Vegetarian
Nutrition - What Every Dietitian Should Know
Today’s Dietitian
By Dina Aronson, MS, RD
Vol. 7, No. 3, p. 32
Don’t rely on old ideas about vegetarians.
Find out what vegetarian nutrition today is really all about.
Our knowledge of vegetarian nutrition and its implications
for health and disease has grown by leaps and bounds over the last
10 years. However, many nutrition professionals are relying on outdated
information, possibly missing real risks and/or overemphasizing
inappropriate dietary concerns for their vegetarian clients. Dietitians
are caring, ethical people who have chosen this profession to help
people achieve optimal health. Yet a lack of knowledge about vegetarian
nutrition can lead a well-intentioned dietitian to not only harm
a vegetarian client but also unknowingly violate the American Dietetic
Association (ADA) Code of Ethics. This article will help the dietitian
prevent these unfortunate outcomes by:
• explaining the need for nonbiased counseling;
• providing a brief overview of the newest
information on vegetarian nutrition;
• identifying and correcting common misconceptions
about vegetarian nutrition; and
• listing accurate, reliable resources for
in-depth information on vegetarian nutrition.
Counseling the Vegetarian Client
The ADA’s Code of Ethics states: “The dietetics practitioner
provides professional services with objectivity and with respect
for the unique needs and values of individuals.” For vegetarians,
consuming certain animal products is simply not a dietary option.
Whatever the reasons our clients have for their vegetarian eating
patterns, our approach remains the same: Help clients achieve their
desired nutritional and health goals, tailored to their specific
needs and preferences. Just as it is inappropriate to suggest pork
as an option to those clients following a Kosher diet, it is equally
inappropriate to directly or indirectly lead vegetarians toward
a diet containing foods they shun.
Dietitians have a duty to respect the dietary convictions
of their clients and a responsibility to optimize health and well-being
through nutritional adjustments—within the bounds of clients’
dietary preferences. It is often challenging to prevent personal
bias from affecting objectivity, but remaining unbiased is required
for the success of medical nutrition therapy. One example of a violation
of the ADA’s Code of Ethics would be to tell vegan clients
that they are “at nutritional risk” without dairy products
in their diets. This is unacceptable not only because it is scientifically
unsound, but also because it fails to respect the client’s
dietary choices. The right approach, in this case, would be to objectively
assess the nutritional adequacy of the current diet and then, if
necessary, help the client identify plant sources of nutrients he
or she may be lacking. Certainly, in a situation where there is
clear evidence of compromised health because of dietary inadequacy,
it is the dietitian’s responsibility to point out potential
health risks and recommend the most acceptable source of one or
more nutrients.
In general, vegetarians do not consider their diet
restrictive or punishing. Rather, they focus on the enormous bounty
of grains, nuts, seeds, beans, vegetables, fruits, seasonings, and
specialty items (such as tofu, wheat gluten, soy milk, and veggie
burgers) available to them. Indeed, many vegetarians easily surpass
their omnivorous counterparts with regard to dietary variety and
nutritional adequacy.
Health Benefits of Plant-Based
Diets
When some dietitians hear the words vegetarian or vegan, there is
an instant association with scenarios of nutritional risk, nutrient
deficiency, and dietary inadequacy. In fact, some nutrition education
materials have listed vegans as a group at risk for conditions such
as folic acid deficiency (despite the fact that plant foods are
the best sources of folic acid) and protein deficiency (despite
the fact that scientific evidence refutes that claim).1 It is important
to keep in mind that there are both healthy and unhealthy vegetarian
diets, just as there are both healthy and unhealthy diets containing
meat and other animal products. A well-planned, balanced vegetarian
or vegan diet is health-supporting, nutritionally adequate, and
not difficult to achieve. At the same time, this can be an opportunity
for dietitians to be of service to clients, helping them create
a nutritionally adequate diet.
There is ample evidence in the scientific literature
demonstrating that people can and do enjoy optimal health and longevity
on plant-based diets. Epidemiological studies, clinical trials,
and meta-analyses have reported links between vegetarian diets and
reduced rates of obesity, cancer, heart disease, hypertension, high
cholesterol, type 2 diabetes, diverticular disease, and gallstones.2
There is also some evidence of successful application of plant-based
diets to treat certain conditions. Many question whether protective
aspects of a vegetarian diet lie in its abundance of known health-supporting
components such as fiber and antioxidants, the relative lack of
components known to be damaging in high amounts such as trans fats
and cholesterol, or a combination of these. The answer is difficult
to determine, due to the complex nature of the relationships between
diet and health. Nonetheless, it is interesting to note that the
vast majority of established nutrition doctrines—increase
intake of fruits and vegetables, eat more beans, limit meat intake,
increase whole grain intake, and increase intake of monounsaturated
fats (at the expense of saturated and trans fats)—recommend
a move toward a more plant-based eating pattern.
It is, of course, not difficult to construct a vegetarian
diet that is damaging to health. Meals based on refined flours,
sugars, overprocessed foods, deep-fried foods, and the like still
fall under the category of vegetarian. This is why it is so important
to judge the adequacy of a diet not on its label but on the foods
and nutrients it provides, as well as the unique needs and considerations
of the individual consuming the diet.
The “Red Flag” Nutrients
In general, well-nourished vegetarians appear to be at an advantage
with respect to intake of protective food components such as dietary
fiber, most minerals, most vitamins, phytochemicals, bioflavanoids,
carotenoids, retinols, sulforaphanes, isoflavones, polyphenols,
plant sterols and stanols, and other substances known to reduce
the risk of chronic diseases. However, there are a few areas where
vegetarians may be at a disadvantage. Fortunately, there are guidelines
vegetarians can follow that will help them overcome these potential
pitfalls.
Vitamin B12
Sufficient intake of B12 is a concern among vegetarians, especially
during pregnancy and lactation. Vitamin B12 status among vegetarians
is, on average, lower than that of nonvegetarians because this vitamin
is commonly consumed through animal products. Even in the absence
of a vitamin B12 deficiency, suboptimal intakes have been associated
with increased levels of homocysteine, an independent risk factor
for heart disease. B12 status may be assessed using urinary methylmalonic
acid (the most reliable method) or serum tests.
Vitamin B12 is produced by bacteria, fungi, and
algae. Neither plants nor animals can synthesize the vitamin; thus,
it is not found in plant products naturally (there might be trace
amounts on plant foods contaminated with B12-producing microorganisms).
Animal foods contain B12 because significant amounts of B12-producing
bacteria are found naturally in animals. Some foods, such as sea
vegetables, contain B12 analogs, which are not active and thus are
not good sources.
Vegans need to get B12 from supplements and/or fortified
foods. The Dietary Reference Intakes recommend these same sources
for people on any diet over the age of 50 years; as we age, a significant
number of us have decreased ability to absorb the form of B12 in
animal products.3 Vegans can rest assured that the B12 added to
foods and supplements are synthetically produced in a laboratory
from bacteria, not animal sources. See Table 1 for some foods that
are typically B12-fortified (encourage your clients to read labels).
The Recommended Dietary Allowance for vitamin B12
is based on the assumption that people consume small amounts of
B12 from foods over the course of the day. If a person uses a supplement
as the main B12 source, needs are probably higher because of the
limited capacity of B12 absorption at any one time. Most multivitamins
contain 10 micrograms of B12; this is a good daily goal from supplements.
Another option is to take one 2,000-microgram dose per week; the
percentage absorbed from a large dose is considerably decreased.4
The client may prefer one method over the other; either is acceptable.
It is important to note that as they age, some people (vegetarian
or not) are unable to absorb B12 from foods or supplements. Such
individuals need to take regular B12 injections.
Omega-3 Fatty Acids
Even though the richest food source of omega-3 fatty acids (n3)
is a plant food (flaxseeds and flaxseed oil), the primary source
in the North American diet is fish. Studies have shown that vegetarians
have considerably lower n3 status than nonvegetarians. Poor n3 status
has been associated with chronic diseases such as cardiovascular
disease and cancer, inflammatory disorders such as arthritis, and
neurological problems such as depression. In fact, studies over
the past few years have shown promise in treatment of such conditions
with n3 supplements.
Vegetarian diets are not only low in n3 fats but
they are also typically high in omega-6 fatty acids (n6). Indeed,
vegetarians consume more n6 fats than nonvegetarians. Vegetarians’
typical n6:n3 ratio is higher than recommended for optimal health.
Vegetarian nutrition and fatty acid expert Brenda Davis, RD, recommends
that vegetarians strive for an n6:n3 ratio of 2:1 to 4:1.
In addition to striving for optimal fatty acid status
by including more vegetarian food sources of n3 (see Table 1), vegetarians
may also opt to take supplements (such as a DHA supplement derived
from algae). According to Davis, vegetarians can also maximize essential
fatty acid status by maximizing overall nutrition; minimizing intake
of trans fatty acids; using whole foods such as nuts, olives, and
avocados for healthy sources of fat; choosing monounsaturated oils
such as olive and canola over n6-rich oils such as safflower, sunflower,
and grape seed; and avoiding alcohol in excess.
Given the importance of essential fatty acids for
brain and neurological development prenatally and during infancy,
pregnant vegetarians are encouraged to optimize their intake of
n3 fats via foods and/or a docosahexaenoic acid (DHA) supplement.
The habit should continue during lactation to ensure milk quality.
Alternatively, the infant may be given a commercial formula with
added DHA and arachidonic acid (ARA).
Vitamin D
Sun exposure is the greatest source of vitamin D. However, in northern
latitudes (including states at the latitude of Massachusetts and
northward), people get enough direct exposure only in warm-weather
months (the recommendation is 10 minutes per day). Add to this the
recommendation to protect skin from the sun with sun block, umbrellas,
and hats, and many people fail to get enough vitamin D from the
sun and thus must depend on food and supplements. Vitamin D deficiency
can be a public health problem for many people, not only vegetarians,
and recent evidence suggests that deficiency is more widespread
than once thought.5 And because the two main dietary sources of
this essential nutrient are fish and fortified milk, vegetarians
need to be sure they’re getting a reliable source of vitamin
D.
Vitamin D status is inversely related to many adverse
health conditions, including weakened muscles, cancer, and certain
autoimmune diseases. Sufficient levels of vitamin D are needed for
calcium metabolism and bone retention. Thus, it is important to
help our vegetarian clients optimize their vitamin D intake by using
supplements and/or fortified foods. Vitamin D2 (ergocalciferol)
is derived from plants and nonanimal sources while vitamin D3 (cholecalciferol)
is derived from animals, so D2 is the form vegetarians will accept.
(Food and supplement labels usually indicate the form of vitamin
D used.) Fortified soy milk contains equivalent amounts of vitamin
D to those added to cow’s milk. Thus, fortified soy milk is
one of the easiest ways to ensure a regular intake for those who
avoid dairy. Fortified rice milk is also a source and can be used
by those with soy allergies. Note that the upper limit (from food
and supplements) is 25 micrograms for babies and 50 micrograms for
children and adults. To prevent toxicity, intakes should be carefully
assessed and monitored. A supplement plus 1 quart of fortified cow’s
milk or soy milk plus fortified cereal plus a nutrition bar might
put a person’s intake over the upper limit for the day.
Breast milk is generally a poor source of vitamin
D, and lactating women with suboptimal vitamin D status will have
very low levels in their milk. Thus, breast-fed infants should be
given a daily vitamin D supplement (available in drops). Formula-fed
infants receive the required amount in the formula.
Setting the Record Straight on Protein, Calcium,
and Iron
It was once widely believed that vegetarians are at risk for a protein
deficiency and that it is necessary to combine different sources
of plant proteins at the same meal. Now, this is known to be unnecessary,
as amino acids are stored in the body and drawn upon when needed.
Protein deficiency among vegetarians with well-planned diets is
not a major concern. A protein deficiency may be seen when there
is also a calorie deficiency, but in such a case, many nutrients
would be a concern. The other possible circumstance in which protein
intake may be insufficient occurs when a vegetarian gets the vast
majority of calories from refined junk food such as sugary drinks,
pastries, and chips.
Dairy products and eggs are rich protein sources
but are not necessary for adequate protein intake. Humans require
approximately 10% to 15% of calories from protein. Most vegetables
(except for root vegetables) and beans contain more than 20% of
calories from protein; most grains, nuts, and seeds contain 10%
to 17%; and fruits contain 1% to 10%. So a variety of these foods,
in adequate amounts, will easily meet a vegetarian’s protein
needs. In addition, plant sources of protein are high in fiber,
free of cholesterol, low in saturated fat, and rich in antioxidants
and minerals. People may need special guidance in using legumes
and seeds, all rich sources of protein, iron, and zinc.
In many countries, there is a widespread belief
that everyone needs dairy products to get enough calcium. This is,
of course, not the case. Certainly, cow’s milk is high in
calcium, but milk offers nothing nutritionally that cannot be obtained
from other foods. For approximately 70% of the world’s adult
population, lactase production drops off after the age of weaning.
Lactose intolerance is a normal adult condition. People around the
world derive adequate amounts of dietary calcium from a wide assortment
of plant foods.
Calcium is present in many plant foods and fortified
foods. The best sources are low-oxalate greens (with calcium bioavailabilities
surpassing that of cow’s milk), seeds, nuts, beans, figs,
blackstrap molasses, calcium-set tofu, tempeh, fortified soy milk,
fortified cereals and bars, and fortified fruit juices. A vegetarian
may easily meet calcium needs by including six to eight servings
of calcium-rich foods each day. (Each serving, such as 1/2 cup fortified
soy milk, provides 150 milligrams of calcium).6
Though we may be led to believe that humans require
dairy products for optimal bone health, this is untrue and the reality
is much more complex. Some studies have shown an inverse correlation
between dairy intake and bone fractures while others, such as the
Nurses’ Health Study, found that intake of dairy products
provided no added protection against bone fractures. Also, population
studies show that high-calcium-intake countries tend to have a higher
rate of bone fracture than low-calcium-intake countries. Does this
mean that milk will harm bones? Of course not. It simply means that
there isn’t enough evidence to claim that dairy intake will
ensure good bone health. There is much more to bone health than
calcium intake. Genetic predisposition to strong bones, sufficient
intake of other vitamins and minerals, limited intake of sodium
and caffeine, moderate (not too high or too low) protein intake,
regular physical activity, not smoking, and other lifestyle factors
all affect bone health.
Though some believe that the adequate intake levels
for calcium are set too high, vegetarians should be advised to achieve
these intakes. They can easily meet needs by consuming six to eight
servings of calcium-rich whole plant foods, calcium-fortified foods,
and/or taking a calcium supplement.6 The bonus feature about calcium-rich
plant foods, such as seeds, greens, and beans, is that they also
meet the recommendations for servings of other nutrients and food
groups, as they supply a wealth of other protective vitamins, minerals,
antioxidants, phytochemicals, and fiber.
Most dietitians are surprised to learn that vegans
consume more iron than ovo-lacto vegetarians, who in turn consume
more iron than nonvegetarians.2 Furthermore, there is no more iron-deficiency
anemia seen among vegetarians than nonvegetarians.2 Vegetarians
do have lower iron stores than nonvegetarians, but levels are in
the normal range.
Iron deficiency is, nonetheless, a real issue and
one that we very well might see in vegetarian clients. We must make
the same recommendations we would make for nonvegetarians: Eat more
iron-rich foods and take an iron supplement if indicated. The best
plant sources of iron are legumes, spinach, potatoes, tofu, fortified
cereals, grain products made with iron-fortified flour, dried fruits,
nuts, seeds, some whole grains such as quinoa, and blackstrap molasses.
Nonheme iron, the kind found in plant foods, is
not as readily absorbed as heme iron (from animal foods). Plus,
other factors that affect absorption may negatively affect iron
status. Phytates (in legumes and grains), tannins (in tea and coffee),
flavonoids (in red wine), eggs, dairy foods, fiber, and zinc supplements
may interfere with iron absorption. However, competing factors that
enhance iron absorption (vitamin C and other organic acids) also
play a role, making it difficult to assess the degree to which absorption
may be compromised. In general, discouraging large intakes of inhibitors
(like tea and coffee) and encouraging enhancers (such as vitamin
C) is recommended, along with encouragement of iron-rich foods.
The Dietitian’s Role
Vegetarians who seek nutritional guidance from dietitians want and
need assurance that they can be healthy and meet all their nutrient
needs without compromising their principles. It is the dietitian’s
job to direct vegetarian clients to a path of optimal health and
wellness by teaching them about the importance of variety and nutrient-dense
foods and by carefully reviewing the diet to identify where nutritional
improvements may be made.
Sometimes, people with underlying eating problems
will use vegetarianism as a guise for their eating disorder. This
does not mean that vegetarians are at risk for eating disorders.
It means that vegetarianism is perhaps a convenient and seemingly
valid way to eliminate many foods. The vegetarian who exhibits some
questionable resistance, such as complete elimination of all fats
or the refusal to consume sufficient calories, should be approached
with special care. In such cases, the dietitian should refer the
client to a team that specializes in eating disorders.
— Dina Aronson, MS, RD, is a nutrition
consultant, freelance writer, and speaker specializing in dietetics-related
technology and vegetarian nutrition.
References
1. Messina V, Mangels R, Messina M. A Dietitian’s Guide
to Vegetarian Diets: Issues and Applications. 2nd ed. Jones
and Bartlett: 2004.
2. Position of the American Dietetic Association
and Dietitians of Canada: Vegetarian diets. J Am Diet Assoc.
2003;103(6):748-765.
3. Dietary Reference Intakes for Thiamin, Riboflavin,
Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin,
and Choline. A Report of the Standing Committee on the Scientific
Evaluation of Dietary Reference Intakes and its Panel on Folate,
Other B Vitamins, and Choline and Subcommittee on Upper Reference
Levels of Nutrients. Food and Nutrition Board, Institute of Medicine:
1998.
4. Melina V, Davis B. The New Becoming Vegetarian.
Book Publishing Company: 2003.
5. Raiten DJ, Picciano MF. Vitamin D and health
in the 21st century: Bone and beyond. Executive summary. Am
J Clin Nutr. 2004;80(6):1673S-1677S.
6. A new food guide for North American vegetarians.
J Am Diet Assoc. 2003;103(6):771-775.
Reliable Sources of Information
on Vegetarian Nutrition
Position of the American Dietetic Association and Dietitians of
Canada: Vegetarian diets. J Am Diet Assoc. 2003;103(6):748-765.
Available at: http://www.eatright.org
Davis B, Melina V. Becoming Vegan.
Book Publishing Company: 2000.
Loma Linda University Nutrition & Health Letter. Available at:
http://www.llu.edu/llu/vegetarian
Melina V, Davis B. The New Becoming Vegetarian.
Book Publishing Company: 2003.
Messina V, Mangels R, Messina M. A Dietitian’s
Guide to Vegetarian Diets: Issues and Applications. 2nd
ed. Jones and Bartlett: 2004.
A new food guide for North American vegetarians.
J Am Diet Assoc. 2003;103(6):771-775. Available at
http://www.eatright.org/Public/NutritionInformation/92_17086.cfm
Stepaniak J, Melina V. Raising Vegetarian
Children. McGraw-Hill: 2002.
The Vegetarian Nutrition Dietetic Practice Group
of the American Dietetic Association. Available at: http://www.vegetariannutrition.net
Vegetarian Resource Group. Available at: http://www.vrg.org.
(All material on vegetarian nutrition written by Reed Mangels, PhD,
RD, and Suzanne Havala Hobbs, DrPH, MS, RD.)
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