Post on 01-Jan-2016
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
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 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 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