Vitamins ch9 and 11

Vitamins

Two Categories of Vitamins Fat-soluble

A, D, E, K Water-soluble

The 8 B vitamins, vitamin C

Vitamin Storage in the Body Vitamin storage in the body

Fat-soluble vitamins are stored in adipose cells

Water-soluble vitamins are not well stored, easily excreted by the kidneys

Vitamin Toxicity Megadose = 10 times the RDA

Toxic levels of vitamins are usually achieved only with supplements

Although foods may be excellent sources of vitamins, it is difficult to have toxic effects without supplementation

Because fat-soluble vitamins are stored and excess water-soluble vitamins are excreted by the kidneys, toxicity from fat-soluble vitamins is more likely

Preserving Vitamin Content Keep fresh produce cool, away from light Peel and cut only right before serving Use soon after purchase Frozen and canned products do provide

substantial vitamin content still, particularly if use the fluid packed with it

For cooking, less water is best (steam, microwave, stir-fry)

Fig. 8.15

Processing grains reduces natural vitamin and mineral content.Some processed grain products are fortified, but much micronutrient content is not restored.

Vitamin AVitamin A = retinol, retinal, retinoic acidPreformed vitamin A = retinol

Found in animal products (organ meat)Provitamin A

Found in plant products Beta-carotene, lycopene

Only retinol can be toxic

Vitamin A Functions:

Eyes Prevents night blindness Protects mucus-producing cells in the eyes

Helps prevent xerophthalmia (“dry eye”) Growth/reproduction

Vitamin A attaches to DNA to stimulate the production of proteins necessary for healthy growth

Antioxidant: may protect against some cancers Lycopene and prostate cancer

Vitamin A Deficiency

Common in countries with poor access to food

Toxicity Caused by

excessive intake of retinol

Acne cream, pregnancy

Vitamin D: The Sunshine Vitamin Non-food source: sunlight exposure on skin

About 25% of the time it takes to get a sunburn, 2-3 times per week

In Colorado, not between October and March Body converts a cholesterol derivative into

inactive vitamin D when exposed to sun radiation Inactive vitamin D (also form found in

supplemented foods/beverages) is activated in the kidneys

Fig. 8.5

Vitamin D

Function: encourages calcium absorption and deposition in bones

Deficiency: Rickets – malformation of skeletal tissue,

soft bones from inadequate calcium (“bowlegged”)

Osteoporosis – bone loss disease

Vitamin E Tocopherols Function:

Most potent fat-soluble antioxidant, protects PUFAs and LDL from free radical damage

Deficiency: Hemolytic anemia – preterm babies who

do not have good vitamin E accumulation Food sources: vegetable oils, nuts

Fig. 8.8

Vitamin K Non-food source: bacteria in the large

intestine Function: maintains healthy levels of

blood clotting factors “koagulation”

Deficiency: Newborns – sterile large intestine Long-term antibiotic use

Fig. 8.11

Vitamin C Ascorbic acid Functions:

Maintains healthy collagen Major structural protein in teeth, bones,

tendons, blood vessels Antioxidant – prevents some free radical

damage May help protect against cardiovascular

disease, cancers, cataracts in the eye Immune system function

Vitamin C So, does vitamin C cure colds?

No, but…. Vitamin C can reduce the duration of cold

symptoms by about 1 day Body is saturated with 200 mg/day Supplements often provide 1000 to 2000

mg Eat citrus!

Vitamin C Deficiency:

Scurvy – disease characterized by poor quality collagen Fragile capillary walls, easy bruising, poor wound

healing, bone pain and fractures, diarrhea, pinpoint hemorrhages on arms and legs

RDA for cigarette smokers: 35mg extra Toxicity:

UL = 2 grams (2000 mg), stomach inflammation, diarrhea

Cooking, water causes vitamin C loss

Fig. 8.31

Coenzymes All B vitamins are

coenzymes

Fig. 8.13

Fig. 8.14

Thiamin Functions:

Coenzyme in energy metabolism Used in nutrition therapy with alcoholism (alcohol

interferes with thiamin absorption) Deficiency:

Beriberi Means “I can’t, I can’t” Peripheral nerve disease, pain and paralysis of

extremities, edema, muscle wasting

Sources: Animal protein foods, whole grains, enriched grain

products, some vegetables and fruits Easily lost in cooking water

Riboflavin Function:

Coenzyme in energy and protein metabolism Deficiency:

Tissue inflammation and breakdown Swollen, reddened tongue

Food sources: milk, organ meats, whole or enriched grains, vegetables

Easily destroyed by light Milk in opaque containers

Fig. 8.18

Niacin Function:

Coenzyme in system that converts protein into glucose

Deficiency Pellegra – dermatitis, sometimes fatal

effects on nervous system Tryptophan can be converted to niacin

Milk has no niacin but is high in tryptophan Milk can prevent deficiency

www.medscape.com

Vitamin B6 Pyridoxine Function:

Coenzyme in protein metabolism in over 100 amino acid reactions Produces neurotransmitters, new amino acids, niacin

from tryptophan, hemoglobin Deficiency:

Anemia Nervous system problems (irritability, convulsions) Infant formulas – if sterilized, destroys B6

Pantothenic acid Function: coenzyme in energy metabolism

Biotin Function: coenzyme in the synthesis of

fatty acids, amino acids, DNA Some made by intestinal bacteria

Folate Folic acid Function:

Coenzyme that transfers single carbons to build larger molecules

May help prevent heart disease

Folate Deficiency:

Macrocytic anemia Chemotherapy drugs inhibit folate

metabolism Neural tube defects – inability of nerve cells

to divide and make new cells Neural tube closes within 28 days of

pregnancy Spina bifida Anencephaly

Fig. 8.26

Fig. 8.27

Folate Food sources: green leafy vegetables,

legumes, tomatoes, enriched grains and flours

RDA: 400 micrograms, average intake 220 micrograms for women

Vitamin B12 Cobalamin Function:

Coenzyme in amino acid metabolism and hemoglobin production

Assists in placing lipid coat on nerve cells Deficiency:

Pernicious anemia Neurological problems – tingling in arms

and legs, paralysis, mental decline

Vitamin B12 Sources:

Naturally only found in animal products Fortified foods Supplements/injections

B12 is poorly absorbed without intrinsic factor made by stomach

Vitamin B12 People at risk for B12 deficiency:

Elderly Reduced intrinsic factor production with age

Vegans Eat no animal products, must use injections

or enriched foods Infants nursed by vegan mothers

Symptoms: diminished brain growth, spinal cord degeneration, anemia