Vitamins & Vitamins & AntioxidantsAntioxidants

Two Classes Fat-Soluble

– A– D– E– K

Water-Soluble– Vitamin C– 9 B-vitamins

• Thiamin• Riboflavin• Niacin• Pantothenic Acid• B6• B12• Folate• Biotin• Choline

Effects of SolubilityEffects of Solubility Solubility affects absorption, transport,

storage, and excretion Fat-soluble vitamins

Lipid-like; mix well with fats Require bile for digestion and absorption;

absorbed along with fat Travel through lymphatic system to blood

Excesses are stored Liver and adipose tissue Intakes can vary day to day without deficiency

risk, but toxicity possible with high doses

Water-Soluble Vitamins Absorbed directly into blood

– No carriers needed Kidneys filter out excesses of most (not

all!)– Excretion in the urine

Most are not stored in the body– Need frequent replenishing

Megadoses of some can still cause adverse effects

More is not necessarily better…

Bioavailability Quantity provided by food Amount absorbed and used by body Factors influencing bioavailability

Efficiency of digestionNutrition statusMethod of food preparationSource of nutrientOther foods consumed at same time

Antioxidants Some vitamins

– E– C– Beta-carotene (provitamin A)

Many phytochemicals Body’s own antioxidant enzymes assisted by

some minerals– Selenium– Zinc– Copper– Manganese

Free RadicalsFree Radicals Free radical: active oxidant

Compound with one or more unpaired electronsLook to steal electron from vulnerable

compoundElectron-snatching chain reaction: damage

to DNA, lipids, and cell structures Free radical production

Normal bodily functions Environmental factors

Free Radicals & Free Radicals & AntioxidantsAntioxidants

Free Radicals and Free Radicals and DiseaseDisease

Antioxidants Neutralize free radicals Donate an electron, but remain stable

Free radical attacks Some are helpful

Immune system destruction of viruses, bacteria

Most cause damage

Free Radicals and Free Radicals and DiseaseDisease

Free radical damage Interferes with cell function Contributes to disease progression and

agingOxidation of polyunsaturated fatty acids

in lipoproteins and membranesAlteration of DNA, RNA, and proteins Illicits inflammatory response

Free-Radical DamageFree-Radical Damage

Free Radicals and Free Radicals and DiseaseDisease

Body’s natural defenses and repair systems Enzymes that destroy free-radicals and

repair damage Not 100% effective Less effective with age

Dietary antioxidants help to defend against oxidative stress

Why do we need Why do we need antioxidants?antioxidants? Limit free-radical formation Destroy free radicals or precursors Stimulate antioxidant enzymes Repair oxidative damage Support healthy immune system

Foods, Supplements, or Foods, Supplements, or Both?Both?

Replenish antioxidants regularly Foods

Contain other valuable nutrientsAntioxidant actions of fruits and

vegetables are greater than their nutrients alone

SupplementsResearch inconclusiveContents are limited

Physiological levels vs. pharmacological doses