dietary Guidelines for Americans recommends that adults consume three cups of dairy products daily for a 2000 calorie diet (table 2) [21].
The dairy food group is composed of milk and foods made from milk, and examples of healthier dairy products include low- or non-fat milk and low- or non-fat plain (unsweetened, unflavored) yogurt. Dairy products are a good source of protein, calcium, vitamin D, and potassium. Diets that include limited amounts of dairy should ensure adequate intake of these nutrients from other sources.
Intake of dairy products likely lowers the risk of colorectal cancer [87] and possibly cardiovascular disease [107-109]. Low-fat dairy is also integral part of the DASH diet (see 'DASH diet' above), which has been shown to help control blood pressure as well as lower the risk of colorectal cancer, cardiovascular disease, premature mortality, and gout (in males) [29,46-50].
Protein-rich foods — The Dietary Guidelines for Americans recommend that individuals consume 5.5 ounces of protein-rich foods daily for a 2000 calorie diet (table 2) [21]. Healthy protein-rich foods include poultry, beans, peas, seeds, nuts, fish, and soy products (eg, tofu and tempeh). (See 'Healthy fats' below.)
Nuts — Nut consumption is associated with lower risk for cardiovascular disease. One study that combined data from three large cohorts found that the risk of myocardial infarction or stroke was reduced among participants who consumed nuts five or more times per week compared with participants who rarely ate nuts (hazard ratio [HR] 0.86, 95% CI 0.79-0.93) [110]. Peanuts, tree nuts, and walnuts were all associated with similar reductions in the risk of cardiovascular disease.
Fish — One to two servings (total of eight ounces) of oily fish (eg, salmon and tuna) per week is suggested for most adults, with special consideration regarding mercury content of particular seafoods for individuals who are pregnant, planning pregnancy, and breastfeeding (table 4) [21,111]. (See "Fish consumption and marine omega-3 fatty acid supplementation in pregnancy", section on 'Fish consumption'.)
In a 2014 meta-analysis of 11 prospective cohort studies, fish consumption ≥4 times per week was associated with a decreased risk of acute coronary syndrome (RR 0.79, 95% CI 0.70-0.89) with a dose-response relationship (each additional 100 g serving per week associated with RR 0.95, 95% CI 0.92-0.97) [112]. In a subsequent pooled analysis of several international cohort studies, consuming two servings of fish weekly was associated with lower risk of major CVD and mortality among persons with existing CVD (HR 0.84, 95% CI 0.73-0.96; and HR 0.82, 95% CI 0.74-0.91, respectively), but not in those without CVD [113]. (See "Overview of primary prevention of cardiovascular disease", section on 'Omega-3 fatty acids'.)
Healthy fats — Saturated fat should make up no more than 10 percent of total caloric intake, as recommended by the Dietary Guidelines for Americans [21].
The type of fat consumed appears to be more important than the amount of total fat (table 5). Individuals should choose poly- and monounsaturated fats in place of saturated and trans fats [114] (see 'Unhealthy fats' below). Consumption of polyunsaturated fats can improve serum lipids and lower the risk of CVD and total mortality [114-116]. In a meta-analysis of four randomized controlled trials including individuals without coronary heart disease, replacement of dietary saturated fat with polyunsaturated fat reduced the risk of coronary heart disease by 29 percent compared with no intervention (RR 0.71, 95% CI 0.62-0.81) [114]. (See "Dietary fat", section on 'Quality of fat' and "Lipid management with diet or dietary supplements".)
Good sources of polyunsaturated and monounsaturated fats are certain oils (eg, corn, peanut, olive, and canola oils) (figure 1), as well as avocados, certain nuts, and fatty fish.
DIETARY PATTERNS WITH LIMITED OR DEVELOPING EVIDENCE — The list of diets with limited evidence of benefit is very long and potentially unlimited, as new diets and eating patterns regularly emerge both in the medical literature and popular media. Here, we highlight diets that patients may be likely to inquire about or that show potential evidence of health benefits.
Low-carbohydrate diet — Low-carbohydrate diets emphasize protein and fat intake with limited carbohydrate intake. The level of carbohydrate restriction in low-carbohydrate diets can vary significantly.
Ketogenic diets (high in dietary fat and low in carbohydrates, which causes the body to produce ketones from body fat to use for fuel) can have very few carbohydrates, often under 50 g per day, while some low-carbohydrate diets can have 40 percent of total calories from carbohydrates. The more restrictive the diet, however, the more difficult long-term maintenance can be for patients.
Low-carbohydrate diets may aid in weight loss and possibly improve serum lipids over the short term, although results for low-density lipoprotein (LDL) cholesterol are mixed [117,118]. In addition, the health effects of low-carbohydrate diets over the longer term remain unclear and may depend upon overall dietary food quality; unhealthy low-carbohydrate diets (eg, higher in animal protein and saturated fat) have been found in observational studies to be associated with an increased mortality risk, while healthy low-carbohydrate diets (higher in plant protein and unsaturated fats) associated with a lower risk [74,119,120].
Organic diet — There is significant interest in the potential health benefits of eating an organic diet. Although there are regulatory definitions for what qualifies as organic produce and organic egg, meat, and dairy products [121], there is a lack of established methodology in assessing what actually qualifies as an organic diet. In addition, complicating the research on the impact of organic food on health is the difficulty of taking fully into account the potential confounders linked with organic food consumption (eg, other elements of a healthy lifestyle) [122].
Despite great interest in the area, high-quality data are still lacking on the links between the consumption of organic food and improved health. While eating a diet high in organic foods can lessen exposure to synthetic pesticides, it is unclear if this actually translates to improved health outcomes [122,123]. Growing evidence does, however, point to a possible link between high organic food intake and a lower risk of cancer, particularly non-Hodgkin lymphoma [124,125]. Further evidence from well-designed studies is needed to confirm this association.
Antiinflammatory diet — The antiinflammatory diet focuses on food choices that may reduce systemic inflammation. Chronic inflammation is linked to an increased risk of multiple chronic diseases, including cardiovascular disease, type 2 diabetes, and cancer [126].
There is no specific antiinflammatory diet, and aspects of other healthy diets qualify as antiinflammatory (see 'Mediterranean diet' above). Overall, however, an antiinflammatory diet emphasizes choices such as olive oil, nuts, fruits, leafy green vegetables, and fatty fish; and limits processed meats, refined grains, sugar, and fried food. Compared with antiinflammatory diets, those diets that "promote" inflammation have been linked in observational studies with multiple health risks, including an increased risk of total, cancer, and cardiovascular disease-related mortality [126-128]. The science on antiinflammatory diet continues to develop.
Gluten-free diet — A gluten-free diet eliminates or substantially limits grains that contain the protein gluten, such as wheat and barley (table 6). In individuals with Celiac disease and non-Celiac gluten sensitivity, a gluten-free diet has demonstrated benefits (see "Management of celiac disease in adults" and "Management of celiac disease in children"). Outside of those with gluten sensitivity, however, little evidence supports health benefits from a gluten-free diet, and some evidence suggests increased risk of cardiovascular disease due to related reductions in whole grain intake [129].
DIETARY PATTERNS AND COMPONENTS TO LIMIT OR AVOID — There is good evidence associating certain dietary patterns and individual dietary components with adverse health outcomes. Individuals should be encouraged to limit and, in some instances, avoid these components. Realistically, however, elimination may be too drastic for many patients, and a reduction in consumption is a more attainable goal, at least initially.
"Western" diet — Studies consistently show that the typical Western diet increases the risk of multiple chronic diseases. The Western diet is marked by consumption of red and processed meats, full-fat dairy products, refined grains, high-sodium foods, and sugar, as well as and low amounts of fiber, whole grains, legumes, and fruits and vegetables.
Compared with healthy eating patterns, the Western diet is linked to an increased risk of cardiovascular disease, type 2 diabetes, cancer, overweight and obesity, and other conditions. In 2016, poor diet was the leading cause of death and the third leading cause for disability-adjusted life-years in the United States [1]. Individuals should be encouraged to avoid the typical Western diet in favor of healthier eating patterns that are more plant-based, with a focus on healthy fats and fewer processed products.
Unhealthy fats — Saturated and trans fats intake can adversely impact serum lipids and increase the risk of cardiovascular disease [114]. Saturated fats are common in animal products, such as red meat and whole-fat dairy, and in some plant products, such as coconut and palm oils. Trans fats used to be common in many foods in the United States but since 2018 have been largely removed from the food supply following a US Food and Drug Administration (FDA) ban on their use [130]. However, some foods can still include some trans fat, such as some fast foods and shortenings and oils with hydrogenated oil listed in the ingredients. Individuals should limit saturated and trans fats, replacing them with healthy fats such as polyunsaturated and monounsaturated fats. (See 'Healthy fats' above and "Dietary fat", section on 'Quality of fat'.)
Added sugars and sugar-sweetened beverages — Added sugars should be limited in the diet and comprise less than 10 percent of total calories consumed [21]. These sugars often come from sweetened beverages and processed foods. If a higher percentage of caloric intake comes from added sugars, it may be difficult for individuals to meet their nutritional needs within caloric limits. Naturally occurring sugars (eg, from fruit or milk) are not considered added sugars. However, fruit juices should still be limited to small daily amounts, if any, as they tend to be high in calories without the added benefit of fiber, which is found in whole fruit.
The consumption of soft drinks and other sugar-sweetened beverages (eg, fruit drinks, sports drinks, and energy drinks) should also be discouraged [21]. Sugar-sweetened beverages are a key contributor to weight gain and obesity [87]. Their consumption is also associated with lower intake of key nutrients because they replace nutrient-dense foods in the diet. In addition to excess weight, intake of sugar-sweetened beverages has been found to increase the risk of coronary heart disease, type 2 diabetes, hypertension, and metabolic syndrome [131-136]. Individuals should be encouraged to drink plain water rather than sweetened beverages.
Red and processed meats — Increased consumption of red meats (eg, beef, lamb, veal, venison, goat) and processed meats (eg, sausage, hot dogs, beef jerky, bologna) has been consistently associated with a small to moderate increased risk of numerous diseases and premature mortality [137]. Although modest, and unconfirmed by randomized trials, these risks are potentially important given the high level of red meat consumption in the United States and increasing consumption of red meat globally.
As examples, in meta-analyses and pooled analyses of prospective cohort studies, increased consumption of red and processed meat has been associated with an increased risk of type 2 diabetes [138], stroke [139], and colorectal cancer [140], as well as increased cardiovascular disease mortality [141].
In similar studies, increased intake of processed meat has been associated with increased risks of coronary heart disease [141,142] and all-cause mortality [143,144].
In the Adventist Health Study 2, an observational study including over 77,000 participants with healthy, often vegetarian diets, higher red meat consumption was associated with an increased mortality risk (hazard ratio [HR] 1.14, 95% CI 1.08-1.22) [145].
In the 2021 Prospective Urban Rural Epidemiology (PURE) Study, an international cohort study including over 134,000 participants followed for 9.5 years, a higher risk of major CVD and mortality was noted among those whose diets contained high amounts of processed meat (HR 1.46, 95% CI 1.08-1.98; and HR 1.51, 95% CI 1.08-2.10, respectively); the risks were not increased with consumption of unprocessed red meat [146].
In 2019, dietary recommendations proposed by the Nutritional Recommendations Consortium (NutriRECS) indicate that the recommendation for adults to reduce their current red and processed meat consumption is not supported by the NutriRECS’ analysis [31]. This is a weak recommendation, however, based upon the impact of a reduction in meat consumption of three servings of unspecified size per week. In addition, the recommendation was based upon the results of four meta-analyses showing low-certainty evidence of the small health effects of red and processed meat consumption [147-150], as well as a systematic review evaluating consumer values and preferences [151]. It is unclear where these recommendations should fit in relation to those of multiple other dietary guidelines that support limiting consumption of red and processed meat [5,152]. While the results of their meta-analyses are similar to others, their use of the GRADE system, which classifies observational data as low-quality evidence, remains a point of contention. (See "Overview of clinical practice guidelines", section on 'Grading guidelines' and "Evidence-based medicine", section on 'Categories of evidence' and "Overview of clinical practice guidelines", section on 'Disagreement among guidelines'.)
Of note, the International Agency for Research on Cancer classifies processed meat as a Group 1 human carcinogen [152]. (See "Colorectal cancer: Epidemiology, risk factors, and protective factors", section on 'Red and processed meat'.)
Highly processed foods — There is a growing body of evidence linking consumption of highly processed foods with a number of health risks. Although the specific definition of highly or ultra-processed foods can vary, it typically includes items such as sweet and savory snacks, reconstituted meats, packaged frozen entrées, instant soups, and sweetened drinks. Highly processed foods are often calorie-dense; higher in refined grains, sugar, saturated fat, and salt; and lower in fiber and other important nutrients.
Results from the observational NutriNet-Santé study, which included over 100,000 participants, have linked higher consumption of ultraprocessed foods with increased risks of cardiovascular disease, type 2 diabetes, cancer, and total mortality [153-156]. Similar findings were observed in the Adventist-Health Study 2, which included over 77,000 participants with healthy, often vegetarian, diets; those with the highest consumption of processed foods had an increased mortality risk compared with those with the lowest consumption (HR 1.14, 95% CI 1.07-1.21) [145]. Most dietary guidelines promote the consumption of unprocessed or minimally processed foods as an essential component of a healthy eating pattern.
Alcohol — Although moderate alcohol use may have beneficial effects on cardiovascular health in older adults, the increased risks of cancer and other harms likely offset such benefits [1,157]. Even light alcohol consumption of three to six drinks per week has been associated with a small increased risk for breast cancer in women as well as increased risk for oropharyngeal and esophageal cancer [158]. A Global Burden of Disease Study analysis found that cancer risk increased monotonically with increasing alcohol intake [1]. (See "Overview of the risks and benefits of alcohol consumption", section on 'Cardiovascular disease'.)
While certain diets and dietary guidelines allow for moderate alcohol consumption, growing evidence supports the message that zero alcohol is the best choice for patients’ overall health [1]. This is discussed in detail elsewhere. (See "Overview of the risks and benefits of alcohol consumption", section on 'Is there a safe dose of alcohol?'.)
SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Vitamin deficiencies" and "Society guideline links: Healthy diet in adults".)
INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5th to 6th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10th to 12th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.
Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)
●Basics topics (see "Patient education: Diet and health (The Basics)" and "Patient education: Vegetarian diet (The Basics)" and "Patient education: Vitamin supplements (The Basics)" and "Patient education: Can foods or supplements lower cholesterol? (The Basics)")
●Beyond the Basics topics (see "Patient education: Diet and health (Beyond the Basics)" and "Patient education: High-fiber diet (Beyond the Basics)")
SUMMARY AND RECOMMENDATIONS
●Impact of a healthy diet – Healthy food choices can extend longevity and reduce the risk of cardiovascular disease, diabetes, hypertension, and cancer, among other important chronic diseases. A healthy diet can also help with weight management and improve health-related quality of life. (See 'Impact of a healthy diet' above.)
●Choosing a healthy diet or dietary pattern – The specific diet or dietary pattern an individual chooses is influenced by a wide range of factors, including personal preference, social and cultural influences, as well as economic considerations. Clinicians should work with individuals to determine the best healthy diet pattern based upon their unique circumstances. (See 'Choosing a healthy diet: Patient counseling' above.)
●What are healthy dietary patterns? – Specific dietary guidelines may vary, but in general, a high-quality, healthy diet emphasizes limited consumption of red and processed meats, unhealthy fats (saturated and industrial trans-fats), sugar, sodium, and alcohol, and a greater intake of fruits, vegetables, legumes, nuts, and whole grains. (See 'Dietary guidelines: Recommended dietary patterns' above.)
•Examples of healthy dietary patterns associated with health benefits include the Mediterranean diet, the Dietary Approaches to Stop Hypertension (DASH) diet, plant-based and vegetarian diets, a low-fat diet, and a low-cholesterol diet. Most of these dietary patterns share some similar aspects but are further defined by regional characteristics or a specific focus or restriction on dietary components or types of foods. (See 'Mediterranean diet' above and 'DASH diet' above and 'Plant-based and vegetarian diets' above and 'Low-fat diet' above and 'Low-cholesterol diet' above.)
●Specific healthy dietary components – Although we focus on overall dietary patterns, individual dietary components can play an important role in nutrition and health outcomes and can offer patients specific areas to focus their efforts at improving their diet. (See 'Dietary components associated with health benefits' above.)
•Specific healthy dietary components include fruits and vegetables, whole grains, fiber, reduced-fat dairy, and certain protein-rich foods, such as nuts, fish, and soy products. (See 'Fruits and vegetables' above and 'Whole grains' above and 'Fiber' above and 'Reduced-fat dairy' above and 'Protein-rich foods' above.)
●Dietary patterns with limited evidence of health benefits – The list of diets with limited evidence of benefit is very long and potentially unlimited, as new diets and eating patterns regularly emerge. Examples of dietary patterns with limited supporting evidence include a low-carbohydrate diet, an organic diet, an antiinflammatory diet, and a gluten-free diet. (See 'Low-carbohydrate diet' above and 'Organic diet' above and 'Antiinflammatory diet' above and 'Gluten-free diet' above.)
●Dietary patterns and specific components to avoid – Individuals should avoid consumption of a typical "Western" diet (characterized by consumption of red and processed meats, full-fat dairy products, refined grains, high-sodium foods, and sugar, as well as low amounts of fiber, whole grains, legumes, and fruits and vegetables), and avoid or minimize consumption of unhealthy fats (ie, saturated and trans fats), added sugars (including sugar-sweetened beverages), red and processed meats, highly processed foods, and alcohol. (See 'Dietary patterns and components to limit or avoid' above.)