Dear Reader,
In the April issue of CAM News we are going to start our review on the vitamins and minerals. Let us start with a brief review of common terms.
AI or Adequate Intake is the suggested daily intake of a nutrient to meet daily needs and support health. It comes into play when there is not enough research to develop a RDA.
UL or Tolerable Upper Intake Level describes it all. It is the highest amount of a nutrient we are able to consume without jeopardizing our health.
EAR is the Estimated Average Requirement for the day of any given nutrient to meet the requirement for half of the healthy people of any given age and gender.
AMDR is the Acceptable Macro-nutrient Distribution Range of calories across all nutrients. Carbohydrates should provide 45% to 65% of total kcal, fat 20% to 35% of total kcal, and protein should provide 10% to 35% of total kcal. Having said this, on to the Fat Soluble Vitamins. Which are A, D, E, K. In this newsletter we will cover:
VITAMIN A: (Schlenker, Long, 2007)
Functions: Vitamin A is responsible for the bodies abilities to adjust to light and darkness. It is also important to keep the body’s epithelial tissues (linings and coverings such as skin and mucous membranes) in good working order. Vitamin A is also responsible for healthy growth, the immune response, and proper functions of the reproductive organs.
Forms: Vitamin A is available in two dietary forms.
• Preformed Vitamin A a.k.a. Retinol: Retinol is the naturally available form of Vitamin A consumed from foods of animal origin. Vitamin A is stored mainly in the liver, but is also found in minute amounts in the kidneys, lungs and fatty tissue of the body.
• Provitamin A (beta carotene): Plants are unable to “work” with Vitamin A but instead manufacture compounds called carotenoids. These carotenoids from plants are eaten by animals and humans and converted to Vitamin A. You can obtain your Vitamin A either from eating animal products, or the good news for vegans, you can eat foods high in carotenoids and your body will convert these into Vitamin A. Keep in mind that this process is a lot less efficient then ingesting Vitamin A from animal sources. 1μg retinol from the diet yields 1 μg retinol to the body. However, you need to eat 12 μg of beta-carotene to get the same amount of 1 μg of retinol for the body to use, and 24 μg of alpha-carotene or beta-cryptoxanthin to yield 1 μg of retinol. Supplementation for vegetarians is probably a good idea.
Dietary Sources:
• Retinol is available in animal products such as liver, milk, cheese, butter, egg yolk, and fish. Many non-animal products such as breakfast cereals are fortified with Vitamin A.
• Beta Carotene can be derived from yellow, orange, red and green vegetables and fruits as they contain a wide spectrum of carotenoids, which can be converted to Vitamin A in the body. Blanching the veggies will help the release of the carotenoids thus increase their bioavailability. Do not cook them as the cooking process will destroy vital enzymes!
Absorption, Transport, Storage: For proper absorption the body needs to have bile salts in the small intestine. Bile salts are needed to carry fat soluble stuff into the intestinal wall for further breakdown. Obstructed bile ducts, infectious hepatitis, and liver cirrhosis cause malfunction of bile salt production and in turn hinder Vitamin A absorption. Pancreatic lipase is an enzyme doing its job in the upper intestine starting the breakdown of emulsions which contain Vitamin A. Patients suffering from cystic fibrosis or pancreatitis can obtain water based preparations of retinol. And since we are talking about fat soluble Vitamins, Vitamin A requires fat to be present to stimulate bile production in order for Vitamin A to be absorbed most efficiently. Studies have shown that absorption is best if daily fat intake is more than 10g per day. The body stores enough Vitamin A to prevent deficiency for about 6 to 12 months.
Vitamin A Deficiency
Vision: Vitamin A deficiency might lead to night blindness.
Cell Differentiation: Deficiency in Vitamin A also causes mucous membranes and the skin to dry out. This drying out is called keratinization. Keratinization is good for healthy hair and nails, but definitely abnormal for skin and mucous membranes.
Keratinization in the:
Eye: The cornea dries and becomes hard, this is called xerophthalimia. This may lead to blindness.
Respiratory Tract: Lining of the nasal passages dries and cause the little hairs to be lost, which in turn leaves plenty of room for little
infectious organisms to enter.
Gastrointestinal Tract: A drying out of the mucosal tissues affects digestion and absorption of food.
Genitourinary Tract: Without proper functioning of epithelial tissue possible complaints are urinary tract infections, vaginal infections.
Skin: What appears to be “chicken skin” is actually dried skin around hair follicles in a condition called follicular hyperkeratosis.
Growth: Vitamin A is essential for healthy growth of bone and soft tissues. Post-menopausal women should be careful with intakes in
excess of Dietary Reference Intake (DRI) of preformed Vitamin A, as it may lead to increased risk of hip fractures. Vitamin A derived
from beta carotene in the diet does not lead to this excessive bone loss which may lead to hip fractures.
Reproduction: Vitamin A plays a key role in normal sexual function.
Immunity: A deficit of Vitamin A may compromise the immune system, by weakening the body’s resistance to infection.
Dietary Reference Intake: RDA (Recommended Daily Allowance)
Men 19+…..900μg
Women 19+…..700μg
Vitamin A Toxicity: As mentioned earlier, Vitamin A is stored and this allows for the possibility of Hypervitaminosis A. The Tolerable Upper Intake Level or UL is set at 3000μg. As you can see this is a pretty large amount and if amounts like this are ingested for long period of times the following symptoms may occur:
Vomiting
Headache
Joint Pain
Thickening of Long Bones
Hair Loss
Jaundice
Liver Damage
I hope to have put the first fat soluble Vitamin into perspective and in next month’s CAM News I will cover Vitamin D.
Beste Gesundheit,
Werner
1: Schlenker E., Long S. Williams’ Essential of Nutrition & Diet Therapy, 9th Edition. Mosby Elsevier. St. Louis Missouri. pp.109-114.
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