An upper limit for safe levels of protein intake has not been
determined. Most patients believe no upper limits for protein
exist. Americans frequently eat 150% to 200% of the RDA
for protein. Excessive protein intake can contribute to obesity
because any energy-providing nutrient consumed in excess
of physiological needs is converted to fat and stored.
   One concern regarding high protein intake is its effect on
calcium balance. The adequate intakes (AIs) established for
calcium in the United States are approximately double the
recommendations for most other nations. For many years,
general consensus in the medical community was that high
protein intake had a negative impact on calcium and bone
metabolism. Numerous studies contradict this theory,
however, and research generally indicates meat intake may
have a favorable impact on bone health if calcium intake is
adequate, at least in older men and women.
   When protein intake is excessive, fluid imbalances may
occur in all age groups, but especially in infants. Metabolism
of 100 kcal of protein requires 350 g of water compared with
50 g of water for a similar amount of carbohydrates or fats.
Water requirements are increased as well as the end products
of protein metabolism in the bloodstream.
   It is controversial whether the popular high-protein diets
are excessive in protein content. Regardless, this trend has
stimulated scientific research that has expanded the scien-
tific knowledge base in this realm. Higher protein diets are
beneficial for weight control by enhancing loss of body fat
with less muscle loss and improved control of blood glucose
levels. Dietary protein may aid in weight loss by increasing
satiation; increasing muscle mass, which burns more kilo-
calories and increases thermogenesis (production of body
heat); and decreasing energy efficiency. Protein intake
generally increases satiety to a greater extent than carbohy-
drate or fat and may facilitate a reduction in ad libitum (as
desired) energy consumption. Obtaining adequate protein,
or within the upper range of recommended amounts, is an
important dietary concern, especially for weight loss or
management or for physical activity.
   Clinicians are concerned about the long-term effects of a
high-protein diet, especially when the principal source of
Protein is red meat and regular dairy products because of
Their large cholesterol and saturated fat content. A study
Involving 29,000 postmenopausal women found subjects
Who reported the highest protein intakes from red meat and
Dairy products had approximately a 40% higher risk of dying
of heart disease than subjects with the lowest intake of these
foods. Although high protein intake is not associated with
kidney function decline in individuals with healthy kidneys,
protein intake three times the RDA can lead to kidney prob-
lems in people with mild kidney impairment. The American
Diabetes Association recommends limiting protein intake
to less than 20% of total kilocalories (100 g protein for a
2000-kcal diet).

Dental Hygiene Considerations

• Protein intake exceeding daily caloric needs results in additional fat stores and obesity.

 

Nutritional Directions

• Extremely high protein intake is especially undesirable in infants.
• Because proteins must be metabolized by the liver and filtered
  by the kidneys, excessive amounts (more than 200% of the RDA)
  result in additional work by or stress on these organs.

 

Vegetarianism 

 Despite the fact that protein is not limited in the U.S. food
supply, some people choose plant sources of protein for
health reasons or because of their philosophical, ecologi-
cal, or religious convictions. The large numbers of vegetar-
ian cookbooks and meatless “veggie” burgers and
sausage-style products would lead one to believe vegetari-
anism is a growing consumer movement. The Vegetarian
Resource Group indicates only 2% to 3% of the population
are true vegetarians; in 2006, 6.7% of adults said they never eat meat.
   Technically, the major types of vegetarian diets differ in
the types of foods included. In a lactovegetarian diet,
dairy products are consumed in addition to plant foods
(lacto– comes from the Latin word for milk, lactis). Meat,
poultry, fish, and eggs are excluded. Milk and cheese prod-
ucts, which complement plant foods and enhance the
amino acid content, are included. The ovolactovegetarian
diet is supplemented with milk, cheese, and eggs (ovo–
comes from the Latin word for egg, ovum). Only meat, poultry
and fish are excluded. If adequate quantities of eggs, milk,
and milk products are consumed, all nutrients
are likely to be provided in sufficient quantities. Strict
supervision is not warranted. The ovovegetarian diet con-
sists of foods from plants with the addition of eggs. Meat,
poultry, fish, and dairy products arc excluded. The vegan
(or strict vegetarian) diet is the strictest type and contains
only food from plants, including vegetables, fruits, and
grains. No foods of animal origin are allowed (e.g., meat,
milk, cheese, eggs, butter). Some “self-described” vegetar-
ians are not true vegetarians because they occasionally eat
fish and poultry. These people are known as “semi-
vegetarians” or flexitarians.
   Some groups, especially Seventh-Day Adventists, sup-
plement protein intake with many textured vegetable
protein (TVP) products. These meat substitutes are pro-
duced from vegetable proteins, usually soybeans. The
protein in TVP products is of good quality, but these prod-
ucts may have a high sodium content.
   EAAs can be provided by plants, but larger amounts of
these plant products must be consumed to match the protein
obtained from animal sources. EAAs present in low levels
in grains are abundant in other plants, such as legumes.
Beans are low in methionine and tryptophan, and corn is
low in lysine and threonine. When eaten together, as in
pinto beans and cornbread, they are said to be complemen-
tary foods, and less volume is required.
   Protein from a single source is seldom consumed alone.
Foods are usually combined without awareness they are
complementary to each other (e.g., beans are usually com-
bined with rice, bread, or crackers (wheat), or tortillas or
cornbread (corn)). When a combination of plant proteins
is eaten throughout the day, the amino acids provided by
each complement each other—that is, the deficiencies of
one are offset by the adequacies of another. Additionally,
small amounts of high-quality proteins can be combined
with plant foods, as in macaroni and cheese or cereal and
milk, to provide adequate amounts of EAAs. If caloric
requirements are met, protein requirements are met when
a variety of protein-containing foods are eaten throughout
the day. The foods providing complementary amino acids
do not have to be consumed at the same time.
   With some basic nutrition knowledge, vegetarian foods
can be selected that are healthy and nutritionally balanced.
The major difference is the protein source. The Vegetarian
Food Guide Pyramid and Vegetarian Food Guide Rainbow
are designed specifically to address the nutrient
inadequacies and reduced mineral bioavailability of vege-
tarian diets. Vegetarian diets generally result in lower
dietary intake of saturated fat and cholesterol, and high
levels of carbohydrate, fiber, magnesium, boron, folate,
and vitamins C and E. Key nutrients that may fall short
of the DRI in the vegetarian diet include zinc, calcium,
riboflavin, vitamins D and B12, and n-3 fatty acids.
Laboratory tests show reduced blood levels of vitamins B12
and D and the minerals calcium, zinc, and iron in vegetar-
ians. Commonly available fortified foods (i.e., fortified
breakfast cereals and nondairy soy milks) are emphasized
to ensure good sources of vitamins B12 and D and
calcium.
   By using a variety of principally unrefined foods, and enough
kilocalories to promote good health, protein quality and
quantity and other nutrients can be adequate for most individuals.
   Because of the difficulty of consuming adequate volumes
of food to meet kilocaloric requirements, the vegan diet is
not recommended for infants, children, or pregnant/lactat-
ing women. Breastfed infants of two vegan mothers in the
United Stales developed brain abnormalities as a result of
vitamin B12 deficiency.
   Much can be said of the healthy aspects of vegetarian
diets. Vegetarian diets can meet the DRIs as long as the
variety and amounts of foods are adequate. The fact that
vegetarian diets and lifestyles seems to be conducive to
good health is exemplified by vegetarians exhibiting better
weight control, improved gastrointestinal function, fewer
breast and colon cancers, better glucose control, a lower
incidence of gallstones, lower blood pressure, and a
decreased rate of coronary heart disease; they also live
longer. These advantages are not attributed solely to
avoidance of meal products, but benefits from additional
plant food selections. For instance, beans, legumes, and
whole-grain products help with blood glucose control;
plant foods are associated with a lower risk of cardiovas-
cular disease. People who have an interest in pursuing a
vegetarian diet should be encouraged to do so; all people
should have more meatless meals and to consume more
plant foods.