Water-soluble Vitamins

• Water-soluble vitamins include B-complex vitamins and vitamin C.
• Vitamins can be classified as either fat-soluble (A, D, E, K) or water-soluble.

B-Complex

• B-complex vitamins play key roles in:
  • Hematopoiesis: Folate and vitamin B12.
  • Energy production and nutrient metabolism: Thiamin, riboflavin, niacin, folate, biotin, pantothenic acid, vitamin B6 and vitamin B12
  • Gene expression: Biotin, pantothenic acid, folate, vitamin B6 and niacin.

Vitamin C

• Vitamin C functions as an antioxidant and enzyme cosubstrate.
• An enzyme cosubstrate helps an enzyme perform its function.

Thiamin (Vitamin B1)

• The structure of thiamin consists of a pyrimidine ring and a thiazole ring.
• The coenzyme forms of thiamin are thiamin diphosphate (TDP) and thiamin pyrophosphate (TPP).
• Sources: yeast, pork, legumes, whole and enriched grains, and sunflower seeds.
• Processing can reduce thiamin content, while whole and enriched foods retain it.
• Thiamin is not stable in alkaline solutions or when exposed to light and heat.
• TDP (TPP) functions as a coenzyme in catalyzing the decarboxylation of pyruvate and α-ketoglutarate.
• Reactions are important for the release of energy from food and the formation of ATP.
• Thiamin is needed for the transketolase reaction, which forms pentoses.
• Pentoses are used in the synthesis of nucleic acids for RNA and DNA.
• Thiamin is released during nerve stimulation.

B1 Deficiency

• Beriberi is a deficiency syndrome characterized by:
  • Dry beriberi: Muscle weakness and wasting.
  • Wet beriberi: Heart failure with edema.
  • Infantile beriberi.

Wernicke-Korsakoff Syndrome

• A thiamin deficiency associated with alcoholism.
• Causes of deficiency:
  • Decreased intake.
  • Increased requirement due to liver damage.
  • Decreased absorption.
• Populations at risk:
  • Elderly.
  • Individuals with increased metabolic needs (e.g., fever, hyperthyroidism).
• Thiamin is needed for energy production and the breakdown of food.

B1 Toxicity & Assessment

• Thiamin supplementation is considered safe and has no established Upper Level (UL).
• High doses of thiamin may be helpful for individuals with Maple Syrup Urine Disease (MSUD).

Erythrocyte Transketolase Activity

• Sensitive measure to elevated thiamin addition.
• Indicates deficiency when elevated after thiamin addition.
• Low or no enzyme activity indicates low or no thiamin.

Riboflavin (Vitamin B2)

• Its structure includes a flavin molecule and ribitol.
• The coenzyme forms are flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD).
• Sources: milk, dairy products, eggs, meat, legumes, and enriched grains in the US.
• It is sensitive to UV light.

B2 Functions

• B2 is needed for:
  • Energy transformation, including the electron transport system and dehydrogenase reactions.
  • Purine catabolism, involving xanthine oxidase.
  • Vitamin activation of B6 and folate.
  • Reduction of glutathione.
  • Niacin synthesis.

B2 Deficiency

• Symptoms of B2 Deficiency:
  • Cheilosis is cracking of the lips.
  • Angular stomatitis is characterized by cracking at the corners of the mouth.
  • Glossitis is inflammation of the tongue.
• Populations at Risk:
  • Elderly.
  • Individuals with certain cancers (cancer medication can interfere with the B2 absorption).
  • Alcoholism.
  • Elevated metabolism.

B2 Toxicity & Assessment

• No toxic effects reported
• Red Cell Glutathione Reductase, an assessments for Riboflavin, is important in reducing glutathione.

Niacin (Vitamin B3)

• Nicotinic acid and nicotinamide are forms of niacin.
• The coenzyme forms include NAD, NADH, NADP, and NADPH.
• Sources: MFP, enriched grains, and legumes.
• Niacin can be synthesized from tryptophan, though not very efficiently.
• Niacin Equivalents are calculated to give a better indication of intake.
  • 60 mg of tryptophan is equivalent to 1 mg of niacin.

B3 Functions

• Energy transformation through ETS, glycolysis, pyruvate dehydrogenase, Krebs cycle, and β-oxidation.
• HMP shunt (NADP).
• Fatty acid synthesis (NADPH).
• Conversion of vitamin C, glutathione, and folate to reduced states.
• Nicotinic acid in large doses may decrease VLDL and LDL and increase HDL.
  • Side effects release of histamine (flushing), liver injury, competition with urate for excretion, itching, and elevated glucose.

B3 Deficiency

• Pellagra includes dermatitis, diarrhea, dementia, and death.
• At risk:
  • Those taking isoniazid tuberculosis medication.
  • Low intake (alcoholics).
  • Elevated metabolism.
  • Low protein/low tryptophan diet (corn).

B3 Toxicity & Assessment

• Side effects of nicotinic acid include histamine release (flushing), liver injury, competition with urate for excretion, itching, and elevated glucose.
• Niacinamide has few known side effects.
• Assessment: Ratio of N'methly-2-pyridone-5-carboxamide to N'methly nicotinamide (urinary metab of nicotinamide)

Pantothenic Acid B5

• The structure is usually part of coenzyme A.
• Al : 5 mg/day
• Sources: Widely distributed in foods (pantos mean everywhere).
  • Liver, meats, egg yolk, whole grains, mushrooms, broccoli, and avocados.
  • There is no RDA for this vitamin.

B5 Functions

• Acyl group donor as part of coenzyme A.
• Involved in Kreb's cycle (acetyl CoA, succinyl CoA), gluconeogenesis (succinyl CoA), fatty acid oxidation (fatty acyl CoA, acetyl CoA), pyruvate and alpha-ketogulatarate decarboxylase.

B5 Deficiency, Toxicity & Assessment

• Deficiency is only seen in severe malnutrition of vitamin spread widely.
• Symptoms include burning feet, vomiting, fatigue, and weakness.
• Only happens in alcoholics, diabetes mellitus, and inflammatory bowel disease.
• B5 Toxicity:
  • May cause gastrointestinal with everything consumed in excess.
  • Deficiency leads to a vague, and can't tell if deficiency.
  • There is no Upper Level (UL).
• Plasma and urinary pantothenic acid are used for assessment.

Biotin (Vitamin B7)

• Once called vitamin H referring to haut in "skin" in German.
• It has a ureido ring and a thiophene ring.
• Biotin sources:
  • Liver, soybeans, egg yolk, cereals, legumes, nuts
  • Produced by bacteria in the colon

Biotin

• Avidin, a glycoprotein in raw egg whites, can tightly binds to biotin, frequently preventing absorption.
  • A potential outcome known as "egg white injury"
• Biotin functions as a carboxyl group carrier in carboxylation reactions involving transcarboxylation and decarboxylation.

B7 Toxicity, Deficiency & Assessment

• Deficiency is caused by raw egg intake:
  • GI disorders and alcoholism.
  • Symptoms include anorexia, alopecia, dermatitis, hallucination, depression
• No toxic effect in humans.
  • Only AI = 30 microgram/day.
• Assessment:
  • Blood/serum/plasma biotin.
  • Urinary biotin excretion.

Folate (Vitamin B9 - Folic Acid)

• Folate's structure includes pteridine, p-aminobenzoic acid (PABA), and glutamic acid.
• The active forms are coenzyme tetrahydrofolate found as polyglutamate forms in food.
• Sources include yeast, mushrooms, green vegetables, legumes, liver, fortified foods, and citrus fruits, especially strawberries and oranges.
• Folate is easily destroyed due to processing.
• Folate is found as polyglutamate and hydrolyzed prior to absorption.
• Inhibitors include conjugase, alcohol, inhibitors from legumes, cabbage, and oranges.
• Folate functions in single-carbon transfers.
• Functions for nucleic and amino acids synthesis

Folate deficiency & Toxicity

• Causes megaloblastic anemia
• At risk: Pregnancy, alcoholism, elderly, phenytoin users
• Toxicity: supplementation can mask Vit B12 deficiency

Folate Evaluation

• Interacts with Vitamin B12 trap. • Decreased Zinc. • Vitamin B12 deficiency: Methyl group in N5 methyl THF cannot be removed. Plasma. • Serum. • RBC for evaluation.

Interactions and Evaluation

• Plasma, serum, or RBC folate are used for evaluation. • Deoxyuridine test (dUMP to dTMP). • Plasma homocysteine testing is also done.

Vitamin B12 (Cobalamin)

• B12 is made by microbes in the rumen and ileum of animals.
• It is found as animal products such as MFP, egg, milk.
• It is absorbed through the Intrinsic Factor and Diffusion

Vitamin B12 (Cobalamin) Absorption

• Intrinsic Factor mediated absorption:
  • Intrinsic factor (IF, a glycoprotein) is synthesized in the stomach.
  • B12 combines with R protein in stomach and travels to small intestine.
  • B12 releases R protein and complexes with IF.
  • B12-IF is absorbed in the ileum through a receptor.
  • B12 is released once complex is in the enterocyte.
• Diffusion is not of importance with normal intakes:
  • With large doses, some non-intrinsic factor mediated absorption takes place.

B12 Functions, Deficiency & Toxicity

• Converts homocysteine to methionine transfer, and methylmalonyl CoA to succinyl CoA
• Deficiency: Megaloblastic Anemia can be identified the looks, if high B9 or B12.
• Due to decreased absorption secondary to lack of IF as opposed to deficient- low intake, which is called is called pernicious anemia
  • Give them injection instead.
  • Toxicity:
  • None Known.

Methods to Assess Vitamin B12 (Cobalamin)

• Use serum.
• Test to see Test B12 absorption/presence of IF.
• And presence of increased plasma homocysteine.

Pyridoxine (Vitamin B6)

• Structure: Pyridoxine (PN), Pyridoxal (PL), Pyridoxamine (PM), Pyridoxine phosphate (PNP)
• Coenzyme forms: PL, PM, PN, PLP, PMP, PNP
• Sources: Liver, nuts, bananas, legumes, meat, whole grains, salmon, sirloin steak, white meat chicken

B6 Functions

• Amino acids need PLP/B6, Transamination coenzyme , Decarboxylation, Transulfhydration/desulfhydration , Cleavage Can also lead to anemia and can't be niacin synthesis.
• Need it to Glycogenolysis (glycogen phosphorylase).

B6 Effective & Toxicity

• Effective with coronary heart.
• Effectic for premenstrual Pms syndrome
• Effectic for carpal tunnel . • Neuropathy • UL: 100 mg/day Assessment: • Plasma PLP • Transaminase activities • Tryptophan load-B6 (not synthesized- needs available B6)