9.4 Fat-Soluble Vitamins

Question 1

How is vitamin A processed in our bodies?

Answer 1

• Provitamin A and its vitamers are found in plants
• These carotenoids must be be converted into retinol
• Preformed vitamin A is found in its almost-active forms: retinol and retinal ester; found in animal products
• Must convert retinold into retinal and retinoic acid = active form of vitamin A

Question 2

Describe how vitamin A is used for the visual pathway

Answer 2

• Rhodopsin is a visual pigment found in the retina, composed of retinal bound to opsin
• Rhodopsin is stimulated when visual stimuli is projected onto the retina
• Retinal changes shape, and a nerve message is sent to the brain about what was seen
• Retinal and opsin breaks apart
• Retinal is lost, but is replenished with retinal from dietary vitamin A intake
• Retinal and opsin come together again to repeat this process

Question 3

Besides vision, what are other uses of vitamin A?

Answer 3

Gene expression

Immune Function - Contributes to formation of infection-fighting T-cells

Carotenoid form (plants) functions as an antioxidant

Promotes skin health by switching on the genes that cause immature skin cells to become mature and healthy . Thus found in many skin products

However, can have severe skin, gastrointestinal, nervous and cardiovascular side effects and increase risk of birth defects if taken by pregnant women

Question 4

What are sources of Vitamin A?

Answer 4

Preformed vitamin A is found in animal products

Provitamin A is found in plant products

Question 5

What are the effects of Vitamin A toxicity?

Answer 5

Carotenoids may turn skin slightly orange, but otherwise have no toxicity symptoms

Preformed vitamin A toxicity can have serious side effects: Elevated pressure around the brain, dizziness, nausea, headaches and can be fatal

Typically due to over-supplementation and eating polar bear liver

Question 6

What are the effects of Vitamin A deficiency and what causes it?

Answer 6

Rare in North America, common in developing countries: Often linked with poverty, low diet variability

Can lead to xeropthalmia - abnormal dryness of the eye that affects the body’s ability to form tears - If untreated, can lead to breaks in cornea, even blindness

Night blindness is an early sign of xeropthalmia

Question 7

What are the uses of vitamin D?

Answer 7

generic name for a group of compounds including vitamin D3 (cholecalciferol) and vitamin D2 (ergocalciferol)

Their main role is maintaining calcium homeostasis: Increase calcium, phosphorus and magnesium absorption

Also plays roles in cellular growth, immune function and the reduction of inflammation

May prevent cancer

Question 8

What are sources of Vitamin D?

Answer 8

Fish and sunlight

Question 9

How does the sun give us Vitamin D?

Answer 9

When UVB light hits skin, it promotes vitamin D3 synthesis

Liver turns this into the form of vitamin D that circulates in blood

Kidneys convert this form into active form

Question 10

What are the effects of Vitamin D toxicity?

Answer 10

Toxicity from food is rare, typically due to over-supplementation

Can promote anorexia, weight loss, increased urination, irregular heart rhythms

Can also increase blood calcium
Can harden blood vessels, eyes and negatively impact kidneys and heart

Question 11

What are the effects of Vitamin D deficiency and what causes it?

Answer 11

Common; due to inadequate dietary consumption, limited sun exposure - Older adults, individuals with black skin, individuals with obesity, breastfed infants, people who have undergone gastric surgery are all at higher risk

In children, can promote rickets (Outward leg bones)

In adults, can lead to osteomalacia=softening of bones
Can progress to osteoporosis

Question 12

What are the uses of vitamin E?

Answer 12

generic term for eight vitamers

Antioxidant

Also involved in immune function, cell signalling

May decrease risk for cancer, CVD, and Alzheimer’s, but supplementation does not work

Question 13

What are sources of Vitamin E?

Answer 13

Fatty shellfish and fatty plants such as nuts, seeds, fortified cereals and nut butter

Question 14

What are the effects of Vitamin E toxicity?

Answer 14

due to over-supplementation

Increases mortality rate
Has been linked to lung illnesses in those that vape

Question 15

What are the effects of Vitamin E deficiency and what causes it?

Answer 15

rare; typically due to compromised fat absorption

Symptoms may include peripheral neuropathy, movement difficulties, muscle disorders and an impaired immune response

Question 16

What are the uses of vitamin K?

Answer 16

Prothrombin synthesis is dependent on a vitamin K coenzyme

Prothrombin is needed for the pathway that leads to the formation of sticky fibrin fibres – which help red blood cells clump together

Question 17

What are sources of Vitamin K?

Answer 17

leafy-green vegetables, such as

spinach and broccoli, as well as oils and nuts

Question 18

What are the effects of Vitamin K toxicity?

Answer 18

Toxicity has not been observed

Question 19

What are the effects of Vitamin K deficiency and what causes it?

Answer 19

Deficiency is rare except in newborns, those with compromised absorption, and those who overuse antibiotics

Can lead to excessive bleeding, hemorrhaging

Newborns get a shot of vitamin K to prevent this

Question 20

What is Warfarin?

Answer 20

An anticoagulant that block the vitamin K-dependent coagulation pathway.

Question 21

When is Warfarin used?

Answer 21

prescribed for those at high risk for heart attacks and strokes

Question 22

Why should we watch out for vitamin infused beverages?

Answer 22

Make vague promises based on vitamin provision

Do not have to have nutrient facts box as it’s an NHP

Typically contain water-soluble vitamins – those that are much less likely to be deficient in the diet

May have lots of added sugar