Chapter 30: Nutrition

K. DunlapChem 104

Nutrition

the study of food and how the body uses it

Function of Nutrients:1) supply energy2) supply materials for building and

replacing body tissues3) supply other substances needed for

various life processes

Nutrition• Nutrients:Nutrients: the components of food and drink

that provide growth, replacement, and energy:1. Carbohydrates

2. Lipids

3. Proteins

4. Vitamins

5. Minerals

6. Water

• DigestionDigestion: the hydrolysis of starches, fats, and proteins into smaller units that can be absorbed and metabolized.

Elemental Composition of the Human Body

Digestive Tract• breakdown of food is done through a series of enzyme-catalyzed reactions

• CHO start breaking down into maltose and disaccharides in the mouth by salivary amylase

• pepsin begins the breakdownof protein into polypeptides

• acids are neutralized• CHO to monosaccharides and absorbed• polypeptides to amino acids and absorbed• triglycerides to FAs and glycerol

Digestion Continued…

• Bile acids are like soaps. They have a polar and nonpolar groups that aid water soluble lipase and the incorporation of fats into chylomicrons for transport. They are synthesized in the liver and stored in the gallblader

• Lipase cleaves triglycerides to fatty acids and glycerol

• Fatty acids, glycerol, amino acids, monosaccharides are absorbed in the small intestine and travel through the blood stream to the liver for further modification

Proteins• Different enzymes catalyze the hydrolysis of

peptide chains at different specific sites.

Carbohydrates Proteins Fats

Mouth Salivary amylase

Disaccharides

Maltose

Stomach Pepsin

Polypeptides

Small

Intestine

Pancreatic enzymes

Simples sugars

Glucose

Pancreatic enzymes

Amino acids

Lipase

Bile salts

Glycerol

FAs

Bloodstream

Liver Glycogen Body proteins Body fats

Calorimeter• Food energy is measured in Calories (capital C)

1 Cal = 1 kcal = 1000 cal = 4180 joules

• a Calorie is defined as the amount of energy required to raise 1 kg of water 1C

•Measured in a bomb calorimeter

Calculating the Caloric Value of Food

Carbohydrate = 4 Cal per gramProteins = 4 Cal per gramFats = 9 Cal per gram

Determining Fat Content of Foods

Recommended Dietary Needs

Recommended Daily Intake:

Adults: 0.8 g per kg of body weight

Children and Pregnancy: 1.5-2.0 g per kg body weight

Complete Protein - contains all essential amino acids-meat, eggs, dairy, fish

Incomplete Protein - missing one or more essential amino acids

-legumes and grains combined make a complete protein

Proteins

Proteins– Gelatin, which is denatured collagen, is an

incomplete protein because it lacks Trp, and is low in Ile and Met.

– Corn protein is low in Lys and Trp.– Rice is low in Lys and Thr.– Wheat protein is low in Lys.– Legumes are low in Met and Cys.– Soy protein is very low in Met.

Protein complementation:Protein complementation: a diet in which two or more proteins complementation each other’s deficiencies; for example:– grains + legumes (rice + beans)

Fats • recommended 30% of diet-10% monounsaturated-10% saturated-10% unsaturated

Essential Fatty acids:Omega-3

EPA, DHA, linoleic

Omega-6Arachidonic acid, -linolenic

• EPA, DHA, AA are 20 carbon hormone-like fatty acids that play an important part in the immune function

Percentage of Calories in Common Foods

Energy Needs

Woman 2000 CalMen 2200 Cal

-physical activity and lifestage affects energy needs

-need to burn 3500 Cal to lose 1 pound

Basal Caloric Requirements -the requirements for a resting body

Vitamins-Organic compounds required in small amounts for normal metabolism and good health- not a source of energy

Water soluble - C and Bs-must be replenished everyday-Difficult to overdose

Fat soluble - A, D, E, K-does not need to be replenished everyday-can cause toxicity

Fat Soluble Vitamins

Water Soluble Vitamins

Recommended Daily Allowances (RDA)

Vitamin Absorption and Storage

• All absorption takes place in the small intestine

• Fat-soluble vitamins – Are absorbed in the duodenum– Storage

• Vitamin A is mainly stored in the liver • Vitamins K and E are partially stored in the liver• Vitamin D is mainly stored in the fat and muscle tissue• Can build up in body to point of toxicity

Vitamin Absorption and Storage

• Water-soluble vitamins– Absorbed with water and enter directly into the

blood stream– Most absorbed in the duodenum and jejunum– Most are not stored in the body– Excess intake excreted through the urine– Important to consume adequate amounts daily– Dietary excesses can be harmful

Digesting and Absorbing Water-Soluble Vitamins

Figure 10.1

Water-Soluble Vitamins

Fat-SolubleVitamins

Absorbed in the Small Intestine Small IntestineHydrophobic or

Hydrophilic Hydrophilic Hydrophobic

Absorbed into the Blood Lymph

Stored in the body Not Generally Yes

Can build up and become toxic Not Generally Yes

Need to consume daily Yes No

Bioavailability

• Varies based on– Amount in food– Preparation– Efficiency of digestion and absorption of food– Individual nutritional status– Natural or synthetic

• Fat-soluble vitamins are generally less bioavailable than water-soluble vitamins

• Vitamins from animal foods are generally more bioavailable than those in plant foods

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vitamin D• A prohormone synthesized

from cholesterol• Vitamin D3 = cholecalciferol• Found in animal products• Vitamin D2 = egocalciferol• Found in plants and fortified

foods

Vitamin D3 and D2

• Time spent outdoors

• Amount of skin exposed

• Skin color

• Clothing

• Body fat

• Latitude

• Season and time of day

What affects your vitamin D level?

Vitamin D Synthesis and LatitudeVitamin D Synthesis and Latitude

Childhood rickets

• Epidemic with industrialization in 19-20th centuries

• With discovery of vitamin D and fortification, rickets was almost entirely eliminated

• Until now…

London 1889

Idaho 1989

• 40-90% of US community dwelling elderly• 50% of premenopausal women• 50% of Hispanic and black adolescents• 48% of French preteens• 30-50 % of adults in Saudi Arabia and

UAE• 73 % of pregnant women taking prenatal

vitamins …are DEFICIENT

How to get vitamin D...

• 100 IU/d raises level by about 1 ng/mL

• Sunlight 3000 IU/10 minutes• Oily fish 300 IU/3 oz

– Salmon, sardines, mackerel, tuna

• Mushrooms 100 IU/3 oz• Fortified drinks 100 IU/8 oz

– Milk, orange juice, yogurt, cereals

Updated Recommendations In Process

• Studies suggest that the daily vitamin D intakes should be much higher than 400 IU/d.

• Daily intakes in the range of 800 to 1000 IU/d should be strongly considered.

• Although there are concerns regarding vitamin D toxicity, side effects at intakes exceeding the current upper limit of 2000 IU/d have not been reported to date.

• Assessment of vitamin D status with serum measurements of 25(OH) vitamin D levels for a broader range of patients should be encouraged.

Vitamin Deficiency

Scurvy - vitamin C (ascorbic acid) deficiency-bleeding gums, vomiting, weight loss, anemia, poor wound healing

Beri beri - vitamin B1 (thiamine) deficiency-stiffness of limbs, heart disease, mental disorders, paralysis of limbs

Pellagra - vitamin B3 (niacin) deficiency-reddening and drying of skin, gastrointestinal and nervous system disorders

blindness - vitamin A (retinol) deficiency-night blindness, scaly and hard skin, eye degeneration-retinol is required for the generation of rhodopsin, a photosensitive material

Rickets and Osteomalacia - vitamin D (calciferol) deficiency-required for the absorption of Ca and P-skeletal problems, knock knees, protruding forehead-Rickets in children-Osteomalacia in adults

Vitamin Deficiency cont….

Minerals

-defined as those elements, other than carbon, oxygen, hydrogen, and nitrogen that are needed for normal growth and maintenance

Major or Macrominerals - those required in amounts of 1 gram or moreCa, P, K, Na, Cl, Mg,

Trace or micromineral - those required in amounts less than 1 gramCu, Co, Z, Fe, I, F, Se

Minerals

Source and function of common Vitamins and Minerals

Fiber - indigestible carbohydrates -lowers risk of cardiovascular disease, diabetes, colon cancer, diverticulitis and obesity

• absorbs water and promotes frequent bowl movements• fermented in the Large intestine by microbes• lowers LDL cholesterol

1) Soluble

2) Insoluble

• slows gastric emptying• causes satiety• adds fecal bulk

Problems with Processed Food

• nutrients are lost in processing• some but not all nutrients are added back (Enriched)• Fortified is when other ingredients are added that were not originally the food• are lower in fiber • processed foods are digested more quickly andlend to weight gain

Nutritional Diseases

Kwashiorkor - protein deficiency-often provides enough calories-common b/w the ages of 1-4 b/c of premature weaning

Nutritional Diseases

marasmus - protein and calorie deficiency-more serious condition

Nutritional Diseases

Anorexia Nervosa- a psychological disorder characterized by low body weight and poor body image

Bulimia Nervosa- psychological disorder characterized by periods of binging and purging-often eat over 20,000 Cal

Nutritional DiseasesObesity - excessive weight gain that is associated with heath concerns and increased risk of mortality

-characterized by a BMI of greater than 30

BMI (body mass index) = weight in kg divided by the square of the height in m

-25% of Americans are obese-60% of Americans are overweight (BMI 25-29.9)

Nutritional DiseasesDiabetes - condition in which body is unable to utilize glucose in a normal way

Type I - an auto immune disease that results in the permanent destruction of insulin producing beta cells in the pancreas

Type II - metabolic disorder that is usually characterized by insulin resistance, insulin deficiency and hyperglycemia-associated with obesity-Increased prevalence

Food Supplements

- vitamins, minerals, herbal remedies, etc…

-$60 billion a year industry

-Balanced diet provides adequate needs

-Elderly, dieters, alcoholics, pregnant, lactation may require supplementation

- often supplements are not in a form that is as available as it is in food

SupplementLabel

NutritionLabels

Food Additives-added to prevent spoilage, sweeten, enhance flavor, color, appearance, emulsify

Food Preservatives

-mostly used to prevent food spoilage

Antimicrobial:Nitrites-clostridium botulism- identified as cancer-causing

Sulfites-wine and dried fruit-can cause allergic rxn

Others-Na, K, Ca salts, benzoic acid, propionic acid, sorbic acid

Food Preservatives cont….

Antioxidants: added to slow the oxidative process-usually phenols

Butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT)-Prevent oxidation of fats by combining with free radicals

Natural Antioxidants-Vitamin E, Vitamin C, carotenoids, other polyphenols-also stop oxidation by combining with free radicals

Chemical Structures of Flavorings-largest class of food additive

-natural and synthetic

-Mostly aldehydes and esters

-Many synthetics have not been thoroughly tested

Chemical Structures of Artificial Sweeteners

-growing market for dieters and diabetics

NutriSweet

SucraloseSplenda

Sweetness of Sweeteners

Phytonutrients

What are functional foods?• International food information council “those foods that

provide health benefits beyond basic nutrition”

BioactiveNutraceutical

• Considered non-essential for

growth and development

• Decrease risk of chronic diseases

dietary supplements

• Regulated as foods• Safety of supplement regulated by

FDA only after they have entered the market

• DSHEA states that a dietary supplement is “adulterated” only if it presents a “significant or unreasonable risk of illness or injury”

Dietary supplement health & education act of 1994

Definition of a supplement:“Is a product (other than tobacco) that is intended to supplement the diet that bears or contains one or more of the following dietary ingredients: a vitamin, a mineral, an herb or other botanical, an amino acid, a dietary substance for use by man to supplement the diet by increasing the total daily intake, or a concentrate, metabolite, constituent, extract, or combinations of these ingredients.”

•Is intended for ingestion in pill capsule, tablet, or liquid form•Is not represented for use as a conventional food or as the soled item of a meal or diet•Is labeled as a “dietary supplement”•Includes products such as an approved new drug, certified antibiotic, or licensed biologic that was marketed as a dietary supplements or food before approval, certification, or license (unless the Secretary of Health and Human Services waives this provision).

the challenge of assessing dietary supplements

• Need surrogate endpoints!

• Example assessment of risk of cancer, inflammation

• Bioactive components decrease inflammation via multiple mechanisms, i.e. activation of transcription factor and other epigenetic regulations

• Act as antioxidant etc.

secondary metabolites• phytonutrients

content vary by location, harvest & storage

• Sometimes phytonutrient cocktail is better than isolated nutrient – SYNERGY

carotenoids• Yellow and orange fruits, dark

green leafy vegetables

• α and β-carotene and β cryptoxantin – precursor to Vitamin A

• lycopene, lutein, and zeaxantin – not precursors to vit A

• Foods rich in carenoids may be safer than purified supplements

• Typical western diet contains about 6 mg/day of carotenoids, 60% from animal sources

• Bioavailability enhanced by fat

lycopenes• accumulates in

certain tissues, such as prostate

• Lycopene commonly in plasma associated with LDLs

• Lutein and zeaxantin have high binding affinity to HDLs – accumulate in macula lutea of retina, act as photoreceptors

the benefits of salmon…

astaxanthin

Plant sterols & stanols• Most abundant Sterols = β-sitosterol,

stigmasterol, campesterol• Inhibit growth of various forms of lung,

stomach, ovarian and breast cancer.

•Stanols = sitostanol, campestanol• Sterols essential component cell membrane• Have sterol ring – differ in side chain.• Stanols are saturated form of sterol• Phytosterol absorption from intestine is a

fraction of cholesterol

Sterols and stanols cont…• Cholesterol lowing

effect by lowering absorption

• FDA authorized health claims – must contain at least 0.65 g of plant sterols or 1.70 g stanol esters (esters have higher lipid solubility and are more easily incorporated into foods)

• Typical diet .15 - .4 g/day of sterols and stanols

• To achieve 1.5 g/day, use supplement

Polyphenols• 1) flavanoids, 2) phenolic acids• Secondary metabolites

– more than 8000• Hydroxyl groups might provide

reducing power or antioxidant potential (ROS)

• Usually lots of conjugated double bonds

• Usually in free form or Ο-glycosides

Phytoestrogens• Majority phytoestrogens

belong to 4 subclasses: isoflavanoid, coumestans, isoflavones, lignans, stilbenes

• Composed of a planar aromatic ring system with one or more hyroxyl

• Phytoestrogens proposed to mimic estrogen and act as weak agonist, promoting estrogen signaling in the absence of estrogen.

• favorably affect hormone-dependent cancers, menopausal symptoms, glycemic control and weight maintenance, decrease thrombus and platelet aggregation, lower TGL, LDL.

• Recommended as alt to hormone replacement therapy.

• No safety info

ESTRADIOL

Estrogens function in

growth, reproduction,

and maintenance

and integrity of skeleton and

CNS.

Phytoestrogens cont…

• Founds in licorice, kudzu, soy, red clover, saw palmetto

• Wine, grapes and peanuts good source of resveratrol

• Flax seed, whole grain products, vegies, tea good source of lignans.

• FDA approved health claim of 25 g or more soy flour for CVD

Indole-3-carbinol• A chemically, mechanistically,

and phylogenetically separate phytoestrogen is indole-3-carbinol

• does not mimic estrogen, but alters alters estrogen metabolism via a different mechanism.

• Acid condensate of I-3-C binds to aryl hydrocarbon receptor which is capable of upregulating expression of cytochrome P450, which is involved in endogenous estrogen metabolism

Organosulfurs• Contains a derivative of

cysteine called alliin, released when allium vegetables are crushed.

• the enzyme allinase produces a lipid-soluble, unstable intermediate called allicin that decomposes to produce allyl sulfides, including diallyl sulfide (DAS, DAD and DATS)

• Onions, leaks, chives, scallions, garlic (richest source)

Polyols• Sugar alcohols are used

as sweeteners – Xylitol, Sorbitol, Mannitol

• Fewer calories (1.5 – 3 kcal/g) and lower glycemic index due to reduced absorption by intestine

• Excessive consumption of sugar alcohols lead to osmotic diarrhea – >50g of sorbitol or 20 g mannitol

Stevia• A natural zero calorie South

American herb• Steviol contains two hydroxyl groups• Sugar residues are esterified to one or

both of the –OH groups to form glycosides which are 200 – 450 times sweeter than sucrose.

• Microflora in intestine release sugars and steviol

• May lower blood pressure

Food Pyramid

The Food Guide Pyramid

2005 Food Pyramidwww.mypyramid.gov

2011 My Plate

1. How does the body store energy?

2. How many Cal of energy are released 180 grams of glucose are converted to CO2 and H2O?

3. There are 2 fatty acids that the body needs but cannot synthesize. What are they?

4. What is meant by a complete protein?

5. Are vitamins organic or inorganic?

6. Identify each vitamin.a) tocopherolb) calciferolc) ascorbic acidd) cobalamine) retinol

7. What are the fat soluble vitamins?

8. What is kwashiorkor?