Podcast
Questions and Answers
Why might reference intakes for vitamins and minerals differ among national and international authorities?
Why might reference intakes for vitamins and minerals differ among national and international authorities?
- Inconsistent methods for determining individual requirements.
- Discrepancies in defining the standard deviation.
- Varying interpretations of available data. (correct)
- Different statistical methods for calculating the mean requirement.
Which statement accurately describes the function of lipid-soluble vitamins?
Which statement accurately describes the function of lipid-soluble vitamins?
- They play diverse roles, such as vision and calcium metabolism. (correct)
- They each have a very specific and singular function within the body.
- They require direct blood transport without lipoproteins.
- They are easily absorbed even with fat malabsorption.
Why is deficiency of a single B vitamin relatively rare?
Why is deficiency of a single B vitamin relatively rare?
- The body efficiently converts one B vitamin into others as needed.
- B vitamins are stored extensively in adipose tissue, preventing rapid depletion.
- Because the body can synthesize most B vitamins if one is available.
- Poor diets typically lack multiple nutrients, leading to multiple deficiencies. (correct)
How do depletion/repletion studies determine nutrient requirements?
How do depletion/repletion studies determine nutrient requirements?
Why are recommended nutrient intakes set higher than the average requirement?
Why are recommended nutrient intakes set higher than the average requirement?
How does vitamin D differ from the strict definition of a vitamin?
How does vitamin D differ from the strict definition of a vitamin?
Why might dietary intake of vitamin D still be necessary even with adequate sunlight exposure?
Why might dietary intake of vitamin D still be necessary even with adequate sunlight exposure?
How do all-trans-retinoic acid and 9-cis-retinoic acid regulate gene expression and tissue differentiation?
How do all-trans-retinoic acid and 9-cis-retinoic acid regulate gene expression and tissue differentiation?
What is the primary reason vitamin A deficiency is a major public health problem worldwide?
What is the primary reason vitamin A deficiency is a major public health problem worldwide?
Why does excessive vitamin A intake lead to toxicity?
Why does excessive vitamin A intake lead to toxicity?
Why doesn't excessive sunlight exposure lead to vitamin D toxicity?
Why doesn't excessive sunlight exposure lead to vitamin D toxicity?
How does vitamin E function as an antioxidant in cell membranes and plasma lipoproteins?
How does vitamin E function as an antioxidant in cell membranes and plasma lipoproteins?
What is the role of vitamin K in the postsynthetic modification of calcium-binding proteins?
What is the role of vitamin K in the postsynthetic modification of calcium-binding proteins?
How does warfarin lead to impaired blood clotting?
How does warfarin lead to impaired blood clotting?
Why does thiamin deficiency primarily affect carbohydrate metabolism?
Why does thiamin deficiency primarily affect carbohydrate metabolism?
How can thiamin deficiency lead to life-threatening lactic acidosis?
How can thiamin deficiency lead to life-threatening lactic acidosis?
What is the role of flavin coenzymes in oxidoreduction reactions, and why does this make them significant contributors to oxidant stress?
What is the role of flavin coenzymes in oxidoreduction reactions, and why does this make them significant contributors to oxidant stress?
Why is niacin considered not strictly a vitamin?
Why is niacin considered not strictly a vitamin?
How does NAD contribute to intracellular calcium regulation?
How does NAD contribute to intracellular calcium regulation?
Why are women affected twice the rate of men during outbreaks of pellagra?
Why are women affected twice the rate of men during outbreaks of pellagra?
How does pyridoxal phosphate influence steroid hormone action?
How does pyridoxal phosphate influence steroid hormone action?
What is the most accurate description of vitamin B12-dependent enzymes?
What is the most accurate description of vitamin B12-dependent enzymes?
How can pancreatic insufficiency be a factor in the development of vitamin B12 deficiency?
How can pancreatic insufficiency be a factor in the development of vitamin B12 deficiency?
Why does vitamin B12 deficiency lead to a functional folate deficiency?
Why does vitamin B12 deficiency lead to a functional folate deficiency?
How can high intakes of folic acid mask B12 deficiency?
How can high intakes of folic acid mask B12 deficiency?
Why is dietary biotin deficiency virtually unknown in humans?
Why is dietary biotin deficiency virtually unknown in humans?
What is the function of biotin in carboxylation reactions?
What is the function of biotin in carboxylation reactions?
How does pantothenic acid function as a carrier of acyl groups?
How does pantothenic acid function as a carrier of acyl groups?
How can vitamin C enhance iron absorption?
How can vitamin C enhance iron absorption?
Outline the relationship between the essential minerals and food sources:
Outline the relationship between the essential minerals and food sources:
Why are some people genetically more susceptible with iron overload, even with normal intakes?
Why are some people genetically more susceptible with iron overload, even with normal intakes?
What are the functions of vitamin C in the copper-containing hydroxylases and the α-ketoglutarate-linked iron-containing hydroxylases?
What are the functions of vitamin C in the copper-containing hydroxylases and the α-ketoglutarate-linked iron-containing hydroxylases?
Why is the production of interleukins by activated t-lymphocytes and of immunoglobin inhibited by activated B-lymphocytes?
Why is the production of interleukins by activated t-lymphocytes and of immunoglobin inhibited by activated B-lymphocytes?
Why may vitamin D status be protective against various cancers but increased sunlight exposure may increase chances of skin cancer?
Why may vitamin D status be protective against various cancers but increased sunlight exposure may increase chances of skin cancer?
Though required in small amounts, what happens when minerals are not consumed?
Though required in small amounts, what happens when minerals are not consumed?
Why might genetic defects of calcidiol 24-hydroxylase lead to hypercalcemia with relatively low vitamin D intakes?
Why might genetic defects of calcidiol 24-hydroxylase lead to hypercalcemia with relatively low vitamin D intakes?
In the context of vitamin A deficiency, how does the reduced synthesis of retinol-binding protein exacerbate infectious disease susceptibility?
In the context of vitamin A deficiency, how does the reduced synthesis of retinol-binding protein exacerbate infectious disease susceptibility?
What is the primary mechanism by which excessive intake of vitamin A leads to toxicity?
What is the primary mechanism by which excessive intake of vitamin A leads to toxicity?
How does the absence of gulonolactone oxidase in certain species determine the necessity of vitamin C as a dietary component?
How does the absence of gulonolactone oxidase in certain species determine the necessity of vitamin C as a dietary component?
How does B12 deficiency lead to neurological damage, specifically irreversible degeneration of the spinal cord?
How does B12 deficiency lead to neurological damage, specifically irreversible degeneration of the spinal cord?
What is the key distinction between pernicious anemia and dietary B12 deficiency in terms of the underlying cause and mechanism?
What is the key distinction between pernicious anemia and dietary B12 deficiency in terms of the underlying cause and mechanism?
How does the inhibition of dihydrofolate reductase by methotrexate lead to its effectiveness as a chemotherapeutic agent?
How does the inhibition of dihydrofolate reductase by methotrexate lead to its effectiveness as a chemotherapeutic agent?
How does vitamin K contribute to the function of proteins involved in blood clotting and bone metabolism?
How does vitamin K contribute to the function of proteins involved in blood clotting and bone metabolism?
What is the biochemical mechanism by which warfarin inhibits blood clotting, and how can vitamin K reverse this effect?
What is the biochemical mechanism by which warfarin inhibits blood clotting, and how can vitamin K reverse this effect?
How can high carbohydrate diets exacerbate the symptoms and severity of thiamin deficiency?
How can high carbohydrate diets exacerbate the symptoms and severity of thiamin deficiency?
In the context of riboflavin deficiency, why is there efficient conservation of tissue riboflavin despite its central role in metabolism?
In the context of riboflavin deficiency, why is there efficient conservation of tissue riboflavin despite its central role in metabolism?
How does the dual role of NAD in both redox reactions and calcium regulation contribute to the diverse physiological effects of niacin deficiency?
How does the dual role of NAD in both redox reactions and calcium regulation contribute to the diverse physiological effects of niacin deficiency?
What is the significance of pyridoxal phosphate's role in modulating steroid hormone action, and how does vitamin B6 deficiency affect hormone sensitivity?
What is the significance of pyridoxal phosphate's role in modulating steroid hormone action, and how does vitamin B6 deficiency affect hormone sensitivity?
In the context of biotin's role in carboxylation reactions, how does its impact on gluconeogenesis and fatty acid synthesis contribute to its regulation of the cell cycle?
In the context of biotin's role in carboxylation reactions, how does its impact on gluconeogenesis and fatty acid synthesis contribute to its regulation of the cell cycle?
How does Vitamin C enhance iron absorption, and what is the biochemical rationale behind co-prescribing them for iron deficiency anemia?
How does Vitamin C enhance iron absorption, and what is the biochemical rationale behind co-prescribing them for iron deficiency anemia?
What explains the fact that some individuals are genetically more susceptible to iron overload, even with normal iron intakes?
What explains the fact that some individuals are genetically more susceptible to iron overload, even with normal iron intakes?
In the context of vitamin C's role as a reducing agent, what is the underlying enzymatic mechanism facilitated by vitamin C in copper-containing hydroxylases and α-ketoglutarate-linked iron-containing hydroxylases?
In the context of vitamin C's role as a reducing agent, what is the underlying enzymatic mechanism facilitated by vitamin C in copper-containing hydroxylases and α-ketoglutarate-linked iron-containing hydroxylases?
What is an example of a trace mineral required by the body, and what is the primary consequence of its deficiency?
What is an example of a trace mineral required by the body, and what is the primary consequence of its deficiency?
What is the key benefit of expressing vitamin A content in foods as retinol activity equivalents (RAE)?
What is the key benefit of expressing vitamin A content in foods as retinol activity equivalents (RAE)?
How do genetic variations in selenoproteins influence individual susceptibility to selenium deficiency or toxicity, particularly in regions with selenium-poor soil?
How do genetic variations in selenoproteins influence individual susceptibility to selenium deficiency or toxicity, particularly in regions with selenium-poor soil?
How does the absence of vitamin D fortification policies in some regions impact public health outcomes related to bone health and chronic diseases, particularly in populations with limited sun exposure?
How does the absence of vitamin D fortification policies in some regions impact public health outcomes related to bone health and chronic diseases, particularly in populations with limited sun exposure?
How does vitamin A deficiency impact the function of other hormone receptors?
How does vitamin A deficiency impact the function of other hormone receptors?
What is the primary mechanism by which increased concentrations of unbound vitamin A cause toxicity?
What is the primary mechanism by which increased concentrations of unbound vitamin A cause toxicity?
Why are individuals with fat malabsorption syndromes more susceptible to vitamin E deficiency?
Why are individuals with fat malabsorption syndromes more susceptible to vitamin E deficiency?
How does warfarin exert its anticoagulant effect at the molecular level?
How does warfarin exert its anticoagulant effect at the molecular level?
Why might a high carbohydrate diet exacerbate the symptoms of thiamin deficiency?
Why might a high carbohydrate diet exacerbate the symptoms of thiamin deficiency?
Despite its central role in metabolism, why is riboflavin deficiency not typically fatal?
Despite its central role in metabolism, why is riboflavin deficiency not typically fatal?
How does NAD's role in intracellular calcium regulation contribute to the diverse symptoms of niacin deficiency?
How does NAD's role in intracellular calcium regulation contribute to the diverse symptoms of niacin deficiency?
How might high estrogen levels affect the risk of pellagra?
How might high estrogen levels affect the risk of pellagra?
How does pyridoxal phosphate (PLP) modulate steroid hormone action at the molecular level?
How does pyridoxal phosphate (PLP) modulate steroid hormone action at the molecular level?
How does B12 deficiency lead to a 'functional folate deficiency'?
How does B12 deficiency lead to a 'functional folate deficiency'?
Avidin in raw egg whites leads to which vitamin deficiency?
Avidin in raw egg whites leads to which vitamin deficiency?
Why is vitamin D considered conditionally essential?
Why is vitamin D considered conditionally essential?
Regarding Vitamin A, why are retinol activity equivalents (RAE) used?
Regarding Vitamin A, why are retinol activity equivalents (RAE) used?
In vitamin K metabolism, why can a high does of vitamin K act as an antidote to an overdose of warfarin?
In vitamin K metabolism, why can a high does of vitamin K act as an antidote to an overdose of warfarin?
Why is genetic testing recommended for individuals experiencing Vitamin D toxicity?
Why is genetic testing recommended for individuals experiencing Vitamin D toxicity?
With Vitamin A deficiency and infectious diseases, why does reduced synthesis of retinol-binding protein exacerbate infectious disease susceptibility?
With Vitamin A deficiency and infectious diseases, why does reduced synthesis of retinol-binding protein exacerbate infectious disease susceptibility?
Why can't humans synthesize Vitamin C?
Why can't humans synthesize Vitamin C?
Why is the irreversible degeneration of the spinal cord a result of pernicious anemia?
Why is the irreversible degeneration of the spinal cord a result of pernicious anemia?
What is the differences is pernicious anemia from dietary B12 deficiency?
What is the differences is pernicious anemia from dietary B12 deficiency?
What enzyme does methotrexate inhibit?
What enzyme does methotrexate inhibit?
What can result from a sever deficiency in Vitamin K?
What can result from a sever deficiency in Vitamin K?
Why is B6 difficultly assessed?
Why is B6 difficultly assessed?
How does selenium relate to genetics and Vitamin/mineral toxicity?
How does selenium relate to genetics and Vitamin/mineral toxicity?
What is the effect of the long term overdosing of Zinc?
What is the effect of the long term overdosing of Zinc?
What is the effect of a Vitamin E tocopherol radical?
What is the effect of a Vitamin E tocopherol radical?
What are general roles of minerals for the body?
What are general roles of minerals for the body?
Vitamins are inorganic nutrients required in large quantities for various biochemical functions.
Vitamins are inorganic nutrients required in large quantities for various biochemical functions.
Water-soluble vitamins, like lipid-soluble vitamins, are transported in the blood via lipoproteins.
Water-soluble vitamins, like lipid-soluble vitamins, are transported in the blood via lipoproteins.
Vitamin K plays a crucial role in calcium and phosphate metabolism.
Vitamin K plays a crucial role in calcium and phosphate metabolism.
Excessive intake of both vitamins A and D can lead to toxicity.
Excessive intake of both vitamins A and D can lead to toxicity.
Folic acid functions primarily as an antioxidant.
Folic acid functions primarily as an antioxidant.
Deficiency of a single B complex vitamin is commonly observed due to generally poor diets.
Deficiency of a single B complex vitamin is commonly observed due to generally poor diets.
The adequate level of nutrient intake lies between the extremes of deficiency and toxicity.
The adequate level of nutrient intake lies between the extremes of deficiency and toxicity.
Reference intakes are set at the average requirement minus 2 standard deviations to meet requirements of most of the population.
Reference intakes are set at the average requirement minus 2 standard deviations to meet requirements of most of the population.
Vitamin D is strictly defined as a vitamin because the body cannot synthesize it.
Vitamin D is strictly defined as a vitamin because the body cannot synthesize it.
Carotenoids, like beta-carotene, found only in animal products, are precursors to vitamin A.
Carotenoids, like beta-carotene, found only in animal products, are precursors to vitamin A.
All-trans-retinoic acid and 11-cis-retinoic acid regulate growth, development, and tissue differentiation; they have different actions in different tissues.
All-trans-retinoic acid and 11-cis-retinoic acid regulate growth, development, and tissue differentiation; they have different actions in different tissues.
Vitamin A deficiency primarily affects cardiovascular function before impacting vision.
Vitamin A deficiency primarily affects cardiovascular function before impacting vision.
Excessive exposure to sunlight can lead to vitamin D poisoning.
Excessive exposure to sunlight can lead to vitamin D poisoning.
The most bioactive form of Vitamin E is β-tocopherol.
The most bioactive form of Vitamin E is β-tocopherol.
Vitamin K functions as a coenzyme for transamination reactions.
Vitamin K functions as a coenzyme for transamination reactions.
Thiamin triphosphate directly participates in the decarboxylation of alpha-keto acids.
Thiamin triphosphate directly participates in the decarboxylation of alpha-keto acids.
Niacin is considered a true vitamin since the body cannot synthesize it from tryptophan.
Niacin is considered a true vitamin since the body cannot synthesize it from tryptophan.
Pyridoxine is the active coenzyme form of Vitamin B6 that is associated with glycogen phosphorylase.
Pyridoxine is the active coenzyme form of Vitamin B6 that is associated with glycogen phosphorylase.
Pernicious anemia is primarily caused by dietary deficiency of vitamin B12.
Pernicious anemia is primarily caused by dietary deficiency of vitamin B12.
Folic acid supplementation always prevents neural tube defects, regardless of when started during pregnancy.
Folic acid supplementation always prevents neural tube defects, regardless of when started during pregnancy.
Match each vitamin with its corresponding primary function:
Match each vitamin with its corresponding primary function:
Match the vitamin deficiency with its associated disease:
Match the vitamin deficiency with its associated disease:
Match the following enzymes with the vitamin that acts as its coenzyme:
Match the following enzymes with the vitamin that acts as its coenzyme:
Match the vitamin with its role in gene expression:
Match the vitamin with its role in gene expression:
Match each condition with the vitamin that can help prevent or treat it:
Match each condition with the vitamin that can help prevent or treat it:
Match the form of Vitamin A with its biological activity
Match the form of Vitamin A with its biological activity
Match the location with where Vitamin D is activated and stored:
Match the location with where Vitamin D is activated and stored:
Match the mineral with their biological role:
Match the mineral with their biological role:
Match the vitamin with a food source it can be found in:
Match the vitamin with a food source it can be found in:
Match the term with its correct definition relating to vitamins:
Match the term with its correct definition relating to vitamins:
Flashcards
What are Vitamins?
What are Vitamins?
Organic nutrients required in small amounts that can't be synthesized by the body.
What are Lipid-soluble Vitamins?
What are Lipid-soluble Vitamins?
Absorbed with fats and transported in lipoproteins. Include vitamins A, D, E, and K.
What are Vitamin A Deficiency Symptoms?
What are Vitamin A Deficiency Symptoms?
Night blindness and xerophthalmia due to impaired vision and cell differentiation.
What are Vitamin D Deficiency Symptoms?
What are Vitamin D Deficiency Symptoms?
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What is Vitamin E?
What is Vitamin E?
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What is Vitamin K?
What is Vitamin K?
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What are Water-Soluble Vitamins?
What are Water-Soluble Vitamins?
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What are Thiamin Deficiency Symptoms?
What are Thiamin Deficiency Symptoms?
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What are Riboflavin Deficiency Symptoms?
What are Riboflavin Deficiency Symptoms?
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What are Niacin Deficiency Symptoms?
What are Niacin Deficiency Symptoms?
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What are Folic Acid Deficiency Symptoms?
What are Folic Acid Deficiency Symptoms?
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What are Cobalamin (B12) Deficiency Symptoms?
What are Cobalamin (B12) Deficiency Symptoms?
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What are Pantothenic Acid Deficiency Symptoms?
What are Pantothenic Acid Deficiency Symptoms?
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What are Biotin Deficiency Symptoms?
What are Biotin Deficiency Symptoms?
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What are Ascorbic Acid Deficiency Symptoms?
What are Ascorbic Acid Deficiency Symptoms?
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What defines a Vitamin?
What defines a Vitamin?
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What compounds have Vitamin A activity?
What compounds have Vitamin A activity?
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What is the role of Vitamin A?
What is the role of Vitamin A?
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Vitamin D
Vitamin D
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What is Vitamin E's Function?
What is Vitamin E's Function?
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What is Vitamin K's Function?
What is Vitamin K's Function?
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What is the role of Thiamin (B1)?
What is the role of Thiamin (B1)?
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What is Riboflavin's role?
What is Riboflavin's role?
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What is Niacin's Function?
What is Niacin's Function?
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What is Role of Vitamin B6?
What is Role of Vitamin B6?
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What is Folic Acid's role?
What is Folic Acid's role?
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What is Vitamin B12's Role?
What is Vitamin B12's Role?
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What is Pantothenic Acid's Role?
What is Pantothenic Acid's Role?
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What is Biotin's function as a coenzyme?
What is Biotin's function as a coenzyme?
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What is Ascorbic Acid's Function?
What is Ascorbic Acid's Function?
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Vitamin D Toxicity
Vitamin D Toxicity
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What is Vitamin A deficiency?
What is Vitamin A deficiency?
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What is the role of Thiamin triphosphate?
What is the role of Thiamin triphosphate?
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Vitamin E deficiency
Vitamin E deficiency
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Thiamin deficiency results in
Thiamin deficiency results in
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Recommended Dietary Allowance (RDA)
Recommended Dietary Allowance (RDA)
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Adequate Intake (AI)
Adequate Intake (AI)
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Tolerable Upper Intake Level (UL)
Tolerable Upper Intake Level (UL)
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Retinol Activity Equivalent (RAE)
Retinol Activity Equivalent (RAE)
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Retinaldehyde in Vision
Retinaldehyde in Vision
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Retinoic Acid
Retinoic Acid
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Osteomalacia
Osteomalacia
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Tocopherol Radical Reduction
Tocopherol Radical Reduction
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NAD in DNA Repair
NAD in DNA Repair
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Niacin Toxicity
Niacin Toxicity
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What are Minerals?
What are Minerals?
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What are severe Vitamin A deficiency symptoms?
What are severe Vitamin A deficiency symptoms?
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What are the effects of acute pernicious beriberi?
What are the effects of acute pernicious beriberi?
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How does Vitamin K function at a molecular level?
How does Vitamin K function at a molecular level?
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What is Hartnup disease?
What is Hartnup disease?
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What is Avidin?
What is Avidin?
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What role do bile salts play in absorption?
What role do bile salts play in absorption?
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What role does the pancreas play in Vitamin B12 absorption?
What role does the pancreas play in Vitamin B12 absorption?
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What are symptoms of Vitamin A toxicity?
What are symptoms of Vitamin A toxicity?
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What happens in prolonged Vitamin A deficiency?
What happens in prolonged Vitamin A deficiency?
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What is Dopamine β-hydroxylase?
What is Dopamine β-hydroxylase?
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How does calcitriol act to maintain plasma calcium?
How does calcitriol act to maintain plasma calcium?
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How are micronutrient requirements determined?
How are micronutrient requirements determined?
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How are lipid-soluble vitamins transported?
How are lipid-soluble vitamins transported?
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What is Calcitriol's main function?
What is Calcitriol's main function?
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What is Vitamin C's role at a molecular level?
What is Vitamin C's role at a molecular level?
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What happens with excessive Vitamin A?
What happens with excessive Vitamin A?
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Why is Vitamin D not strictly a vitamin?
Why is Vitamin D not strictly a vitamin?
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What kind of antioxidant is Vitamin E?
What kind of antioxidant is Vitamin E?
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Vitamin K's role at a molecular level?
Vitamin K's role at a molecular level?
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What can cause pellagra?
What can cause pellagra?
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Wernicke encephalopathy
Wernicke encephalopathy
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Calcidiol 24-hydroxylase
Calcidiol 24-hydroxylase
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Vitamin definition
Vitamin definition
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Retinol Activity Equivalent
Retinol Activity Equivalent
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Calcitriol
Calcitriol
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Calcinosis
Calcinosis
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Lactic acidosis
Lactic acidosis
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Carboxylase
Carboxylase
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Intrinsic factor
Intrinsic factor
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Folate trap
Folate trap
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Study Notes
Micronutrients: Vitamins & Minerals
- Vitamins are organic nutrients, needed in small amounts, that can't be synthesized and must be provided in the diet
- Organic nutrients are required in small amounts for normal function
Objectives of Vitamin Mineral Intake
- Describe how reference intakes for vitamins and minerals are determined
- Explain why reference intakes published by different national and international authorities differ
- Define a vitamin and describe its metabolism, principal functions, deficiency diseases associated with inadequate intake, and the toxicity of excessive intakes of the vitamins
- Explain why mineral salts are required in the diet
Lipid-Soluble Vitamins
- Hydrophobic compounds, absorbed efficiently with normal fat absorption
- Transferred in blood via lipoproteins or specific binding proteins
- Functions are diverse including vision, cell differentiation, calcium and phosphate metabolism, antioxidant and blood clotting
- Digestion and absorption issues, low fat diets, steatorrhea, and biliary disorders can lead to deficiency syndromes including night blindness and xerophthalmia (vitamin A); rickets in young children and osteomalacia in adults (vitamin D); neurologic disorders and hemolytic anemia of the newborn (vitamin E); and hemorrhagic disease of the newborn (vitamin K).
- Excessive intake of vitamins A and D can be toxic.
- Vitamins A, carotenes, and E act as antioxidants
- In excess these can be damaging pro-oxidants
Water-Soluble Vitamins
- Vitamins B and C, folic acid, biotin, and pantothenic acid are water soluble
- These function mainly as enzyme cofactors
- Folic acid serves as a carrier of one-carbon units
- Deficiency of a single B vitamin is rare
Deficiencies
- Poor diets often comes with several deficiencies
- Syndromes show in individual vitamins e.g. beriberi (thiamin), cheilosis (riboflavin), pellagra (niacin), megaloblastic anemia, methylmalonic aciduria and pernicious anemia (vitamin B₁₂), megaloblastic anemia (folic acid), scurvy (vitamin C)
- Inorganic mineral elements are needed, can lead to deficiencies and toxicity e.g. anemia (iron), and cretinism and goiter (iodine)
Micronutrient Requirements
- A range of intakes exists for each nutrient
- Ranges from a level of inadequacy, leading to disease, to levels of toxicity
- Requirements are determined with depletion/repletion trials, and normalizing abnormalities
- Individual needs vary by as much as 25% around the mean
- Reference intakes are set to exceed the needs of 97.5% of the population
International Standards
- Reference intakes vary because of different data interpretations in publications
- Requirements are set at an average requirement plus two standard deviations
Vitamins Compounds and Metabolic Functions
- Organic compounds are required in the diet in small amounts
- Maintains normal function
- Deficiency results in diseases cured by restoring vitamins to the diet
- Vitamin D is formed in the skin from 7-dehydrocholesterol with sunlight exposure
- Niacin can be formed from tryptophan
- Vitamin D and Niacin do not strictly comply with the vitamin definition
Vitamin A
- Retinoids are retinol, retinaldehyde, and retinoic acid, found in animal foods
- Carotenoids are carotenes abundant in plants
- Carotenoids can yield retinaldehyde, then retinol/retinoic acid
- a-, β-, and y-carotenes and cryptoxanthin are key provitamin A carotenoids
- Cleavage of B-carotene occurs in the intestinal mucosa via carotene dioxygenase, yielding retinaldehyde
- Intestinal activity can be low
- Large amounts of ingested B-carotene pass into circulation unchanged
- Isoenzymes of carotene dioxygenase exist: One to cleave the central bond of B-carotene, the other leading asymmetric cleavage
- 6 µg of B-carotene is equivalent to 1 µg preformed retinol, micrograms of retinol equivalents = µg preformed vitamin A + 1/6 × µg β-carotene + 1/12 × µg other provitamin A carotenoids
- International units (IU) were used in biological assays, and are still used in labeling
- 1 IU = 0.3 µg retinol, 1 µg retinol = 3.33 IU
- Retinol activity equivalent (RAE) of 1 RAE = 1 µg all-trans-retinol, 12 µg β-carotene, 24 µg a-carotene or β-cryptoxanthin
- 1 IU of vitamin A is equal to 3.6 µg B-carotene or 7.2 µg of other provitamin A carotenoids
Vitamin A and Vision
- Retinaldehyde functions as a prosthetic group for light-sensitive opsin proteins in the retina
- Rhodopsin present in rods, iodopsin present in cones
- Cone cells contain a type of opsin for sensitivity to a single color
- In the pigment epithelium, all-trans-retinol is isomerized to 11-cis-retinol and oxidized to 11-cis-retinaldehyde
- 11-cis-retinaldehyde reacts with a lysine residue in opsin, forming rhodopsin holoprotein
- Light absorption by rhodopsin causes retinaldehyde conformational change, releasing retinaldehyde from the protein, and triggering nerve impulse
- Excited rhodopsin, bathorhodopsin, forms quickly upon illumination
- Conformational changes form metarhodopsin II, initiating guanine nucleotide amplification cascade
- Hydrolysis releases all-trans-retinaldehyde and opsin
- Vitamin A key. Impairment occurs in deficiency in time taken to adapt to darkness and ability to see well in low light.
Vitamin A and Nucleic Acids
- Retinoic acid regulates gene expression and tissue differentiation
- All-trans-retinoic acid and 9-cis-retinoic acid regulate growth and has different actions in different tissues
- Retinoic acid binds to nuclear receptors, which bind to DNA
- Two families of retinoid receptors are retinoic acid receptors (RAR), and retinoid X receptors (RXR)
- RAR binds to all-trans/9-cis-retinoic acid, while RXR binds 9-cis-retinoic acid
- RXRs form dimers with vitamin D, thyroid, and other nuclear acting hormone receptors
- Vitamin A deficiency can impair thyroid hormones
- Unoccupied RXRs forms dimers with occupied vitamin D and thyroid hormone receptors
- Not only are these unable to activate gene expression, they may repress it.
- A Vitamin A Deficiency can have a more severe effect on hormones
- Excessive vitamin A also impairs hormone function
Vitamin A Deficiency
- Most preventable cause of blindness
- Loss of sensitivity to green light
- Cannot adjust to dim light or darkness
- Prolonged deficiency causes keratinization of the cornea, blindness, and immune system complications
- Synthesis of retinol-binding protein, to transport vitamin in blood, decreases in response to infection, further impairing immune responses
Vitamin A Toxicity
- Limited capacity to metabolize Vitamin A
- Excess intake leads to accumulation to a point that exceeds limit of intracellular binding proteins
- Causes membrane lysis and tissue damage
- Nausea, ataxia, and anorexia are associated with increased cerebrospinal spinal fluid pressure
- Hepatomegaly, hyperlipidemia, thickening of long bones, calcification , and dry skin can occur
Vitamin D
- Vitamin D synthesization is the major source of this vitamin
- Functions to regulates calcium absorption and homeostasis
- Intake considerably can reduce the risk of insulin resistance
- Deficiency is a problem at Northern latitudes
Vitamin D Synthesis
- 7-Dehydrocholesterol in the skin yields previtamin D non enzymatically when exposed to ultraviolet light
- Plasma concentration is highest after the summer, and lowest after winter
- Vitamin D has two hydroxylations to create active metabolite in liver and kidney
Vitamin D Metabolism Regulation
- Functions to control calcium homeostasis, and reduces kidney synthesis
- Achieves functions via intestinal absorption of calcium
- Reduces excretion of calcium
- Mobilizes bone mineral
- Calcitriol involves insulin production and parathyroid/thyroid hormones
High Vitamin D levels
- Protective against against cancers
- May require fortified foods
Vitamin D Deficiency
- Bone doesn't fully deposit bone in children
- Causes bone demineralization in adults
Vitamin E
- Functions as a lipid soluble antioxidant in cells
- Maintains fluidity of cell membranes and signal
- Generic name to Tocopherols and tocotrienols
- Has more activity with d-a-tocopherol
Vitamin E Deficiency
- Deficiency in animals leads to testes and fetus issues
- Severe fat leads to muscle and nerve damage caused by being unable to transport
- Premature infants with low reserves leads to erythrocyte fragility
Vitamin K
- Discovered after investigation into bleeding of cattle and chicks
- Three compounds with activity: phylloquinone, menaquinones, and menadione
- Menaquinones are synthesized by intestinal bacteria whereas phylloquinone is a normal dietary source
- Leads to glutamate residues
Thiamin (B1)
- Key role in carbohydrate metabolism
- Thiamin diphosphate leads to three reactions
- Pyruvate dehydrogenase
- a-ketoglutarate dehydrogenase
- Keto acid dehydrogenase
- Important for nerve conduction through chloride channels
Thiamin (B1) Deficiency
- Three syndromes caused: peripheral neuritis, acute/pernicious, and Wernicke encephalopathy
- High glucose leads to lactic acidosis
Riboflavin (B2)
- Provides reactive qualities of flavin mononucleotide and flavin adenine dinucleotide
- Milk and dairy are good sources
- Added in food additive due intense color
Riboflavin (B2) Cont
- Flavin coenzymes work as electron carriers
- Formation of flavin leads to superoxides
- Seldom causes intense damage because of high levels of conservation
Niacin (B3)
- Not strictly a vitamin because can be created from tryptophan
- Nicotinic acid and nicotinamide have have activity
- 60mg tryptophan to 1 mg niacin
- Niacin is discounted, not biologically available
Pantothenic Acid:
- Acts like carrier through Acetyl CoA (CoA) or Acyl Carrier Protein (ACP)
B6
- Six compounds with activity including phosphate
- Active coenzyme is pyridoxal 5-phosphate which is 80% of body´s supply
B6 Function
- Transamination etc
- Glycogen phosphorilation
- Actions of hormones are are terminated by this vitamin
Vitamin C
- Ascorbic Acid
- Required by Humans and Other non synthesizers
- Gulo - Absent
Vitamin C Needs
- Cu containing & a-ketoglutarate Linked
- Increase Activity In Vitro
- A Non specific Action
Biotin
- Biotin is used to transfer CO2 which then yields
- Methylcrotonyl CoA
Vitamin K Mechanism
- Initially, vitamin K hydroquinone is oxidized to the epoxide activating a glutamate residue in the protein substrate
- To A carbanion which then reacts to form y-Carboxygultamate
- Vit K epoxide is resynthesized via warfarin sensitive and insensitive enzymes
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