Module 2: Nutrition Basics
This class will begin with a review of the core framework of the field of nutritional anthropology. The module will also provide an introduction to the basics of nutrition. The material will include a discussion of the function of the nutrients in the body, what they are and how they are classified. The material will be presented through lecture, discussion and video. Material on deficiency diseases will also be introduced, although covered in more depth at a later time in the course.
1. To understand and learn the basic principles of nutrition
2. To gain a better understanding of the role of the nutrients in the body
3. To gain a basic understanding of the deficiency diseases.
A. Questions from reading assignment: Module #1.
This activity provides a review of the material from Module 1 and provides a forum for discussion and group learning.
Working in a small group in class (Wed 4/3/13) answer one of these questions and prepare a “teaching” presentation for the rest of the class. Your presentation should include discussion.
1. How do the three articles (Pelto et al.; Lee; Mintz) illustrate some of the different interests of nutritional anthropologists – and what are these interests?
2. What is the interplay between food as a biological necessity and the social and cultural factors that condition its availability and consumption?
3. What is the concept of a food system and why do the authors (Pelto et al.) say it is integral to the development of theory in Nutritional anthropology?
B. Food for Thought: Focuses on the nutrition basics material in Module 2.
Think about these questions. Choose one and develop an answer. Prepare to discuss the issue with the rest of the class. We will have a brief discussion on Monday April 8, 2013. You should be prepared with a short (~ 1 page answer – typed to turn in).
1. Although vegetable foods do not contain complete proteins they are important for other nutrients, and the slightly less efficiency of proteins is not significant in our contemporary situation. Under what circumstances might it be significant?
2. Why do we need carbohydrates in our diet? Briefly explain the different types of carbohydrates and the ways we obtain them. What are the main dietary problems associated with consumption of a diet high in carbohydrates?
3. Explain what lipids are and why they are an excellent source of energy. Imagine you are a hunter/gatherer (forager). What might your diet look like? What types of nutrient -related problems might the diet you imagined contain? Then summarize how foragers can try to offset the dietary deficiencies of high protein diets by focusing on fat rich foods.
Class Notes: Nutrition Review:
Input = Output
I = Growth + Development + Maintenance + Respiration + Waste
- promote growth
- sustain life
- enable reproduction
Role of Food/ nutrients
1. Food – supplies nutrients: carbohydrate, protein, vitamin, mineral, fat/oils
2. Food/nutrients important for: growth, development, reproduction etc
3. Food/nutrition plays a major role in human adaptation because:
a) it is an independent stressor
b) modifier of other stressors (disease)
Carbohydrates are an important fuel source for some cells – especially those of the nervous system. We obtain about 50% of our energy from carbohydrates. Some researchers suggest that sweetness, for which there are receptors on the tongue, signaled a safe energy source and thus became an important energy source for humans.
We need carbohydrates to add sugars to other molecules – glycoproteins, glycolipids – receptors for hormones. There are no essential sugars. (However, carbohydrate intake is considered to be essential because sugar provides all the fuel for the brain)
Most forms of carbohydrates are composed of carbon, hydrogen and oxygen in the ratio of 1:2:1. The general formula is CH2O:
The simple forms of carbohydrates (monosaccharides and disaccharides) are called sugars. More complex forms of carbohydrate (polysaccharide) are called starch and dietary fiber.
Simple carbohydrates = SUGARS
Monosaccharides (1 carbon ring)
• Serve as the basic unit of all sugar structures
• Rapidly absorbed into bloodstream from small intestine
• glucose (also known as dextrose) – the major monosaccharide found in the human body. Glucose is stored in the body as glycogen. It has many branches and is actually a polysaccharide. The many arms or branches provide numerous sites for enzyme activity and thus enables it to be broken down quickly.
• fructose (also known as fruit sugar)-absorbed in small intestine and then transported to liver. Much is converted to glucose the rest converted to other compounds such as fat. We consume considerable amounts of fructose as corn syrup which is found in many processed foods. (Check your labels!)
• galactose – large quantities of this sugar do not occur i nature but it is usually found bonded to glucose in lactose (milk sugar)
Disaccharides (2 carbon units)
• Broken down into monosaccharides by enzymes in small intestine (e.g. lactase)
• sucrose = glucose + fructose
Sugarcane, honey, maple sugar
• lactose = glucose + galactose
Complex Carbohydrates = Polysaccharides (many carbon units)
• Starches = glucose polymers (complex strings of same carbon rings)
• Cooking helps to break down starch grains… highly digestible
• amylose – long, straight chain of glucose, forms about 20% of the starch in vegetables, beans, bread, pasta and rice.
(AMYLASE = enzyme in saliva begins breakdown of starch)
“Dietary Fiber” – sometimes referred to as “Structural Carbohydrates”
• differ from starches because the chemical links that join the individual sugar units cannot be digested by human enzymes in the digestive tract. Consequently the sugars are not absorbed.
• Insoluble fiber- do not dissolve readily in water and are not metabolized by intestinal bacteria:
• important because these compounds increase fecal bulk
cellulose – a cotton ball is pure cellulose
hemicellulose – decrease intestinal transit time. Bran fiber is rich in hemicellulose
lignin – can have estrogen-like effects. Commonly found in whole grains and flax seeds. The woody fibers in brocolli are partly lignin
• Soluble fiber – dissolve or swell in water. Readily fermented by intestinal bacteria in the large intestine.
• Soluble starch have important physiologic effects:
delay gastric emptying
slow glucose absorption
may lower blood cholesterol
• Commonly found in apples, bananas, oranges, barley, oats and kidney beans.
• Consuming large amounts of sweets, empty calorie-foods can leave little room for important nutrient-dense foods such as vegetables and fruit.
• sugars and starches that are readily broken down in the mouth increase the risk of dental caries. Bacteria use these sugars to build plaque which adheres bacteria to the teeth. In addition the sugars are metabolized in the mouth and form acids which dissolve tooth enamel.
Strings of Amino Acids (polymers) joined by PEPTIDE BONDS
Amino Acids (aa) = macromolecules containing NITROGEN
Generic Amino acid:
Proteins are crucial to the maintenance and regulation of the body
- structural materials
- source of amino acids used to make protein in the body
- contributes to immune function
- can provide some energy
- can make glucose from amino acids
- 20 aa used in human protein of those 9 are essential (they must be obtained from food).
- Complete protein contain all essential a a.
The Amino Acids:
|Essential Amino Acids (indespensible)||Nonessential Amino Acids (despensible)|
† These amino acids are sometimes considered to be semi-essential This means if they are not consumed in sufficient quantities they need to be made from essential amino acids.
Animal and plant proteins differ in the proportion of essential and nonessential amino acids. Plant proteins, except for soybeans, don’t match our needs for essential amino acids as well as animal proteins. Many plant proteins are low in one or more of the amino acids that are essential for humans. Human tissue resembles animal tissue more than it resembles plant tissue. Consequently humans can use animal protein sources more efficiently than plant sources. Thus animal proteins are considered to be high quality proteins and plant sources are considered low quality proteins. For humans to obtain a sufficient amount and variety of amino acids from plant sources we need to consume a variety of plant foods. Vegetable foods however are important for other nutrients and the slightly less efficient proteins is not significant in our contemporary situation. Under what circumstances might it be significant?
Egg= complete essential aa balance = scored at 100 vs Wheat = 37
|food||limiting amino acid||Good plant source of limiting amino acid||Complementary combinations|
|Legumes (beans)||Methionine||Grains, nuts, seeds||Beans & rice|
|Grains||Lysine, threonine||Legumes||Beans & rice; lentils, curry & rice|
|Nuts and seeds||Lysine||Legumes||soybeans & ground sesame seeds (miso); peanuts, rice & black-eyed peas|
|Vegetables||Methionine||Grains, nuts and seeds||Green beans & almonds|
|Corn||Tryptophan, lysine||Legumes||Corn tortillas & beans|
Cultural Mixes solve the AA balance challenge – this will be discussed in more detail in later modules.
Protein Digestion: in STOMACH
- COSTLY: must break peptide bonds = PEPSIN enzymes
- each aa has a specific enzyme (e.g. trypsin for tryptophan)
- NH-2 = ammonia = toxic on its own… excrete as urea = water + NH-2
- If you eat too much Nitrogen — need LOTS of water… can survive 5-6x requirements, but not much more: (3 lbs steak= toxic dose)
- rest broken into monosaccharides (glucose) & absorbed in small intestine
If protein is only source of energy (very lean diet) the body can easily go into energy debt…
This is the equivalent of starvation mode:
• first use up glycogen stored in liver (several hours supply)
• then will start to break down muscle tissue (glucose synthesized in liver)… for 5 days
• then will attack body fat (prolonged starvation)
“protein sparing effect” =
a little carbohydrate or fat goes a long way (and sugars are more efficient to metabolize… especially for big-headed folks like humans).
- Diets high in protein can increase calcium loss in the urine, compromise kidneuy health in people with diabetes, kidney stones or a history of kidney disease.
Speth, John and Katherine Spielman 1983 Energy source, protein metabolism, and hunter-gatherersubsistence strategies. Journal of Anthropological Archaeology 2: 1-31
lipids , fats & oils:
Fats are used in the body for the production of fatty acids for the production of phospholipids – in structure of cell membranes. Cholesterol is also made from fatty acids and is used for prod of sex and adrenal hormones. Fats are also important for lubrication, especially in joints and around muscles. Additionally fats and lipids are important for temperature regulation through the insulation they provide. They are also important for the transport of certain vitamins (fat-soluble vitamins).
Lipids are composed of a backbone molecule called GLYCEROL to which are attached 2 or 3 long chains of carbon called FATTY ACIDS. Fatty acids are long chains of carbons bonded with hydrogens.
Saturation of fatty acids depends on ratio of hydrogens to carbons on chain… the more saturated the fat, the higher the melting temperature. These fatty acid attributes distinguish the melting point, digestibility, & nutritional properties of the lipids — the chemical and physical properties. A fat or oil is classified as saturated, monosaturated or poluunsaturated based on the nature of the fatty acids present in the greatest concentration. If all the bonds between the carbons and te hydrogens are single the fatty acid is said to be saturated. Saturated fats usually remain solid at room temperature. If hydrogens are missing in the carbon chain the fatty aid is considered to be unsaturated. If a fatty acid has one double bond between the carbons it is monounsaturated. If two or more bonds between the carbons are double bonds, the fatty acid is called a polyunsaturated fatty acid.
Only certain polyunsaturated fatty acids are considered to be essential. They form parts of vital body structures, are important for immune system function, play a role in vision, produce hormone-like compounds and are an important part of cell membranes. These fatty acids only need to be consumed in small quantities – 1 to 2% of our total energy intake.
- alpha-linolenic acid (omega-3)
- linoleic acid (omega-6)
Fats are digested in large intestine:
- NOT water soluble, must be emulsified
- bile acids break down = “salts” or detergents (e.g. lauryl sulfate in shampoo)
- slowly absorbed by mucosal cells
- long/saturate fatty acid chains poorly absorbed
- physiological feedback slows stomach to maximize absorption
- HDL = high density lipoprotein
- LDL = low density lipoproteins
Dietary issues and controversies:
- Saturated fats vs unsaturated fats
- Trans vs. cis hydrogen bonds and cancer
- The omegas
Vitamins and Minerals
Vitamin: essential organic (carbon compounds) compounds needed in small amounts – body can not make.
- Many serve as parts of enzymes (co-factors)
- needed for vision, blood clotting
For a substance to be classified as a vitamin:
- not synthesized in the body
- absence from the diet over a period of time leads to a deficiency disease
- Vitamin D – synthesized under skin in presence of sunlight
- Niacin – tryptophan, an amino acid, is a precursor
- Vitamin and biotin – synthesized to some extent in intestinal by bacteria
Two types of vitamins:
- Fat soluble – A, D, E, K
- Water soluble: B group, C
Minerals: inorganic nutrients – some serve as part of vitamins, vital constituents of body fluids, structural part of bone
- Major minerals
- Sodium (Na)
- Potassium (K)
- Calcium (Ca)
- Phosphorus (P)
- Chlorine (Cl)
- Magnesium (Mg)
- Sulfur (S)
- Trace Minerals
- Iron (Fe)
- Zinc (Zn)
- Selenium (e)
- Iodine (I)
- Copper (Cu)
- Manganese (Mn)
Water: solvent medium for much of the living system
Deficiency Diseases: the lack of an essential nutrient leads to deficiency disease.
PCM: Protein: Kwashiorkor
Protein + Calorie: Marasmus
Most common nutritional problems: WHO