Fat Soluble Mod 8

What are the three active forms of vitamin A?

Retinol, retinal, and retinoic acid.

How are retinol, retinal, and retinoic acid related?

They are forms of vitamin A that have different functions. Retinol supports transport and storage, retinal is important for vision, and retinoic acid regulates cell growth and differentiation.

How is vitamin A stored and transported?

Vitamin A is stored mainly in the liver. It travels in the blood bound to retinol-binding protein.

What are the main functions of vitamin A?

Supports vision, immune function, reproduction, growth, and the maintenance of healthy epithelial tissues, including skin and the lining of organs.

What is the RDA for vitamin A?

For adults, 900 micrograms RAE per day for males and 700 micrograms RAE per day for females. Needs vary by age and life stage.

What are food sources of vitamin A?

Preformed vitamin A is found in liver, eggs, and dairy products. Provitamin A carotenoids are found in carrots, sweet potatoes, spinach, and other colorful vegetables.

What are the signs of vitamin A deficiency?

Night blindness, dry eyes, impaired immune function, and problems maintaining healthy epithelial tissues.

What increases the risk of vitamin A deficiency?

Inadequate food intake, fat-malabsorption conditions, and illnesses that interfere with absorption or use of vitamin A.

What can vitamin A toxicity cause?

Excessive preformed vitamin A can cause headache, nausea, liver damage, bone problems, and birth defects during pregnancy.

What are carotenoids?

Plant pigments found in colorful fruits and vegetables. Some, such as beta-carotene, can be converted into vitamin A; others have antioxidant activity.

How are carotenoids absorbed, and should they be taken as supplements?

Carotenoids are absorbed better when eaten with some dietary fat. Eating carotenoid-rich foods is generally preferable to taking high-dose supplements; beta-carotene supplements can increase lung-cancer risk in smokers and some other high-risk groups.

How are carotenoids stored, and what foods contain them?

Carotenoids can be stored in body tissues, including body fat. Sources include carrots, sweet potatoes, pumpkin, tomatoes, spinach, and other colorful produce.

Why is vitamin D described as hormone-like?

The body can make vitamin D in the skin, and its active form acts like a hormone by binding to receptors and regulating processes in different tissues.

What are the main functions of vitamin D?

Helps the body absorb calcium and phosphorus, supports bone and tooth mineralization, and contributes to muscle and immune function.

How does sunlight help the body make vitamin D?

Ultraviolet B (UVB) radiation triggers vitamin D production in the skin. The amount produced depends on factors such as season, latitude, skin pigmentation, age, clothing, and sunscreen use.

What are the recommended daily amounts of vitamin D?

For most people ages 1–70, including pregnancy and breastfeeding, the RDA is 600 IU (15 micrograms) daily. For adults over 70, it is 800 IU (20 micrograms) daily.

What are food sources of vitamin D?

Fatty fish, egg yolks, and fortified milk or plant-based beverages. Some cereals and other foods are also fortified.

How is vitamin D stored and transported?

Vitamin D is fat-soluble and can be stored in body fat and the liver. It circulates in the blood mainly bound to vitamin D-binding protein.

What are the signs of vitamin D deficiency in children and adults?

In children, deficiency can cause rickets, which leads to poor bone mineralization and may cause bone deformities. In adults, deficiency can cause osteomalacia, which results in soft, weak bones and bone pain.

Who is at increased risk of vitamin D deficiency?

People with limited sun exposure, older adults, people with darker skin, people who cover most of their skin, breastfed infants without supplementation, and people with fat-malabsorption conditions.

What can vitamin D toxicity cause?

Excessive vitamin D supplements can cause high blood calcium, nausea, weakness, kidney stones, and kidney damage. Toxicity is usually caused by supplements, not ordinary sunlight exposure.

What is the main antioxidant function of vitamin E?

Vitamin E helps protect cell membranes and their fats from oxidative damage caused by free radicals.

What is the RDA for vitamin E, and what is its main active form?

The adult RDA is 15 milligrams per day of alpha-tocopherol, the main form maintained in the body.

What are vitamin E food sources, and what happens with deficiency?

Sources include vegetable oils, nuts, seeds, and wheat germ. Deficiency is uncommon but can cause nerve and muscle problems, especially when fat absorption is impaired.

How is vitamin E stored?

Vitamin E is fat-soluble and is stored in body fat and other tissues.

What can vitamin E toxicity cause?

High-dose supplements can interfere with blood clotting and increase bleeding risk, especially when taken with anticoagulant medicines.

What are the functions of vitamin K, and what is its AI?

Vitamin K is needed to activate proteins involved in blood clotting and supports bone health. The adult Adequate Intake (AI) is 120 micrograms per day for males and 90 micrograms per day for females.

What are food sources of vitamin K?

Green leafy vegetables such as kale, spinach, and broccoli; vegetable oils; and some foods produced through bacterial fermentation.

How is vitamin K stored, and is toxicity common?

Vitamin K is fat-soluble, but body stores are relatively limited compared with vitamins A and D. Toxicity from naturally occurring vitamin K in foods is rare.

What causes vitamin K deficiency, and who is at risk?

Deficiency can cause excessive bleeding because blood-clotting proteins cannot function normally. Newborns and people with fat-malabsorption conditions are at increased risk; newborns are routinely given vitamin K after birth.