Vitamin A

Question 1

• 1: Description /forms of the micronutrient
• 2: Digestion / Absorption /Activation where relevant
• 3: Transport /Storage/ Excretion
• 4: Functions and Mechanisms of action (MOA)
• 5: Deficiency & toxicity signs /symptoms where relevant
• 6: Units and conversion to international units where relevant
• 7: Food sources

Answer 1

…

Question 2

Vitamins

Answer 2

• 14 essential organic dietary components required in small amounts
• Humans can not make their own vitamins, or not in sufficient amounts (e.g body cannot make vitamin C; skin vitamin D formation declines with ageing or is insufficient with poor sun exposure etc.)
• When not consumed, health declines and deficiency symptoms occur
• Deficiency symptoms disappear as soon as vitamins supplementation or rich food sources are given

Question 3

Fat-soluble vitamins

Answer 3

Absorption
– With dietary fats;requires bile,pancreatic lipase and efficient
intestinal absorption
– 40-90% absorbed when intake is within recommended amounts
– What happens in situation of poor fat absorption?
Transport
– In lymphatic system via chylomicrons
–Then in the blood via lipoproteins packed in the liver
– Note:genetic polymorphism in lipoprotein synthesis will therefore lead to potential deficiency in these vitamins
Storage
- generally in adipose tissue and liver
Toxicity
- Toxicity occurs at doses of 5-10x the NRV’s