Chapter 8: Vitamins Flashcards
define: vitamins
Vitamins are organic micronutrients that facilitate body processes
What is the main function of vitamins?
Vitamins can function as coenzymes
Fill in the blank: all vitamins must be converted first before it can be a coenzyme except ________
Vitamin C
Compare water soluble vitamins to fat soluble vitamins in terms of
- transport
- storage
- consumption frequency
- toxicity
water soluble vitamins
- transport: none needed
- storage: not stored; free in aqueous compartments; excreted in urine
- consumption frequency: required more frequently from diet (everyday)
- toxicity: excreted by kidney; less likely to be toxic (possible from too much supplements)
fat soluble vitamins
- transport: lipoprotein transporter required
- storage: stored in adipose tissue
- consumption frequency: required less frequently from the diet (every few days)
- toxicity: build up in adipose tissue; more likely to be toxic
define: bioavailability
Bioavailability: Rate and extent to which a nutrient is absorbed and used in the body
Fill in the blank: _____ of vitamins in food are absorbed
- What is the absorption of vitamins affected by (5)?
40-90%
- Efficiency of digestion and time of transit through the digestive tract
- Previous nutrient intake and nutrition status
- Other foods consumed at the same time (medication too)
- Methods of preparation
- Sources of the nutrient (foods verses supplements)
Vitamins can be destroyed by what (3)?
- Heat
- UV light
- Oxidation
How can we prevent the loss of vitamins in our food?
- Refrigeration of fruits and vegetables
- Storing cut vegetables, fruits, and juices in airtight containers to avoid oxidation
- Wash fruits and vegetables before cutting
- Steam vegetables in small amounts of water, avoid over cooking
Define: primary deficiency
Primary deficiency: intake of vitamins decreased
Define: secondary deficiency
Secondary deficiency: intake of vitamins are normal but absorption is decreased
What food group offers the largest variety of vitamins
meat and alternatives
Which type of vitamin can be absorbed directly into the blood. Why can’t the other type be absorbed directly?
water soluble vitamins; Fat soluble are too large to be filtered in kidney capillaries
Describe vitamin digestion in the mouth
Mouth: mechanical digestion releases vitamins in food
Describe vitamin digestion in the stomach
Stomach: digestion of food releases vitamins; some niacin is absorbed here
Describe vitamin digestion in the gallbladder
Gallbladder: releases bile which emulsifies fat and helps absorb fat soluble vitamins
Describe vitamin digestion in the pancreas
Pancreas: secretes digestive enzymes that aid in the release of vitamins from food
Describe vitamin digestion in the small intestine
Small intestine: fat soluble vitamins are incorporated into micelles then absorbed by simple diffusion. Once they are inside the mucosal cells fat soluble vitamins are packaged into chylomicrons which enter the lymph before passing into the blood. Water soluble vitamins are absorbed from the small intestine directly into the blood. May depend on energy requiring transport systems or must bind to specific molecules in the gastrointestinal tract to be absorbed. Vitamin B12 is absorbed in the lower portion of the small intestines
Describe vitamin digestion in the large intestine
Large intestine: bacteria synthesizes small amounts of vitamins, some of which are absorbed
Fill in the blank: Vitamins, except _______, must be separated out from other food components during digestion before absorption
fat soluble vitamins,
Fill in the blank: ___ vitamins act as coenzymes for energy metabolism (cellular respiration)
8
Do vitamins provide energy to the body?
No: they help in the process that converts food energy; they themselves are not a fuel for the body and therefore do not provide any calories
What vitamins function primarily as coenzymes?
B vitamins