HTHSCI 3BB3 - F2023 - 5B - Fat-soluble Vitamins

Why are fat-soluble vitamins potentially poorly absorbed in low- fat diets?

Not enough bile is released to allow micelle formation

Chylomicrons

the transport system for these molecules, travel with triglycerides in the lymph to enter bloodstream

Fat-soluble vitamins able to:

stored in body in adipose tissue.

Why can fat soluble vitamins be toxic?

because they are stored in the body, so too much can cause toxic levels

Vitamin A

important for vision

Can be found as a pre-formed or pro-vitamin

In Canada, dairy products are fortified with

Vitamin A nutrition

RDA: 700-900 μg/day

Toxicity: Headache, vomiting, hair loss, liver damage, skin changes, bone and muscle pain, fractures, birth defect

UL: 3000 μg/day pre-formed vitamin A

Vitamin A bioavailability

Must be released from food by acidity and enzymes

Stable when heated, but destroyed by exposure to light and oxygen

Combines with bile and fats to be absorbed

70-90% of pre-formed vitamin A is absorbed, pro-vitamin A (i.e. β-carotene) is less absorbed

Active form of Vitamin A found in

animal sources

Pre-form of vitamin A found in:

plant sources

Vitamin A uses in the body

- Stored in the liver

• Must be transported in the blood by a carrier protein, retinol-binding protein

• Acts as an anti-oxidant

- Critical to vision and the conversion of light to signals in the brain

- Control of gene transcription and cell differentiation

Vitamin A deficiency

Impaired vision, including night blindness

Impaired cell differentiation

Not common in developed countries, but most common in India, Africa, Latin America and the Caribbean

Impaired cell differentiation

Increased keratin production

Impaired immunity

Impaired growth and development

Vitamin A Supplementation

Can be toxic at extreme doses

Retinoic Acid (Retin A, Accutane)

Carotenoids (pro-vitamin A)

Golden Rice

Retinoic Acid (Retin A, Accutane)

- used to treat acne, wrinkles due to sun damage

- Increases turnover of cells

- Can have side effects

Carotenoids (pro-vitamin A)

are less toxic as our body will stop absorbing them when levels are high

Golden rice

A strain of rice genetically modified to produce β-carotene

Has to potential to reduce the impact of vitamin A deficiency in low-income regions

Caught up in the pushback against GMO foods

Vitamin D nutrition

RDA: 15-20 μg/day

Toxicity: Calcium deposits in soft tissues,

growth retardation, kidney damage • UL: 100 μg/day

Vitamin D bioavailability

Major source is exposure to sunlight

Animal products contain Cholecalciferol (Vitamin D3)

Vitamin D uses in the body

Made from cholesterol and converted into Vitamin D3 in the skin

Vitamin D3 is consumed in the diet from animal products

Vitamin D3 circulates in the blood but is still inactive

Processing in the liver and kidney produces the active for of vitamin D

Vitamin D levels work with parathyroid hormone to control calcium levels in the body

T OR F: vitamin D maintains calcium and phosphorus levels in the blood

true

Vitamin D deficiency

Calcium absorption is inadequate without vitamin D so bones form poorly

rickets in children (breast milk is deficient in Vitamin D)

Osteomalacia is manifestation of Vitamin D deficiency in adults - results in greater risk of bone fracture, muscle and bone pain

Who is at greater risk for Vitamin D deficiency?

Individuals who follow a vegan or vegetarian dietary pattern appear to be at greater fracture risk

Rickets symptoms

delayed growth, bow legs, weakness, and pain in spine, pelvis, and legs

Vitamin D deficient population

Those living above 40° latitude N and below 40° South receive insufficient UV radiation for Vitamin D synthesis

It is estimated that there are a billion people throughout the world who are vitamin D deficient

Vitamin D supplementation

Breastfed infants until they can consume vitamin D in their diet

Higher for those living in northern Canada during the winter north (above 55° latitude, approximately Edmonton)

All Canadians over 50

Vitamin D supplements do not appear to reduce fracture risk in adults with no other risk factors for fractures

Vitamin E nutrition

required for fertility + anti-oxidant

RDA:15mg/day

Toxicity:relatively non-toxic but can inhibit vitamin K activity (blood clotting)

UL:1000mg/day from supplements

Vitamin E bioavailability

Sensitive to destruction by oxygen, metals, light, and heat

Much is lost during processing

Vitamin E uses in the body

Incorporated into chylomicrons and transported throughout the body

Transfer proteins in the liver incorporate vitamin E into VLDL particles for delivery

Scavenges free radicals before damage to unsaturated fatty acids in lipid membrane; also protects proteins; DNA from oxidative damage

VitaminE's antioxidant function is regenerated by Vitamin C

Vitamin E deficiency

rare

characterized by neurological symptoms associated with nerve degeneration

Symptoms observed in humans include poor muscle coordination, weakness, and impaired vision

Newborns and especially infants born premature have low vitamin E

Most Vitamin. E transfer occurs....

in the last weeks of pregnancy

Premature babies vitamin E deficiency

increased risk of hemolytic anemia bc RBC membranes are less stable

Vitamin E supplementation

hair growth

restore, maintain, or increase sexual

potency and fertility;

alleviate fatigue;

maintain immune function;

enhance athletic performance;

reduce the symptoms of premenstrual syndrome (PMS) and menopause;

slow aging

(no evidence)

Vitamin K nutrition

No RDA, AI:90-120μg/day

Toxicity: Can interfere with anti-coagulant drugs•

UL:Not-determined

Vitamin K bioavailability

destroyed by exposure to light and low or high-acid conditions

Vitamin K can be produced by bacteria in the human gut, but not enough for dietary needs

Vitamin K uses in the body

necessary to enable blood clots to form

Clotting Factors II, VII, IX and X require carboxylase modification to function

The enzymes that add this modification use Vitamin K as a

cofactor. If Vitamin K is not present, these modifications don't occur

These clotting factors can't bind to platelets and can't stimulate the formation of fibrin, forming a blood clot

Vitamin K deficiency

Abnormal blood coagulation - Blood does not clot, and uncontrolled bleeding occurs

Deficiency is rare but may occur due to fat malabsorption or long-term use of antibiotics

Most common in newborns because of low transfer from mother to infant

Why do newborns have vitamin K deficiency?

Newborn gut is free of bacteria, no vitamin k is made there

Infants typically injected with vitamin k with 6 hours of birth

Vitamin K Supplementation

Injections of vitamin K pre-surgery to aid in blood clotting

Since blood clots contribute to strokes and heart attacks, vitamin k antagonists are used to prevent blood clots (Warfarin AKA Coumadin)

Why would antibiotics lead to decrease vitamin k?

Kills bacteria in the large intestine that produce Vitamin K