There are four vitamins considered fat-soluble; vitamins A, D, E, and K. Vitamin A has several different forms and the compounds are known as retinoids. Retinyl ester is the form that is found in food and also stored in the liver. Foods rich in retinyl ester include fish, meat, dairy, and egg yolks. In plant food sources, compounds known as carotenoids supply retinyl ester. Carotenoids can be found in Oz Vitamins Better Joints Supplement orange and yellow fruits and vegetables, dark green vegetables and tomatoes. Once absorbed into the body, vitamin A is used for several functions. Retinal is the form of vitamin A responsible for vision and the ability to adjust to changes in brightness. Retinoic Acid is the form of vitamin A responsible for reproduction, growth, immune system function and cellular health. Vitamin A deficiency can lead to a condition called Night Blindness, where vision recovers slowly after a bright flash of light. Night blindness is an early indicator of developing deficiency and continuing deficiency can lead to complete loss of vision. Deficiency also causes retarded growth, failure to reproduce and decreased immunity. As vitamin A is stored long-term in the body, toxicity can be caused by consuming too much of this vitamin. Excess can cause headache, vomiting, liver damage, hemorrhage, and even coma. Vitamin A is also a teratogenic, causing birth defect if too high in pregnant mothers. The recommended daily intake for vitamin A is 600mcg a day for adults, 700 for pregnant mothers.
Vitamin D is synthesized in the presence of sunlight but is also available in fish and fortified milk and milk alternatives. As a multifunctional vitamin, an individual should make sure to consume the recommended 5mcg a day to maintain good health. Vitamin D has not toxicity linked to higher dosages and many now take up to five times the recommended intake daily. Vitamin D is critical to calcium and phosphorus homoeostasis in the body by assisting the kidneys in recovering calcium and phosphorus if needed. Vitamin D aids in bone growth and maintenance, and ensured healthy bone density. Vitamin D is also shown to help regulate immune function and aid in disease prevention. Vitamin D deficiency can lead to improper bone formation in children, a condition known as Rickets, or loss of bone density in adulthood, a condition called osteoporosis. Both conditions are link to low dietary calcium and lack of physical activity.
Vitamin E, also known as tocopherol, contributes in many roles in the body, the best known function being its potent anti-oxidant ability. This vitamin protects cells and molecules from oxidant damage that may cause harm to the body or inhibit the functions of cells.