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Vitamin A (Retinol)

Description	Vitamin A is a fat-soluble vitamin stored mainly in the liver. Dietary Reference Values express the requirement for vitamin A in terms of retinol equivalents.
Function/ Used for	Vital for maintaining good eyesight, particularly for the normal function of the retina and visual adaptation to darkness, and healthy skin. It is also important for growth in children. Vitamin A helps metabolise iron, maintain healthy mucous membrane, immune function and cell specialisation.
Intake	Recommended intake EU NRV: 800µg Chief Medical Officer recommendations are that all children aged six months to five years should take a daily supplement containing vitamins A, C and D. UK average daily intake Requirements vary depending on age and gender. The UK National Diet and Nutrition Survey lists up-to-date intake requirements and average intakes.¹
As a supplement	Not generally available as a single supplement. Commonly available as part of a multivitamin and mineral formula. Different multivitamin and minerals products will vary in the percentage NRVs they include. People should always check the label for information about a specific product.
Found in (dietary sources)	The richest natural sources are fish liver oils. It is also very concentrated in animal liver. Other sources include oily fish, egg yolk, fortified margarine, butter and full fat milk.
Deficiency	Vitamin A deficiency is prevalent in young children in developing countries and is associated with general malnutrition in these countries.^2,3 In the UK, deficiency is relatively rare (especially in adults). Deficiency symptoms include an increased susceptibility to infections, scaly skin, flaking scalp, brittle, dull hair; poor eyesight and night vision, loss of appetite.^2,3
Precautions and contraindications	Just before, or during the first three months of pregnancy, women are advised by the Department of Health that they should not eat liver, or take vitamin A supplements which contain more than the 800µg NRV unless under medical supervision. As vitamin A (retinol) is teratogenic, it may induce developmental abnormalities in a foetus if taken in high amounts just before, or during the first three months of pregnancy. However, too little vitamin A in pregnancy can also cause problems.³ Safe Upper Level: 1500µg/day²
Use in pregnancy and breastfeeding	The Department of Health recommends that women who are (or may become) pregnant should not take dietary supplements that contain vitamin A (including fish liver oil), except on the advice of a doctor or antenatal clinic, and should also avoid eating liver and products containing liver (e.g. liver pate and liver sausage).⁴
Interactions e.g. with other medications	People taking anticoagulants, retinoids, or statins should seek medical advice before taking Vitamin A. The weight-loss drug orlistat and cholesterol-reducing drugs may reduce the absorption of vitamin A and other fat-soluble vitamins (D, E, K).^3,5
Adverse effects	Acute toxicity may be induced by single doses of 300mg retinol in adults, 60 mg retinol in children or 30 mg retinol in infants. Signs and symptoms are usually temporary (usually occurring about 6 hours after ingestion of acute dose and disappearing after 36 hours) and include severe headache (due to raised intracranial pressure), sore mouth, bleeding gums, dizziness, vomiting, blurred vision, irritability and (in infants) bulging of the fontanelle. Signs of chronic toxicity may appear when daily intake is >15mg retinol in adults and 6 mg in infants and young children. Signs may include dryness of the skin, dermatitis, skin rash, skin scaliness, disturbed hair growth, bone and joint pain, headache, fatigue, irritability, insomnia, anorexia, nausea, vomiting, diarrhoea, and weight loss.²
References	1. https://www.gov.uk/government/collections/national-diet-and-nutrition-survey 2. Expert Group on Vitamins and Minerals, 2003. 3. Mason, P. Dietary Supplements. Pharmaceutical Press, London, 2001. 4. NHS website. Foods to avoid in pregnancy. http://www.nhs.uk/conditions/pregnancy-and-baby/pages/foods-to-avoid-pregnant.aspx#vitamin 5. Gaby, A. R. A-Z Guide to Drug-Herb-Vitamin Interactions. HealthNotes 2006.

Page content last reviewed: March 20, 2017

Vitamin B1 (Thiamin or Thiamine)

Description	Thiamin is water soluble and part of the B-vitamins group.
Function/ Used for	Thiamin aids the nervous system and is essential for the functioning of some important enzymes. These enzymes have vital roles in the processes that make energy available in the body. Thiamin is essential for the transmission of certain types of nerve signal between the brain and the spinal cord. Thiamin is also important for good brain and heart function.
Intake	Recommended intake EU NRV: 1.1mg Thiamin requirements depend on energy intake; values are therefore often given as mg/1000 kcal and also as total values based on estimated average energy requirements for the majority of people in the UK. UK average daily intake Requirements vary depending on age and gender. The UK National Diet and Nutrition Survey lists up-to-date intake requirements and average intakes¹.
As a supplement	Not generally available as a single supplement. Commonly available as part of a multivitamin and mineral formula. Different multivitamin and minerals products will vary in the percentage NRVs they include. People should always check the label for information about a specific product.
Found in (dietary sources)	Brown rice, peas, beans and other vegetables, fortified breakfast cereals, wholemeal breads and cereals, eggs, pork, bacon and liver.
Deficiency	Thiamine deficiency may lead to beri-beri (rare in the UK) which affects the cardiovascular and nervous systems. Deficiency is associated with abnormalities of carbohydrate metabolism. Early signs of deficiency include depression, poor memory, muscle weakness and stiffness, nerve tingling, burning sensation and numbness, tiredness, headache, loss of appetite and nausea.³
Precautions and contraindications	Known hypersensitivity to thiamin. Safe Upper Level: 100mg/day²
Use in pregnancy and breastfeeding	There is no evidence of adverse effects in pregnancy.
Interactions e.g. with other medications	Excessive alcohol intake induces thiamin deficiency. Prolonged use of oral contraceptives may induce thiamin deficiency. Adequate amounts of all B vitamins are required for optimal functioning; deficiency or excess of one B vitamin may lead to abnormalities in the metabolism of another.³
Adverse effects	There appear to be no toxic effects (except possibly gastric upset) with high oral doses. There have, however, been rare reports of anaphylactic reactions (coughing, difficulty in breathing and swallowing, flushing, skin rash, swelling of face, lips and eyelids).
References	1. https://www.gov.uk/government/collections/national-diet-and-nutrition-survey 2. Expert Group on Vitamins and Minerals, 2003. 3. Mason, P. Dietary Supplements. Pharmaceutical Press, London, 2001.

Page content last reviewed: March 20, 2017

Vitamin B12 (Cyanocobalamin)

Description	Vitamin B12 is a water soluble vitamin and a member of the B-vitamins group.
Function/ Used for	Vitamin B12 is essential in the functioning of the nervous and immune systems; red blood cell formation and RNA and DNA synthesis. It is also involved in energy production and works synergistically with vitamin B6 and folic acid in homocysteine (an amino acid) metabolism. It also helps to reduce tiredness and fatigue.
Intake	Recommended intake EU NRV: 2.5µg (micrograms) UK average daily intake Requirements vary depending on age and gender. The UK National Diet and Nutrition Survey lists up-to-date intake requirements and average intakes¹.
As a supplement	Available as a single supplement. Also commonly available as part of a multivitamin and mineral formula. Different multivitamin and minerals products will vary in the percentage NRVs they include. People should always check the label for information about a specific product.
Found in (dietary sources)	Vitamin B12 is found only in animal products and certain foods fortified with the vitamin, therefore, vegans and strict vegetarians are at risk of deficiency. Good sources include meat, liver, kidney, poultry, fish, eggs, dairy products and fortified breakfast cereals.
Deficiency	Deficiency of vitamin B12 leads to enlarged, but fewer red blood cells (megaloblastic anaemia). Other deficiency symptoms include mood changes, sore tongue, fatigue, weakness and lack of concentration.³
Precautions and contraindications	None known. Safe Upper Level: 2000µg/day¹
Use in pregnancy and breastfeeding	There is no evidence of adverse effects in pregnancy with normal intakes.
Interactions e.g. with other medications	Excessive intake of alcohol may reduce the absorption of vitamin B12. Oral contraceptives may reduce blood levels of vitamin B12. Large doses of folic acid given continuously may reduce vitamin B12 in blood or may mask symptoms of megaloblastic anaemia. Vitamin C may destroy vitamin B12 (avoid large doses of vitamin C within one hour of taking oral vitamin B12).^3,4 All B vitamins act synergistically and excess levels of one may lead to imbalance or deficiency in others. It is advisable to take B vitamins as a complex rather than as single substance supplements.
Adverse effects	Vitamin B12 may occasionally cause diarrhoea and itching skin. Megadoses may exacerbate acne.
References	1. https://www.gov.uk/government/collections/national-diet-and-nutrition-survey 2. Expert Group on Vitamins and Minerals, 2003. 3. Mason, P. Dietary Supplements. Pharmaceutical Press, London, 2001. 4. Gaby, A. R. A-Z Guide to Drug-Herb-Vitamin Interactions. HealthNotes 2006.

Page content last reviewed: March 20, 2017

Vitamin B2 (Riboflavin)

Description	Riboflavin is water soluble and part of the B-vitamins group.
Function/ Used for	Riboflavin is essential for the formation of two substances: FAD (flavin adenine dinucleotide) and FMN (flavin mononucleotide). Both are vital for the processes that make energy available in the body. Riboflavin works effectively with iron, vitamin B6 and folic acid. It is important for the nervous system, skin and eye health. It also helps keep red blood cells healthy, protects cells from oxidative stress and helps reduce tiredness and fatigue.
Intake	Recommended intake EU NRV: 1.4mg UK average daily intake Requirements vary depending on age and gender. The UK National Diet and Nutrition Survey lists up-to-date intake requirements and average intakes¹.
As a supplement	Not generally available as a single supplement. Commonly available as part of a multivitamin and mineral formula. Different multivitamin and minerals products will vary in the percentage NRVs they include. People should always check the label for information about a specific product.
Found in (dietary sources)	Liver, kidneys, fortified breakfast cereals, meat, milk, some green vegetables, eggs, cheese, yeast extracts. Riboflavin is degraded by heat and also exposure to light. This is significant with respect to milk, which is a major source of riboflavin (i.e. if milk is exposed to bright sunlight/light for long periods of time).
Deficiency	Trembling, dizziness, poor concentration and memory. Also, blood-shot, red, tired or gritty eyes; Mouth ulcers or sores and cracks at the corner of the mouth; Red, inflamed tongue and lips and scaly eczema-like skin rash.³
Precautions and contraindications	Safe Upper Level: 40mg/day²
Use in pregnancy and breastfeeding	There is no evidence of adverse effects in pregnancy.
Interactions e.g. with other medications	Excessive alcohol intake induces riboflavin deficiency. Prolonged use of oral contraceptives may induce riboflavin deficiency. Deficiency of riboflavin may impair iron metabolism and produce anaemia. Adequate amounts of all B vitamins are required for optimal functioning; deficiency or excess of one B vitamin may lead to abnormalities in the metabolism of another.³
Adverse effects	None known, although large doses may cause a yellow discolouration of the urine.
References	1. https://www.gov.uk/government/collections/national-diet-and-nutrition-survey 2 Expert Group on Vitamins and Minerals, 2003. 3 Mason, P. Dietary Supplements

Page content last reviewed: March 20, 2017

Vitamin B3 (Niacin)

Description	Niacin is water soluble and is part of the B-vitamins group. Vitamin B3 comes in two common forms: Nicotinamide (the active form) and Nicotinic Acid.
Function/ Used for	Niacin is vital for energy release in tissues and cells. It helps form NAD (nicotinamide adenine dinucleotide) and NADP (nicotinamide adenine dinucleotide phosphate), two coenzymes which are involved in the release of energy from food. Niacin helps maintain healthy nervous and digestive systems. It is also essential for normal growth and for healthy skin and contributes to a reduction in tiredness and fatigue.
Intake	Recommended intake EU NRV: 16mg (nicotinamide) Niacin requirements depend on energy intake; values are therefore given as mg/1000 kcal and also as total values based on estimated average energy requirements for the majority of people in the UK. UK average daily intake Requirements vary depending on age and gender. The UK National Diet and Nutrition Survey lists up-to-date intake requirements and average intakes¹.
As a supplement	Not generally available as a single supplement. Commonly available as part of a multivitamin and mineral formula. Different multivitamin and minerals products will vary in the percentage NRVs they include. People should always check the label for information about a specific product.
Found in (dietary sources)	Meat, oily fish, poultry, bread, potatoes and breakfast cereals. Niacin can be synthesised from tryptophan (an essential amino acid).
Deficiency	Niacin deficiency (rare in the UK) may lead to pellagra which means ‘raw skin’. Early signs of deficiency are vague and non-specific and may include loss of appetite, headache, nausea, fatigue, mouth ulcers, dry skin, difficulty sleeping, poor memory and irritability. The severe deficiency state of pellagra is characterised by dermatitis (predominantly in the areas of skin exposed to sunlight), dementia (associated with confusion, disorientation, seizures and hallucinations) and diarrhoea.³
Precautions and contraindications	Large doses of niacin are best avoided in gout (may increase uric acid levels); peptic ulcer (large doses may activate an ulcer); and liver disease (large doses cause deterioration). Large doses should also be used with caution in diabetes mellitus.³ Safe Upper Level: 500mg/day² (nicotinamide); 17mg/day² (nicotinic acid).
Use in pregnancy and breastfeeding	There is no evidence of adverse effects in pregnancy.
Interactions e.g. with other medications	Prolonged use of oral contraceptives may induce niacin deficiency. Adequate amounts of all B vitamins are required for optimal functioning; deficiency or excess of one B vitamin may lead to abnormalities in the metabolism of another.³
Adverse effects	Doses of over 150mg of the nicotinic acid form may cause temporary flushing of the skin in some people.
References	1. https://www.gov.uk/government/collections/national-diet-and-nutrition-survey 2. Expert Group on Vitamins and Minerals, 2003. 3. Mason, P. Dietary Supplements. Pharmaceutical Press, London, 2001.

Page content last reviewed: March 20, 2017

Vitamin B6 (Pyridoxine)

Description	Vitamin B6 is also known as pyridoxine. It is a water soluble vitamin and member of the B-vitamins group.
Function/ Used for	Vitamin B6 is important in the functioning of more than 60 enzymes including those responsible for energy production; protein metabolism; RNA and DNA synthesis and the production of red blood cells and antibodies which fight infections. It also supports healthy skin and is essential for maintaining a healthy nervous system. It may also be helpful in reducing the severity of pre-menstrual syndrome.
Intake	Recommended intake EU NRV: 1.4mg UK average daily intake Requirements vary depending on age and gender. The UK National Diet and Nutrition Survey lists up-to-date intake requirements and average intakes¹.
As a supplement	Available as a single supplement. Also commonly available as part of a multivitamin and mineral formula. Different multivitamin and minerals products will vary in the percentage NRVs they include. People should always check the label for information about a specific product.
Found in (dietary sources)	Wholemeal bread, meat (especially liver and pork), fish, bananas, wheat bran and fortified breakfast cereals.
Deficiency	Vitamin B6 deficiency is unusual. Symptoms include anaemia; cracks in the corners of the mouth; red and inflamed tongue; sensation of burning skin and poor blood sugar balance. Advanced deficiency may produce weakness, irritability, depression, dizziness, peripheral neuropathy and seizures. Diarrhoea, anaemia and seizures are particular characteristics of deficiency in infants and children.²
Precautions and contraindications	Safe Upper Level: 10mg/day³
Use in pregnancy and breastfeeding	There is no evidence of adverse effects in pregnancy with normal intakes.
Interactions e.g. with other medications	Oral contraceptives may increase requirement for vitamin B6.⁴ Deficiency of vitamin B6 may lead to vitamin C deficiency. All B vitamins act synergistically and excess levels of one may lead to imbalance or deficiency in others. It is advisable to take B vitamins as a complex rather than as single substance supplements.
Adverse effects	Adverse effects usually occur with large doses only. Taking more than 200mg a day for a long time can lead to a loss of feeling in the arms and legs (peripheral neuropathy), unsteady gait, numbness and tingling in feet and hands, loss of limb reflexes, impaired or absent tendon reflexes, photosensitivity on exposure to sun, dizziness, nausea, breast tenderness, and exacerbation of acne.²
References	¹ https://www.gov.uk/government/collections/national-diet-and-nutrition-survey ² Mason, P. Dietary Supplements. Pharmaceutical Press, London, 2001. ³ Expert Group on Vitamins and Minerals, 2003. ⁴Gaby A.R. A-Z Guide to Drug-Herb-Vitamin Interactions. Health Notes. Three Rivers Press. New York. 2006

Page content last reviewed: March 20, 2017

Vitamin C (Ascorbic acid)

Description	Vitamin C, also known as ascorbic acid, is a water soluble vitamin.
Function/ Used for	Vitamin C acts as an anti-oxidant, neutralising free radicals to protect cells. Vitamin C is involved in the synthesis of collagen and other constituents of bone, teeth and capillaries. It aids wound healing. It is also necessary for the function of several enzymes and it increases the absorption of iron in the gut. Vitamin C may have a role in protecting against the common cold as well as conditions such as cancer, cardiovascular disease, cataracts, diabetes and Parkinson’s disease. It also helps contribute to normal energy metabolism and nervous system function and reduces tiredness and fatigue.
Intake	Recommended intake EU NRV: 80mg Chief Medical Officer recommendations are that all children aged six months to five years should take a daily supplement containing vitamins A, C and D. UK average daily intake Requirements vary depending on age and gender. The UK National Diet and Nutrition Survey lists up-to-date intake requirements and average intakes¹.
As a supplement	Available as a single supplement. Also commonly available as part of a multivitamin and mineral formula. Different multivitamin and minerals products will vary in the percentage NRVs they include. People should always check the label for information about a specific product.
Found in (dietary sources)	Foods of plant origin, particularly citrus and soft fruits (such as oranges, strawberries, kiwi, blackcurrant, guava) and vegetables (such as kale, broccoli, brussels sprouts, peppers, potatoes, tomatoes) are major sources of vitamin C. Vitamin C is readily lost during storage and cooking.
Deficiency	Vitamin C deficiency may lead to scurvy. Early symptoms in adults include fatigue, weakness, aching joints and muscles. In later stages, symptoms of scurvy include anaemia, swollen and bleeding gums and delayed wound healing. In children, bones, teeth and blood vessels develop abnormally and growth is affected. Low levels of vitamin C have been associated with poor wound healing and ulceration.³
Precautions and contraindications	Vitamin C supplements should be used with caution by people with diabetes and by sufferers of disorders of iron metabolism or storage e.g. haemochromatosis and thalasaemia.³ Safe Upper Level: 1000mg/day²
Use in pregnancy and breastfeeding	Long term intakes of large doses of vitamin C in pregnancy may result in increased requirements for the vitamin and scurvy in the offspring.
Interactions e.g. with other medications	Vitamin C has an impact on how drugs are metabolized in the liver. Large doses of vitamin C may affect how drugs are absorbed and utilized. Prolonged use of oral contraceptives may reduce blood levels of vitamin C. Taking aspirin may lead to increased loss of vitamin C. Vitamin C may reduce the activity of the anti-coagulant warfarin (a blood-thinner). People taking warfarin should consult with their doctor before taking vitamin C supplements.^3,4
Adverse effects	There is no evidence of serious health risks associated with high doses of vitamin C but daily doses over 1g may lead to diarrhoea and gastric discomfort. Doses of 2g and above may result in increased risk of kidney stones.
References	https://www.gov.uk/government/collections/national-diet-and-nutrition-survey Expert Group on Vitamins and Minerals, 2003. Mason, P. Dietary Supplements. Pharmaceutical Press, London, 2001. Gaby, A. R. A-Z Guide to Drug-Herb-Vitamin Interactions. HealthNotes 2006.

Page content last reviewed: March 20, 2017

Vitamin D (Cholecalciferol)

Description	A fat-soluble vitamin.
Function/ Used for	Vitamin D helps the body to absorb and use calcium and phosphorus; which are essential for maintaining strong and healthy bones and teeth, as well as other body functions such as heart and muscle function. Vitamin D is also important for blood clotting, the immune system and muscle growth, development and function.
Intake	Recommended intake EU NRV: 5µg (micrograms) In July 2016 Public Health England published guidelines for vitamin D¹: · Babies from birth to 1 year: 8.5-10µg/day all year round. · Children over 1 year and adults: 10 µg /day in the winter months · Pregnant and breastfeeding women and population groups at risk of vitamin D deficiency (those with minimal exposure to sunshine and those from minority ethnic groups with dark skin): 10 µg /day all year round Chief Medical Officer recommendations are that all children aged six months to five years should take a daily supplement containing vitamins A, C and D. UK average daily intake Requirements vary depending on age and gender. The UK National Diet and Nutrition Survey lists up-to-date intake requirements and average intakes².
As a supplement	Available as a single supplement. Also commonly available as part of a multivitamin and mineral formula. Different multivitamin and minerals products will vary in the percentage NRVs they include. People should always check the label for information about a specific product. In 2018 the UK food supplements industry agreed a voluntary safe upper level of vitamin D for food supplements of 75µg. Read statement
Found in (dietary sources)	Good food sources include full-fat dairy products, oily fish, egg yolks and fortified margarine. Food alone is unlikely to provide sufficient vitamin D. Vitamin D is also formed by the action of sunlight on the skin (from May to September in the UK).
Deficiency	Vitamin D deficiency results in poor growth, bone pain and deformities (rickets in children and osteomalacia in adults), osteoporosis, gum disease, constipation and muscle weakness.⁵
Precautions and contraindications	Vitamin D should be avoided in hypercalcaemia (high levels of calcium in the blood). Safe Upper Level: there are differences of opinion. In 2003 the UK Expert Group on Vitamins and Minerals set a safe upper level of 25µg for vitamin D in food supplements. In 2010 the American Institute of Medicine set a safe upper intake level of 100µg for total vitamin D intake³ In 2012 the European Food Safety Authority set a safe upper intake level of 100µg for total vitamin D intake⁴ In 2018 the UK food supplements industry set a voluntary safe upper level of 75µg for vitamin D in food supplements which allows for dietary intakes of up to 25µg without exceeding the most widely accepted safe upper level.
Use in pregnancy and breastfeeding	There is no evidence of adverse effects in pregnancy at normal intakes.
Interactions e.g. with other medications	Anticonvulsants (used to prevent epileptic seizures) may reduce the effect of vitamin D by accelerating its metabolism. The weight loss drug orlistat and cholesterol-lowering drugs can reduce the absorption of vitamin D and other fat-soluble vitamins (A, E and K). Calcium may increase risk of hypercalcaemia.^5,6
Adverse effects	There is no risk of vitamin D toxicity from prolonged exposure to sunlight. Excessive dietary intake may lead to hypercalcaemia, which can weaken the bones and damage the kidneys and heart.
References	¹ https://www.gov.uk/government/news/phe-publishes-new-advice-on-vitamin-d ² Expert Group on Vitamins and Minerals, 2003. ³ Institutes of Medicine. Dietary reference Intakes for Calcium and Vitamin D. November 2010. ⁴ European Food Safety Authority. Scientific Opinion on the Tolerable Upper Intake Level of Vitamin D. June, 2012 ⁵ Mason, P. Dietary Supplements. Pharmaceutical Press, London, 2001. ⁶ Gaby, A. R. A-Z Guide to Drug-Herb-Vitamin Interactions. HealthNotes 2006.

Page content last reviewed: March 20, 2017

Vitamin E (Tocopherol)

Description	Vitamin E is a family of fat soluble vitamin substances which include both tocopherols and tocotrienols.
Function/ Used for	Vitamin E acts as an antioxidant helping to neutralise potentially damaging free radicals in the body. Vitamin E is particularly important for the protection of cell membranes as well as maintaining healthy skin, heart and circulation, nerves, muscles and red blood cells.
Intake	Recommended intake EU NRV: 12mg UK average daily intake Requirements vary depending on age and gender. The UK National Diet and Nutrition Survey lists up-to-date intake requirements and average intakes¹.
As a supplement	Available as a single supplement. Also commonly available as part of a multivitamin and mineral formula. Different multivitamin and minerals products will vary in the percentage NRVs they include. People should always check the label for information about a specific product.
Found in (dietary sources)	Seed oils, and the outer germ of cereals are the richest sources of vitamin E as well as olive oil, avocado pear, muesli, nuts, leafy green vegetables, wholemeal bread, cereals and egg yolks. Vitamin E is not very stable and is readily lost during storage and cooking, particularly if there is significant exposure to heat and oxygen.
Deficiency	None known.
Precautions and contraindications	Vitamin E supplements should be avoided by patients taking oral anticoagulants and by patients with iron deficiency anaemia and hyperthyroidism. Safe Upper Level: 540mg/day²
Use in pregnancy and breastfeeding	There is no evidence of adverse effects in pregnancy at normal intakes.
Interactions e.g. with other medications	Prolonged use of oral contraceptives may reduce blood levels of vitamin E. The weight loss drug orlistat and cholesterol-lowering drugs can reduce the absorption of vitamin E and other fat-soluble vitamins (A, D and K). Vitamin E supplements may affect blood coagulation and should be avoided by patients taking oral anticoagulants such as warfarin (blood thinners).³
Adverse effects	Vitamin E is relatively non-toxic. Large doses in excess of 1000mg daily for prolonged periods have occasionally been associated with increased bleeding tendency in vitamin K-deficient patients; and rarely, blurred vision, diarrhoea, dizziness, fatigue and weakness, headache and nausea.³
References	1. https://www.gov.uk/government/collections/national-diet-and-nutrition-survey 2. Expert Group on Vitamins and Minerals, 2003. 3. Mason, P. Dietary Supplements. Pharmaceutical Press, London, 2001. 4. Gaby, A. R. A-Z Guide to Drug-Herb-Vitamin Interactions. HealthNotes 2006.

Page content last reviewed: March 20, 2017

Vitamin K (Phytomenadione)

Description	Vitamin K is a fat-soluble vitamin.
Function/ Used for	Vitamin K is required for the formation of several of the proteins, called ‘clotting factors’ that regulate blood clotting, which means it helps heal wounds. Vitamin K is also required for the formation of some proteins which are important for the maintenance of healthy bones and teeth
Intake	Recommended intake EU NRV: 75µg UK average daily intake UK dietary intake is unknown.
As a supplement	Commonly available as a single supplement. Different multivitamin and minerals products will vary in the percentage NRVs they include. People should always check the label for information about a specific product.
Found in (dietary sources)	Green vegetables such as kale and spinach, potatoes, liver, soya beans and vegetable oils. Vitamin K is also synthesised by gut bacteria and this contributes significantly towards the daily requirement of the vitamin.
Deficiency	None known.
Precautions and contraindications	Safe Upper Level: 1000µg/day¹
Use in pregnancy and breastfeeding	There is no evidence of adverse effects in pregnancy at normal intakes. New-born infants are routinely given vitamin K injections or supplements.
Interactions e.g. with other medications	Those taking anti-coagulants (such as warfarin) should not take supplements containing over 100mg Vitamin K except on the advice of a doctor. Antibiotics can destroy vitamin K producing bacteria in the gut and may increase requirements for vitamin K. The weight-loss drug orlistat and cholesterol-reducing drugs may reduce the absorption of vitamin K and other fat-soluble vitamins (A, D, E)^2,3
Adverse effects	None known.
References	1. Expert Group on Vitamins and Minerals, 2003. 2. Mason, P. Dietary Supplements. Pharmaceutical Press, London, 2001. 3. Gaby, A. R. A-Z Guide to Drug-Herb-Vitamin Interactions. HealthNotes 2006.

Page content last reviewed: March 20, 2017