Chapter 9: Vitamin Overview and Fat-Soluble Vitamins

What is a vitamin?

a complex organic compound that regulates certain metabolic processes

How do vitamins differ from macronutrients?

They are not metabolized for energy

Generally, they are present in foods in smaller amounts

The body needs smaller amount of them

Fat-soluble vitamins

Vitamins that are digested and absorbed with fats.

What are some features of fat-soluble vitamins?

They are stored in the body (primarily in liver and fat tissue) and can accumulate to cause a damaging toxicity disorder.

Water-soluble vitamins

Vitamins that dissolve in watery components of the body

What are other features of water-soluble vitamins?

They are stored in limited amounts (except B12)

The kidneys filter excess of them and eliminate them in the urine

They are less likely to be toxic

How do we obtain the needed vitamins?

By eating foods from all the food groups, plus oils

Which food groups lack B12?

Fruits, vegetables, and grains <--plant-based foods

Which food groups are low in Vitamin C?

Grains, protein, and dairy

Which are the fat-soluble vitamins?

Vitamins A, D, E, and K

Which are the water-soluble vitamins?

All the B vitamins and vitamin C

What are the 8 B vitamins?

Thiamin, riboflavin, niacin, folate/folic acid, B6, B12, biotin, and pantothenic acid

What is a sometimes government-mandated source of vitamins?

Fortification and enrichment

What products are required to be enriched with iron and thiamin, riboflavin, niacin, and folic acid?

Refined grain products

What kind of milk is required to be enriched with vitamin A?

Lower-fat milk

What is a concern with "voluntary"/discretionary fortification?

There is a risk of exceeding the tolerable upper intake levels (ULs), which could cause nutrient toxicities and adverse health effects

What can cause nutrient losses?

Heat, light, oxygen, passage of time, food processing, food preparation (e.g., cooking), and storage

What are some tips for preserving the vitamins in food?

-eat locally grown fresh produce soon after purchase

-store produce away from heat and light

-don't soak vegetables

-cook vegetables with as little water as possible (no boiling)

-don't rinse rice before cooking it to keep water-soluble vitamins

Where does most vitamin absorption occur?

In the small intestine

What helps to "release" vitamins from food?

mechanical digestion (chewing) and chemical digestion (small intestine pancreatic enzymes)

What is the first step of fat-soluble vitamin absorption?

They are incorporated into micelles to allow for simple diffusion

What is the second step of absorbing fat-soluble vitamins?

After they diffuse, they are incorporated into chylomicrons to allow for transportation out of the absorptive cells

How do fat-soluble vitamins leave the absorptive cells?

Via lacteals

What is the first part in absorbing water-soluble vitamins?

Transport proteins carry them, or they bind to a specific molecule.

What is the second part of water-soluble vitamin absorption?

Once they are absorbed into the enterocytes, they go directly into the blood, still bound to transport proteins, which take them to cells

What is a shared requirement for all vitamins after absorption?

They must be transported to the cells.

What happens in the large intestine regarding vitamins?

Resident bacteria can make certain vitamins there

What is bioavailability?

The amount of a nutrient that can be effectively digested, absorbed, and used by the body.

What is vitamin bioavailability influenced by?

Diet composition, nutrient source, nutrient status, GI tract health, and overall body health

What are coenzymes?

They are organic compounds that assist enzymes with chemical reactions by binding to an enzyme to promote activity

What is true of enzymes that require coenzymes?

Those enzymes are incomplete--a coenzyme has to bind with the enzyme to activate it

What is true of all B vitamins regarding coenzymes?

All the B vitamins serve as coenzymes or are components of coenzymes in metabolic reactions

What are antioxidants?

Substances that give up electrons to free radicals to protect cells against oxidative damage

What is oxidative damage?

Damage caused by highly reactive oxygen molecules that steal electrons.

What are free radicals?

Highly reactive atoms or molecules that cause oxidative damage because they have unpaired electrons

What do antioxidants donate? And what is the significance of that?

They donate electrons, which stabilize free radicals, making them no longer "reactive" and therefore no longer destructive.

Which vitamins are antioxidants?

Vitamin E, Provitamin A (inactive form), and Vitamin C

What does the K in Vitamin K come from?

The Danish word for "blood clotting"--> "Koagulation"

What is the main function of Vitamin K?

It is essential for blood clotting through its role in making four blood-clotting factors

How does Vit. K impact blood clotting factors?

It converts prothrombin to thrombin, which is needed to convert fibrinogen to fibrin

What is fibrin?

It is an insoluble, fibrous protein that forms a solid blood clot by trapping blood cells and platelets

What are other functions of Vitamin K?

Synthesis of vitamin K-dependent proteins involved in bone making and breakdown, inhibition of blood vessel calcification, and regulation of growth

What is the relationship between vitamin K and bone formation?

Vitamin K-dependent proteins ensure that bone density is high

How is Vitamin K used in the body compared with other fat-soluble vitamins?

It is used more rapidly, so a constant supply is needed

Can the body make Vitamin K?

Yes. Bacteria in the large intestine can make about 10% of what is needed.

Why do newborns need Vitamin K supplementation?

They do not possess intestinal bacteria that make vitamin K

How does long-term antibiotic usage impact vitamin K levels?

Over time, antibiotics can kill the good intestinal bacteria that make vitamin K

How do anticoagulant medications impact vitamin K?

They can interfere with vitamin K and vice versa

What kinds of diseases can impact vitamin K?

Diseases that impair fat absorption, like liver disease and cystic fibrosis

What is the AI for Vit. K?

90 mcg/day for women + 120 mcg/day for men

What are some dietary sources of Vitamin K?

Liver, dark green leafy vegetables, broccoli, Brussels sprouts, cabbage, kiwi, canola oil, and soybeans (whole and oil)

What are the two kinds of Vitamin A?

Retinoids, which are preformed, "active" vitamin A, and carotenoids, which are the precursor/provitamin forms of Vitamin A

What are the three retinoids active in the body?

Retinol, retinal, and retinoic acid

How is retinol often stored?

As retinyl esters

What is the main source of retinoids?

Animal-based foods, like liver, fish liver oils, butter, and eggs

What is the main source of carotenoids?

Plant-based foods, like carrots, broccoli, spinach, kale, collards, mustard greens, red peppers, winter squash, pumpkin, apricots, papaya, cantaloupe, and watermelon

What is an example of a carotenoid?

Beta-carotene, which is found in yellow and orange fruits and veggies as well as dark green vegetables (covered by the chlorophyll)

What is the most potent vitamin A precursor?

Beta-carotene because it's converted into retinoids more efficiently than the other two carotenoids

What is the function of beta-carotene and other carotenoids that are not converted into "active" vitamin A?

They serve as antioxidants, which may have a protective role against cancer and heart disease

What are both forms of vitamin A bound to in food?

Food proteins

How are both forms of vitamin A "released"?

They are released by the enzymatic actions of pepsin and pancreatic proteases

How are retinoids and carotenoids absorbed?

they are incorporated into micelles

How could a diet deficient in fats lead to a deficiency in vitamin A?

Micelles, made of fat, are needed for the absorption of vitamin A

Which form of vitamin A is more readily absorbed?

Retinoids

12 mcg of beta-carotene =

1 mcg RAE (retinol activity equivalents)

Where is most vitamin A stored in the body?

The liver

How does vitamin A leave the liver?

It binds to retinol-binding proteins

What is needed to make retinol-binding proteins?

Zinc

A deficiency in what two things could lead to vitamin A deficiency because it can't leave the liver?

Protein and zinc

What are the functions of vitamin A?

Regulates gene expression for protein synthesis, growth and replenishment of epithelial cells, light processing, cornea health, making WBCs, reproduction, and growth of bone and teeth

How does vitamin A impact gene expression?

It regulates (activates/deactivates) the genes involved in protein synthesis

How does Vitamin A help with the growth and replenishment of epithelial cells?

It has a role in cell differentiation, which is the process of immature cells being stimulated to "mature" and specialize

How does Vitamin A impact light processing?

The photoreceptors need retinal to function properly, so they convert retinol to retinal to form rhodopsin (rods), which is necessary for vision in dim light

How does vitamin A help keep the cornea healthy?

Vitamin A helps with cell differentiation, which includes making sure the cornea is made up of mucus-secreting epithelial cells. Vitamin A deficiency means those cells don't differentiate and therefore don't produce mucus to keep the cornea moist and clean.

What role does Vitamin A play in the body's immune system?

It helps make and stimulate activity of white blood cells

What role does Vitamin A play in reproduction?

It is needed for sperm production in males and, in females, it helps regulate menstrual cycles and normal fetal development in pregnant women

How does vitamin A assist in the growth of bone and teeth?

It helps with remodeling, which is where old bone structure is replaced by new bone. Vitamin A deficiency could play a role in tooth decay due to underdeveloped enamel.

How is vitamin D obtained?

through food sources and sunlight

How is vitamin D made?

UV light causes a cholesterol compound in the skin to create a vitamin D precursor to which the liver and kidneys donate hydroxyl groups to activate the vitamin

Would diseases of the liver and kidney impair the conversion of vitamin D to its active form?

YES

What factors affect the synthesis of vitamin D?

Skin color, age, geography, climate, time of year, air pollution, concealing clothing (religious or cultural reasons), sunscreen

What is the main function of vitamin D?

It regulates calcium and phosphorus in the bones and teeth

How does vitamin D regulate calcium?

It controls the amount of calcium absorbed across the GI tract and the amount entering/exiting the bones. It also cooperates with the kidneys to regulate the amount of calcium excreted in urine.

What is the role of the parathyroid hormone in increasing blood calcium levels?

When blood calcium levels are low, PTH is released, which stimulates the activation of vitamin D

What is vitamin D deficiency caused by?

- Malabsorption

- Low sunlight

- Poor diet (low in liver, egg yolks, dairy, and oily fish)

- Chronic kidney failure

What is rickets?

Vitamin D deficiency in children, in which newly formed bones are not mineralized, so they bow because they can't support body weight

What is osteomalacia?

Vitamin D deficiency in adults, in which bones soften due to lower-than-normal amounts of calcium. Muscle weakness also results

Why is vitamin D potentially the most toxic vitamin?

Its UL is 100mcg/day, and the culprit is primarily supplements

Which tocopherol compound is the basis for vitamin E's RDA? Why?

Alpha-tocopherol which is the only form that can be used by the body.

Can the antioxidant function of Vitamin E be restored?

Yes, because Vitamin C can give an electron back to it

What are some molecules and cells that vitamin E helps to protect?

Plasma membrane lipids, DNA, proteins, red and white BCs, nerve cells, and lung cells. E protects these from heavy metals, toxins, and an assortment of drugs

How does vitamin E reduce the risk of developing heart disease and cancer?

As an antioxidant, it is anti-inflammatory and helps with the immune response

Why is a deficiency of vitamin E rare?

It is found in many foods, and the body recycles it

Which population groups are at risk of vitamin E deficiency?

1. Premature infants, which puts them at risk of hemolytic anemia

2. Adults with diseases that interfere with fat absorption

3. People who consume too little fat

4. People who consume large amounts of heavily processed foods (high temperatures destroy vit E)

How is vitamin E absorbed?

It is incorporated into micelles and then into absorptive cells

Where is vitamin E stored in the body?

In fatty tissue, the liver, and muscles

Which type of vitamin E is more readily available?

Naturally occurring vitamin E