Vitamins and Nutrition in Medicine

History of Vitamins

• 500 BC: Hippocrates discovered that liver consumption could cure night-blindness
• 1757: Lind discovered that fresh fruit and vegetables could cure scurvy in the British Navy
• 1893: Eijkman described and cured beri-beri in patients who consumed polished rice
• 1912: F.G. Gowland Hopkins found that milk contains factors necessary for rat growth
• 1912: Hopkins and Funk introduced the "vitamine theory" of disease, proposing that specific diseases are caused by a lack of specific nutritional factors

The Vitamine Theory of Disease

• The theory proposed that diseases such as beri-beri, scurvy, and rickets are caused by a lack of specific nutritional factors
• This was a difficult concept to accept at the time, as diseases were thought to be caused by toxic factors rather than the absence of a factor

Origin of Vitamin Names

• McCallum and Davis (US) discovered fat-soluble factor A in butter and egg yolk
• Heat-labile factor B was found in wheat germ and was necessary for rat growth
• McCallum and Davis later found that these factors were mixtures of vitamins

Definition of Vitamins

• Vitamins are complex organic substances required in the diet in small amounts
• Vitamins are essential for normal growth and development, and their absence leads to a deficiency disease
• Vitamins can be classified as either water-soluble (B and C) or fat-soluble (A, D, E, and K)

Water-Soluble Vitamins

• B group and C vitamins are not stored extensively in the body
• Water-soluble vitamins are needed regularly and are not toxic in excess (within reason)

Fat-Soluble Vitamins

• A, D, E, and K vitamins are stored in the body
• Fat-soluble vitamins are not absorbed easily and are not excreted easily
• Fat-soluble vitamins can be toxic in excess (A and D)

B Group Vitamins

• All B vitamins act as co-enzymes in metabolic pathways
• Thiamin (B1) was isolated in 1926 as the anti-beri-beri factor
• Thiamin deficiency can lead to Wernicke-Korsakoff syndrome, which is often seen in alcoholics
• Riboflavin (B2) is UV-sensitive and mainly found in milk
• Riboflavin is protein-bound and is not toxic in excess
• Niacin (B3) is found in cereals, but its bioavailability is low
• Niacin deficiency can lead to pellagra, which is characterized by dermatitis, diarrhea, and dementia
• Pyridoxine (B6) is essential for amino acid metabolism and haem synthesis
• Pyridoxine deficiency can lead to seizures, Down's syndrome, and autism
• Folate and vitamin B12 are essential for the synthesis of 1-carbon units

Folate and Vitamin B12

• Folate and vitamin B12 are essential for the synthesis of 1-carbon units
• Folate is a carrier of 1-C fragments, and its active form is tetrahydrofolate
• Vitamin B12 is a carrier of methyl groups and is essential for the synthesis of methionine
• Folate and vitamin B12 are essential for the synthesis of purines and pyrimidines
• Deficiency in folate and vitamin B12 can lead to megaloblastosis, which is characterized by giant germ cells and a lack of DNA synthesis

Methotrexate

• Methotrexate is a drug used in chemotherapy, as an immunosuppressant, and to treat ectopic pregnancies
• Methotrexate works by inhibiting the enzyme dihydrofolate reductase, which is necessary for the synthesis of tetrahydrofolate

Folate and Neural Tube Defects

• Folate supplementation around conception time can prevent neural tube defects (anencephaly, spina bifida, encephalocele) in women who have had a previous pregnancy affected by these defects
• In the UK, all pregnant women attending ante-natal clinics are prescribed folate supplements

Folate, B6, and B12 and Cardiovascular Mortality

• Some studies have shown a link between high homocysteine concentrations and cardiovascular disease, but it is unclear whether this is a cause or effect
• Some studies have shown that high-dose supplements of B vitamins can reduce the risk of cardiovascular disease, but others have not found this association

Folate, B6, and B12 and Alzheimer's Disease

• Some studies have shown that high-dose supplements of B vitamins can reduce the rate of brain shrinkage in elderly people with mild memory problems.

This quiz covers the basics of vitamins and nutrition, including their history, importance, and how to determine nutrient intake. It's suitable for MBBS stage 1 students studying Nutrition and Metabolism.