Module 9 Vitamins

Vitamin D

• Vitamin D toxicity occurs due to overuse of supplements.
• Symptoms of vitamin D toxicity include nausea, vomiting, diarrhoea, and calcification of soft tissues.
• Vitamin D fortification in food is subject to strict regulations.
• High levels of vitamin D deficiency occur in the U.S.
  • 90% of ethnic populations with dark skin.
  • 75% of the Caucasian population.
• Potential links between vitamin D deficiency and chronic disease:
  • heart disease.
  • respiratory infections.
  • diabetes.
  • hypertension.

Vitamin E

• Vitamin E is a fat-soluble vitamin primarily found in cell membranes.
• It is not a single compound, but a group of compounds called tocopherols, with four different types: alpha, beta, gamma, and delta.

Functions of Vitamin E

- Acts as an antioxidant and neutralizes free radicals that damage cell membranes, DNA, and proteins.
- Enhances immune function.
- Required for nerve cell development.
- Past recommendations for vitamin E supplements to protect against cancer and CVD. 

Vitamin E and Free Radicals

- Vitamin E fights against free radicals, which are unstable compounds with an unpaired electron.
- These free radicals attack other molecules with electrons, initiating a chain reaction that damages cells.
- Vitamin E donates an electron to neutralize free radicals.

Recommended Intakes for Vitamin E

- RDA: 15mg per day for adults.
- Tolerable Upper Intake Level (UL): 1,000mg per day for adults.
- UL may be lower for certain populations, particularly smokers, as increased vitamin E supplements can lead to brain hemorrhages.

Vitamin E Deficiency

- Vitamin E deficiency is uncommon.
- Most likely to occur in premature infants with insufficient stores.
- Deficiency can lead to anemia due to red blood cell fragility and subsequent rupture.
- Other symptoms include: loss of muscle coordination and reflexes, muscle weakness, reproductive failure, and impaired vision. 

Vitamin E Toxicity

- Vitamin E toxicity is possible due to its fat-soluble nature.
- Signs include headache, nausea, blurred vision, reduced sexual function in men, accelerated aging signs, inflammation of the mouth, chapped lips, fatigue, GI disturbances, muscle weakness, and increased bleeding.

Vitamin K

• Primarily functions in blood clotting by activating proteins required for fibrin formation, which forms blood clots.
• It also plays a role in the synthesis of the bone protein osteocalcin.

Vitamin K Deficiency

- Vitamin K deficiency is uncommon in adults.
- It is more common in newborns due to:
   - relatively sterile GI tract at birth.
   - breast milk contains low levels of vitamin K.
   - a single dose of vitamin K is given at birth.
- Other potential risk factors include prolonged antibiotic use. 

Vitamin K Sources

- **Non-Food Source:** Bacteria in the large intestine, the most significant source for humans.
- **Food Sources:** Green vegetables (spinach, kale, cruciferous vegetables); green fruits (avocado, kiwi); and some vegetable oils.

Water soluble and fat soluble vitamins

• Water-soluble vitamins include vitamin C and B vitamins.
• They are less toxic than fat-soluble vitamins.
• Adverse effects are possible when taken in large quantities (3x-4x RDA), particularly in extreme cases of supplement use.

Vitamin C

• Also known as ascorbic acid
• Importance in diet discovered in the 1800s by observing sailors
• Sailors died from scurvy, a disease caused by Vitamin C deficiency
• Scurvy is characterized by:
  • Bleeding gums
  • Tooth loss
  • Poor wound healing
  • Small hemorrhages on skin
• Vitamin C is an antioxidant
• Plays a role in immune system health
• Involved in collagen synthesis, which is a protein that forms connective tissue of tendons, bone, teeth, and skin
• Collagen is important for wound healing and maintaining blood vessel structure
• Vitamin C facilitates iron absorption in the GI tract
• The RDA for Vitamin C is 90 mg per day for males and 75 mg per day for females
• Smokers require an additional 35 mg of Vitamin C per day to protect the body against damaging compounds in tobacco smoke
• Good sources of Vitamin C include fruits and vegetables like orange juice, citrus fruits, kiwis, strawberries, sweet potatoes, and Brussels sprouts
• Vitamin C is vulnerable to heat and oxygen, so food preparation affects levels in food
• A severe deficiency of Vitamin C can lead to scurvy, due to improper formation of collagen
• A deficiency can also cause anemia due to poor iron absorption
• Signs of Vitamin C deficiency include: bleeding gums, loss of appetite, small hemorrhages on skin, impaired growth, weakness, and a scorbutic rosary in infants
• The UL for Vitamin C is 2,000 mg per day
• Supplementing with more than 1,000 mg of Vitamin C per day can cause diarrhea and bloating

B Vitamins

• Includes thiamin (B1), riboflavin (B2), niacin (B3), Vitamin B6, folate, Vitamin B12, pantothenic acid, and biotin
• B vitamins are coenzymes or cofactors in energy metabolism
• Coenzymes assist enzymes with energy release
• Without a coenzyme, an enzyme cannot function

Thiamin

• First identified B vitamin
• Part of the coenzyme thiamin pyrophosphate (TPP)
• TPP assists in the metabolism of carbohydrates and some amino acids
• Involved in the conversion of pyruvate to acetyl CoA and the Kreb’s cycle
• Involved in the function of nerve and muscle cell activity
• The RDA for thiamin is 1.2 mg per day for males and 1.1 mg per day for females
• There is no UL for thiamin as no adverse effects have been observed with excess consumption
• Good sources include: pork, whole grains, fortified breakfast cereals, enriched grains, and peanuts
• A thiamin deficiency can occur in malnourished individuals and alcoholics
• In malnourished individuals, it can lead to beriberi which causes an enlarged heart, fluid accumulation beneath the skin, and muscle weakness and atrophy - if the condition primarily affects the cardiovascular system, it is called wet beriberi
• If the condition primarily affects the nervous system it is called dry beriberi
• In alcoholics, a severe deficiency can lead to Wernicke–Korsakoff syndrome

Riboflavin

• Part of the coenzymes flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD)
• Involved in energy release from macronutrients
• FAD is an “electron shuttle”
• The RDA for riboflavin is 1.3 mg per day for males, and 1.1 mg per day for females
• There is no UL for riboflavin

Folate

• Folate is a naturally occurring form, folic acid is the synthetic form.
• Folic acid is easier to absorb by the GI tract.
• Folate is an essential nutrient for cell division.
• DNA replication during cell division requires folate.
• Folate is essential for red blood cell synthesis.
• Adequate folate levels are required during fetal development for central nervous system formation.
• The recommended daily allowance (RDA) of folate is 400 µg DFE (dietary folate equivalent) per day for adults 19 years and older.
• Requirements are increased for women planning pregnancy, pregnant and lactating women.
• The tolerable upper intake level (UL) of folic acid is 1 mg per day.

Food Sources of Folate

• Good sources of folate include:
  • Orange juice
  • Green leafy vegetables
  • Legumes
• Good sources of folic acid include:
  • Supplements
  • Enriched grains

Folate Deficiency

• Folate deficiency can result in the inability to synthesize DNA.
• A lack of folate leads to large, immature red blood cells, resulting in macrocytic anemia.
• Folate deficiency during pregnancy can lead to severe neural tube defects in the fetus.
• Neural tube defects:
  • Spina bifida: spinal cord fails to close completely
  • Anencephaly: lack of or incomplete development of the brain and skull

Vitamin B12

• Vitamin B12 is unique because it contains the mineral cobalt.
• It is synthesized by bacteria and other microorganisms, and is found naturally only in foods of animal origin.
• Vitamin B12 is stored in the body in significant amounts.
• Vitamin B12 requires intrinsic factor for absorption.

Functions of Vitamin B12

• Vitamin B12 is essential for converting folate into its active form.
• It maintains the myelin sheath, the insulating lining covering nerve fibers.

Vitamin B12 Dietary Recommendations and Food Sources

• The RDA for vitamin B12 is 2.4 µg per day for adults.
• There is no UL for vitamin B12.
• Sources of naturally occurring vitamin B12:
  • Milk, cheese, meat (especially organ meats), poultry, and seafood.
• Foods fortified with vitamin B12:
  • Ready-to-eat cereals
  • Soy products
  • Supplements

Vitamin B12 Absorption

• Vitamin B12 must be released from dietary protein before absorption.
• This occurs in the stomach, through the actions of hydrochloric acid and pepsin.
• After release, it binds to intrinsic factor, a protein secreted in the stomach.
• Intrinsic factor protects vitamin B12 from degradation before absorption.
• Vitamin B12 is absorbed in the lower ileum.