Chapter 8 THE WATER- SOLUBLE VITAMINS. Vitamin Talk Vitamins are organic compounds essential in the diet to promote growth and health maintenance. Water-soluble

Chapter 8THE WATER-SOLUBLE VITAMINS

Vitamin Talk Vitamins are organic compounds essential in

the diet to promote growth and health maintenance.

Water-soluble vitamins include the B vitamins and vitamin C.

Fat-soluble vitamins include A, D, E and K. B vitamins were originally thought to be one

chemical substance but are actually many different substances. That is the reason for B1, B2, B12, etc.

Copyright 2012, John Wiley & Sons Canada, Ltd.

The Vitamins


Finding Vitamins in Foods


Fortified and Enriched Foods Fortification: process of adding nutrients to

foods. The added nutrients are generally not found in the food, such as fortifying orange juice with calcium.

Enrichment: adding nutrients back to foods that have lost nutrients due to processing. An example is the addition of B vitamins to white rice.


Fortification Health Canada regulates which foods must

be fortified and which nutrients should be added.

Example: table salt with iodine milk with Vitamin D grains with thiamine, riboflavin, niacin, iron

and folic acid


Dietary Supplements Dietary supplements can be another source of

vitamins in the modern diet. Dietary supplements contain some combination

of vitamins, minerals, herbs, botanicals, amino acids, enzymes or extracts.

Dietary supplements cannot replace the benefits of a diet containing a wide variety of foods.

Dietary supplements are regulated by Health Canada’s Natural Health Products Directorate.


Dietary Supplements (continued) There is a concern that natural health

products in food format may confuse the consumer.

Dietitians of Canada is concerned that the consumer may perceive these products as food, be unaware that there are maximum doses and exceed the ULs for some nutrients, with potential adverse effects, as there are no nutritional facts on these products’ labels.


Absorptionof Vitamins


Bioavailability of Vitamins Vitamins must be absorbed by the body in order to

perform their functions. Approximately 40-90% of vitamins are absorbed in

the small intestine. Fat-soluble vitamins require fat in the diet to be

absorbed. Water-soluble vitamins may require transport

molecules or specific molecules in the GI tract. Some vitamins are absorbed in inactive provitamin

or vitamin precursor forms that must be converted into active forms by the body.


Thiamin Thiamin was the first B vitamin to be

identified and is also called B1. Thiamin is widely available in foods,

especially in enriched grains, whole grains, legumes, nuts and seeds.

Thiamin assists in energy production, carbohydrate metabolism, the production of ribose and the health of the nervous system.


Thiamin


Riboflavin Dairy products are a good source of riboflavin. Plant sources of riboflavin include mushrooms, broccoli,

asparagus, whole grains and green, leafy vegetables. Animal sources include red meat, poultry and fish. Riboflavin is easily destroyed by heat and exposure to

light. Riboflavin is an important component in the citric acid

cycle and for assisting the body with the absorption of other vitamins.


Riboflavin


Niacin Niacin is added to enriched flours in North America. A niacin deficiency disease is pellagra. Niacin can be synthesized in the body from the essential

amino acid tryptophan if the diet is adequate in tryptophan.

Niacin plays an important role in the production of energy and in general metabolism.

Two forms of niacin are nicotinic acid and nicotinamide.


Niacin


Niacin Advanced pellagra’s symptoms include the 3

D’s: dermatitis, diarrhea and dementia. Niacin toxicity from overuse of niacin

supplements can result in elevated blood pressure, cardiac arrhythmia, nausea, vomiting, elevated blood sugar levels and impaired liver function.


Pantothenic Acid


Vitamin B6


Vitamin B6

Vitamin B6 is also called pyridoxine and comprises a group of compounds including pyridoxal, pyridoxine, and pyridoxamine.

All three forms can be converted into pyridoxal phosphate, which is required for many enzyme reactions in the body.

Vitamin B6 deficiency may result in anemia due to impaired hemoglobin synthesis and neurotransmitter issues.


Folate or Folic Acid


Folate or Folic Acid Folate coenzymes are needed for DNA

synthesis and the metabolism of some amino acids.

Low folate intake in early pregnancy is associated with an increased risk of neural tube defects.

Low folate intake has been associated with an increased risk of heart disease related to the metabolism of the amino acid homocysteine.


Folate Deficiency and Neural Tube Defects


Folate Fortification Neural tube defects have decreased by 50%

in Canada since food fortification. Newfoundland rates have dropped by 80%. Alberta and Quebec have found a reduction

in the number of congenital heart defects. Ontario reported a reduction in

neuroblastoma.


Folate Fortification Some studies have shown an increase in

colon cancer since folate fortification began in 1998.

This maybe the result of folate stimulating DNA synthesis and promoting growth of pre-existing cancerous cells.

When considering food fortification it is important to consider that what may benefit one segment of the population may harm another segment.


Macrocytic Anemia and Folate Deficiency


Calculating Dietary Folate Amounts


Vitamin B12


Vitamin B12

Pernicious anemia is a form of anemia that does not respond to iron supplementation.

Vitamin B12 is necessary for the proper absorption of iron in the body.

Excessive intake of folic acid can mask B12 deficiencies.

Vitamin B12 is most readily absorbed from animal products.

Vegan diets need to be supplemented with readily-absorbable forms of B12.

Atrophic gastritis may lead to B12 deficiencies.


Absorption of Vitamin B12


Vitamin C


Vitamin C Vitamin C is also known as ascorbic acid or

ascorbate. Vitamin C in foods can be destroyed by

oxygen, light and heat, as well as contact with copper or iron cookware.

Vitamin C functions as an antioxidant in the body, helps maintain the immune system, is important in the production of collagen and aids in iron absorption.


How Antioxidants Work


Summary of Water-Soluble Vitamins and Choline


Summary of Water-Soluble Vitamins and Choline (continued)


Summary of Water-Soluble Vitamins and Choline (continued)


Benefits and Risks of Water-Soluble Vitamin Supplements


Copyright

Copyright © 2012 John Wiley & Sons Canada, Ltd.

All rights reserved. Reproduction or translation of this work beyond that permitted by Access Copyright (The Canadian Copyright Licensing Agency) is unlawful. Requests for further information should be addressed to the Permissions Department, John Wiley & Sons Canada, Ltd. The purchaser may make back-up copies for his or her own use only and not for distribution or resale. The author and the publisher assume no responsibility for errors, omissions, or damages caused by the use of these programs or from the use of the information contained herein.

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Chapter 8 THE WATER- SOLUBLE VITAMINS. Vitamin Talk Vitamins are organic compounds essential in the diet to promote growth and health maintenance. Water-soluble