Keeping teenage vegetarians healthy and in the know

By Peter F. Belamarch, MD, and Keith Thomas Ayoob, EdD, RD

With nutrition so essential to adolescent growth and development, pediatricians must be prepared to offer sound nutritional advice to teen vegetarians. This review summarizes health and nutritional research on teenage vegetarianism and provides information you can use to counsel patients and their parents.

Amanda, a 17-year-old who has been a patient of yours since childhood, is in for her yearly check-up. She became a vegetarian a month ago. Today, she is accompanied by her mother, hoping you can resolve an ongoing disagreement about the risks and benefits of vegetarianism. Her mother is concerned about weight loss and whether Amanda is getting enough iron and vitamins. Amanda is asking you to convince her mother that a vegetarian diet is nutritionally adequate, safe, and, in fact, healthier than the typical American omnivorous diet that her parents eat.

Amanda is like many adolescents who are, or who are thinking of becoming, a vegetarian. The fact is that Amanda can have a perfectly healthy diet without eating meat, poultry, or fish, and that she can indeed reap health benefits from vegetarianism. The practice of vegetarianism does not, however, guarantee a healthy diet, any more than consumption of an omnivorous diet does. An exclusive menu of soda, chips, french fries, and pizza is a vegetarian diet, but clearly not a healthy one. What's more, if Amanda is like most adolescents, she doesn't eat enough whole grains, low-fat dairy foods, vegetables, and fruit—cornerstones of a healthy vegetarian diet. The answer to the disagreement between Amanda and her mother, therefore, lies in the details of Amanda's dietary practices.

If you are unsure how to adjudicate an argument such as theirs, you are like most health professionals, who can speak generally about the benefits of vegetarianism and the risk of nutritional deficiencies but who need specifics to be helpful to patients. This article summarizes health and nutritional research on teenage vegetarianism and serves as a basic resource for counseling vegetarian teens and their parents.

What the literature shows

Regrettably, the number of studies on adolescent vegetarianism in the medical literature is small, and what literature does exist has several limitations. Many studies are based on a very small sample or study population. Often, subjects were recruited through advertisements and flyers in health food stores. Consequently, those most motivated to learn about healthy eating practices may have been overrepresented. Furthermore, subjects in the largest studies of adolescent vegetarians in the United States are not a heterogeneous mix of vegetarians but Seventh Day Adventists, a Christian-faith group whose members often adhere to a lacto-ovovegetarian diet. (For a definition of this and other vegetarian terms, see "A glossary of vegetarianism," below.) While this group has made an enormous contribution to the understanding of lacto-ovovegetarian health and nutrition, it is unclear how representative it is of the larger pool of vegetarians.

Conflicting findings about vegetarianism abound in the literature, particularly among studies that assess whether vegetarian diets adequately provide individual nutrients. The disparate findings not only reflect differences in research methodology and outcome measures but suggest that no one group of vegetarians is representative. This is logical because the practice of vegetarianism is quite varied from group to group and within a group.

It is important to note that, despite these limitations, expert groups, nutritional authorities, and respected individual physicians (such as the American Academy of Pediatrics [AAP], the American Dietetic Association [ADA], and Benjamin Spock, MD), have all concluded that a well-planned vegetarian diet is safe and nutritionally adequate for infants, children, and adolescents.^1,2

Last, history speaks in favor of vegetarianism. For hundreds of generations, huge populations have thrived as vegetarians, either by choice or by necessity.

How many adolescents go vegetarian?

The prevalence of vegetarianism among teenagers in the United States is unknown. Among the 17,000 participants in the Minnesota Adolescent Health Survey, 0.6% identified themselves as vegetarians. Of these, 81% were girls.³ From convenience samples and restaurant surveys of adults in the US, it has been estimated that 1% to 5% of the adult population is vegetarian.

A number of secular trends suggest that the prevalence of vegetarianism is increasing. These include a growing number of colleges and corporate cafeterias that offer a vegetarian meal plan, the marked growth of the organic and vegetarian food industry, the increasing number of restaurants (including fast food restaurants) that offer meatless entrees, and the array of cookbooks, magazines, and World Wide Web sites devoted to vegetarianism.

Health benefits

Large epidemiologic surveys of adult vegetarians have demonstrated an association between the practice of vegetarianism and a reduction in adult mortality from ischemic heart disease, cerebral vascular disease, and certain forms of cancer.⁴ Other reported health benefits of vegetarianism include a lower body mass index (BMI) and a lower incidence of cholelithiasis.⁵ Recently, Key and colleagues examined results of five large, prospective studies of Western-style vegetarians and controls.⁶ Mortality data were available for 76,000 subjects. Mortality from ischemic heart disease was 24% lower among vegetarians than among controls. No difference was noted in mortality from other causes.

The reduction in mortality from coronary artery disease is a biologically plausible effect of vegetarianism; decreases in blood pressure and in atherogenic lipoproprotein levels are common in vegetarians.^7,8 While the cardiovascular health benefits of vegetarian diets are not clinically apparent in teens, a prospective study shows that levels of lipoproteins obtained in childhood predict the degree of early atherosclerotic lesions. Such lesions were observed in autopsy studies of adolescents who died accidentally.⁹ These data directly support the value of early atherosclerosis prevention.

Reported reductions in BMI among adolescent vegetarians suggest that vegetarianism could confer protection from obesity—the most prevalent nutritional problem in our nation—and associated type 2 diabetes.¹⁰

Epidemiologic evidence suggests that fruit and vegetable consumption lower the risk of colon cancer. Controlled trials of daily fiber supplementation and of a low-fat, high-fruit, and high-vegetable diet— both intended to reduce colorectal adenomas (the precursor of colon cancer)—have, however, been disappointing.¹¹

Last, vegetarianism may confer protection from some food-borne illnesses. There is evidence that the widespread use of antibiotics in livestock and poultry is creating a significant reservoir of multiply-resistant bacterial pathogens that can cause severe food-borne illnesses.¹²

Nutritionally, does the diet pass muster?

Several methods have been used to study the nutritional adequacy of the diet of vegetarian teenagers. These include nutritional analysis of typical three-day diet records of vegetarian and omnivorous teens; comparison of serum or tissue concentrations of single nutrients such as vitamin B₁₂ or of bone mineral density; and growth rates. The growth rate in an otherwise healthy person is the best measure of overall nutritional adequacy.

Several longitudinal studies of the growth of adolescent vegetarians exist. The largest study was conducted by Sabate and colleagues, who compared the growth of 1,090 Seventh Day Adventist students in first to tenth grade with that of 1,182 public school children.¹³ The Seventh Day Adventist students follow a predominantly lacto-ovovegetarian diet. The study found that, after adjusting for height, Seventh Day Adventist boys and girls tended to be roughly 1 kilogram leaner than the omnivores. No differences in height were found among the girls. But Seventh Day Adventist boys were 1.6 cm taller than the public school boys. These findings are consistent with the observation that adult vegetarians tend to have a lower BMI than omnivores.⁵ Most important, adult height of vegetarians has been shown to be identical to population standards.^14­16

Some data support the notion that, on average, menarche may occur later among adolescent vegetarian girls than among their omnivorous counterparts.¹⁷ This may be related to the fact that these girls, as a group, tend to be thinner.¹³ A normal age of menarche has, however, been reported in a sample of 32 lacto-ovovegetarian girls who were thinner than the reference population.¹⁶

Taken together, available information suggests that a balanced vegetarian diet during adolescence can support normal growth and attainment of normal final adult height. Although teen vegetarians may be thinner and have a later onset of menarche, clinicians should expect adolescent vegetarians to meet established norms for growth velocity and for onset and tempo of pubertal events. (A brief guide to monitoring growth in adolescents is presented in "Assessing nutritional status," below.)

Nutritional deficits: Potential problems

While growth data for vegetarian adolescents support the overall nutritional adequacy of a well-planned vegetarian diet, some vegetarian practices may result in a deficiency of certain nutrients. These nutrients are found either almost exclusively in animal products, as with vitamin B₁₂, or in high concentration or with high bioavailability in foods of animal origin, as in the case of iron, zinc, and calcium.

Protein. The recommended daily allowance (RDA) of protein is 0.8 g/kg/d for a female adolescent and 0.9 g/kg/d for a male adolescent. These values are easily achieved by most vegetarian teens.¹⁸ Lacto-ovovegetarians consume eggs and dairy products rich in high-quality protein. Vegans obtain proteins primarily from legumes, whole grains, and nuts. The body's utilization of vegetable protein is, however, marginally decreased relative to animal protein because of two main factors. Individual vegetable proteins may contain less of certain essential acids, particularly lysine.¹⁹ In addition, some sources of vegetable protein may contain inhibitors of digestion (trypsin inhibitors) or other compounds such as lectins, tannins, or fiber that decrease the bioavailability of certain amino acids.¹⁹

Protein malnutrition has been reported in vegan infants and toddlers who were weaned from breast milk to a highly restricted vegan diet.²⁰ Protein malnutrition is not observed among vegetarian teens, including vegans, who are meeting their caloric needs, and current recommendations are simply to include varied sources of vegetable protein in the diet. The widely held notion that vegetables and grains with complementary essential amino acid contents need to be consumed in the same meal to meet protein needs has not been substantiated.¹⁹

Calcium. Achieving maximal bone mineral deposition is critical during the adolescent years, given that 40% to 60% of peak bone mass is acquired during this time.²¹ Preventing osteoporosis by maximizing bone calcium accretion beginning in childhood is now recognized as an important pediatric challenge.²² This challenge is seriously threatened by an alarming increase in soda consumption among US teens combined with a reciprocal decrease in milk consumption.²³ This trend is as likely to apply to vegetarians as it is to omnivores.

Literature on the dietary calcium intake of lacto-ovovegetarian adolescents is sparse. One study of food diaries suggests that these teens have a calcium intake comparable to that of omnivores, although neither group of girls studied achieved the Dietary Reference Intake (DRI, which now replaces the RDA) for calcium of 1,300 mg/d.^18,24

For the vegan patient, achieving the DRI for calcium requires more knowledge and effort because unsupplemented vegetable sources of calcium tend to have a lower amount of calcium per serving than dairy products do.²⁵ In some vegetables, the bioavailability of calcium is diminished by the presence of high concentrations of oxalate (as in spinach) or phytates (sweet potatoes). In contrast, the bioavailability of calcium in other vegetables, such as broccoli, kale, and bok choy, exceeds bioavailability in dairy products and partially offsets the diminished concentration of calcium.

Both high-protein and high-sodium intake have been shown to increase urinary loss of calcium and, consequently, to diminish calcium retention.²⁶ It has been argued by some vegetarian groups that the current DRI for calcium factors in the excessive urinary calcium losses inherent in the typical high-protein, high-salt, omnivorous diet, and that vegetarians, whose protein intake tends to be lower, may require less dietary calcium. Bone mineral density of vegetarian adult women, however, has been noted to be higher, lower, and no different than that of omnivores. These findings undoubtedly reflect the complexity of both the nutritional and non-nutritional determinants that govern attainment and maintenance of bone density.

Very few investigations have focused on the bone density of adolescent vegetarians. One study of 93 adolescents who during childhood had consumed a macrobiotic diet known to be low in calcium and Vitamin D found measurable reductions in bone mineral density when compared with controls.²⁷

Physicians should counsel lacto-ovovegetarians to consume calcium-rich vegetables and dairy products. Strongly encourage vegan teens to not only consume calcium-rich vegetables (see the Guide for Patients, below) but to also use the numerous, widely available, calcium-supplemented vegan food products regularly. The latter include calcium-supplemented soy and rice beverages, orange juice, breakfast cereals, and waffles.

For both vegetarians and omnivores, excessive amounts of protein, sodium, and soft drinks may significantly undermine optimal mineralization by producing excessive urinary calcium loss. Carefully monitor growth, pubertal development, and body composition, as periods of inadequate growth and excessive thinness (loss of lean body mass) significantly compromise bone mineralization.²⁸ In keeping with the public health campaign to optimize bone health, encourage regular physical activity and discourage smoking.

Vitamin D. Unfortified and vegetable-based foods are trivial sources of vitamin D; some vegans prefer to rely on sun exposure to convert endogenously synthesized 7-dehydrocholesterol into Vitamin D. It is reported that an adequate level of Vitamin D can be maintained by five to 15 minutes a day of direct exposure of hands, face, and arms to the sun. Numerous variables may compromise the conversion process, however, including season, sun screen use, smog, frequent clouds, dark skin pigment, and northerly latitude.²⁹ Consequently, no recommendations exist for ensuring adequate vitamin D status using sun exposure, and teen vegans should either take a vitamin D supplement containing 5 µg of vitamin D or ensure adequate intake by consuming fortified foods. If a patient's vitamin D status is in question, you can obtain a serum vitamin D concentration, which reflects hepatic stores.

Dietary history appears to be the best method of monitoring the adequacy of vitamin D and calcium intake of the teenage patient. Teens do not develop rickets, and inadequate bone mineralization or osteoporosis is often clinically inapparent. Consider obtaining bone mineral density measurement in high-risk teens, particularly when there is a coexisting medical risk factor. We refer readers to a recent, excellent review of osteoporosis in pediatric patients.³⁰

Vitamin B₁₂ is perhaps the most widely known potential deficiency among vegetarians in general, yet very little data exist about the B₁₂ status of teen vegetarians. Vitamin B₁₂ is an organic compound containing cobalt that is crucial to DNA synthesis and the structural and functional integrity of the nervous system. It is synthesized only by microorganisms and is not found in plants. A lacto-ovovegetarian diet provides a reliable supply of B₁₂, but a vegan diet does not.^1,2

B₁₂ deficiency may produce megaloblastic anemia or a spectrum of neurologic disease ranging from mild, reversible peripheral neuropathy to severe, irreversible dementia or blindness.^31,32 Be particularly aware that breastfed infants of vegan mothers who are not taking a B₁₂ supplement are vulnerable to severe, irreversible neurologic damage.³² Very little literature addresses the B₁₂ status of long-term vegan teens but, among adult vegans who do not consume vitamin B₁₂, there is a substantial prevalence of deficiency due to inadequate intake.^33­35 Furthermore, high intake of folate, typical of the vegan diet, may prevent megaloblastic anemia from developing even as neurologic symptoms progress. Therefore, anemia is not a reliable early marker of impending neurologic disease in the vegan.

Adolescent vegans must obtain the RDA of B₁₂ (2 µg) through a vitamin supplement or supplemented foods such as soy beverages, cereal, and waffles. For those who refuse the supplementation in standard form, vitamin B₁₂ is also available in a nutritional yeast (Red Star Vegetarian Support Formula).

Consumption of certain sea vegetables and seaweed has been associated with vitamin B₁₂ sufficiency in some adult strict vegans who refuse B₁₂ supplementation. Seaweed contains variable amounts of B₁₂, however, and may contain isomers of vitamin B₁₂ that are biologically inactive; it is not recommended as a reliable source of B₁₂ by nutritional authorities such as AAP and ADA.^1,2

Certain vegan groups argue that B₁₂ supplementation is unnecessary because most B₁₂ deficiency in the US is the result of malabsorption, not inadequate intake. This is true, but it is irrelevant to vegan adolescents, who do not experience the common adult causes of B₁₂ malabsorption. It is also argued that vegans living in other cultures have thrived without B₁₂ supplements. This is also true, but these vegans live in places where water and food are contaminated with soil or manure organisms that produce B₁₂—which is not the case in the United States. Last, the anti-supplement contingent may also contend that two Asian yeast-fermented soy products, tempeh and miso, provide B₁₂. As these products are manufactured in the United States, however, this is also not true.

If you are caring for a vegan teen, warn her (or him) about this misinformation and insist that her diet contain a reliable source of B₁₂. Symptomatic deficiency may take years to develop. The serum level of B₁₂, which reflects total body stores, can be monitored.

Iron deficiency is common among all teens, including omnivores, and strong evidence that adolescent vegetarians are worse off than omnivores with respect to iron status is lacking. Nonetheless, because teens have an increased iron requirement and deficiency is commonly observed, consideration of this nutrient is warranted.

Iron is essential for hemoglobin and myoglobin synthesis and for cytochrome enzymes. The increase in the RDA for iron—from 10 mg/d during childhood to 12 mg/d for male adolescents and 15 mg/d for females adolescents—reflects marked increases in myoglobin synthesis in boys and the need to replace menstrual losses in girls during adolescent years. The factors governing iron absorption are exceedingly complex. We refer interested readers to an excellent review by Fairbanks.³⁶

Briefly, iron is present in both plant and flesh foods. The bioavailability of heme iron that has been ingested alone is greater than it is in most plant-based sources. But absorption of iron is highly influenced by substances coingested in the meal. Phytates, found in cereals, typically inhibit iron absorption, as do tannins, which are found in high concentration in coffee and tea (including iced tea, a favored drink of teens).

Meat, independent of its heme content, increases absorption by providing cysteine, a sulfur-containing amino acid that binds with iron and forms a soluble complex. But this same function is provided by vitamin C and organic acids found in high concentration in fruits and vegetables. Furthermore, host factors can increase the fractional absorption of iron in response to decreases in body iron stores. Studies of the iron status of vegetarian teens suggest these adolescents, like omnivores, must include iron-rich foods in their diet to achieve iron sufficiency.

Zinc is a concern for vegans because of the lower zinc content of vegetarian diets and because zinc bioavailability is limited by phytates, tannins, and fiber found in cereals. However, clinically appreciable zinc deficiency is rare.³⁷

Advising teen vegetarians

As most parents and pediatricians know, parents lose direct control of their child's dietary intake way before they become teenagers—between the ages of 1 and 2 years! Whether we like it or not, the adolescent ultimately controls what he or she eats. Quickly judging and criticizing the adolescent's decision to become a vegetarian can create a conflict in communication and is counterproductive. Physicians should remain nonjudgmental and maintain their authority as a source of sound nutritional information.

It is valuable to begin a discussion by exploring the teen's motives for becoming a vegetarian (see "Why teens choose vegetarianism," below). This allows you to recognize the emergence of autonomous decision making on the part of the patient, and to explore the particular dietary patterns he follows and get a sense of how knowledgeable he is. Questions to ask include: What type of vegetarianism do you practice? Why? Is your family accepting of this? If not, why not? Where are you getting your advice about how to stay healthy on your new diet? Do you know how to get an adequate amount of calcium? Iron? Vitamins D and B₁₂?

Keep in mind that some teens use vegetarianism as a way of disguising an eating disorder. (For a discussion of eating disorders and how to assess for them, see Primary Care of Adolescent Girls by Susan M. Coupey [Philadelphia, Hanley and Belfus, 2000] or "When you suspect an eating disorder," November 1996 Contemporary Pediatrics.)

Review with the teen the information in the accompanying patient handout. Focus on the major nutrients that pose problems for adolescents, including calcium and iron. For vegans, stress that B₁₂ supplements and vitamin D need to be an essential part of their regimen. For those teens and families who want or need more counseling, refer them to a registered dietitian who specializes in vegetarian nutrition. The ADA has a toll-free referral number, and finding a local referral is also possible through its Web site at www.eatright.org .

Stress how much misinformation is on the Web. Chat rooms and Web sites may look legitimate and offer what appears to be authoritative nutritional information, but such information is often wrong, unsupported by careful science, or just plain dangerous. Direct teens to sites (listed in the handout) that offer sound nutritional advice. The Tufts Web site ranks other nutritional sites for accuracy, content, and usefulness to consumers.

Don't forget to offer yourself as a resource for your teen patients. It is likely that you have an established record of promoting their health and will be able to answer most questions that arise. If you're stumped, employ the help of a hospital- or community-based dietitian.

Finally, arrange for follow-up. Although no formal recommendations exist, we believe that at least two visits in the first year following transition to a vegetarian diet are justified to monitor growth, assess dietary practices, answer questions, and reiterate your interest in your patient's nutritional health.

REFERENCES

1. Committee on Nutrition, American Academy of Pediatrics: Nutritional aspects of vegetarian diets, in Nutrition Handbook, Elk Grove Village, Ill., American Academy of Pediatrics, 1998, p 573

2. Messina VK, Burke KI: Position of the American Dietetic Association: Vegetarian diets. J Am Diet Assoc 1997;97:1317

3. Neumark-Sztainer D, Story M, Resnick M, et al: Adolescent vegetarians. Arch Pediatr Adolesc Med 1997;151:833

4. Appleby PN, Thorogood M, Mann JI, et al: The Oxford vegetarian study: An overview. Am J Clin Nutr 1999; 70(suppl):525S

5. Appleby PN, Thorogood M, Mann JI, et al: Low body mass index in non-meat eaters; the possible roles of animal fat, dietary fibre and alcohol. Int J Obes Relat Met Disord 1998;22:454

6. Key TJ, Fraser GE, Thorogood M: Mortality in vegetarians and non-vegetarians: Detailed findings from a collaborative analysis of 5 prospective studies. Am J Clin Nutr 1999;70(suppl):516S

7. Beilin U: Vegetarian and other complex diets, fats, fiber and hypertension. Am J Clin Nutr 1994;59(suppl):1130S

8. Rescinow K, Barone J, Enle A, et al: Diet and serum lipids in vegan vegetarians: A model for risk reduction. J Am Diet Assoc 1991;91:447

9. Newman WP, Freedman DS, Voors AW, et al: Relation of serum lipoprotein levels and systolic blood pressure to early atherosclerosis: The Bogalusa Heart Study. N Engl J Med 1986;314:138

10. American Diabetes Association: Type 2 diabetes in children and adolescents. Pediatrics 2000;105:671

11. Byers T: Diet, colorectal adenomas and colorectal cancer. N Engl J Med 2000;342:1206

12. Osterholm MT: Emerging infections—another warning. N Engl J Med 2000;342:1280

13. Sabate J, Lindsted KD, Harris RD, Sanchez A: Attained height of lactoovovegetarian children and adolescents. Eur J Clin Nutr 1991;45:51

14. Faber M, Gouws E, Benade AJ, et al: Anthropometric measurements, dietary intake and biochemical data of South African lactoovovegetarians. S Afr Med J 1986;69:733

15. Sanders TAB: Growth and development of British vegan children. Am J Clin Nutr 1988;48:822

16. Kissinger DG, Sanchez, A: The association of dietary factors with age of menarche. Nutr Rev 1987;7:471

17. Hebbelinck M, Clarys P, DeMaIsche A: Growth, development, and physical fitness of Flemish vegetarian children, adolescents, and young adults. Am J Clin Nutr 1999;70(suppl):579S.

18. Donovan U, Gibson R: Dietary intakes of adolescent females consuming vegetarian, semi-vegetarian and omnivorous diets. J Adol Health 1996;18:292

19. Acosta PB: Availability of essential amino acids and nitrogen in vegan diet. Am J Clin Nutr 1988;48:868

20. Jacobs C, Dwyer JT: Vegetarian children: Appropriate and inappropriate diets. Am I Clin Nutr 1988; 48:811

21. Bonjour JP, Thientz G, Buchs B, et al: Critical years and stages of puberty for spinal and femoral bone mass accumulation in adolescence. J Clin Endocrin Metab 1991;73:555

22. Golden N: Osteoporosis prevention. A pediatric challenge. Arch Pediatr Adol Med 2000;154:543

23. Harnack L, Stang J, Story M: Soft drink consumption among U.S. children and adolescents. J Am Diet Assoc 1999;99:436

24. Tayter M, Stanek KL: Anthropometric and dietary assessment of omnivores and lacto-ovo-vegetarian children. J Am Diet Assoc 1989;11:1661

25. Weaver CM, Proulx WR, Heaney R: Choices for achieving adequate dietary calcium with a vegetarian diet. Am J Clin Nutr 1999;70(suppl):543S

26. Zemel M: Calcium utilization: Effect of varying level and source of dietary protein. Am J Clin Nutr 1988; 48:880

27. Parsons TJ, Dusseldorp M, Van der vliet M, et al: Reduced bone mass in Dutch adolescents fed a macrobiotic diet in early life. J Bone Miner Res 1997;12:1486

28. Kreipe RE, Forbes GB: Osteoporosis: A new morbidity. for dieting adolescents. Pediatrics 1990;86:478

29. Speckler BL, Valanis B, Hertzberg V, et al: Sunshine exposure and serum 25 hydroxyvitamin D concentrations in exclusively breast-fed infants. J Pediatrics 1985; 107:372

30. Steelman J, Zeitler P: Osteoporosis in pediatrics. Pediatr Rev 2001;22:56

31. Melia D, Cassoux N, Lehoang P: Blindness in a strict vegan. N Engl J Med 2000;342:897

32. Von Schenck M, Bender-Gotze C, Koletzko B: Persistence of neurologic damage induced by dietary B₁₂ deficiency in infancy. Arch Dis Child 1997;77:137

33. Hokin BD, Butler T: Cyanocobalamin status in Seventh-day Adventist ministers in Australia. Am J Clin Nutr 1999;70 (suppl):576S

34. Rauma AL, Torronen R, Hunninen O, et al: Vitamin B₁₂ status of long-term adherents of a strict uncooked vegan diet is compromised. J Nutr 1995;125:2511

35. Ashkenazi S, Weitz R, Varsano I, et al: Vitamin B₁₂ deficiency due to a strictly vegetarian diet in adolescence. Clin Pediatr (Phila) 1987;26:662

36. Fairbanks V: Iron in medicine and nutrition, in Modern Nutrition in Health and Disease, Maurice E. Shils (ed). Baltimore, Williams and Wilkins, 1999,

37. Donovan U, Gibson R: Iron and zinc status of young women aged 14-19 consuming vegetarian and omnivorous diets. J Am Coll Nutr 1995;14:463

DR. BELAMARICH is associate professor of clinical pediatrics, department of pediatrics, Albert Einstein College of Medicine/Children's Hospital at Montefiore, Bronx, N.Y.

DR. AYOOB is associate professor of pediatrics and director of nutrition, Rose F. Kennedy Children's Evaluation and Rehabilitation Center, Albert Einstein College of Medicine, Bronx, N.Y.

A glossary of vegetarianism

These terms and definitions are found in both the lay and scientific literature on vegetarianism.

Vegetarian General term. Anyone who excludes animal flesh—specifically meat, fish, and poultry—from his or her diet.

Lacto-ovovegetarian Vegetarian whose diet includes dairy products and eggs

Vegan Vegetarian who does not eat any animal products—eschewing dairy products, eggs, and honey. A vegan may also avoid using any nonfood animal products whatsoever, including leather, silk, and wool. Veganism is sometimes referred to as strict vegetarianism. Groups that embrace veganism often promote animal rights.

Ethical vegetarian Vegetarian who maintains a moral objection to consuming animal products

Fruitarian Vegetarian who believes that fruit is the intended diet of humans. A fruitarian eats fruit, nuts, seeds, and berries.

Living-food diet Diet of uncooked fruits and vegetables

Macrobiotics Eating style that links stages of spiritual growth to a progressively more restrictive vegan diet. Developed by Georges Oshawa. A macrobiotic diet is largely vegan and includes a number of traditional Japanese foods. Small amounts of fish are allowed, although most practitioners of macrobiotics in America do not eat any animal products.

Semi-vegetarian Person who maintains a diet in which red meat is generally avoided, but fish or chicken is eaten in moderation. Ethical vegetarians disapprove of the use of "vegetarian" to describe this practice. Nonetheless, many self-described adolescent vegetarians are in reality semi-vegetarians. Semi-vegetarians have, in general, a dietary pattern that is largely plant-based and closely resembles general guidelines promoted by the surgeon general, as recommended in the food pyramid. Semi-vegetarians are not at greater risk of nutrient deficiency than omnivores are, and are not included in studies quoted in this article.

Assessing nutritional status

Inadequate growth in a teen vegetarian may be the result of a poor diet with inadequate energy intake, an eating disorder, or a medical illness. Your assessment should include:

Visual inspection. Look for absence of subcutaneous fat, muscle wasting, and depression of affect.

Anthropometric measurements. A decline in a child's percentile position on a weight or height chart before the growth spurt of mid-adolescence is cause for concern. But the most telling measurement is height velocity, calculated in cm/yr or cm/6 mo. This requires careful measurement of stature. Height velocity peaks between Tanner stages 3 and 5 in girls and stages 4 and 5 in boys. Values of height velocity should be compared with norms from Tanner¹ as published in The Harriet Lane Handbook.

To determine whether the patient is at risk of underweight, find the 50th percentile weight for the adolescent's height using growth charts of the National Center for Health Statistics. Divide the patient's true weight by this number (true weight/50th percentile weight for height). If this ratio is less than 0.85 or 85% the patient is at risk of underweight. [Editor's note: For a discussion of growth charts, see "Understanding growth patterns in short stature" in the June issue.]

According to the new body mass index (BMI) growth charts, an adolescent with a BMI below the 15th percentile is at risk of underweight. An adolescent with a BMI below the 5th percentile is underweight.

A constitutionally (or genetically) thin teen may meet the above criteria for underweight. But, unlike a pathologically thin teen, she (or he) remains thin through childhood, often has thin parents, and maintains normal growth velocity.

REFERENCE

1. Tanner JM, Davis PS: Clinical longitudinal standards for height and height velocity for North American children. J Pediatr 1985;107:317

The patient guide on being a vegetarian may be photocopied and distributed to families in your practice without permission of the publisher.

GUIDE FOR PATIENTS

On being a vegetarian teenager

Ever thought about going vegetarian? Millions of people have, and about a third of teenagers in the United States consider becoming a vegetarian. But what about nutrition and health?

Truth is, you can have a perfectly healthy and nutritious diet without meat, poultry, or fish. But being a vegetarian does not guarantee a healthy or balanced diet; indeed, the more food groups you exclude, the more difficult it can be to get everything you need from your meals. Example: A steady diet of soda and potato chips would fit the strictest of vegetarian diets. But it is neither healthy nor balanced.

Not all vegetarians share the same dietary practices. Lacto-ovovegetarians do not eat animal flesh, but they do eat eggs and dairy products. Lactovegetarians eat dairy products but no other animal foods. Vegans, the strictest vegetarians, eat absolutely no products of animal origin—not even honey.

Some teenagers choose to become a vegetarian or vegan for personal or moral reasons, such as an objection to the killing of animals. Others decide to avoid some or all animal foods for health reasons. Research tells us that eating fewer animal products, especially animal fats, may lower the risk of heart disease and cancer. Teenagers may choose vegetarianism for any of these reasons, or because a friend is a vegetarian, or simply as part of the normal process of experimenting with new practices.

What are the risks and potential disadvantages of vegetarianism?

• If you do not replace nutrients normally supplied by excluded foods or food groups, you may not get enough of certain vitamins and minerals important to your health. (The boxes in this patient guide list alternate sources of essential nutrients.)

• For vegans in particular, getting enough calcium and vitamin B₁₂ can be difficult.

• You must be willing and able to give more thought and planning to meals and snacks.

• You may be limited in what you can eat in social situations.

What are the potential benefits of vegetarianism?

• It can promote healthy eating. Most vegetarians eat more fruits, vegetables, and dairy products—the very foods most teen diets lack.

• It can be more economical because meat is expensive.

• It can increase your awareness of how foods are processed and prepared.

• It can help make you a more informed food consumer.

Getting started

Going meat-free can be easier than you think. Meatless substitutes are convenient, lower in fat, high in protein, and often cheaper than meat. Here are some suggestions if you are switching to a meat-free diet.

• Try "veggie burgers," or meatless chicken or sausages.

• Experiment with beans, fruits, and vegetables you haven't tried before.

• Make vegetable, bean, or fruit salads with lots of colors for eye appeal and taste.

• Search your bookstore for vegetarian cookbooks and try a new recipe each week.

Ask the professionals

Pediatricians. Your pediatrician is an ideal source to consult if you are considering becoming a vegetarian. He or she is knowledgeable about your medical history and the risks and benefits of this style of eating.

Registered dietitians (RDs). Ask for a referral to an RD for a detailed dietary evaluation or to individualize your vegetarian diet.

Reputable Web sites where you can find out more

www.VRG.org The Vegetarian Resource Group, a nonprofit organization promoting veganism, runs this highly rated Web site that offers sound, practical advice, including specific advice for teenagers.

www.navigator.tufts.edu Tufts University Navigator rates nutrition Web sites for accuracy, content, and usefulness to consumers.

www.nutrition.gov The US Department of Agriculture's Web site has information and links to consumer information on vegetarianism and other nutrition topics.

www.eatright.org The Web site of the American Dietetic Association provides consumer information on vegetarian diets and can help you locate a registered dietitian in your area.

If you are surfing for nutrition information, remember that the Web is completely unregulated. Be suspicious of the following:

• Web sites not linked to reputable major health organizations

• Recommendations that promise a quick fix

• Claims that sound too good to be true

• Claims that are refuted by reputable scientific organizations

• Recommendations made to help sell a product

Suggested reading

A Teen's Guide to Going Vegetarian by Judy Krizmanic (Puffin Books)

The Teen's Vegetarian Cookbook by Judy Krizmanic (Puffin Books)

This Guide for Patients may be photocopied and distributed without permission to give to your patients and their parents. Reproduction for any other purpose requires express permission of the publisher. Copyright © 2001 Medical Economics Company.

Why teens choose vegetarianism

An adolescent may become a vegetarian for any number of reasons. Many teenagers try vegetarianism as a means of forging an identity different from that of their parents. Others have a philosophical or ethical objection to animal slaughter or a strongly felt compassion for, and spiritual kinship with, animals. This may be associated with feelings of revulsion toward the ingestion of meat or blood.

Teenagers may either be raised as, or convert to, one of several religious groups that espouse vegetarianism. Seventh Day Adventists, Buddhists, members of certain Hindu sects, and Rastafarians abide by vegetarian diets.

Health-conscious teens may become vegetarian because of research suggesting that the diet can lower the risk for certain diseases, such as heart disease.

Environmentally-conscious teens may subscribe to a number of compelling ecologic arguments about the benefits of plant-based diets. Such diets, it is argued, use much fewer resources and are less destructive environmentally. Reallocating resources to the production of plant foods could, in theory, create enough food to significantly address world hunger. Indeed, vast resources are devoted to livestock production in the United States. Seventy percent of the grain produced in this country is fed to livestock. Seven pounds of grain are required to produce one pound of pork. A full 2,500 gallons of water is needed to produce one pound of beef—compared with just 25 gallons needed for one pound of wheat. Furthermore, the amount of animal waste generated by livestock and poultry production in the United States is staggering. From a 1997 Senate report on animal waste it can be calculated that US farm animals create five tons of manure per person per year. Animal waste is a significant polluter of rivers, streams, estuaries, and aquifers that ultimately supply drinking water.

Last, some teenagers may use vegetarianism as a means of disguising an eating disorder. Numerous clinical case reports suggest this possibility, as does an analysis of the results of the Minnesota Adolescent Health Survey. That survey found that, compared with nonvegetarians, vegetarians were twice as likely to report dieting and four times as likely to report self-induced vomiting. They were also more likely to report laxative use. Physicians should screen adolescent vegetarians for eating disorders.

Take-home points

• Available information suggests that a well-balanced vegetarian diet during adolescence supports normal growth and attainment of normal final adult height.

• Eating disorders are seen with increased frequency among vegetarian teenagers.

• Reported reductions in body mass index among adolescent vegetarians suggest that vegetarianism may confer protection from obesity and associated type 2 diabetes.

• A reduction in mortality from coronary artery disease has been demonstrated in surveys of adult vegetarians and is a biologically plausible effect of vegetarianism.

• Some vegetarian practices, notably veganism, may result in a deficiency of certain nutrients, particularly vitamin D, calcium, and vitamin B₁₂. Individuals can easily avoid these deficiencies by making informed food choices or taking supplements.

 

Peter Belamarich, Keith-Thomas Ayoob. Keeping teenage vegetarians healthy and in the know. Contemporary Pediatrics 2001;10:89.