Diets for Health: Goals and Guidelines

June 1, 2018

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Volume 97, Number 11 www.aafp.org/afp American Family Physician 721

Although diet is the single most signicant risk factor

for disability and premature death,

most Americans do not

adhere to U.S. dietary recommendations,

and nutrition is

minimally addressed in health care.

When nutrition is dis-

cussed with patients, much of what is presented is inconsis-

tent with existing evidence.

Patients and clinicians are oen

overwhelmed with information on diet and the nutritional

value of foods. Although weight loss is a common focus,

no diet has been proven superior to others. However, when

health is considered, specic dietary patterns—including

particular macronutrients and foods—have good evidence

for primary and secondary prevention of several chronic

diseases. Patients are more likely to understand information

about foods rather than nutrients, so focusing on food cate-

gories may be useful. Diets for the treatment of specic med-

ical conditions are beyond the scope of this article.

Dietary Patterns

Recommending an eating style can be one way to support

healthy dietary changes. e list of popular diets is lengthy,

and most have not been carefully evaluated. e Mediter-

ranean diet has moderate to strong evidence for preventing

type 2 diabetes mellitus,

decreasing cancer incidence and

mortality,

preventing age-related cognitive decline,

pre-

venting cardiovascular disease (CVD) incidence and mor-

tality,

decreasing overall mortality,

and treating obesity

(Table 1

4-15

e Dietary Approaches to Stop Hypertension (DASH)

diet is promoted by the National Institutes of Health to treat

hypertension. It has strong evidence for improving risk fac-

tors for CVD and lowering blood pressure,

and more lim-

ited evidence for weight loss

and managing or preventing

type 2 diabetes.

e 2015 Dietary Guidelines for Americans is another

healthy eating pattern.

Choose My Plate (U.S. Department

Diets for Health: Goals and Guidelines

Amy Locke, MD, University of Utah Health, Salt Lake City, Utah

Jill Schneiderhan, MD, University of Michigan Medical School, Ann Arbor, Michigan

Suzanna M. Zick, ND, MPH, University of Michigan School of Public Health, Ann Arbor, Michigan

CME

This clinical content conforms to AAFP criteria for

continuing medical education (CME). See CME Quiz on

page 707.

Author disclosure: No relevant ﬁnancial aliations.

Patient information: A handout on this topic, written by the

authors of this article, is available at https:// www.aafp.org/

afp/2018/0601/p721-s1.html.

Diet is the single most signiﬁcant risk factor for disability and premature death. Patients and physicians often have diculty

staying abreast of diet trends, many of which focus primarily on weight loss rather than nutrition and health. Recommending

an eating style can help patients make positive change. Dietary patterns that support health include the Mediterranean diet,

the Dietary Approaches to Stop Hypertension diet, the 2015 Dietary Guidelines

for Americans, and the Healthy Eating Plate. These approaches have beneﬁts that

include prevention of cardiovascular disease, cancer, type 2 diabetes mellitus,

and obesity. These dietary patterns are supported by strong evidence that pro-

motes a primary focus on unprocessed foods, fruits and vegetables, plant-based

fats and proteins, legumes, whole grains, and nuts. Added sugars should be

limited to less than 5% to 10% of daily caloric intake. Vegetables (not including

potatoes) and fruits should make up one-half of each meal. Carbohydrate sources

should primarily include beans/legumes, whole grains, fruits, and vegetables. An

emphasis on monounsaturated fats, such as olive oil, avocados, and nuts, and

omega-3 fatty acids, such as ﬂax, cold-water ﬁsh, and nuts, helps prevent cardio-

vascular disease, type 2 diabetes, and cognitive decline. A focus on foods rather

than macronutrients can assist patients in understanding a healthy diet. Addressing barriers to following a healthy diet and

utilizing the entire health care team can assist patients in following these guidelines. (Am Fam Physician. 2018; 97(11):721-728.

Illustration by Scott Bodell

mercial use of one individual user of the website. All other rights reserved. Contact copyrights@aafp.org for copyright questions and/or permission requests.

722 American Family Physician www.aafp.org/afp Volume 97, Number 11

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June 1, 2018

DIETS FOR HEALTH

of Agriculture [USDA]) and the Healthy Eating Plate (Har-

vard University) provide useful tools for achieving these

dietary guidelines (Table 2

2,16-18

). e Healthy Eating Plate

is consistent with the Mediterranean diet and emphasizes

covering one-half of the plate with fruits and vegetables,

one-fourth with whole grains, and the remaining one-fourth

with healthy protein; consuming water as the primary bever-

age; and engaging in regular physical activity. Plant oils and

proteins are highlighted. e Healthy Eating Plate recom-

mendations are closely aligned with the suggestions in this

article and oer another tool to help patients achieve compre-

hensive changes to their diets. All of these diets limit added

sugars, sweetened beverages, and highly rened grains.

Large, prospective cohort studies show that primarily

vegetarian diets reduce the risk of coronary artery disease

(CAD) and type 2 diabetes, and that vegan diets benet

patients with obesity, hypertension, type 2 diabetes, or other

CVD risk factors.

14,15

Each of the dietary patterns discussed

in this article is consistent with dietary advice recommended

by the American Academy of Family Physicians.

19,20

FRUITS AND VEGETABLES

Most dietary guidelines recommend that one-half of each

meal consist of vegetables and fruits.

11,16

Whole fruits and

vegetables are preferred over juices because of their higher

ber content and lower glycemic index (a measure of how

quickly a food is digested). Potatoes are not included in

this recommendation because they are more nutritionally

similar to grains. Observational studies have examined

the relationship between disease and intake of fruits and

vegetables. Higher intake has been associated with reduc-

tions in CAD,

cerebrovascular disease,

cancer,

and

TABLE 1

Summary of Common Dietary Patterns

Diet Includes Restricts Health beneﬁts Special considerations

Dietary

Approaches

to Stop

Hypertension

52% to 55% carbo-

hydrates, 16% to 18%

proteins, and 30% total

fats; rich in fruits, vege-

tables, whole grains, and

low-fat dairy products

Limits saturated fats,

cholesterol, reﬁned

grains, and sugars;

suggested sodium

intake is less than

2,400 mg per day

Decreases CVD risk

factors,

blood pressure,

obesity,

and type 2 diabe-

tes mellitus

—

Mediterranean

Fish, monounsaturated

fats from olive oil, fruits,

vegetables, whole

grains, legumes/nuts,

and moderate alcohol

consumption

Limits red meat,

reﬁned grains, and

sugars

Decreases rates of type 2

diabetes,

cancer incidence

and mortality,

age-related

cognitive decline,

CVD inci-

dence and mortality,

overall

mortality,

and obesity

—

Vegetarian or

vegan

14,15

Plant-based foods:

grains, plant oils, nuts,

seeds, legumes, fruit,

and vegetables

Vegetarian diet avoids

red meat, pork, poultry,

ﬁsh, and possibly eggs;

vegan diet excludes all

animal products and, in

some cases, honey

Vegetarian diet decreases

rates of type 2 diabetes and

coronary artery disease

;

vegan diet decreases rates

of hypertension, obesity,

and CVD mortality

Concern about vitamin

deﬁciencies with vegan

diets, especially vitamin B

;

supplementation may be

necessary; persons choos-

ing a vegetarian diet should

make sure to eat foods

from all food groups

CVD = cardiovascular disease.

Information from references 4 through 15.

WHAT IS NEW ON THIS TOPIC:

DIETS FOR HEALTH

Large, prospective cohort studies show that vegetarian diets

reduce the risk of coronary heart disease and type 2 diabetes

mellitus, and that vegan diets oer additional beneﬁts for

obesity, hypertension, type 2 diabetes, and cardiovascular

mortality.

Eating nuts, including peanuts, is associated with decreased

cardiovascular disease and mortality, lower body weight, and

lower diabetes risk.

In a prospective cohort study, consumption of artiﬁcially

sweetened beverages increased the risk of type 2 diabetes

about one-half as much as sugar-sweetened beverages.

June 1, 2018

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DIETS FOR HEALTH

gastrointestinal conditions.

Participants in the Nurses’

Health Study and the Health Professionals Follow-Up Study

who had the highest intake of fruits and vegetables (more

than ve servings per day) had a 30% decrease in the risk of

CVD compared with those who ate 1.5 servings or less per

day.

Green leafy vegetables seem to have the most benets.

Nine daily servings of vegetables and fruits—in a variety of

colors to maximize intake of various phytochemicals, anti-

oxidants, and vitamins—are recommended (Table 3).

2,16-18

LEGUMES

Legumes include a variety of beans, which are high in solu-

ble ber, protein, iron, B vitamins, and minerals,

and have

a low glycemic index. Because of their unique nutrients,

legumes are considered both a protein and a vegetable, and

are important components of healthy eating patterns. Eat-

ing legumes four times per week compared with less than

once per week is associated with reduced CAD and CVD

risk,

decreased recurrence of colorectal polyps, increased

longevity, improved blood glucose control, and better

weight management.

26,28

USDA dietary guidelines recom-

mend eating 1.5 to 3 cups of beans per week.

GRAINS

Grains are available as highly rened food products that

contribute to poor health (e.g., white bread) or as minimally

processed whole grains that contribute to a healthy diet (e.g.,

brown rice). Patients may have diculty understanding

which grains and grain products are healthy. e glycemic

index and glycemic load, which take into account the amount

of carbohydrate in a food, can help with this understanding.

e way a whole grain is processed determines the glycemic

index: nely ground grains will be digested more quickly

than less processed grains. Diets high

in processed grains are associated with

increased inammation, higher rates of

CVD, poorly controlled type 2 diabetes,

and diculty losing weight.

29-33

Whole

grains have a higher nutritional value

with more vitamins, protein, and ber

than processed grains, and are asso-

ciated with decreased rates of CVD.

USDA dietary guidelines recommend

eating 1.5 to 3 cups of grains per day,

with at least 50% of this amount as

whole grains.

FIBER

Dietary ber is divided into solu-

ble and insoluble ber; each type

has dierent eects on health (Table

4).

35-37

Good sources of ber include

whole grains, fruits, vegetables, and

legumes. Patients may rely on grains,

nuts, legumes, fruits, and vegetables

to increase their intake of soluble and

insoluble ber. Fiber intake is associ-

ated with reduced rates of CVD and

TABLE 2

Evidence-Based Dietary Recommendations

Food Quantity

Fruits and vegetables ½ of every meal

Whole grains ¼ of every meal

Legumes and/or animal

proteins

¼ of every meal

Water Primary beverage

Nuts Small handful daily

Oils/fats In moderation

Salt 2,500 mg daily (1 teaspoon)

Information from references 2, and 16 through 18.

TABLE 3

Dietary Serving Sizes

Food

category Examples Serving size*

Fruits Whole fruits, cooked or raw ½ cup, 1 medium fruit

Grains Brown rice, corn, whole oats, 100%

whole wheat; potatoes and corn

are also included in this category

because they are digested like

grains

½ cup cooked rice, corn, or

pasta; ½ cup cooked cereal or

1 cup ready-to-eat cereal;

1 slice of bread

Nuts Peanuts or tree nuts ¼ cup (1 oz)

Oils and fats Butter, canola oil, olive oil 1 tablespoon

Protein Beans, chicken, eggs, ﬁsh, peanuts,

tree nuts

2 to 3 oz cooked lean meat,

poultry, or ﬁsh; 1 egg; ½ cup

cooked beans; ½ cup tofu;

¼ cup hummus; 1 oz nuts

Vegetables Cooked or raw ½ cup (1 cup for leafy greens)

*—Serving sizes as deﬁned by the U.S. Department of Agriculture’s Choose My Plate.

Information from references 2, and 16 through 18.

724 American Family Physician www.aafp.org/afp Volume 97, Number 11

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June 1, 2018

DIETS FOR HEALTH

premature death; lower blood pressure, low-

density lipoprotein (LDL) cholesterol levels, and

breast cancer risk; and improved insulin sensi-

tivity.

35-38

USDA dietary guidelines recommend

consuming a minimum of 14 g of ber per 1,000

calories per day.

OILS, FATS, AND NUTS

Dietary fat is divided into three categories: satu-

rated, polyunsaturated, and monounsaturated. All

are essential nutrients, and every fat-containing

food has a combination of each type. Trans fats are

dangerous and have been banned. Eorts to reduce

fat consumption over the past 40 years led to

increased intake of rened carbohydrates in place

of fat and overall increased caloric intake, which

increased triglyceride levels and the risk of type 2

diabetes and contributed to weight gain, increased

LDL cholesterol levels, and decreased high-density lipopro-

tein cholesterol levels, but did not aect rates of CAD.

39,40

Dietary fats aect serum cholesterol levels and CAD

risk dierently. Compared with saturated fats, increasing

mono- or polyunsaturated fats decreases the risk of CAD,

although saturated fats found in plants may have a more

benecial eect on lipid levels.

41,42

Omega-3 and -6 fatty acids are polyunsaturated fats. An

unbalanced ratio of these fatty acids favoring omega-6 can

lead to increased activation of the arachidonic acid pathway,

with resulting increases in rates of thrombosis, vasospasm,

cancer, obesity, and allergic and inammatory disorders.

Increasing consumption of foods high in omega-3 fatty

acids (e.g., sh, nuts, canola oil, green vegetables) while lim-

iting the use of corn and vegetable oils can increase the ratio

of omega-3 to omega-6 fatty acids, leading to decreased

inammation and other health benets.

Monounsaturated fats in olive oil, nuts, and avocados

seem to be benecial for preventing CVD.

In general, a

focus on omega-3 and monounsaturated fats from sh and

plants is likely to be most benecial. Eating nuts, including

peanuts, has been associated with health benets such as

decreased risk of diabetes, CVD, and mortality,

and lower

body weight.

When nuts are eaten as part of a Mediter-

ranean diet, good-quality evidence shows decreased age-

related cognitive decline.

ANIMAL PRODUCTS

ere are conicting health benets for animal products,

with red and processed meats having the most signicant

negative eects. For instance, there is a dose-response rela-

tionship between red meat intake and risk of all-cause mor-

tality.

Although higher protein and fat content relative to

carbohydrate generally decreases CVD risk and improves

lipid levels,

data suggest that this is not the case when the

protein comes from animal sources.

Plant-based proteins

are generally preferred as a primary source.

When animal

products are consumed, an emphasis on sh, dairy, eggs,

and fowl is recommended.

Eggs are high in cholesterol but do not contain high

amounts of saturated fats. Observational data suggest that

consumption of up to one egg per day does not contribute

to CVD; however, persons with type 2 diabetes may have a

slightly increased risk.

Eggs are also high in vitamins and

protein.

Up to 70% of the world’s population does not have the

gene to produce lactase into adulthood, and therefore

cannot fully digest dairy products.

Dairy products are

a signicant source of added sugar and saturated fats.

Although dairy products supply calcium, fat, protein,

and carbohydrate, adequate amounts of each of these

components can be obtained from other foods. Neither

dairy consumption nor dietary calcium intake is associ-

ated with a reduction in hip fracture; in fact, they have

been associated with increases in fracture and all-cause

mortality.

Nondairy sources of calcium include greens,

nuts, and legumes. For those who can tolerate dairy, it is

associated with a decreased risk of type 2 diabetes and

metabolic syndrome,

and compared with nondairy milk

consumption, it may be associated with a slight increase in

childhood height.

Consumption of dairy products is not

independently associated with weight gain.

BEVERAGES

Beverages can have a signicant impact on dietary quality.

Persons who consume the most sugar-sweetened beverages

TABLE 4

Health Beneﬁts of Insoluble vs. Soluble Fiber

Fiber type Foods Health beneﬁts

Insoluble (does

not dissolve in

water)

Carrots, cucumbers,

seeds, tomatoes,

whole grains, and

zucchini

Improved insulin sensitivity,

prevention of cardiovascular

disease,

and reduced cancer

incidence

Soluble

(dissolves in

water)

Apples, beans, blue-

berries, lentils, and

oatmeal

Improvement in symptoms

of irritable bowel syndrome,

improved insulin sensitivity,

prevention of cardiovascular

disease,

and reduced cancer

incidence

Information from references 35 through 37.

June 1, 2018

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DIETS FOR HEALTH

have the highest caloric intake and the poorest quality nutri-

tion. However, those who drink coee and diet beverages eat

more high-calorie, low-nutrient-density foods.

Free sugars

include added sugar and other caloric sweeteners such as

honey, fruit juice concentrates, and maple syrup. Sweetened

beverages such as soda and energy drinks are being increas-

ingly linked to the development of multiple chronic diseases,

and the risks of hypertension, type 2 diabetes, and obesity-

related cancers increase with each additional serving.

57-59

Fruit juice, which is high in free sugars, is associated with

diabetes and should be discouraged.

e World Health

Organization recommends limiting free sugars to less than

5% to 10% of daily caloric intake

; the Dietary Guidelines

for Americans recommends less than 10%.

Articially sweetened beverages may increase the risk of

type 2 diabetes at about one-half the rate of sugar-sweetened

beverages.

However, evidence is emerging that compared

with unsweetened beverages, early exposure to articial

sweeteners in utero or during early childhood

may increase the risk of obesity in adulthood.

Replacing sweetened beverages (sugar and arti-

cially sweetened) with unsweetened beverages

may reduce the risk of type 2 diabetes, obesity,

and high blood pressure.

Unsweetened black and green teas have some

evidence of positive eects on LDL cholesterol

and blood pressure,

and coee and tea have

been proven to protect against depression.

Water may be the most important and ben-

ecial beverage. An analysis of data from the

National Health and Nutrition Examination Sur-

vey showed that as plain water intake increased,

total caloric intake decreased, especially from

sugar-sweetened beverages.

Inadequate hydra-

tion (as determined by elevated urine osmolality)

is associated with higher body mass index.

Moderate alcohol consumption (one drink per

day for women, two per day for men) has been

shown to decrease the risk of CAD.

However,

these results have been questioned by ndings

indicating that these studies did not carefully

parse the amount and duration of alcohol con-

sumption.

Potential benets seem to be inde-

pendent of the type of alcohol. Because of risks

associated with heavy use, clinicians should not

recommend that patients start drinking alco-

holic beverages.

SPICES

In addition to increasing the avor complexity

of foods, many spices are being studied for their

potential health benets. Salt is a common avoring and has

long been associated with an increased risk of CVD via its

eect on elevating blood pressure. Approximately 90% of

Americans consume more sodium than the 2,500 mg per

day recommended by the USDA, the National Academy of

Medicine, and the American Heart Association.

Accord-

ing to a Cochrane review, decreasing salt intake from the

current average of 9 to 12 g per day to a more modest 5 to 6

g per day would decrease systolic blood pressure by 5.8 mm

Hg, thereby signicantly reducing the overall population

burden of CVD.

Addressing Barriers to Behavior Change

ere are many barriers to behavior change that can con-

tribute to poor nutrition (Table 5). Addressing these barriers

with patients is as essential as providing information about

the health benets of foods (Table 6). Helping patients with

behavior change can be enhanced by techniques such as

TABLE 5

Barriers to a Healthy Diet

Barrier Intervention Resources

Cultural

barriers

Education Community resources

Information about the U.S. food sys-

tem (http:// www.jhsph.edu/research/

centers-and-institutes/johns-hopkins-

center-for-a-livable-future/education/

opencourseware)

Emotional

eating

Counseling,

education

Referral to psychologist or social

services

Financial

barriers

Educa-

tion, food

assistance

Education on cost of fresh vs.

processed foods

USDA Food Environment Atlas

(https:// www.ers.usda.gov/

data-products/food-

environment-atlas)

Lack of knowl-

edge about

healthy diets

Education

(online, hand-

outs), nutrition

counseling

Harvard University Nutrition Source

(https:// www.hsph.harvard.edu/

nutritionsource)

USDA Choose My Plate (https:// www.

choosemyplate.gov)

Lack of satiety

cues

Counseling,

education on

intuitive eating

Referral to psychologist or dietitian

Limited cook-

ing skills

Education Cooking classes through commu-

nity centers, restaurants, or grocery

stores

USDA = U.S. Department of Agriculture.

726 American Family Physician www.aafp.org/afp Volume 97, Number 11

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June 1, 2018

motivational interviewing or positive inquiry, utilizing

others on the health care team, and making use of commu-

nity resources. e U.S. Preventive Services Task Force rec-

ommends referral to intensive lifestyle programs to assist

with nutrition and physical activity for patients with CVD

risk factors

and considering selective referral for those

without risk factors.

Data Sources: We searched PubMed, the Cochrane database,

and Essential Evidence Plus using the key words diet, vegetable,

fruit, legume, cardiovascular disease, diabetes, meat, dairy, nuts,

carbohydrate, fats, and protein. We also reviewed http:// www.

nutrition.gov and http:// www.nutritionsource.org. Search dates:

January 2017 through March 2018.

The Authors

AMY LOCKE, MD, is an associate professor in the Department

of Family and Preventive Medicine at the University of Utah

Health, Salt Lake City, and adjunct assistant professor at the

University of Michigan Medical School, Ann Arbor.

JILL SCHNEIDERHAN, MD, is clinical faculty in the Depart-

ment of Family Medicine at the University of Michigan Medi-

cal School.

SUZANNA M. ZICK, ND, MPH, is a research associate profes-

sor in the Department of Nutritional Sciences at the Univer-

sity of Michigan School of Public Health.

Address correspondence to Amy Locke, MD, University of

Utah Hospital, 555 Foothill Dr., Salt Lake City, UT 84109

(e-mail: amy.locke@ hsc.utah.edu). Reprints are not available

from the authors.

References

1. Devries S, Dalen JE, Eisenberg DM, et al. A deﬁciency of nutrition edu-

cation in medical training. Am J Med. 2014; 127(9): 804-806.

2. U.S. Department of Agriculture. A snapshot of the 2015-2020

Dietary Guidelines for Americans. December 22, 2016. https://

www.choosemyplate.gov/snapshot-2015-2020-dietary-guidelines-

americans. Accessed January 9, 2018.

3. Lesser LI, Mazza MC, Lucan SC. Nutrition myths and healthy dietary

advice in clinical practice. Am Fam Physician. 2015; 91(9): 634-638.

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tematic review with meta-analyses. BMJ Open. 2015; 5(8): e008222.

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TABLE 6

Dietary Resources for Patients

American Academy of Family Physicians Patient Information

Resource (https:// family doctor.org)

Americans in Motion – Healthy Interventions

(http:// www.aafp.org/patient-care/nrn/studies/all/aim-hi.html)

Centers for Disease Control and Prevention, Division of

Nutrition, Physical Activity, and Obesity

(https:// www.cdc.gov/nccdphp/dnpao)

Harvard University Nutrition Source

(https:// www.hsph.harvard.edu/nutritionsource)

U.S. Department of Agriculture, Choose My Plate

(https:// www.choosemyplate.gov)

SORT: KEY RECOMMENDATIONS FOR

PRACTICE

Clinical recommendation

Evidence

rating References

A dietary pattern that emphasizes

vegetables, fruits, legumes, and

whole grains and minimizes free

sugars and red meats lowers blood

pressure and cholesterol levels.

C 20

One-half of each meal should

consist of fruits and vegetables.

C 11

Plant-based foods should be

emphasized over animal-based

foods in the diet.

B 49

Free sugars should be limited to

less than 10% of daily calories.

C 60

Water should be the primary bev-

erage consumed.

C 65

Intensive lifestyle modiﬁcation

should be recommended to

patients at high risk of cardiovas-

cular disease to assist in health

behavior change.

B 17

A = consistent, good-quality patient-oriented evidence; B = incon-

sistent or limited-quality patient-oriented evidence; C = consensus,

disease-oriented evidence, usual practice, expert opinion, or case

series. For information about the SORT evidence rating system, go

to https:// www.aafp.org/afpsort.

June 1, 2018

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Volume 97, Number 11 www.aafp.org/afp American Family Physician 727

DIETS FOR HEALTH

12 . Saneei P, Salehi-Abargouei A, Esmaillzadeh A, Azadbakht L. Inﬂuence of

Dietary Approaches to Stop Hypertension (DASH) diet on blood pres-

sure: a systematic review and meta-analysis on randomized controlled

trials. Nutr Metab Cardiovasc Dis. 2014; 24(12): 1253-1261.

13. Shirani F, Salehi-Abargouei A, Azadbakht L. Eects of Dietary Approaches

to Stop Hypertension (DASH) diet on some risk for developing type 2

diabetes: a systematic review and meta-analysis on controlled clinical

trials. Nutrition. 2013; 29(7-8): 939-947.

14. McEvoy CT, Temple N, Woodside JV. Vegetarian diets, low-meat diets

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