PART D: SCIENCE BASE
Section 10: Major Conclusions
NUTRIENT ADEQUACY
Question 1: What Nutrients Are Most Likely to Be Consumed
by the General Public in Amounts Low Enough To Be of Concern?
Conclusion
Reported dietary intakes of the following nutrients are low
enough to be of concern:
For adults: vitamins A, C, and E, calcium, magnesium,
potassium, and fiber For children: vitamin E, calcium, magnesium, potassium,
and fiber.
Efforts are warranted to promote increased dietary intakes of
vitamin E, potassium, and fiber regardless of age; increased intakes
of vitamins A and C, calcium, and magnesium by adults; and increased
intakes of calcium and magnesium by children age 9 years or older.
Efforts are especially warranted to improve the dietary intakes
of adolescent females.
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Question 2: What Dietary Pattern Is Associated With Achieving
Recommended Nutrient Intakes?
Conclusion
Two major aspects of the USDA dietary pattern contribute to
meeting nutrient intake recommendations:
- Consumption of foods from each of the basic food groups:
- fruits
- vegetables
- grains
- milk, yogurt, and cheese
- meat, poultry, fish, dry beans,
eggs, and nuts1
- Consumption of a variety of food commodities within each of
those food groups—since higher energy intake is strongly associated
with greater variety and higher nutrient intake, attention also
should be given to food group choices that maintain appropriate
energy balance.
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Question 3: What Factors Related to Diet or Physical
Activity May Help or Hinder Achieving Recommended Nutrient Intakes
Conclusion
A sedentary lifestyle limits the amount of calories needed to
maintain one's weight. Careful food selection is needed to meet
recommended nutrient intakes within this calorie limit. Diets
that include foods with a high nutrient content relative to calories
are helpful in achieving recommended nutrient intakes without
excess calories. Diets that include a large proportion of foods
or beverages that are high in calories but low in nutrients are
unlikely to meet recommended intakes for micronutrients and fiber,
especially for sedentary individuals.
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Question 4: How Can the
Flexibility of Food Patterns Be
Increased?
Conclusion
By careful planning that considers
the relative nutrient content of
different foods, substitutions can
be made to a food intake pattern
to achieve recommended nutrient
intakes.
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Question 5: Are Special
Nutrient Recommendations Needed
for Certain Subgroups?
Conclusion
Special nutrient recommendations
are warranted for the following
subgroups and nutrients:
Adolescent females and
women of childbearing age—iron and
folic acid Persons over age 50—vitamin
B12
The elderly, persons with
dark skin and persons exposed to
insufficient UVB radiation—vitamin
D
A conclusion specific to each group and nutrient can be found in Part D, Section
1, Question 5.
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ENERGY
Question 1: How Is Physical
Activity Related to Body Weight
and Other Nutrition-Related Aspects
of Health?
Conclusion
Regular physical activity is essential to the maintenance of a healthy
weight and reduces risk for the development of a number of chronic diseases.
At least 30 minutes of moderate physical activity on most days provides
important health benefits in adults. More than 30 minutes of moderate to
vigorous physical activity on most days provides added health benefits.
Many adults may need up to 60 minutes of moderate to vigorous physical activity
on most days to prevent unhealthy weight gain.
Vigorous physical activity (e.g., jogging or other aerobic exercise)
provides greater benefits for physical fitness than does moderate
physical activity and burns calories more rapidly per unit of
time.
Exercise that loads the skeleton has potential to reduce the
risk of osteoporosis by increasing peak bone mass during growth,
maintaining peak bone mass during adulthood, and reducing the
rate of bone loss during aging.
Resistance exercise training increases muscular strength and
endurance and maintains or increases lean body weight. These benefits
are seen in adolescents, adults, and older adults who perform
8 to 10 resistance exercises 2 or more days per week.
Children and adolescents need at least 60 minutes of moderate
to vigorous physical activity on most days for maintenance of
good health and fitness and for healthy weight during growth.
Reducing sedentary behaviors, including television- and video-viewing
time, appears to be an effective way to treat and prevent overweight
among children and adolescents.
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Question 2: How Much Physical Activity Is Needed To Avoid Weight
Regain in Weight-Reduced Persons?
Conclusion
Although the contribution of physical activity to weight loss usually
is modest, acquiring a routine of regular physical activity will help an
adult to maintain a stable body weight after successful weight loss. The
amount of physical activity that weight-reduced adults need to avoid weight
regain is estimated to be from 60 to 90 minutes daily at moderate intensity.
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Question 3: What Are the Optimal Proportions of Dietary Fat and
Carbohydrate to Maintain BMI and To Achieve Long-Term Weight Loss?
Conclusion
Weight maintenance depends on a balance of energy intake and energy expenditure,
regardless of the proportions of fat, carbohydrate, and protein in the diet.
Weight loss occurs when energy intake is less than energy expenditure, also
regardless of the proportions of fat, carbohydrate, and protein in the diet.
For adults, well-planned weight-loss diets that are consistent with the
Accepted Macronutrient Distribution Ranges (IOM, 2002) for fat, carbohydrate,
and protein can be safe and efficacious over the long term. The recommended
ranges for fat calories (20 to 35 percent of total calories), carbohydrate
calories (45 to 65 percent of total calories), and protein calories (10
to 35 percent of total calories) provide sufficient flexibility to accommodate
weight maintenance for a wide variety of body sizes and food preferences.
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Question 4: What Is the Relationship Between the Consumption of
Energy Dense Foods and BMI?
Conclusion
Available data are insufficient to determine the contribution of energy
dense foods to unhealthy weight gain and obesity. However, consuming energy
dense meals may contribute to excessive caloric intake. Conversely, eating
foods of low energy density may be a helpful strategy to reduce energy intake
when trying to maintain or lose weight.
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Question 5: What Is the Relationship Between Portion Size and Energy
Intake?
Conclusion
The amount of food offered to a person influences how much he or she eats;
and, in general, more calories are consumed when a large portion is served
rather than a small one. Thus, steps are warranted for consumers to limit
the portion size they take or serve to others, especially for foods that
are energy dense.
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FATS
Question 1: What Are the Relationships Between Total Fat Intake
and Health?
Conclusion
At low intakes of fat (< 20 percent of energy) and high intakes of
carbohydrates (>65 percent of energy), risk increases for inadequate
intakes of vitamin E, α linolenic acid, and linoleic acid and for adverse
changes in high-density lipoprotein (HDL) cholesterol and triglycerides.
At high intakes of fat (> 35 percent of energy), the risk increases for
obesity and coronary heart disease (CHD). This is because fat intakes that
exceed 35 percent of energy are associated with both increased calorie and
saturated fat intakes. Total fat intake of 20 to 35 percent of calories
is recommended for adults and 25 to 35 percent for children age 4 to 18
years. A fat intake of 30 to 35 percent of calories is recommended for children
age 2 to 3 years.
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Question 2: What Are the Relationships Between Saturated Fat Intake
and Health?
Conclusion
The relationship between saturated fat intake and low-density lipoprotein
(LDL) cholesterol is direct and progressive, increasing the risk of cardiovascular
disease (CVD). Thus, saturated fat consumption by adults should be as low
as possible while consuming a diet that provides 20 to 35 percent calories
from fat and meets recommendations for α linolenic acid and linoleic acid.
In particular,
For adults with LDL cholesterol below 130 mg/dL, less than 10 percent
of calories from saturated fatty acids is recommended. -
For adults with an elevated LDL cholesterol (>130 mg/dL), less
than 7 percent of calories from saturated fatty acids is recommended.2
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Question 3: What Are the Relationships Between Trans Fat Intake
and Health?
Conclusion
The relationship between trans fatty acid intake and LDL cholesterol
is direct and progressive, increasing the risk of CHD. Trans fatty
acid consumption by all population groups should be kept as low as possible,
which is about 1 percent of energy intake or less.
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Question 4: What Is the Relationships Between Cholesterol Intake
and CVD?
Conclusion
The relationship between cholesterol intake and LDL cholesterol concentrations
is direct and progressive, increasing the risk of CHD. Thus, cholesterol
intake should be kept as low as possible within a nutritionally adequate
diet. In particular,
For adults with an LDL cholesterol < 130 mg/dL, less than 300 mg of
dietary cholesterol per day is recommended. For adults with an elevated LDL cholesterol (≥130 mg/dL),
less than 200 mg of dietary cholesterol per day is recommended.
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Question 5: What Are the Relationships Between n-6 PUFA Intake
and Health?
Conclusion
An n-6 PUFA intake between 5 to 10 percent of energy may confer beneficial
effects on coronary artery disease mortality.
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Question 6: What Are the Relationships Between n-3 Fatty Acid Intake
and Health?
Conclusion
An α-linolenic acid intake between 0.6 to 1.2 percent of calories will
meet requirements for this fatty acid and may afford some protection against
CVD outcomes.
The consumption of two servings per week of fish high in eicosapentaenoic
acid (EPA) and docosahexaenoic acid (DHA) is associated with reduced
risk of both sudden death and CHD death in adults. To benefit
from the potential cardioprotective effects of EPA and DHA, the
weekly consumption of two servings (approximately 8 ounces) of
fish, particularly fish rich in EPA and DHA is suggested. Other
sources of EPA and DHA may provide similar benefits; however,
further research is warranted.
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Question 7: What Are the Relationships Between MUFA Intake and
Health?
Conclusion
There is an inverse relationship between the intake of monounsaturated
fatty acids (MUFAs) and the total cholesterol (TC):HDL cholesterol concentration
ratio. If equal amounts of MUFAs are substituted for saturated fatty acids,
LDL cholesterol decreases.
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CARBOHYDRATES
Question 1: What Is the Relationship Between Intake of Carbohydrates
and Dental Caries?
Conclusion
The intake of carbohydrates (including sucrose, glucose, fructose, lactose,
and starch) contributes to dental caries by providing substrate for bacterial
fermentation in the mouth. Drinking fluoridated water and/or using fluoride-containing
dental hygiene products help reduce the risk of dental caries. A combined
approach of reducing the frequency and duration of exposure to fermentable
carbohydrates and optimizing oral hygiene practices is the most effective
way to reduce caries incidence.
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Question 2: How Important to Human Health Is the Glycemic Response
to Carbohydrates?
Conclusion
A potential health concern for foods that raise blood glucose levels and
initiate an insulin response is that they may eventually lead to diabetes.
Current evidence suggests that there is no relationship between total carbohydrate
intake (minus fiber) and the incidence of either type 1 or type 2 diabetes.
The intake of fiber-containing foods is associated with a decreased risk
of type 2 diabetes in a number of epidemiological studies.
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Question 3: What Is the Utility of the Glycemic Index/Glycemic
Load for Providing Dietary Guidance for Americans?
Conclusion
Current evidence suggests that glycemic index and/or glycemic load are
of little utility for providing dietary guidance for Americans.
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Question 4: What Is the Significance of Added Sugars Intake to
Human Health?
Conclusion
Compared with individuals who consume small amounts of foods and beverages
that are high in added sugars, those who consume large amounts tend to consume
more calories but smaller amounts of micronutrients. Although more research
is needed, available prospective studies suggest a positive association
between the consumption of sugar-sweetened beverages and weight gain. A
reduced intake of added sugars (especially sugar-sweetened beverages) may
be helpful in achieving recommended intakes of nutrients and in weight control.
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Question 5: What Are the Major Health Benefits of Fiber-Containing
Foods?
Conclusion
Diets rich in dietary fiber have a number of important health benefits
including helping to promote healthy laxation, reducing the risk of type
2 diabetes, and decreasing the risk of CHD. Prospective cohort studies suggest
that decreased risk of heart disease is associated with the intake of 14
g of dietary fiber per 1,000 calories.
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FOOD GROUPS
Question 1: What Are the Relationships Between Fruit and Vegetable
Intake and Health?
Conclusion
Greater consumption of fruits and vegetables (5 to 13 servings or 2 ½
to 6 ½ cups per day depending on calorie needs3)
is associated with a reduced risk of stroke and perhaps other CVDs, with
a reduced risk of cancers in certain sites (oral cavity and pharynx, larynx,
lung, esophagus, stomach, and colon-rectum), and with a reduced risk of
type 2 diabetes (vegetables more than fruit). Moreover, increased consumption
of fruits and vegetables may be a useful component of programs designed
to achieve and sustain weight loss.
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Question 2: What Are the Relationships Between Whole-Grain Intake
and Health?
Conclusion
Consuming at least 3 servings (approximately equivalent to 3 ounces) of
whole grains per day can reduce the risk of diabetes and CHD and help with
weight maintenance. Thus, daily intake of three or more servings of whole
grains per day is recommended, preferably by substituting whole grains for
refined grains.
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Question 3: What Are the Relationships Between Milk Product Intake
and Health?
Conclusion
Consuming three servings (equivalent to 3 cups) per day of milk and milk
products each day can reduce the risk of low bone mass and contribute important
amounts of many nutrients. Furthermore, this amount of milk product consumption
may have additional health benefits and is not associated with increased
body weight. Therefore, the intake of three servings of milk products per
day is recommended.
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FLUIDS AND ELECTROLYTES
Question 1: What Amount of Fluid Is Recommended for Health?
Conclusion
The combination of thirst and usual drinking behavior, especially the
consumption of fluids with meals, is sufficient to maintain normal hydration.
Healthy individuals who have routine access to fluids and who are not exposed
to heat stress consume adequate water to meet their needs. Purposeful drinking
is warranted for individuals who are exposed to heat stress or who perform
sustained vigorous activity.
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Question 2: What Are the Effects of Salt (Sodium Chloride) Intake
on Health?
Conclusion
The relationship between salt (sodium chloride) intake and blood pressure
is direct and progressive without an apparent threshold. Hence, individuals
should reduce their salt intake as much as possible. In view of the currently
high levels of salt intake, a daily sodium intake of less than 2,300 mg
is recommended. Many persons will benefit from further reductions in salt
intake, including hypertensive individuals, blacks, and middle- and older-aged
adults. Individuals should concurrently increase their consumption of potassium
because a diet rich in potassium blunts the effects of salt on blood pressure.
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Question 3: What Are the Effects of Potassium Intake on Health?
Conclusion
Diets rich in potassium can lower blood pressure and lessen the adverse
effects of salt on blood pressure, may reduce the risk of developing kidney
stones, and possibly decrease bone loss. In view of the health benefits
of potassium and its relatively low intake by the general population, a
daily potassium intake of at least 4,700 mg is recommended. Blacks are especially
likely to benefit from an increased intake of potassium.
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ETHANOL
Question 1: Among Persons Who Consume Four or Fewer Alcoholic Beverages
Per Day, What Is the Dose-Response Relationship Between Alcohol Intake and
Health?
Conclusion
In middle-aged and older adults, a daily intake of one to two alcoholic
beverages is associated with the lowest all-cause mortality. Compared with nondrinkers, adults who consume one to two alcoholic beverages
per day appear to have lower risk of CHD. Compared with nondrinkers, women who consume one alcoholic beverage per
day appear to have a slightly higher risk of breast cancer. Relationships of alcohol consumption with major causes of death do not
differ for middle-aged and elderly Americans. Among younger people, however,
alcohol consumption appears to provide little, if any, health benefit; alcohol
use among young adults is associated with a higher risk of traumatic injury
and death.
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Question 2: What Is the Relationship Between Consuming Four or
Fewer Alcoholic Beverages Daily and Macronutrient Profiles, Micronutrient
Profiles, and Overall Diet Quality?
Conclusion
A daily intake of one to two alcoholic beverages is not associated with
inadequate intake of macronutrient or micronutrients, or with overall dietary
quality.
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FOOD SAFETY
Question 1: What Behaviors Are Most Likely To Prevent Food Safety
Problems?
Conclusion
The behaviors in the home that are most likely to prevent a problem with
foodborne illnesses are
Cleaning hands, contact surfaces, and fruits and vegetables (but
not meat and poultry, which should not be washed) Separating raw, cooked and ready-to-eat foods while shopping, preparing,
or storing Cooking foods to a safe temperature Chilling (refrigerate) perishable foods promptly
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Question 2: What Topics, If Any, Need Attention Even Though They
Are Not an Integral Part of the "FightBAC!" Campaign?
Conclusion
Avoiding higher-risk foods is an important protective measure (e.g., deli
meats and frankfurters that have not been reheated to a safe temperature
may contain Listeria). This is especially important for high-risk groups
(the very young, pregnant women, elderly and those who are immunocompromised).
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