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Vitamins

MICRONUTRIENTS- needed in small amounts yet essential for good health (30
needed by body)
Vitamins are not synthesised (produced) by body- obtained from food (otherwise
deficiencies occur)
Primary role= METABOLIC REGULATION

Amount of vitamins/minerals in food vary with:

Growing conditions
Storage conditions
Processing- enriched or fortified
Preparation
Cooking

Supplements…

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Why take Vitamins?

Not synthesized by body

Essential in diet

Vitamins are not chemically similar to each other

Each vitamin has a specific function (or set of functions)



Fat Soluble Vitamins: A,D,E&K Water Soluble Vitamins: C&B group

Dissolve in fats and oils (not water) Dissolves in water (not fat)

Stored…

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Food preparation

Storage



Several biochemical mechanisms can either enhance or diminish nutrient absorption,
e.g.:

Iron, Copper and manganese hinder absorption of Vitamin A,D and E

Vitamin B12 is assisted by adequate folate

Cereals and pulses contain iron and phytate and phytate inhibits iron from being
absorbed

The amount you absorb…

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Fat Soluble Vitamins:

Vitamin A

Retinol: animal foods such as milk, cheese, egg yolk, oily fish (herring)

Beta carotene: in plant foods such as: carrots, mangoes, melon. (darker the
green the more beta carotene it contains)

NB Vitamin A is added to margarine to make it nutritionally equivalent to butter…

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Factors affecting absorption: Low protein or fat intake will adversely affect metabolism
and absorption. Acute infections lower Vitamin A concentrations in the blood.



Effects of cooking and storage: Vitamin A is usually not affected by cooking methods.
During storage retinol in fatty foods may be lost due to oxidation (however…

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Sunlight: Vitamin D is formed in skin on exposure to sunlight. Amount varies
according to latitude, time spent in the sun and degree of pigmentation of skin
etc.

Requirements: Normal sunlight meets requirements. Adults confined indoors, people over
65, pregnant women and during lactation are all times when there is…

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Sources:

Most foods contain at least a small amount of Vitamin E (wheat germ, vegetable oils,
nuts, egg yolk and pulses (especially soya beans) are particularly good sources) Fruit and
veg. contain little

Functions:

Natural antioxidant in cell membranes.
The antioxidant is also used commercially (e.g. in vegetable oils) as…

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Processing and refining flour
Cooking in fats- 70%-90% loss
Boiling- 30% loss
Canning 80% loss



Vitamin K

Properties: -heat stable ­affected by irradiation

Sources:

Obtained in large amounts from leafy green vegetables (broccoli and spinach) also
from eggs, milk, wheat bran and fish oils
Can be synthesised by bacterial action…

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Requirements: Since thiamin is needed for the oxidation of the glucose the amount
required by the body is related to the amount of carbohydrate in the
diet. Requirement for women is less due to less body mass resulting
in a low energy requirement.

Deficiency: Retarded growth
Fatigue, depression and irritability…

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Excess: Body excretes it



Factors affecting Absorbed in the intestine
absorption and
bioavailability:

Effects of cooking Slightly soluble in water
and storing(in this Less stable in alkaline conditions
case sunlight, as Overall loss during cooking is small
well): Riboflavin is sensitive to light (e.g. riboflavin in milk is lost at…

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