The Science of Nutrition
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Learning Outcomes
• Define the terms nutrition, carbohydrates, proteins,
lipids, vitamins, minerals, water, and calories.
• Use the physiological fuel values of energy-yielding
nutrients to determine the energy content in a food
or diet.
• Describe the factors that affect our food choices.
• Discuss the components and limitations of
nutritional assessment.
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Learning Outcomes (2)
• List the attributes of a healthful lifestyle consistent
with the Healthy People 2020 goals.
• Describe the role of genetics in the development of
nutrition-related diseases.
• Explain how the scientific method is used in
developing hypotheses and theories in the field of
nutrition.
• Identify reliable sources of nutrition information.
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Nutrients
• Macronutrients
– Carbohydrates
– Proteins
– Lipids
– Water
• Micronutrients
– Vitamins
– Minerals
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Functional Categories of
Nutrients
• Provide energy
• Promote growth and development
• Regulate body processes
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Carbohydrates
• Composed of the elements
– Carbon, Hydrogen and Oxygen
• Simple carbohydrates
– Table sugar, Blood glucose
• Complex carbohydrates (polysaccharides)
– Starch (in Grains), Glycogen
• Function: provide 4 kcal/gm
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Lipids
• Provide 9 kcal/gm
• Triglycerides
– major form of fat in food, key energy source,
and fat storage in body
– made up of fatty acids and glycerol
• Saturated
• Unsaturated
– Essential fatty acids
» Linoleic acid and Alpha-linolenic acid
– Trans fatty acids
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Proteins
• Composed of the elements
– Carbon, hydrogen, oxygen, and nitrogen
• Functions
– Major part of bone and muscle
– Components in blood, cell membranes,
enzymes, and immune factors
• Provide 4 kcal/gm
• Formed by bonding together amino acids
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Vitamins
Enable Chemical Reactions; Provide no usable energy
• Water-soluble
• Vitamins C and B
complex
• More easily excreted
from the body
• Easily destroyed by
cooking
• Fat-soluble
• Vitamins A, D, E and K
• More easily stored in
the body
• Greater risk for toxicity
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Minerals
Organic compounds required for body functions
• Major Minerals
• Required in gram
amounts
• Sodium, Potassium,
Chloride, Calcium and
Phosphorus
• Trace Minerals
• Required in amounts
<100 mg daily
• Iron, Zinc, Copper and
Selenium
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Water
• Macronutrient required in largest quantity
• Sources
– Beverages and foods
– Some made as byproduct of metabolism
• Functions
– Lubricant, solvent, transportation medium and
regulates body temperature
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Phytochemicals and
Zoochemicals
• Physiologically active compounds in foods
that provide benefits but are not essential
nutrients
• Phytochemicals
– Plant foods (e.g. vegetables, fruits, whole grains)
• Zoochemicals
– Foods of animal origin (e.g. fish)
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Energy Sources
and their physiological fuel values
• Calorie defined
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Carbohydrates: 4 kcal/gm
Protein: 4 kcal/gm
Lipids: 9 kcal/gm
Alcohol (not an essential nutrient): 7 kcal/gm
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Physiological fuel values can be used to
determine the calories in food
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Energy Uses
of the Energy-Producing
Nutrients
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Build new compounds
Perform muscular movements
Promote nerve transmissions
Maintain ion balance within cells
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What Influences Our Food
Choices?
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Hunger versus appetite
Food flavor, texture & appearance preferences
Culture
Lifestyle, routines, and habits
Environment, food cost, and availability
Food marketing
Nutrition concerns, knowledge, and beliefs
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Nutritional Health Status
• Optimal (desirable) Nutritional Status
• Undernutrition
– Subclinical deficiency
– Clinical deficiency
• Overnutrition
– Toxicities
– Excesses of energy nutrients: obesity
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Health Objectives for the U.S.
• Health promotion important since 1970s
• Healthy People 2020
– Issued by USDHHS
– 10-year goals for improving the health of all
Americans
– Main objective
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Nutritional Assessment helps
determine nutritional ‘fitness’
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Anthropometrics
Biochemical
Clinical
Dietary
Environmental
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Genetics and Nutrition
• Lifestyle, diet and genetics influence
disease risk
– DNA directs individual’s use of nutrients
• Genetic mutations increase risk for some
diseases
• Gene Therapy
• Genetic Testing
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Using the Scientific Method to
Learn More about Nutrition
• Making observations, generating, and testing
hypotheses
• Use of animal models versus humans in
research
• Variety of research approaches
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Migrant studies
Cohort studies
Case control studies
Double-blind studies
• Peer review of results and follow-up studies
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Evaluating Nutrition Claims,
Products, and Advice
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Apply basic nutrition principles
Evaluate the claims critically
Examine the scientific credentials of author
Examine the study cited
Beware of ‘hype’
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Buying Nutrition Products and
Supplements
• DSHEA (Dietary Supplement Health and
Education Act of 1994)
• Supplements do not require FDA approval
or rigorous regulation
• Do not need to be proven to be effective if
reasonably safe, with a history of use
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Getting Nutrition Advice
• RD (Registered Dietitian) – in United States
– Find at www.eatright.org
– Uses The Nutrition Care Process
• 4 steps (ADIM/E)
• RDN – in Canada
– www.dietitians.ca
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