Vitamins: Classification and Sources

• Vitamins are organic compounds containing carbon and are essential micronutrients needed from the diet in small amounts.
• Vitamins are classified as either water-soluble (B vitamins and vitamin C) or fat-soluble (A, D, E, K).
• 40% of Canadian adults may benefit from supplements.

Classification

• Water-soluble vitamins dissolve in water, are easily absorbed and excreted, are not stored extensively in tissues, and seldom reach toxic levels.
• Fat-soluble vitamins (A, D, E, K) dissolve in lipid, require bile for absorption and transported in lymph.
• Fat-soluble vitamins are stored in tissues like the liver and adipose, and may be toxic in excess.
• Caution should be exercised when taking supplements of fat-soluble vitamins.

Vitamins In Our Food

• Almost all foods contain vitamins.
• The amount of a vitamin in food depends on the amount in the food naturally, what is added to it, and how the food is processed, prepared, and stored.
• Fortification is the process of adding nutrients to foods generally not found in the food, for example, calcium in orange juice.
• Enrichment is adding nutrients back to foods that have lost nutrients due to processing, for example, B vitamins in white rice.
• Health Canada regulates mandatory and voluntary fortification.
• The premise is to prevent deficiencies leading to diseases, but may also cause toxicity.
• Mandatory fortification includes table salt with iodine and milk with vitamin D.
• Grains are fortified with thiamine, riboflavin, niacin, iron, and folic acid.
• People who may benefit from supplements are those on calorie-restricted diets, vegans, infants, children, young females, and pregnant women.
• Also, individuals with dark pigmentation or who cover their bodies outdoors as well as individuals taking medications, cigarette smokers, and alcohol users.

Vitamins in the Digestive Tract

• Chewing in the mouth helps release vitamins.
• Digestion in the stomach releases vitamins; some niacin is absorbed.
• The gallbladder releases bile, which emulsifies fat and helps absorb fat-soluble vitamins.
• The pancreas secretes digestive enzymes that aid in the release of vitamins from food.
• In the small intestine, fat-soluble vitamins are incorporated into micelles and then absorbed by simple diffusion.
• Once inside mucosal cells, fat-soluble vitamins are packaged in chylomicrons and enter the lymph before entering into the blood.
• Water-soluble vitamins are absorbed from the small intestine directly into the blood.
• In the large intestine, bacteria synthesize small amounts of vitamins, some of which are absorbed.
• Bioavailability is the extent to which the body can absorb and use a nutrient approximately ~40-90% of vitamins are absorbed.
• Fat-soluble vitamins require fat in the diet to be absorbed.
• Water-soluble vitamins may require transport molecules and are absorbed in inactive provitamin or vitamin precursor forms.
• Provitamin must be converted into active forms by the body.
• Vitamin bioavailability factors include efficiency of digestion, nutrient intake, other foods consumed, method of food preparation, source of the nutrient.
• Provitamins are available from foods in inactive forms known as precursors or provitamins; for example, β-carotene converted to retinol.

B Vitamins and Energy Metabolism

• B vitamins are essential for energy metabolism.

Thiamin (Vitamin B₁)

• Thiamin functions as a coenzyme needed for glucose breakdown to provide energy.
• Thiamin is needed for metabolism of other sugars/amino acids and synthesis of ribose (RNA) and deoxyribose (DNA); it promotes nerve function using glucose for nerve cell energy and synthesis of neurotransmitters.
• The RDA for thiamin is 1.2 mg/day for males and 1.1 mg/day for females.
• Food sources include the bran layer of whole grains, enriched grains, pork, legumes, and seeds.
• Thiamin deficiency can cause beriberi, weakness, nerve degeneration, heart changes, and Wernicke-Korsakoff syndrome in alcoholics, causing mental confusion, psychosis, memory disturbances, and coma.
• There are no reported effects associated with excess thiamin and no Upper Limit (UL) set.

Riboflavin

• Riboflavin creates two active coenzymes needed to produce ATP from carbohydrate, fat, and protein. It assists body with absorption of other vitamins.
• It acts as an antioxidant.
• It is also involved in converting folate, niacin, vitamin B6, and vitamin K into their active forms.
• Easily destroyed by heat and exposure to light.
• Riboflavin is an important ingredient for the citric acid cycle.
• RDA for male is 1.3 mg/day while for females it is 1.1 mg/day.
• It can be obtained from dairy products, red meat, poultry, fish, whole grains, enriched grains, asparagus, broccoli, mushrooms, leafy greens.
• Deficiency results in impaired healing, cracking of lips, mouth corners with sensitivity to light, eye burning, tearing, itching, and flaking skin near the nose, eyebrows, and earlobes.
• Excess vitamin consumption has no reported effects, however, it changes urine to bright fluorescent yellow.

Niacin B3

• Niacin is added to enriched flours in North America, synthesized from the essential amino acid tryptophan, and promotes the production of energy and in general metabolism.
• The two forms of niacin are nicotinic acid and nicotinamide.
• Niacin acts as a coenzyme in glucose metabolism and synthesis of fatty acids and cholesterol, also an old treatment for unbalanced cholesterol ratios.
• The RDA-NE is 14-16mg NE/day for niacin equivalents.
• RDA: Male = 16 mg NE/day; Female = 14 mg NE/day.
• Can be found in the form of meats, fish, peanuts, whole and enriched grains, legumes, wheat bran, and synthesized from the essential amino acid tryptophan
• Deficiency can cause pellagra (fatigue, decreased appetite, indigestion, 4Ds: dermatitis, diarrhea, dementia, and death).
• Excess is not reported when sourced from food, however, supplements can be toxic causing skin flushing, rash, tingling in hands and feet, nausea, vomiting, diarrhea, high blood sugar levels, liver function abnormalities, and blurred vision

Biotin

• Biotin Sources include liver, egg yolks, yogurt, and nuts.
• Avoid uncooked egg whites. -The protein, avidin, binds biotin making it unavailable.
• Coenzyme involved citric acid cycle, glucose synthesis
• Recommended biotin intake: AI = 30 micrograms/day

Pantothenic Acid

• Abundant in meat, eggs, whole grains, and legumes, plays an important role as part of coenzyme A and as part of the carrier protein for cholesterol and fatty acid synthesis.
• AI = 5 mg/day, with an increased requirement for pregnancy, 6 mg/day, and lactation, 7 mg/day.

Vitamin B6

• Promotes amino acid and protein metabolism, and synthesis of nonessential amino acids, neurotransmitters, hemoglobin, and conversion of tryptophan into niacin
• Also assists with glucose and amino acid breakdown: three forms pyridoxal, pyridoxine, pyridoxamine.
• Converted into active coenzyme pyridoxal phosphate facilitates the activity of >100 enzymes in carbohydrate, fat, and protein metabolism
• RDA is 1.3 mg/day for a 19 to 50 year old.
• Source via consumption of chicken, fish, pork, organ meats, whole grains, legumes, sunflower seeds, bananas, broccoli, spinach, some fortified cereals
• Refined grains are not good sources.
• Deficiency is linked to poor growth, skin lesions, decreased immunity, anemia, neurological symptoms, anxiety, and nightmares.
• Excess results in severe nerve impairment.

Folate (Folic Acid)

• Folate functions as a coenzyme for DNA synthesis and amino acid metabolism.
• Folate is important early in pregnancy for neural tube formation, which develops into the brain and spinal cord.
• Folate prevents homocysteine levels from rising to prevent heart disease.
• Since food fortification, neural tube defects decreased by 50% in Canada, Newfoundland rates dropped by 80%, Alberta and Quebec reduction in the number of congenital heart defects.
• Since food fortification, Ontario reported reduction in neuroblastoma.
• Since 1998, increased risk of colon cancer has been observed, related to folate fortification.
• RDA is 400 micrograms/day.
• Dietary source available via enriched grains, leafy greens, asparagus, legumes, nuts, oranges, liver and yeast.
• Folate deficiencies are linked to neural defects (spina bifida, anencephaly), macrocytic/megaloblastic anemia, poor growth, nerve development/function problems, diarrhea, tongue inflammation, increased risk of heart disease and some cancers.
• Excess intake can prevent folate-deficiency symptoms and mask B12 deficiencies and is linked to higher breast cancer risk

Vitamin B12 (Cobalamin)

• Vitamin B12 promotes ATP production from certain fatty acids, and conversion of homocysteine to methionine.
• It has major function in the maintenance of myelin coating on nerves and amino acid metabolism.
• Pernicious anemia is a common form of anemia that does not respond to oral B12 supplementation.
• Vitamin B12 is necessary for body´s iron absorption.
• Excessive intake of folic acid can mask B12 deficiencies.
• Vitamin B12 is naturally available only in animal products.
• Vegan diets will need to be supplemented with readily-absorbable forms of B12.
• Atrophic gastritis and GI disorders lead to 12 deficiencies.
• RDA is 2.4 micrograms/day for adults.
• Sources are only animal products.
• B12 Deficiency presents as zero energy, pernicious anemia, increased homocysteine, decreased folate activation, numbness and tingling, gait abnormalities, memory loss, disorientation, paralysis, and death.
• There are no reported effects from intakes of up to 100 micrograms of Vitamin B12 from food or supplements.

Antioxidants: Vitamin C

• Antioxidants decrease the adverse effects of free radicals - unstable compounds that react with body molecules.
• Free radicals are molecules with one or more unpaired electrons.
• Antioxidants neutralize free radicals by donating one of their electrons.
• Free radicals cause harm to DNA and other molecules, oxidative stress is linked to aging, heart disease, cancer, and Alzheimer’s disease.
• Vitamin C is an antioxidant, and promotes synthesis and maintenance of collagen.
• It supports neurotransmitter and hormone synthesis, and bile acids/ carnitine synthesis (needed for fatty acid breakdown).
• The vitamin is found in blood and other body fluids, and is an antioxidant that regenerates the active form of vitamin E and enhances iron absorption.
• RDA: Male = 90 mg/day, female = 75 mg/day.
• Vitamin C sources include citrus fruits, strawberries, kiwis, cantaloupe, cabbage-family and dark-green vegetables, green and red peppers, okra, tomatoes, and potatoes
• Deficiencies provoke scurvy, gum and tooth problems, joint pain, bleeding, poor wound healing, fatigue, depression, and hysteria.
• Vitamin C supplementation can cause diarrhea, nausea, abdominal cramps, possible increased kidney stone formation.

Choline

• Choline is a water-soluble substance included in "vitamin B complex" supplements, synthesized to a limited extent by humans and acts as an essential nutrient.
• Choline is needed for synthesis of neurotransmitter acetylcholine, for structure and function of cell membranes, for lipid transport and for homocysteine metabolism
• Adequate intake via diet: 550 mg/day for males, 425 mg/day for females.
• Sources: Consumption of egg yolks, liver, meat, fish, wheat germ, nuts promotes healthy choline levels.
• Deficiency is linked to fetal brain development in utero, fatty liver and muscle in adults.
• Excess results in fishy body odor, sweating, reduced growth rate, low blood pressure, and liver damage.
• These effects are at levels higher than can be obtained from food.

Serotonin

• Serotonin deficiency signs: Anxiety (social), low Self esteem, Panic Attacks and depression, especially if depression worsens in winter.
• Also include, but are not limited to, OCD tendencies/impulsive behavior, frequent constipation, poor dream recall, as well as insomnia or otherwise poor sleep.
• For mood enhancement, Protein reacts in the Hydrochloric Acid/GIT microflora to create Tryptophan
• Tryptophan is linked to Vitamins B3, B5 and B6 as well Mg, iron and Ca to promote 5 - Hydroxytryptophan (5 HTP)
• Then Vitmains B6, Vit C partnered with Magnesium and Zinc generate mood enhancing Serotonin.