Chapter 8 - VItamins

What are the four fat-soluble vitamins?

Vitamins A, D, E, and K.

Where are fat-soluble vitamins absorbed and stored?

They are absorbed with dietary fat and stored primarily in the liver and adipose tissue.

Why can fat-soluble vitamins cause toxicity?

They can accumulate in body tissues because they are not readily excreted.

What are phytochemicals?

Health-promoting compounds found in plants that provide benefits beyond essential nutrients.

What are the three active forms of vitamin A (retinoids)?

Retinol, retinal, and retinoic acid.

What is the difference between retinoids and carotenoids?

Retinoids are preformed vitamin A found in animal foods. Carotenoids are plant pigments, some of which can be converted into vitamin A.

What are the major functions of vitamin A?

Maintains epithelial tissues and immune function, supports vision, and promotes growth, development, and reproduction.

What form of vitamin A is necessary for vision?

Retinal, which allows the eyes to adjust from bright to dim light.

Which carotenoids support eye health and may reduce age-related macular degeneration risk?

Lutein and zeaxanthin.

What are the major food sources of vitamin A?

Animal sources include liver, fish, eggs, and dairy. Plant sources include carrots, sweet potatoes, spinach, and dark leafy greens.

What improves carotenoid absorption from plant foods?

Cooking and consuming them with dietary fat.

What are the major symptoms of vitamin A deficiency?

Night blindness, dry eyes, impaired immunity, and poor growth.

What is xerophthalmia?

Severe vitamin A deficiency causing dry eyes and corneal damage that can lead to blindness.

What are Bitot's spots?

Foamy patches of dead cells that accumulate on the conjunctiva during vitamin A deficiency.

What is hypercarotenemia?

Yellow-orange skin discoloration caused by excessive carotenoid consumption. Unlike jaundice, it does not turn the whites of the eyes yellow.

Why can excessive vitamin A intake be dangerous?

It can cause liver toxicity and birth defects, especially from excessive preformed vitamin A during pregnancy.

Why is vitamin D called the sunshine vitamin?

The skin can synthesize vitamin D when exposed to UVB sunlight.

What are the two forms of vitamin D?

D2 (ergocalciferol) and D3 (cholecalciferol).

What organs are involved in activating vitamin D?

The skin, liver, and kidneys.

What are the major functions of vitamin D?

Increases calcium and phosphorus absorption, regulates blood calcium, supports bone health, and supports immune function and cellular differentiation.

What are the major food sources of vitamin D?

Fatty fish, cod liver oil, egg yolks, liver, and fortified milk or plant beverages.

What factors can reduce vitamin D synthesis from sunlight?

Darker skin pigmentation, older age, geographic latitude, winter season, sunscreen, clothing coverage, and limited sun exposure.

What happens when vitamin D is deficient?

Calcium absorption decreases, resulting in poor bone mineralization and weakened bones.

What is rickets?

Vitamin D deficiency in children that causes poorly mineralized bones and skeletal deformities, such as bowed legs.

What is osteomalacia?

Softening of bones in adults due to inadequate bone mineralization, commonly associated with vitamin D deficiency.

What causes vitamin D toxicity?

Excessive supplementation or fortified food intake, which can cause dangerously high blood calcium levels.

What is the primary function of vitamin E?

It acts as an antioxidant, protecting cell membranes and polyunsaturated fatty acids from oxidative damage.

What are the major food sources of vitamin E?

Vegetable oils, nuts, seeds, wheat germ, and fortified cereals.

What happens with vitamin E deficiency?

Red blood cell damage (hemolysis), anemia, and possible nerve and muscle problems.

Who is most at risk for vitamin E deficiency?

Premature infants and individuals with fat malabsorption or extremely low-fat diets.

Why can excessive vitamin E supplementation be dangerous?

It can interfere with vitamin K-dependent blood clotting and increase bleeding risk.

What are the three forms of vitamin K?

K1 (phylloquinone), found in plants; K2 (menaquinone), produced by bacteria and found in some animal foods; K3 (menadione), a synthetic form.

What are the primary functions of vitamin K?

K1 supports blood clotting (hemostasis), while K2 supports bone health and calcium regulation.

What are the major food sources of vitamin K?

K1: leafy greens, broccoli, and asparagus. K2: some meats, eggs, and dairy products.

What happens with vitamin K deficiency?

Impaired blood clotting, excessive bleeding, and potentially poor bone health.

Why are newborns at risk for vitamin K deficiency?

They are born with low vitamin K stores and limited intestinal bacterial production. They receive vitamin K shortly after birth to prevent VKDB.

What are the eight B vitamins?

B1 Thiamin; B2 Riboflavin; B3 Niacin; B5 Pantothenic acid; B6 Pyridoxine; B7 Biotin; B9 Folate; B12 Cobalamin.

What is the other water-soluble vitamin besides the B vitamins?

Vitamin C (ascorbic acid).

What is the primary role of B vitamins?

They act as coenzymes that help enzymes metabolize carbohydrates, fats, and proteins and produce energy.

Why must most water-soluble vitamins be consumed regularly?

They are generally stored in limited amounts, and excess is excreted in urine.

What is the primary function of thiamin (B1)?

Helps release energy from carbohydrates and supports normal nerve function.

What is the deficiency disease associated with thiamin (B1)?

Beriberi. Severe deficiency associated with alcohol use disorder can also cause Wernicke-Korsakoff syndrome.

What are the major food sources of thiamin (B1)?

Pork, whole grains, legumes, and enriched cereals.

What is the primary function of riboflavin (B2)?

Helps release energy from food, particularly fats, and supports antioxidant enzyme function.

What is the deficiency disease associated with riboflavin (B2)?

Ariboflavinosis.

What are the major symptoms of riboflavin deficiency?

Cracked corners of the mouth (angular cheilitis), inflammation of the tongue, and dermatitis.

What is the primary function of niacin (B3)?

Helps produce energy from carbohydrates and fats and supports cellular metabolism.

What is the deficiency disease associated with niacin (B3)?

Pellagra, characterized by the three Ds: dermatitis, diarrhea, and dementia. Severe untreated deficiency can cause death.

What is nixtamalization?

Treating corn with an alkaline solution to release bound niacin, making it more bioavailable.

What is niacin flushing?

Redness, itching, and warmth of the skin caused by high doses of nicotinic acid.

What is the primary function of pantothenic acid (B5)?

Helps produce coenzyme A (CoA), which is essential for energy metabolism and fatty acid synthesis.

Why is pantothenic acid (B5) deficiency uncommon?

It is widely distributed in many foods.

What are the major functions of vitamin B6?

Amino acid and protein metabolism, neurotransmitter production, hemoglobin synthesis, and immune function.

What are the symptoms of vitamin B6 deficiency?

Anemia, depression, skin disorders, nerve irritation, and impaired immune function.

Why can excessive vitamin B6 supplementation be dangerous?

It can cause nerve damage, including numbness and difficulty walking.

What is the primary function of biotin (B7)?

Helps synthesize glucose and fatty acids and metabolize certain amino acids.

Why should raw egg whites not be consumed excessively?

They contain avidin, a protein that binds biotin and prevents its absorption. Cooking denatures avidin.

What are the symptoms of biotin deficiency?

Hair loss, scaly skin, brittle nails, muscle weakness, and depression.

What is the difference between folate and folic acid?

Folate is the naturally occurring form of vitamin B9 in foods; folic acid is the synthetic form used in supplements and fortified foods.

Why is folate especially important during pregnancy?

It supports DNA synthesis and fetal development and helps prevent neural tube defects such as spina bifida and anencephaly.

What are the major food sources of folate (B9)?

Leafy green vegetables, legumes, liver, and fortified grains.

What happens with folate deficiency?

Megaloblastic anemia, fatigue, weakness, and increased risk of fetal neural tube defects during pregnancy.

Why can excessive folic acid supplementation be dangerous?

It can mask the anemia associated with vitamin B12 deficiency while neurological damage continues.

What makes vitamin B12 unique?

It contains the mineral cobalt, is naturally found in animal foods, and can be stored in the liver.

What are the major functions of vitamin B12?

Supports DNA synthesis, red blood cell formation, and maintenance of the myelin sheath surrounding nerves.

Why are vegans at risk for vitamin B12 deficiency?

Naturally occurring vitamin B12 is found in animal foods, so vegans need reliable fortified foods or supplements.

What is pernicious anemia?

A form of vitamin B12 deficiency caused by impaired absorption, commonly due to a lack of intrinsic factor.

What are the symptoms of vitamin B12 deficiency?

Megaloblastic anemia, fatigue, tingling in the extremities, nerve damage, and impaired muscle coordination.

What are the major functions of vitamin C?

Antioxidant protection, collagen synthesis, wound healing, immune support, non-heme iron absorption, and neurotransmitter and carnitine synthesis.

What are the major food sources of vitamin C?

Citrus fruits, kiwi, strawberries, bell peppers, broccoli, and potatoes.

What is the deficiency disease associated with vitamin C?

Scurvy, characterized by bleeding gums, bruising, poor wound healing, and tooth loss.

Why is vitamin C important for iron absorption?

It helps keep non-heme iron in a form that is easier for the body to absorb.

What are the major functions of choline?

Supports cell membrane structure, brain development, nerve signaling, and lipid transport from the liver.

What are the major food sources of choline, and what happens with deficiency?

Egg yolks, beef, and some nuts are good sources. Deficiency can cause liver damage, muscle damage, and fatty liver.

What are the most important things to know about dietary supplements and cancer prevention?

Supplements do not replace a healthy diet and excessive supplementation can cause toxicity or medication interactions. Cancer develops through DNA mutations and uncontrolled cell growth. Prevention includes maintaining a healthy weight, exercising regularly, eating a healthy dietary pattern, and avoiding alcohol.