vitamins

• Thiamin (B1)


  Found in cereal grains, especially in the germ and bran. Added to white flour and breakfast cereals in the UK
• Other sources of thiamin

  • Brown rice
  • Meat (especially bacon, ham and pork)
  • Potatoes
  • Peas
  • Beans
  • Nuts
  • Milk
• Functions of thiamin


  • Essential for the release of energy from carbohydrates (acts as a co-enzyme)
  • Essential for the upkeep of nerves
  • Necessary for appetite and good health
• The requirement for thiamin is related to the amount of carbohydrate in the diet
• The requirement for women is less because body mass is usually less, resulting in a lower energy requirement and therefore lower thiamin requirement
• Deficiency symptoms of thiamin


  • Retarded growth
  • Fatigue, depression and irritability
  • Beriberi (nervous disease with loss of appetite, heart enlargement, paralysis and muscular weakness)
• Beriberi rarely occurs in Western diets, although it has been found in anorexics and alcoholics
• A high intake of alcohol increases the requirement for thiamin as thiamin is needed to break down alcohol in the body, making it harder to absorb vitamins
• Factors affecting absorption and bioavailability of thiamin

  • Protein and amino acids protect thiamin in food
  • Starch aids its absorption
  • Thiamin is soluble in water so 20% is lost when potatoes are boiled
  • Thiamin decomposes at high temperatures, particularly in alkaline conditions (e.g. 40% loss when meat is roasted)
• Riboflavin (B2)


  Found in milk, meat, potatoes and green vegetables. Liver is a very rich source
• Functions of riboflavin


  • Forms part of the enzyme system concerned in the oxidation of glucose and the release of energy in body cells
  • Essential for the upkeep of tissues e.g. skin, eyes
  • Necessary for growth and good health
  • Increases during pregnancy (1.4mg per day) and lactation (1.6mg per day)
• Deficiency symptoms of riboflavin


  • Affects the eyes, lips and tongue (cracks at the corner of the mouth, red and swollen tongue)
  • These symptoms are not specific to riboflavin deficiency and may be caused by lack of other B vitamins or other means
• Factors affecting absorption and bioavailability of riboflavin


  • Absorbed in the intestine
  • Slightly soluble in water
  • Fairly stable to heat, although less stable in alkaline conditions
  • Overall loss during cooking is small, much less than that of thiamin
• Niacin (B3)


  Found in fortified breakfast cereals
• Functions of niacin


  • Involved in the release of energy from food
  • Essential for healthy skin
  • Prevents Pellagra (deficiency disease)
• Deficiency symptoms of niacin

  • Dementia
  • Diarrhoea
  • Dermatitis
• Severe niacin deficiency can lead to Pellagra, which results in dementia, diarrhoea and dermatitis, and if untreated is fatal
• Niacin deficiency is rare in the Western world, as it is associated with low living standards
• Excess niacin


  • Toxicity in humans has been observed from its use as a treatment of hyperlipidaemia (high blood lipid levels)
  • Adverse effects are dose related and generally subside with reduction in dose or the cessation of treatment
  • Acute toxic symptoms include flushing, itching of the skin, nausea, and gastrointestinal disturbances
  • Excess amounts can also lead to liver damage
• Factors affecting absorption and bioavailability of niacin

  • Readily absorbed in the small intestine
  • Alcohol inhibits metabolism of niacin
  • Sleeping pills and food processing destroy the vitamin
• Other factors affecting niacin


  • Niacin can be made in the body from the amino acid Tryptophan
  • Soluble in water and small amounts are lost during cooking
  • More resistant to heat
• Vitamin B6 (Pyridoxine)


  Found in meat, fish, eggs, poultry, and breakfast cereals
• Functions of vitamin B6


  • Involved in the metabolism of amino acids, including the conversion of tryptophan to niacin
  • Necessary for the formation of haemoglobin
  • Together with folate and vitamin B12 is required for maintenance of normal blood homocysteine levels
• Deficiency of vitamin B6 is rare in humans but may occur as a complication of disease or drug effects or alcoholism. Vegetarians may have a problem meeting the requirements.
• Very high intakes of more than 50mg of vitamin B6 are potentially dangerous as they can affect sensory nerve function.
• Vitamin B12 (Cobalamin)


  Dietary intake is exclusively from animal sources: meat, milk, cheese, yogurt, fish and eggs. This is an issue for people who do not eat animal products.
• Functions of vitamin B12


  • Together with folate it is needed by rapidly dividing cells such as those in the bone marrow which form blood cells
  • Together with folate and B6 it is required for the maintenance of normal blood homocysteine levels
  • It is also needed for the normal structure and function of nerves.
• Deficiency of vitamin B12 is rare, although it is sometimes seen in vegans who obtain virtually no vitamin B12 in their diet unless it is supplemented. Deficiency is also caused by the lack of intrinsic factor, the substance needed for the absorption of vitamin B12.
• Older adults tend to produce less of the intrinsic factor and so are at risk for B12 deficiency.
• Folic Acid


  The parent molecule for several related compounds known collectively as folates or folate
• Foods rich in folate

  • Liver
  • Green leafy vegetables
  • Kidney
  • Nuts
  • Pulses
  • Flour and cereal foods
• Functions of folate


  • Essential for the growth and health of all cells in the body
  • Needed for the formation of red blood cells
  • Needed for the formation of nerve sheaths
  • Helps to prevent neural tube defects such as spina bifida during pregnancy
• Folate requirements


  • RNI for adults - 200 ug/day
  • During pregnancy - 400 ug/day
• It is recommended that all women likely to become pregnant should increase their folate intake by eating more folate rich foods and foods fortified with folate, and that women planning a pregnancy should take a daily supplement of 400 mg/day of folic acid from the start of trying to conceive to the 12th week of pregnancy, to try and reduce the incidence of neural tube defects occurring in the fetus.
• Deficiency of folate


  • Causes a characteristic type of anaemia called megaloblastic anaemia where the blood cells are larger and fewer than normal
  • Symptoms include extreme tiredness, lack of energy, sore and red tongue, mouth ulcers, muscle weakness, pins and needles, disturbed vision, psychological problems including depression and confusion, and problems with memory, understanding and judgement
  • A low intake during conception and pregnancy increases the risk of babies being born with neural tube defects such as Spina Bifida
• vitamin B12 is water soluble
• The RNI for Vitamin B12 is 1.5ug per day
• Vitamin B12 is found mainly in animal products
• B12 deficiency can cause neurological symptoms like numbness or tingling sensations in hands and feet, difficulty walking, loss of balance, poor coordination, fatigue, short-term memory loss, mood changes, irritability, and depression
• Vitamin B12 deficiency can cause a condition known as Pernicious Anaemia which causes symptoms similar to those caused by folate deficiency but also includes numbness or tingling sensations around the lips and fingers, difficulty walking due to loss of balance, and dementia-like symptoms