INTRODUCTION — Vegetarian diets are becoming increasingly popular [1-4]. Reasons for choosing a vegetarian diet are varied and include potential health benefits and sociopolitical, ecologic, and ethical issues related to allocation of resources and animal rights [1,5-8]. In some cases, and particularly among adolescents, it may be difficult to distinguish whether a choice to eat a vegetarian diet is related to health or ethical concerns versus a desire for dietary restriction [9,10].
The best available data regarding the nutritional quality of vegetarian diets and strategies to prevent nutritional deficiencies while consuming vegetarian diets are reviewed here. Nutrition requirements, deficiencies, and supplementation of specific nutrients are discussed separately. (See appropriate topic reviews.)
PREVALENCE AND TRENDS — Vegetarian diets are becoming increasingly popular in many countries, including among youth [1-4].
In the United States, approximately 5 percent of youth 8 to 17 years old describe themselves as vegetarian and 2 percent as vegan [11]. Among adults in the United States, approximately 6 percent follow some form of vegetarian diet and 3 percent follow a vegan diet [12]. When eating away from home, approximately one-half of Americans "sometimes or always" choose vegetarian meals and one-quarter "sometimes or always" choose vegan meals [11,12]. Vegetarian diets were reported by approximately 8 percent of adolescents in the United Kingdom [13] and 8 to 10 percent of adults in Germany, Austria, Italy, and the United Kingdom [14,15].
Interpretation of these surveys is complicated because of variations in definitions for the term "vegetarian." Definitions range from whether the individual considers himself or herself as vegetarian ("self-defined" vegetarians), avoids meat only, or lives by the strict definition (never consuming meat, fish, and poultry). As an example, one review of dietary patterns and nutrient intakes of self-defined vegetarians (aged six years and older) found that patterns ranged from those who consumed reduced amounts of red meat but included poultry and fish to those who excluded all animal foods [16]. The types and composition of vegetarian diets have important implications for the growth and development of children and adolescents.
TYPES OF VEGETARIAN DIETS — Vegetarian diets vary according to the degree of avoidance of foods of animal origin, and definitions are not consistent across studies [5,17,18].
Vegetarian diets frequently are grouped as follows (listed from less to more restricted):
●Semi-vegetarian – Meat occasionally is included in the diet. Some people who follow such a diet may not eat red meat but may eat fish and perhaps chicken.
●Pescatarian – Fish and shellfish are included in the diet but no meats or poultry. Variations are pescatarian-vegetarian (includes milk and eggs) or pescatarian-vegan (excludes milk and eggs).
●Lacto-ovovegetarian – Eggs, milk, and milk products (lacto = dairy; ovo = eggs) are included, but no meat is consumed.
●Lactovegetarian – Milk and milk products are included in the diet, but no eggs or meat are consumed.
●Macrobiotic – Whole grains, especially brown rice, are emphasized, and vegetables, fruits, legumes, and seaweeds are included in the diet. Locally grown fruits are recommended. Animal foods limited to white meat or white-meat fish may be included in the diet once or twice a week.
●Vegan – All animal products, including eggs, milk, and milk products, are excluded from the diet. Some vegans also avoid honey and may refrain from using animal products such as leather or wool.
Because these terms are used inconsistently, it is important to clarify the intended meaning as part of any discussion of these diets in clinical settings and when interpreting research.
HEALTH EFFECTS
Overall diet quality — Surveys of pediatric populations indicate that those who follow a vegetarian diet are somewhat more likely to meet general targets for a healthy diet compared with those who do not follow a vegetarian diet. As an example, one survey of adolescent schoolchildren in Minnesota compared self-reported dietary intake with the Healthy People 2010 nutritional objectives [19]. Adolescents who identified themselves as vegetarians were more likely than nonvegetarians to meet the objectives for total fat (70 versus 48 percent), saturated fat (65 versus 39 percent), daily servings of vegetables (26 versus 14 percent), and ≥5 servings of fruits or vegetables per day (39 versus 28 percent). The mean calcium intake in both groups was approximately 1100 mg/day, which is less than the recommended 1300 mg/day; only 30 percent of the students, regardless of dietary group, met the recommended target for calcium.
Despite this generally healthy diet profile, the vegetarian population also has some specific nutritional risks, especially for children following a vegan or otherwise restrictive diet, as detailed below. (See 'Energy' below and 'Protein' below and 'Vitamins and minerals' below.)
Potential effects on growth — Although children who follow a vegetarian diet tend to be somewhat leaner than their omnivore counterparts, their physical growth is usually within the normal range, provided that meal planning is adequate and sufficient food is made available [20-22]. By contrast, poorly planned or severely restricted diets can lead to nutrient deficiencies that may compromise or delay growth in children [23]. As an example, among Dutch children who consumed a macrobiotic diet, height and arm circumference were reduced for boys and girls at all ages, although the children experienced catch-up growth as they approached adolescence [23]. Catch-up growth was related to the addition of dairy products to the diet.
Association with eating disorders — Although adolescents may experience the health benefits of a vegetarian diet, in some individuals the vegetarian diet is a manifestation of restrictive dietary habits and other disordered eating behaviors [10,24,25]. In one report, current adolescent vegetarians were more likely than nonvegetarians to report binge eating and vegetarians were more likely than nonvegetarians to engage in unhealthy weight-control behavior [26]. (See "Eating disorders: Overview of epidemiology, clinical features, and diagnosis".)
Benefits for cardiovascular and metabolic health — In general, people who follow a lactovegetarian diet have somewhat better health outcomes compared with those following an omnivorous diet, while a vegan diet may have fewer health benefits and more risks [27,28]. As an example, several observational studies report that consumption of a vegetarian diet is associated with lower incidence of obesity, coronary heart disease, hypertension, and type 2 diabetes compared with consumption of a nonvegetarian diet [1,6,29-36]. These benefits are accompanied by modest decreases in non-high-density lipoprotein (non-HDL) cholesterol, blood pressure, and body mass index (BMI) [6,37]. However, it is difficult to separate the effects of the diet from other characteristics of this population, including associated healthful behaviors (eg, regular exercise and avoidance of tobacco and alcohol products) or socioeconomic privilege. As a consequence, an independent effect of the diet on health outcomes or all-cause mortality has not been shown [38].
Benefits for the gut microbiota — Vegetarian diets appear to be beneficial to human health by promoting more diverse and stable gut microbiota [39]. The diversity of the microbiota have an important association with BMI, obesity, and cardiovascular protection. Vegetarians have a microbiota rich in Prevotella and Ruminococcus and depleted in Bacteroides compared with omnivores. Plant fibers increase lactic acid bacteria such as Ruminococcus and Roseburia, which degrade complex carbohydrates into short-chain fatty acids and reduce disease-producing Clostridium and Enterococcus species. Plant fibers encourage the growth of microbiota that produce short-chain fatty acids, which improve immunity against pathogens and regulate intestinal function. Plant polyphenols increase Bifidobacterium and Lactobacillus, both of which have antiinflammatory effects. Thus, plant-based diets may be an effective way to promote a diverse ecosystem of beneficial microbes that support overall health.
It should be noted that these potential health effects are not intrinsic to every vegetarian diet, for which the nutritional content can be highly variable. The nutritional benefits and adequacy of a vegetarian diet must be judged individually, not on the basis of what it is called but on the type, amount, and variety of nutrients that are consumed [16].
OVERVIEW OF NUTRITIONAL COUNSELING
General considerations — When providing nutritional counseling about a restrictive diet, it is important to use a supportive, nonjudgmental approach to establish a therapeutic relationship so that the patient and caregivers are willing to accept guidance [40].
Vegetarian diets can meet nutrient needs for growth and development if they are carefully planned with attention to energy, protein, iron, calcium, vitamin D, and vitamin B12 (cyanocobalamin) and, to a lesser extent, zinc, long-chain omega-3 fatty acids, and dietary fiber [1,41-44]. Nutritional counseling about these nutrients is detailed in the sections on each nutrient below.
The greatest risks for inadequate nutrient intake from a vegetarian diet occur during periods of growth. The more restrictive the vegetarian diet, the greater the risk of dietary inadequacy [45-47]. The establishment of healthy eating patterns in childhood reduces the likelihood of developing chronic diseases later in life [48-51]. Thus, vegetarian children, like other children, should consume a diet low in fat, saturated fatty acids, and cholesterol and high in complex carbohydrates, fiber, and antioxidants (eg, vitamins A and C, carotenoids, and phytochemicals) [52].
Vegetarian or vegan diets should include a variety of nutrient-rich foods. Examples of foods include cooked legumes, whole grain breads, enriched cereals, nuts and nut spreads (peanut, tahini, almond, and cashew butter), nutlike seeds (sunflower seeds, soybeans, sesame seeds), avocados, and dried fruits. In addition, the inclusion of dairy products in the vegetarian diet provides a substantial portion of essential nutrients. Dairy products are good sources of energy, high-quality protein, calcium, potassium, vitamin B12, magnesium, and vitamin D (if fortified) [27,53].
The United States Department of Agriculture (USDA) "MyPlate plan" is a tool depicting food groups and portion sizes and may serve as a useful reference guide. Food patterns with vegetarian options are provided for different calorie levels [54]. One group has developed a similar tool for planning a vegetarian or vegan diet (VegPlate Junior) that meets Italian and United States dietary reference intakes [55].
Weaning an infant to a vegetarian or vegan diet — Weaning of an infant to a vegetarian diet is particularly challenging and should be undertaken only with guidance to ensure adequate nutrient intake, particularly of total energy and protein, vitamin B12 (if the diet is vegan), vitamin D, iron, zinc, folate, and calcium [46,56-58]. Specific guidance for the maternal and infant diet is summarized in the table (table 1).
Plant-based formulas and beverages
●Homemade formulas – Infants should not be fed homemade formulas, including those made from a recipe that the parent might perceive to be healthy, unless the composition has been closely reviewed and approved by a nutritionist or dietitian with pediatric expertise [59]. Homemade formulas are likely to lack essential vitamins and minerals, including vitamin D, calcium, and iodine. Case reports describe life-threatening consequences of feeding a homemade formula to infants, which was made by their parents using a vegan or "alkaline diet" recipe [60,61]. The infants presented with acute respiratory distress, severe life-threatening hypocalcemia, hypophosphatemia, and rickets, with or without hypothyroidism, and some experienced seizure or cardiac arrest. The infants came to medical attention when they presented with acute respiratory distress after two to three months of feeding on the homemade formula.
●Other plant-based beverages – For toddlers and preschool-aged children (<5 years), plant-based beverages (such as soy-, oat-, or almond-based "milks") should not be used as a primary source of energy and protein. If it is not possible to feed human milk or other mammalian milk (due to the child's intolerance or if the family chooses to follow a vegan diet), dietary review and guidance are suggested. Plant-based infant formulas and "transition" formulas may be appropriate substitutes to increase intake of protein, energy, and other nutrients.
For school-aged children, it is reasonable to include a fortified plant-based beverage in the diet but with dietary review and guidance to ensure adequate overall intake of protein, calcium, and vitamin D. Choose a plant-based beverage that is amply fortified with calcium and vitamin D because there are few other good dietary sources for these nutrients.
These precautions are needed because plant-based beverages are less reliable sources of nutrition for young children compared with cow's milk. The nutrient profiles of plant-based beverages vary substantially, but they tend to be relatively low in protein, fat, and other nutrients compared with cow's milk [62-64]. Even when the beverages are fortified, the plant phytates may reduce the bioavailability of protein and minerals. (See 'Protein' below.)
LABORATORY MONITORING — Laboratory monitoring for children on vegetarian diets depends on the type of diet and other characteristics of the individual patient. To identify possible deficiencies, the first step is to perform a periodic survey of the patient's diet using dietary recall or a diet log. For patients at higher risk for deficiencies, such as those who are underweight or following a vegan diet, we suggest referral to a dietitian for detailed evaluation and counseling.
Once the characteristics of the diet have been identified, we suggest the following approach to laboratory testing:
●For any patient who eats little or no meat or fish, screen for iron deficiency periodically, following recommendations for patients at increased risk. A typical approach would be to do laboratory testing every two to three years if clinically stable and more frequently for patients with abnormal results or with risk factors such as low body weight or heavy menses. In most clinical settings, the most cost-effective measurement is a complete blood count (CBC); serum ferritin is measured either at the same time or in follow-up for those with microcytic anemia. (See "Iron deficiency in infants and children <12 years: Screening, prevention, clinical manifestations, and diagnosis", section on 'Screening recommendations' and "Iron requirements and iron deficiency in adolescents", section on 'Screening'.)
●For patients with low estimated vitamin D intake (eg, those with little or no dairy intake), check 25-hydroxyvitamin D at baseline with follow up testing as needed depending on the result or to monitor supplementation. If a supplement is added, check the level approximately six months later, and if the result is normal, recheck approximately every two to three years. (See 'Vitamin D' below.)
●For patients who follow a vegan diet, supplement empirically with vitamin B12. Measure serum vitamin B12 concentrations if there is a concern for deficiency, eg, question of nonadherence to the supplement or macrocytic anemia. (See 'Vitamin B12' below.)
ENERGY
Energy requirements — Some young children who follow a vegetarian or vegan diet may have difficulty meeting their energy needs because of their relatively small stomach capacity and energy needs for growth [20,21,65,66]. A plant-based diet that has a high fiber content and low caloric density may provide a sense of fullness before an adequate amount of energy is ingested. This situation may be a significant problem in young children, who have small stomach capacities.
To meet energy needs, young children typically need three meals and three snacks per day. Both energy-dense and nutrient-dense foods should be included. Foods higher in healthy fats, such as nuts, seeds, nut and seed butters, and avocado, help meet nutrient and energy needs, especially for children who are underweight. The intake of fat should not be restricted in children younger than two years of age. (See "Dietary history and recommended dietary intake in children", section on 'Energy needs'.)
For adolescents who follow a vegetarian or vegan diet, the clinician should monitor growth and body weight to ensure that energy intake is appropriate. Adolescents who are overweight and who adopt a vegetarian diet as a means of weight management also should be monitored for evidence of disordered eating patterns and given anticipatory guidance to emphasize dietary variety and an appropriate energy intake for healthy weight management [9]. (See "Estimation of dietary energy requirements in children and adolescents".)
Weight concerns — For adolescents who choose to adopt a vegetarian or vegan diet, the clinician should inquire about what prompted the change in the diet. In many cases, the developmental stage or family/cultural preferences may have played a role in his or her dietary choice. Counseling should include information about the nutritional implications of the diet to set appropriate expectations and encourage the adolescent to make responsible food choices.
The clinician should also be alert for any signals that the dietary change may have been triggered by underlying emotional problems, including an eating disorder [9]. Any adolescent whose body mass index (BMI) is less than the 15th percentile, whose actual weight is less than 85 percent of the expected weight for height and age, and/or who has other features suggestive of an eating disorder (including disrupted menses or body image disturbances) is a candidate for referral for more intensive medical and psychological care. (See 'Association with eating disorders' above and "Eating disorders: Overview of epidemiology, clinical features, and diagnosis".)
PROTEIN
Requirements — Protein requirements for children are approximately 1.05 g/kg/day for those one to three years of age, 0.95 g/kg/day for those 4 to 13 years of age, and 0.85 g/kg/day for adolescents [67].
These estimates are based on proteins from animal sources (meat, dairy, and eggs) or well-processed soy isolates, which are more than 90 percent digestible [68,69]. Diets that include these protein sources generally include sufficient protein, as long as the total energy intake is sufficient. This includes semi-vegetarian, pescatarian, or macrobiotic diets, or vegetarian diets that include milk, milk products, and/or eggs [70]. Note that plant-based beverages provide substantially less protein than cow's milk (soy "milk" provides 60 percent of the protein in cow's milk, rice milk provides 8 percent, and almond milk only 2 percent) [58]. Moreover, the protein in the plant-based beverages is less bioavailable than that in mammalian beverages [63]. Therefore, these beverages should not be used as a primary source of energy and protein for young children; plant-based infant formulas and "transition" formulas are appropriate substitutes.
Proteins from legumes are 80 to 90 percent digestible, while proteins from grains and other plant foods are 70 to 90 percent digestible. Therefore, for vegetarians who rely on these protein sources, the protein requirement may be increased by 20 to 30 percent for children aged two to six years and by 15 to 20 percent for children aged six and older, in comparison with nonvegetarians [68].
Protein type — Proteins of plant and animal origin differ in their concentration of essential amino acids, which are necessary for growth and repair. To avoid essential acid deficiency, vegetarian diets must include either complete proteins (from animal foods or soy) or complementary proteins (from complementary types of vegetable proteins).
●Complete proteins – Essential amino acid deficiency is not a concern for diets that include adequate meat, fish, dairy, eggs, or soy. Animal foods are considered complete proteins because they contain all nine essential amino acids. Soybean-based products are also complete proteins, unlike other vegetable proteins [71]. Therefore, soy protein is considered high quality and is a valuable source of protein for vegetarians [72,73]. However, young infants have a relatively high nutritional requirement for essential amino acids, and soybean isolates are relatively deficient in methionine. Soy-based infant formulas are supplemented with methionine to improve the utilization of soy protein by infants [74-76]. The need for essential amino acids decreases as growth and development progress. Thus, children older than two years are capable of utilizing soy protein isolates without methionine supplementation as a primary source of essential amino acids and nitrogen for protein maintenance [77,78].
●Incomplete proteins – Plant-based proteins other than soy are considered incomplete because they lack one or more of the essential amino acids. A diet that relies on these incomplete proteins may not supply sufficient essential amino acids, especially for infants.
This problem can be addressed by combining one incomplete plant food with a complementary plant food that provides adequate amounts of the limited essential amino acid. As an example, grains are low in the essential amino acid lysine and high in methionine, whereas legumes are low in methionine and high in lysine. Together, they combine to make a high-quality protein source. One need not consume complementary proteins at the same time or in the same meal [1,77].
VITAMINS AND MINERALS — Nutritional counseling is important to ensure that the diet provides adequate vitamins and minerals, especially iron, calcium, vitamin D, and vitamin B12 (cyanocobalamin). If the diet cannot be adjusted to provide recommended amounts of each of these nutrients, supplements should be added to ensure adequate intake. In this case, we suggest a general multivitamin and mineral supplement that contains a broad range of water- and fat-soluble vitamins, minerals, and trace elements to ensure dietary intakes of micronutrients that approximate daily nutrient requirements for age (table 2).
Iron — Children who have rapid growth rates have increased iron needs and are at risk for iron deficiency with or without anemia [79-81]. The recommended dietary allowance (RDA) for iron is 7 mg in children 1 to 3 years old, 10 mg in children 4 to 8 years, 8 mg in children 9 to 13 years, and 11 mg for males and 15 mg for females aged 14 to 18 years. The RDA for pregnant adolescents is 27 mg/d [82]. (See "Iron deficiency in infants and children <12 years: Screening, prevention, clinical manifestations, and diagnosis" and "Iron requirements and iron deficiency in adolescents".)
●Potential deficits for a vegetarian diet – Iron deficiency is common among children who consume a vegetarian diet, but the prevalence varies widely [83]. All children who eat little or no meat are at risk, including lacto-ovovegetarians, because milk and eggs are not good sources of absorbable iron. Risk factors include a restrictive vegetarian diet, periods of rapid growth, and menstruation [68,79,84,85]. In a study of 1100 children aged 4 to 18 years, female adolescents who reported being vegetarian were more likely to have low hemoglobin and serum ferritin values than their omnivorous peers [79]. One study of 43 lacto-ovovegetarian and 46 omnivorous children aged 4.5 to 9 years found lower serum hepcidin and ferritin levels in the vegetarian children, despite higher dietary intake of vitamin C, compared with the nonvegetarian children [86]. By contrast, a longitudinal study of young children in Toronto found no association between a vegetarian diet and biomarkers of iron deficiency [22].
Children who do not eat meat are at risk for iron deficiency because nonheme iron (from plants) is less readily absorbed than heme iron (from meat or fish) [79,82,87,88]. Absorption of heme iron is 15 to 35 percent compared with 2 to 20 percent for nonheme iron. In addition, the absorption of nonheme iron is reduced greatly by other dietary components, whereas heme iron is little affected (table 3). In particular, tannins and polyphenols in tea and coffee form iron-tannate complexes that greatly reduce nonheme iron absorption [41,79,89]. Phytate found in legumes, nuts, seeds, whole grains, and soy protein also bind with nonheme iron to form insoluble complexes and reduce iron absorption [41,79,90,91]. In one study, absorption of iron from a variety of commonly eaten legumes (dried beans and peas) prepared as soups was only 1 to 2 percent [84].
●Nutritional counseling – For children who do not eat meat or fish, important strategies to increase iron absorption include intake of ascorbic acid (vitamin C) at each meal, avoidance of large intakes of tannin-containing teas, and increasing dietary iron content [41,79,81,92].
Iron supplements may be necessary for individuals with laboratory markers for iron deficiency (eg, low mean cell volume [MCV] and mean corpuscular hemoglobin [MCH], microcytic anemia, and/or low ferritin) or those with low iron intake as estimated from a dietary recall. This is most likely for individuals eating restricted vegetarian diets with little or no meat or fish [1,41]. Adolescent girls are at increased risk for iron deficiency after menarche, due to menstrual blood loss. (See "Iron deficiency in infants and children <12 years: Screening, prevention, clinical manifestations, and diagnosis" and "Iron requirements and iron deficiency in adolescents".)
Ascorbic acid (vitamin C) is a powerful promoter of nonheme iron absorption because it prevents the formation of less-soluble ferric compounds [84,93-95]. A 75 mg dose of ascorbic acid increases the absorption of nonheme iron three- to fourfold [90]. Because of its mechanism of action, ascorbic acid is effective only when consumed at the same time as the iron-containing food. Important sources of both vitamin C and other facilitators of iron absorption (eg, citric and malic acid) include citrus fruits and strawberries, broccoli, and tomatoes. By increasing absorption of nonheme iron, ascorbic acid helps to counteract the inhibitory effect of phytates in a plant-based diet.
Good plant sources of iron include whole or enriched breads or grains, iron-fortified cereals, legumes, green leafy vegetables, dried fruits, soy products, blackstrap molasses, bulgur, and wheat germ. The widespread fortification of enriched breads, cereals, and pasta products has helped increase iron intake for children.
Calcium — Adequate calcium intake is important throughout life to ensure peak bone mass accumulation, especially during periods of growth. Children with stronger bones may experience fewer fractures and may be more resistant to the development of osteoporosis in later life [96,97]. The recommended intake of calcium is approximately 700 mg for children 1 to 3 years of age, 1000 mg for children 4 to 8 years of age, and 1300 mg for those 9 to 18 years (table 2) [98]. (See "Bone health and calcium requirements in adolescents" and "Dietary recommendations for toddlers and preschool and school-age children", section on 'Dairy products'.)
●Potential deficits for a vegetarian diet – For children who consume lactovegetarian or lacto-ovovegetarian diets, most calcium needs can be met by low-fat milk and dairy products; these provide approximately 75 percent of the calcium in the average American diet [97,99]. Children who avoid dairy products, such as those following a vegan diet, have more difficulty meeting calcium needs. This is in part because they consume plant foods containing oxalates and phytates, and because the calcium content of typical vegetables, fruit, and cereal grains is relatively low [42,100-102]. Children who avoid dairy products generally require either substantial intake of calcium-fortified foods (eg, several servings daily of calcium-fortified soy milk) or a calcium supplement to meet the age-dependent recommended intake (table 2).
Estimates of calcium needs are imprecise because other dietary constituents also affect calcium balance: oxalate and phytate decrease calcium absorption, while salt and protein increase calcium excretion [92,97,103]. Foods high in oxalate include spinach, beet greens, Swiss chard, and yams. Thus, the lower protein intake among vegetarians may decrease urinary calcium loss, which improves their net calcium balance and reduces their risk for calcium stone formation compared with omnivores [104]. (See "Kidney stones in adults: Epidemiology and risk factors", section on 'Protein'.)
●Nutritional counseling – Vegetarian children who do not drink milk should include at least one calcium-rich or calcium-fortified food with each meal and with several snacks each day. Children who follow a vegan diet can obtain calcium from calcium-fortified foods and beverages (such as fortified soy milk), foods naturally rich in calcium, calcium supplements, or a combination of these:
•Calcium-fortified foods include soy milk, soy yogurt, and soy cheese, as well as calcium-precipitated tofu and calcium-fortified cereals, breakfast bars, pastas, waffles, and juices [105,106]. Calcium bioavailability in most of these sources is equivalent to milk. As an example, one eight-ounce glass of calcium-fortified orange juice provides 300 mg of calcium, equivalent to an eight-ounce glass of milk. In contrast, the bioavailability of calcium in soy milk is only 75 percent of that in cow's milk [107]. Ideally, these foods should also be fortified with vitamin D because vitamin D facilitates the absorption of calcium [108].
•Foods that are naturally rich in calcium and low in oxalate include kale, mustard greens, turnip greens, broccoli, bok choy, dried figs, blackstrap molasses, and lime-processed tortillas (table 4) [97]. Most of these foods have additional benefits because they provide other important nutrients. However, it is difficult to meet calcium requirements from these foods alone, even with large portions.
•Calcium supplements also can be used to provide adequate calcium intake. Consuming calcium supplements at the same time as iron or zinc supplements may interfere with the absorption and utilization of these minerals. (See "Bone health and calcium requirements in adolescents".)
The benefits of using fortified foods to increase calcium intake was demonstrated in a double-blind, placebo-controlled study of prepubertal girls with low spontaneous calcium intake who were randomly assigned to receive food products that were or were not fortified with 850 mg of calcium [109]. Calcium fortification increased mean bone mineral density in all girls, but the increase was greatest in those whose baseline calcium intake was less than 850 mg. The gains in bone mass persisted one year after discontinuation of treatment.
Vitamin D — Normal levels of vitamin D metabolites are necessary for adequate intestinal calcium, phosphate absorption, and bone formation [110-112]. Vitamin D is available through sunlight exposure and dietary intake (figure 1). Dietary intake of 15 mg (600 international units) daily is recommended for children one year and older. (See "Vitamin D insufficiency and deficiency in children and adolescents", section on 'Recommended vitamin D intake'.)
Sunlight exposure is an important source of vitamin D but is often insufficient, especially during the winter, for children with dark skin pigmentation or for those who use sunscreen or clothing to protect their skin from sun damage. Maintenance of normal serum vitamin D concentrations requires exposure to the sun on hands, arms, and face for 10 to 15 minutes per day for fair-skinned individuals; individuals with dark skin pigmentation require 6 to 10 times as much exposure as a light-skinned individual [113]. (See "Vitamin D insufficiency and deficiency in children and adolescents", section on 'Skin pigmentation and low sun exposure'.)
●Potential deficits for a vegetarian diet – Few foods contain vitamin D. The principal dietary source of vitamin D for omnivores, lacto-ovovegetarians, and lactovegetarians is milk fortified with vitamin D (2.5 mg [100 international units] per 8 oz) [114]. Vegetarians who do not consume milk are at risk for vitamin D deficiency, which can lead to rickets in young children and osteomalacia in adults [115-118]. In one study of 53 children (one to two years of age) on a macrobiotic diet compared with 57 matched omnivores, symptoms of rickets were present in 28 percent of the children who followed a macrobiotic diet [119].
●Nutritional counseling – For children who do not drink milk (eg, those following a vegan diet), a dietary alternative is fortified soy milk, other fortified alternative milk, or fortified breakfast cereal [108,110]. For children who eat fish (eg, a pescatarian or macrobiotic diet), consuming fatty fish (sardines, salmon, tuna, mackerel) or cod liver oils several times per week can provide sufficient vitamin D. Cheese and egg yolks provide small amounts of vitamin D [110].
To meet the recommended intake for vitamin D, children generally require either substantial intake of these vitamin D-rich foods (eg, several servings daily of fortified milk or soy milk) and some additional vitamin D from sunlight exposure (eg, from participating in outdoor sports or active play). Otherwise, they will require a vitamin D supplement to meet the target, especially if they have risk factors for vitamin D deficiency such as dark skin pigmentation, low sun exposure, or residence in northern latitudes [120,121]. (See "Overview of vitamin D", section on 'Sources'.)
Vitamin B12 — Vitamin B12 (cobalamin) is only found in foods from animal sources (meat, fish, eggs, and dairy products) [42,122]. The RDA for cobalamin is 0.9 mcg for children 1 to 3 years of age, 1.2 mcg for those 4 to 8 years, 1.8 mcg for 9 to 13 years, 2.4 mcg for 14 to 18 years, and 2.6 mcg for pregnant adolescents [123]. Because substantial amounts of vitamin B12 are stored in the body (primarily in the liver), the deficiency develops gradually. Once vitamin B12 is removed from the diet, deficiency develops within four to six months in infants (eg, the breastfed infant of a mother with vitamin B12 deficiency) or one to two years in adults [123]. Vitamin B12 deficiency in infants can present with tremor, irritability, or spells (apneas, absences, and motor seizures) [124,125]. (See "Clinical manifestations and diagnosis of vitamin B12 and folate deficiency".)
●Potential deficits for a vegetarian diet – Lacto-ovovegetarians and lactovegetarians can, but do not always, consume sufficient amounts of vitamin B12 from eggs, milk, and milk products. Vegans, whose diets are based entirely on plant food, are at considerable risk for vitamin B12 deficiency [126,127]. For example, in one study, 10 of 25 vegans had vitamin B12 deficiency manifested by macrocytosis (picture 1) and low serum vitamin B12 [128]. In another report, serum vitamin B12 concentrations were determined in 83 volunteer subjects attending an American vegetarian society conference [129]. Among subjects who did not supplement their diets with vitamin B12 or multivitamin tablets, the percentage with serum vitamin B12 levels below the normal range was associated with the degree of dietary restriction:
•Vegans – 92 percent
•Lactovegetarians – 64 percent
•Lacto-ovovegetarians – 47 percent
•Semi-vegetarians – 20 percent
●Nutritional counseling – For children who eat fish (eg, those following a pescatarian diet), eating fish two to three times per week can provide a good source of vitamin B12. Vegan children and other vegetarians whose diet does not contain significant amounts of meat or fish should consume a regular and reliable source of the vitamin, either in fortified foods or an oral B12 supplement. Commonly used vitamin B12-fortified foods include most ready-to-eat cereals, many meat substitutes, some milk alternatives, and fortified nutritional yeasts [16]. Fortified soy milk is another good source of vitamin B12 for children [130]. Vitamin B12 supplements typically provide 6 to 9 mcg/day [127]. This dose is higher than the RDA to ensure adequate intake and because there are no adverse effects of the higher dose [123]. Of note, only cyanocobalamin is the active form of the vitamin, and some listings of vitamin B12 content in foods do not differentiate between this form and its inactive analogs. As examples, much of the vitamin B12 present in spirulina, sea vegetables, tempeh, and miso is inactive and does not contribute to the vitamin B12 requirement [106,131]. Moreover, the inactive forms can compete with active forms for absorption.
Zinc — Recommended intake for zinc is 3 mg/day for children aged 1 to 3 years, 5 mg/day for children aged 4 to 8 years, 8 mg/day for children aged 9 to 13 years, 9 mg/day for adolescent females, and 11 mg/day for adolescent males (table 5).
●Potential deficits for a vegetarian diet – Children who do not consume dairy products are at risk of a suboptimal zinc status because of high requirements for growth, although the clinical significance of mild zinc deficiency is unclear. Severe zinc deficiency can be associated with growth impairment and an increased risk of infections, particularly diarrhea and pneumonia. Adult vegetarians do not typically develop zinc deficiency, because they have a compensatory increase in fractional absorption. (See "Zinc deficiency and supplementation in children".)
Zinc is found in foods of both animal and plant origin. Animal sources include oysters, shellfish, liver, meat, poultry, and dairy products [87,132]. The zinc in vegetarian diets has a lower bioavailability because of the high content of phytate and dietary fiber [41,68,133,134]. Certain food-preparation techniques, such as the soaking of sprouting beans, grains, and seeds, as well as leavening breads, can mitigate this problem by reducing binding of zinc by phytates, thus increasing zinc bioavailability [1,135,136].
●Nutritional counseling – Milk and milk products are the primary source of zinc for children on vegetarian diets who also consume dairy products. For children who do not consume milk (eg, vegans), cereals are the primary source of zinc; secondary sources are meat substitutes (eg, legumes, nuts, and soy products). Plant sources of zinc include whole grains, legumes, wheat germ, and nuts.
Omega-3 fatty acids — Dietary requirements for omega-3 fatty acids in infants, children, and adolescents have not been established [137]. However, indirect evidence suggests that they have some health benefits.
●Potential deficits for a vegetarian diet – Vegetarian diets generally are rich in omega-6 fatty acids but may be marginal in omega-3 fatty acids unless the diet includes fish, eggs, or generous amounts of algae. Omega-3 fatty acids, which include docosahexaenoic acid (DHA) or eicosapentaenoic acid (EPA), or their precursor alpha-linolenic acid (ALA), are important for cardiovascular health and eye and brain development [43,138,139]. Vegetarians, particularly vegans, have lower blood levels of EPA and DHA than nonvegetarians [1,140].
●Nutritional counseling – We suggest that vegetarian children include either oily fish or other good sources of omega-3 fatty acids in their diet, such as flaxseed, walnuts, canola oil, and soy. Infant formulas, soy milk, and breakfast bars that are fortified with DHA also are available [1]. (See "Fish oil: Physiologic effects and administration".)
Fiber — Recommended fiber intake for children is approximately 19 g/day for ages 1 to 3 years, 25 g/day for ages 4 to 8 years, and 26 to 31 g/day for ages 9 to 13 years [67]. Because these targets are difficult to achieve, somewhat lower targets may be more realistic for children whose diets are not plant-based [141].
The optimum level of dietary fiber for infants and children younger than two years of age is not known. For this age group, studies of weaning diets with increased fiber suggested that 5 g/day is beneficial and found no negative effect on the absorption of energy, zinc, and calcium or iron bioavailability [142,143]. However, other studies have shown that growth is poor among infants and toddlers weaned onto very high-fiber, low-calorie diets that often are deficient in vitamins and minerals [144,145]. (See "Dietary recommendations for toddlers and preschool and school-age children", section on 'Fiber'.)
●Potential issues for a vegetarian diet – Vegetarians tend to have a relatively high fiber intake compared with omnivores. In populations following a vegan or macrobiotic diet, the average fiber intake is in a healthy range. In a study of 51 adults, average fiber intake among omnivores was 23 g compared with 37 g among vegetarians and 47 g among vegans [146]. In a similar study of 106 children 6 to 16 months of age, mean daily fiber intake was 13 g among those following a macrobiotic diet compared with 7 g among omnivores [147].
The consumption of a high-fiber diet in childhood promotes regular bowel movements and possibly reduces the risk of developing certain diseases in adulthood. However, during childhood, a diet with very high fiber content can compromise dietary energy intake and reduce the bioavailability of minerals such as iron, calcium, and zinc [1,41,68,148]. A small loss of energy, primarily as fat, and protein may occur with a high intake of dietary fiber. Daily fecal energy loss is estimated to increase by 1 percent for every 6 g increase in dietary fiber. This loss is unlikely to be significant in children who consume adequate energy.
The amount of dietary fiber recommended above, or even fiber intake that exceeds this recommendation, does not have an adverse effect on mineral bioavailability, provided that the dietary mineral intake is adequate. However, mineral bioavailability may be problematic in children who follow strict macrobiotic or vegan diets with low intake of calcium, iron, and zinc.
●Nutritional counseling – Most vegetarian children have a healthy intake of fiber. Because a very high-fiber diet can compromise energy intake and mineral absorption, vegetarian children should be monitored to ensure that they have adequate growth and adequate intake of minerals such as iron, calcium, and zinc.
Dietary fiber goals can be met best by eating a variety of fiber-rich fruits, vegetables, cereals, and grain products while consuming adequate energy intake for growth and development [148]. Fiber supplements are not recommended to meet dietary fiber goals.
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: Healthy diet in children and adolescents".)
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: Vegetarian diet (The Basics)")
SUMMARY AND RECOMMENDATIONS
●Overview – Children can safely ingest vegetarian diets and attain normal growth and development, provided that the diet is well planned and balanced. More restrictive diets (eg, vegan) require particular care to ensure that all nutritional needs are met. In general, a lactovegetarian diet has greater health benefits and fewer health risks than a vegan diet. (See 'Types of vegetarian diets' above and 'Benefits for cardiovascular and metabolic health' above.)
●Counseling
•Infants and young children – Weaning of an infant to a vegetarian diet is particularly challenging and should be undertaken only with expert guidance to ensure adequate nutrient intake, particularly of total energy and protein, vitamin B12 (if the diet is vegan), vitamin D, iron, zinc, folate, and calcium (table 1). Homemade plant-based formulas should not be used for infants or toddlers unless the composition of the formula is closely reviewed and approved by a dietitian or nutritionist with pediatric expertise. Plant-based beverages (such as soy-, oat-, or almond-based "milks") should not be used as a primary source of energy and protein for young children, except those designed as a "transitional" formula. (See 'Weaning an infant to a vegetarian or vegan diet' above and 'Plant-based formulas and beverages' above.)
•Older children and adolescents – Some older children or adolescents choose a vegetarian diet as a means of weight control, and clinicians should be alert for evidence of inappropriate dietary restriction and other disordered eating behaviors. An adolescent whose body mass index (BMI) is less than the 15th percentile, or whose actual weight is less than 85 percent of ideal body weight, is a candidate for referral for more intensive medical and psychological care. (See 'Weight concerns' above.)
●Specific nutrients – Nutritional counseling is important to ensure that the diet provides adequate nutrients, especially energy, protein, iron, calcium, vitamin D, and vitamin B12 (cyanocobalamin). If the diet cannot be adjusted to provide recommended amounts of each of these nutrients, supplements should be added to ensure adequate intake.
•Iron – Children who do not eat meat or fish are at risk of iron deficiency, especially during periods of rapid growth and in menstruating girls. To enhance the absorption of nonheme iron (from plants), a source of ascorbic acid should be provided at each meal. Teas containing tannin should be limited. Iron supplements may be necessary for some individuals eating restricted vegetarian diets. (See 'Iron' above.)
•Calcium and vitamin D – Children who consume little or no dairy products are at risk for calcium and vitamin D deficiencies. Ready-to-eat cereals and alternative milks (such as soy milk) are good sources of these nutrients, provided that they are fortified. However, the recommended intake for these nutrients is high and requires several servings daily of milk, fortified alternative milk, or fortified cereal. Many children require supplementation to meet their requirements. (See 'Calcium' above and 'Vitamin D' above.)
•Vitamin B12 – Children who follow a vegan diet are at risk for vitamin B12 (cobalamin) deficiency because animal products (meat, fish, and dairy products) provide the only dietary source of vitamin B12 (cobalamin) for humans. Individuals following a vegan diet should consume a regular and reliable source of the vitamin, either in fortified foods (soy milk or cereals) or an oral vitamin B12 supplement. (See 'Vitamin B12' above.)
ACKNOWLEDGMENT — The UpToDate editorial staff acknowledges Kathleen J Motil, MD, PhD, who contributed to earlier versions of this topic review.
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