Introduction to Human Nutrition

the science of foods and the nutrients they contain

DIET: THE FOOD ONE CONSUMES

The food choices you make daily have a cumulative impact on your health. Poor food choices lead to chronic disease.

What is Food?

• Food contain nutrients and are derived from plant or animal sources

• Nutrients are used by the body to provide energy and to support growth, maintenance and repair of body tissues

Functional Foods

• Functional foods contain substances that provide health benefits beyond those of their nutrients

• May be a natural functional food or as a result of additives– Tomatoes – contain lycopene– Orange juice with calcium

THE 6 CLASSES OF NUTRIENTS

1. Carbohydrates2. Lipids (fats)3. Proteins4. Vitamins5. Minerals6. Water

Body Composition

Classification of Nutrients

– Organic or inorganic– Essential or nonessential– Macronutrient or micronutrient– Energy yielding or not

Essential Nutrients

• Nutrients the body either cannot make or cannot make enough of to meet its needs

• Must be obtained from foods• Examples:

• Vitamins• Calcium, iron, and other minerals• Some of the amino acids

Nonessentail Nutrients

• Body can make from other nutrients ingested• Examples:

• Cholesterol• Some amino acids

Classifying Nutrients by Composition

• Organic nutrients - contain carbon• Carbohydrates• Lipids• Proteins• Vitamins

• Inorganic nutrients - do not contain carbon• Minerals• Water

Quantity Needed

• Macronutrients: need in relatively large amounts– Carbohydrates, lipids, proteins

• Micronutrients: need in relatively small amounts– All other nutrients

A little more on energy

• Measure energy in kilocalories in U.S.– What most think of as a “calorie” is really a

kilocalorie– Kcal = amount of energy needed to raise the

temperature of 1 kg of water by 10C• Measure energy in kilojoules (kJ) in most

other countries

Energy-Yielding Nutrients

Carbohydrates– C H O– 4 kcal/gram– Body’s primary source of energy

• Use as glucose– Brain’s only source of energy– Stores are limited ~12-24 hours (in liver and

muscle)

Carbohydrates• Dietary sources

– Starch (complex carbohydrates) in grains and vegetables

– Sugars in fruits, sugarcane, sugar beets, honey and milk

– Insoluble fiber: cellulose in vegetables; provides roughage

– Soluble fiber: pectin in apples and citrus fruits; reduces blood cholesterol levels

Lipids

– C H O (P)– 9 kcal/gram– Body’s alternate source of energy

• Use fat along with glucose as an energy source most of the time

– Stores are unlimited

Lipids• Dietary sources

– Triglycerides• Saturated fats in meat, dairy foods, and tropical

oils• Unsaturated fats in seeds, nuts, olive oil, and

most vegetable oils– Cholesterol in egg yolk, meats, organ

meats, shellfish, and milk products

Lipids• Essential fatty acids

– Linoleic and linolenic acid, found in most vegetable oils

– Must be ingested

Lipids• Essential uses of lipids in the body

– Help absorb fat-soluble vitamins– Major fuel of hepatocytes and skeletal muscle– Phospholipids are essential in myelin sheaths

and all cell membranes

Protein

– C H O N – 4 kcal/gram– Body’s least desirable source of energy

• WHY? – Protein is used for energy only when there isn’t

any carbohydrate available as an energy source.

Proteins

• Enzymes • Structural proteins (shape and

form of cells and tissues)• Hormones• Immunoglobulins (antibodies)

Proteins

• Dietary sources– Eggs, milk, fish, and most meats contain

complete proteins – Legumes, nuts, and cereals contain

incomplete proteins (lack some essential amino acids)

– Legumes and cereals together contain all essential amino acids

Proteins

• Use of amino acids in the body1. All-or-none rule

• All amino acids needed must be present for protein synthesis to occur

2. Adequacy of caloric intake• Protein will be used as fuel if there is insufficient

carbohydrate or fat available

Energy Density

• Measure of the kcal per gram of food• Fat has the highest energy density of the 3

energy-yielding nutrients.• Foods with a high energy density provide

more kcal per gram than low density foods.

Energy Density

Vitamins• Essential• Organic, micronutrient• Not energy-yielding• Fairly easily destroyed/damaged• Can be water-soluble or fat-soluble

Minerals• Essential• Inorganic, micronutrient• Not energy-yielding• Indestructible

Improving your Health

• Goal is to reduce the number of risk factors that are in your control – Risk factor = something that statistically increases

the incidence of a disease• Risk factors may not be the cause of the disease………

Nutritional Deficiencies

• Overt vs. covert deficiency– Overt – outward signs of the deficiency

– Covert or sub-clinical– deficiency may be detected by lab tests, but not outward signs of the deficiency

Nutritional Deficiencies

Primary vs. secondary deficiency– Primary – inadequate intake of the nutrient

– Secondary – body doesn’t absorb adequate amounts, excretes too much….

• Body “mishandles” the nutrient

Here are the top 5 obese countries:

• United States • 34% of adults were overweight in 2008 • 66% are overweight in 2012

• Mexico• New Zealand• Australia• United Kingdom

Lowest: Japan & Korea 3.2%

Obesity

Obesity

Artificial Sweeteners

• Reduced calories• Reduce tooth decay• Diabetes• Lower cost

Artificial Sweeteners

• Acesulfame potassium (Sunett, Sweet One)

• Aspartame (Equal, NutraSweet)• Neotame• Saccharin (SugarTwin, Sweet'N

Low)• Sucralose (Splenda)http://www.youtube.com/watch?v=A-hUyw2lcio

Find one source saying that artificial sweeteners are safe and one saying

that they are dangerous.

Which source is more credible?• Why?

» Is it backed by SCIENTIFIC research» Is it from a credible entity?