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Chapter 6

Vitamins

Learning Objectives

1. State the general characteristics of vitamins

2. Identify the functions and food sources of each of the 13 vitamins

3. Identify which vitamins are most likely to be deficient in the American diet and which vitamins are most toxic

4. List two health benefits of eating a diet rich in fruits and vegetables

Learning Objectives (cont’d)

5. Discuss the use of fruits and vegetables on the menu

6. Describe ways to conserve vitamins when handling and cooking fruits and vegetables

7. Give examples of functional foods and discuss their role in the diet

8. Define phytochemicals and give examples of foods in which they are found

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Characteristics of Vitamins

1. Very small amounts are needed by the body and very small amounts are in foods

2. The roles they play in the body are very important

3. Most vitamins are obtained through food. Some are made by bacteria in the intestine and one is made in the skin

4. There is no perfect food that contains all the vitamins in the right amount

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Characteristics of Vitamins (cont’d)

5. Vitamins do not contain kcalories, but they are involved in extracting energy from the macronutrients

6. Some vitamins in foods are precursors

Water-soluble vs. Fat-soluble vitamins

Fat-soluble vitamins Vitamin A Vitamin D Vitamin E Vitamin K

Water-soluble vitamins Vitamin C B-complex vitamins

such as thiamin,

folate, and B12

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Fat-Soluble Vitamins

Fat-soluble vitamins are generally found in foods containing fats and are stored in the body either in the liver or in adipose tissue until needed

Excessive intake of A or D causes them to be stored and can be undesirable. Vitamin D, when taken in excess, is the most toxic of all the vitamins

Fat-soluble vitamins are absorbed and transported around the body like other fats

If anything interferes with fat absorption, these vitamins may not be absorbed

Low intake of vitamins A and E is a concern for adults, children may have low intakes of vitamin E

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Forms of Vitamin ARetinoids

Retinol

Retinal

Retinoic Acid

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Carotenoids

Beta-carotene Retinol

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Functions of Vitamin A

Essential for health of the cornea (clear membrane surrounding eye)- deficiency causes xerosis and eventually xerophthalmia

Essential for retina of eye – deficiency causes night blindness

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Functions of Vitamin A (cont’d.)

Needed to make and maintain the epithelial cells that form the protective linings of your lungs, GI tract, and urinary tract

Also essential to make and maintain epithelial cells that produce mucus (protects cells)

Role in reproduction, growth and development, bone growth and teeth developing in children

Proper functioning of immune system

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Beta Carotene

A precursor of vitamin A Functions as an antioxidant in the body – a

compound that combines with oxygen to prevent oxygen from oxidizing or destroying important substances

Rich sources: Deep green vegetables – spinach Deep orange fruits and veggies – carrots

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Retinol

Preformed vitamin A Found in animal

products such as: Liver Vitamin A-fortified milk Eggs Fortified cereals Butter and margarine

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Measurement of Vitamin A

Measured in retinol activity equivalents (RAE) One RAE =

1 microgram retinol 12 micrograms beta-carotene 24 micrograms of other vitamin A precursors

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Vitamin A: Deficiency and Toxicity

Deficiency is of most concern in developing countries where it causes night blindness, blindness, poor growth, and other problems

Prolonged use of high doses of preformed vitamin A may cause hypervitaminosis A Hair loss Bone pain Skin problems Liver damage Nausea/diarrhea

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Vitamin D

When ultraviolet rays shine on your skin, a cholesterol-like substance is converted into a precursor of vitamin D and absorbed in the blood

Over the next few days, the precursor is converted to vitamin D3 (cholecalciferol)

Vitamin D3 is converted into its active form – a hormone – by enzymes in the liver and then the kidney

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Functions of Vitamin D

Maintains blood calcium levels by: Increasing calcium absorption in the intestine Decreasing the amount of calcium excreted by the kidney Pulling calcium out of the bones

Blood calcium levels must be kept high so there is enough calcium to build bones and teeth, contract muscles, and transmit nerve impulses Bone growth

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Sources of Vitamin D

Vitamin D fortified milk and cereals Fatty fish

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Vitamin D: Deficiency and Toxicity

Deficiency in children: rickets Deficiency in adults: osteomalacia

Toxicity: Vitamin D is most toxic of all vitamins About 4 to 5x the Adequate Intake: symptoms

will include nausea, vomiting, diarrhea, fatigue, and confusion; can lead to calcium deposits in the heart, blood vessels, and kidneys

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Functions of Vitamin E

Antioxidant – especially helps the red blood cells and cells in the lungs and brain

May protect against heart disease by preventing the oxidation of LDL

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Food Sources of Vitamin E

Widely distributed in plant foods: Vegetable oils, margarine, and shortening Salad dressing made from vegetable oils Seeds and nuts Whole-grain breads and cereals

Many Americans don’t consume enough vitamin E

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Vitamin K

Essential role in producing blood-clotting factors, such as prothrombin

Needed to make an important protein used to form bone

Bacteria in the intestines produce a form of vitamin K

Food sources: liver, green leafy vegetables, broccoli, vegetable oils

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Water-Soluble Vitamins

Includes Vitamin C and B-complex vitamins B vitamins work in every cell as coenzymes Only small amounts of water-soluble vitamins

are stored in body (except B6 and B12) American adults take in too little vitamin C Excessive supplementation of certain water-

soluble vitamins can cause toxic effects

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Functions of Vitamin C

Needed to make collagen, a fibrous protein that is part of skin, bone, teeth, ligaments, and other connective structures. (Vitamin C acts like Cement)

Needed to make some hormones, such as thyroxine

Needed for immune system Antioxidant (like vitamin E and beta-carotene) Helps iron to be absorbed

Vitamin C as an Antioxidant

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Food Sources of Vitamin C

Citrus fruits Bell peppers Kiwi fruit Strawberries Tomatoes Broccoli Potatoes Fortified juices and

cereals

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Vitamin C: Deficiency and Toxicity

Deficiencies resulting in scurvy are rare Situations that require additional vitamin C:

Pregnancy, lactation, growth, fever, infections, burns, surgery, smoking

UL is 2 grams: Over 2 grams causes gastrointestinal symptoms. High levels interfere with certain medical tests.

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Thiamin, Riboflavin, and Niacin

All play key roles as part of coenzymes in energy metabolism: they are essential to release energy from carbohydrates, fats, and proteins

All are needed for normal growth Thiamin also plays a role in nerve function Riboflavin is needed to help form vitamin B6

coenzyme and to make niacin in the body

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Food Sources of Thiamin, Riboflavin, and Niacin

Thiamin – pork, sunflower seeds, wheat germ, peanuts, dry beans, whole-grain & enriched breads/cereals

Riboflavin – Milk & milk products, organ meats, whole-grain &enriched breads and cereals

Niacin – Meat, poultry, fish, organ meats, whole-grain and enriched breads and

cereals, peanut butter

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Amino Acid

TryptophanNiacin

Tryptophan (Amino Acid) Found in Protein Foods is Converted to Niacin in the Body

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Functions of Vitamin B6

Important role as part of a coenzyme involved in carbohydrate, fat, and especially protein metabolism

To make hemoglobin Important to the immune system – WBCs

Also used to break down glycogen to glucose and to make neurotransmitters

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Sources of Vitamin B6

Meat, poultry, fish Not as well absorbed

from plant foods Potatoes Some fruits (bananas

and watermelons) Some leafy green

vegetables (broccoli and spinach)

Fortified ready-to-eat cereals

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Vitamin B6: Deficiency and Toxicity

Deficiency: may occur in women and older adults Deficiency symptoms: fatigue, depression, irritability

More than 2 grams daily for 2 months or more than 200 mg daily for longer can cause irreversible nerve damage and symptoms such as numbness in hands and feet and difficulty walking

B6 is stored in the muscles

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Functions of Folate

Part of coenzymes required to make DNA, the genetic material contained in every cell

Therefore folate is needed to make all new cells, especially those that need to be replenished frequently:

RBC, WBC, and digestive tract cells

Needed for amino acid metabolism

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Sources of Folate

Green leafy vegetables (such as spinach)

Legumes Orange juice Fortified breads and

ready-to-eat cereals Much folate is lost

during food prep and cooking

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Dietary Folate Equivalents (DFEs)

RDA for folate is measured in micrograms of DFEs

DFEs take into account the amount of folate absorbed from natural and synthetic sources

Synthetic folate is used in fortified foods such as breads and in supplements

Synthetic folate is absorbed at 1.7 times the rate of naturally-occurring folate

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Folate Deficiency

Deficiency causes megaloblastic anemia – RDC are large and immature

Other deficiency symptoms: digestive tract problems such as diarrhea, mental confusion, and depression

During earliest weeks of pregnancy, women need folate because a deficiency can cause neural tube defects

Some medications interfere with the normal use of folate in the body

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Functions of Vitamin B12

Convert folate into its active forms so that it can make DNA

Functions of Vitamin B12 (cont’d)

Also functions as part of a coenzyme needed to make new cells and DNA

Helps in the normal functioning of the nervous system by maintaining the protective cover around nerve fibers

Bone cells depend on vitamin B12

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Sources of Vitamin B12

Only animal foods. Meat Poultry Fish and Shellfish Eggs Milk Milk Products

Vegetarian concerns

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Vitamin B12 Deficiency

Deficiency is usually due to problem with absorption – lack of intrinsic factor or lack of hydrochloric acid – both are more so problems as you get older

Pernicious anemia develops when B12 is not properly absorbed. Symptoms: Macrocytic anemia Extreme weakness and fatigue Nervous system problems – balance,

numbness, confusion

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Pantothenic Acid and Biotin

Parts of coenzymes involved in energy metabolism

Pantothenic acid is also needed to make lipids, neurotransmitters, and hemoglobin

Biotin is also involved in the metabolism of carbohydrates, fats, and protein

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Sources of Pantothenic Acid & Biotin

Both pantothenic acid and biotin are widespread in foods

Pantothenic acid: Fortified cereals, beef, poultry, mushrooms, potatoes, tomatoes

Biotin: Egg yolks (Intestinal bacteria make considerable amounts of biotin)

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Choline

Choline can be made in the body in small amounts

Needed to make the neurotransmitter acetylcholine and the phospholipid lecithin (major component of cell membranes)

Widespread in foods Choline is a conditionally essential nutrient

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Vitamin-like Substances

Carnitine, lipoic acid, inositol, and taurine are needed for normal metabolism but the body makes enough so they are not vitamins. Some are added to formula for infants

Other substances promoted as vitamins, such as pangamic acid or bioflavonoids, are clearly not vitamins

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Ingredient Focus: Fruits & Veggies

Low in kcalories Low or no fat (except

avocados) No cholesterol Good sources of fiber Excellent sources of

vitamins and minerals Low in sodium (except

some canned veggies)

Culinary Science

Fruits and vegetables are mostly water Plant cells in picked fruits and vegetables

continue to be alive and take in oxygen for breathing

To slow down the breathing which causes the fruit/vegetable to deteriorate, keep it cold and moist

Culinary Science (cont’d)

Cooking causes plant

cells to die, lose water,

and soften

When cooking, you

need to control changes

in texture, flavor, and

color

Culinary Science (cont’d)

How to control color changes Green vegetables

Yellow/orange veggies

Red veggies

White veggies

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Functional Foods and Superfoods

Functional foods: Foods supplemented with ingredients thought to help prevent diseases or to improve health Margarine with an ingredient to lower

cholesterol Drinks with herbs such as ginseng

Phytochemicals: Substances such as beta-carotene that are found largely in fruits and veggies and that seem to be helpful in preventing cancer and/or heart disease when consumed regularly

Superfoods

Beans

Nuts

Cocoa

Tea

Spinach Plant stanols and sterols

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PhytochemicalsPhytochemical Names Good For Food Sources

Green Vegetables & Fruits

Lutein and Zeaxanthin Healthy eyesight Turnip, collard, and mustard greens; kale; spinach; lettuce; broccoli; green peas; kiwi; honeydew melon

Indoles Anti-cancer Broccoli, cabbage, Brussels sprouts, bok choy, arugula, Swiss chard, turnips, rutabaga, watercress, cauliflower, kale

Yellow/Orange Vegetable & Fruits

Bioflavonoids Healthy heart, healthy anti-cancer

Oranges, grapefruit, lemons, tangerines, clementines, peaches, papaya, apricots, nectarines, pears, pineapple, yellow raisins, yellow pepper

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Phytochemicals (cont’d)Red Vegetables and Fruits

Anthocyanins Healthy circulation, healthy nerve function, anti-cancer

Raspberries, cherries, strawberries, cranberries, beets, apples, red cabbage, red onion, kidney beans, red beans

Blue/Purple Vegetables and Fruits

Anthocyanins Healthy circulation, healthy nerve function, anti-cancer

Blueberries, purple grapes, blackberries, black currants, elderberries

Phenolics Healthy cells, anti-cancer.

Raisins, prunes, plums, eggplant

White Vegetables and Fruits

Allium and Allicin Healthy immune system, healthy cholesterol levels, anti-cancer

Garlic, onions, leeks, scallions, chives

Source: National Cancer Institute

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