Vitamins and minerals: functions, benefits and doses

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Vitamins and minerals are important for a healthy lifestyle. Find out about what they do in your body.

Medically reviewed by Dr Juliet McGrattan (MBChB) and based on a text by Dr Carl J Brandt

This vitamin and mineral guide’s recommended daily amount (RDA) is based on EU guidance that is used for nutrition tables on food products.

Nutritional requirements are often slightly different for young children, adolescents, and during pregnancy and breastfeeding.

Ask your doctor or pharmacist if you are concerned about your vitamin intake.

Micro vs milli: Check the letters after the RDA carefully. One microgram (mcg or µg) is a thousand times smaller than a milligram (mg).

Vitamin A

Vitamin A is good for:

  • eyesight
  • growth
  • immunity

Good sources for vitamin A

Vitamin A is found in many types of food.

Good sources include:

  • liver
  • fish liver oils
  • carrots
  • green leafy vegetables
  • egg yolks
  • enriched low fat spreads
  • milk products
  • yellow fruits

How much vitamin A do I need?

The RDA of vitamin A in adults is:

  • men: 700μg
  • women: 600μg

Vitamin A deficiency signs

One of the man signs of vitamin A deficiency is night-blindness.

What happens if I take too much vitamin A?

Vitamin A is fat-soluble and so is stored in the body for a long time, especially in pregnancy. An overdose may be dangerous.

What destroys vitamin A?

Vitamin A may be destroyed by high temperatures.

Vitamin B1 (thiamine)

Thiamine is good for:

  • nervous system
  • digestion
  • muscles
  • heart
  • alcohol-damaged nerve tissues

Good sources for thiamine

Good sources of thiamine include:

  • liver
  • yeast
  • egg yolk
  • cereal
  • red meat
  • nuts
  • wheatgerm

How much thiamine do I need?

The RDA of thiamine in adults is:

  • men: 1mg
  • women: 0.8mg

Thiamine deficiency signs

The following may be signs of thiamine deficiency:

What happens if I take too much thiamine?

Unknown danger. It dissolves in water, so any excess is generally passed in urine.

What destroys thiamine?

High temperatures, alcohol and coffee.

Vitamin B2 (riboflavin)

Riboflavin is good for:

  • growth
  • skin
  • nails
  • hair
  • eyesight
  • the breakdown of protein, fat and carbohydrates

Good sources for riboflavin

Good sources of riboflavin include:

  • milk
  • yeast
  • cheese
  • green leafy vegetables
  • fish

How much riboflavin do I need?

The RDA of riboflavin in adults is:

  • men: 1.3mg
  • women: 1.1mg

Riboflavin deficiency signs

The following may be signs of riboflavin deficiency:

  • itchy irritated eyes
  • itchy mucous membranes (nose, mouth, throat)
  • cracked corners of lips

What happens if I take too much riboflavin?

Unknown danger. It dissolves in water, so any excess is generally passed in urine.

What destroys riboflavin?

Alcohol and light (this is why milk-cartons are better than bottles).

Vitamin B6 (pyridoxine)

Vitamin B6, also known as pyridoxine, is good for:

  • making red blood cells
  • preventing skin conditions
  • nerve problems
  • helps the body absorb protein and carbohydrate

Good sources for vitamin B6

Vitamin B6 is found in a variety of foods, including:

  • fish
  • bananas
  • chicken
  • pork
  • wholegrains
  • eggs
  • dried beans

How much vitamin B6 do I need?

The RDA of vitamin B6 in adults is:

  • men: 1.4mg
  • women: 1.2mg

Vitamin B6 deficiency signs

The following may be signs of vitamin B6 deficiency:

  • skin inflammation
  • confusion
  • anaemia

What happens if I take too much vitamin B6?

May cause nerve problems in large doses. Evidence is conflicting about the maximum safe dose, so get medical advice before exceeding the RDA.

What destroys vitamin B6?

Cooking, alcohol and oestrogen (the female hormone).

Vitamin B12 (cobalamin)

Vitamin B12 is good for:

  • making red blood
  • the formation of the nerves

Good sources for vitamin B12

Vitamin B12 is found in a variety of foods, including:

  • eggs
  • shellfish
  • poultry
  • meat
  • fish
  • milk
  • cheese
  • fortified cereal

How much vitamin B12 do I need?

The RDA of vitamin B12 in adults is:

  • 1.5μg

Vitamin B12 deficiency signs

The following may be signs of vitamin B12 deficiency:

  • tiredness and fatigue
  • tingling and numbness in hands/feet
  • smooth tongue
  • memory problems
  • anaemia

What happens if I take too much vitamin B12?

Unknown danger. It dissolves in water, so any excess is generally passed in urine.

What destroys vitamin B12?

Water, sunlight and alcohol.

Vitamin C (ascorbic acid)

Vitamin C is good for:

  • immune defence system
  • protection from viruses and bacteria
  • healing wounds
  • reducing cholesterol
  • cell lifespan
  • preventing scurvy

Good sources of vitamin C

Good sources of vitamin C include:

  • citrus fruits
  • kiwi fruit
  • berries
  • tomatoes
  • cauliflower
  • potatoes
  • green leafy vegetables
  • peppers

How much vitamin C do I need?

The RDA of vitamin C in adults is:

  • 40mg

Vitamin C deficiency signs

The following may be signs of vitamin C deficiency:

  • tiredness
  • bleeding gums
  • slow-healing wounds

What happens if I take too much vitamin C?

Large doses can cause diarrhoea and nausea, eg 2g/day . Some scientists have argued that 1000-5000mg per day may damage your DNA.

What destroys vitamin C?

Boiling food, light, smoking and heat.

Vitamin D

Coronavirus update: the NHS recommends considering taking 10µg of vitamin D a day to keep your bones and muscles healthy. This is because you may not be getting enough vitamin D from sunlight if you are indoors all day during lockdown.

Vitamin D is good for:

  • strong bones, muscles and teeth

Good sources of vitamin D

Good sources of vitamin D include:

  • sunlight (sunlight on the skin allows our bodies to make vitamin D)
  • cod liver oil
  • sardines
  • herring
  • salmon
  • tuna
  • eggs
  • milk
  • milk products

How much vitamin D do I need?

The RDA of vitamin D in adults is:

  • 10μg

Vitamin D deficiency signs

The following may be signs of vitamin D deficiency:

  • unhealthy teeth
  • osteomalacia (causes weakening of bones)
  • rickets in children

What happens if I take too much vitamin D?

This vitamin is fat-soluble so can accumulate in the body. Overdoses are dangerous, but there is wide variability in the toxic level especially for children.

What destroys vitamin D?

Slightly sensitive to light.

Vitamin E (tocopherol)

Vitamin E is good for:

  • skin, eyes and fighting toxins – vitamin E is a powerful antioxidant.

Good sources of vitamin E

Vitamin E is found in a range of foods, including:

  • nuts
  • soya beans
  • vegetable oil
  • broccoli
  • sprouts
  • spinach
  • wholemeal products
  • eggs

How much vitamin E do I need?

The RDA of vitamin E in adults is:

  • men: 4mg
  • women: 3mg

Vitamin E deficiency signs

The following may be signs of vitamin E deficiency:

  • nerve and muscle damage including weak muscles and visual problems

What happens if I take too much vitamin E?

Potential effect with warfarin increasing risk of bleeding. Excessive intake may increase risk of heart failure and death in long term illness.

What destroys vitamin E?

Vitamin E is very stable. It is not known to be significantly destroyed by freezing or cooking.

Folic acid

Folic acid is good for:

  • production of red blood cells
  • essential in the first three months of pregnancy to prevent birth defects such as spina bifida and potentially, cleft palate or cleft lip

Good sources of folic acid

Folic acid is found in a range of foods, including:

  • carrots
  • yeast
  • liver (don’t eat during pregnancy)
  • egg
  • yolks
  • melon
  • apricots
  • pumpkin
  • avocado
  • beans
  • rye
  • wholewheat
  • green leafy vegetables

How much folic acid do I need?

The RDA of folic acid in adults is:

  • 200µg
  • Women planning to conceive should take a daily supplement of 400mcg, continued for the first 12 weeks of pregnancy.

Folic acid deficiency signs

The following may be signs of folic acid deficiency:

  • tiredness due to anaemia
  • red tongue

What happens if I take too much folic acid?

High doses may hide the symptoms of B12 deficiency and cause nervous system damage, more common in the elderly.

What destroys folic acid?

Water, sunlight and heat.

Calcium

Calcium is good for:

  • strong bones and teeth
  • nerve function
  • muscle contraction
  • blood clotting

Good sources of calcium

Good sources of calcium include:

  • milk
  • cheese
  • butter
  • yoghurt
  • nuts
  • green leafy vegetables

How much calcium do I need?

The RDA of calcium in adults is:

  • 700mg

Calcium deficiency signs

The following may be signs of calcium deficiency:

  • poor teeth
  • brittle bones

What happens if I take too much calcium?

High doses can lead to headaches, stomach pain, high blood pressure and diarrhoea. Excess calcium can be deposited as kidney and gall bladder stones. It has been linked to an increased risk for heart attack in recent research.

Iron

Iron is good for:

  • red blood cells and muscle function
  • white blood cells
  • immune system

Good sources of iron

Good sources of iron include:

  • lean red meat
  • oily fish
  • egg yolks
  • green leafy vegetables
  • nuts
  • wholegrains
  • wholewheat

How much iron do I need?

The RDA of iron in adults is:

  • men: 8.7mg
  • women: 14.8mg
  • women over 50: 8.7mg

Iron deficiency signs

The following may be signs of iron deficiency:

  • tiredness
  • irritability
  • difficulties concentrating

What happens if I take too much iron?

Iron is stored in the body and high doses (over 17mg) can lead to constipation, vomiting, nausea and diarrhoea. Very high doses can be fatal.

Magnesium

Magnesium is good for:

  • converting energy from food
  • cell repair
  • building strong bones
  • teeth and muscles
  • regulating body temperature

Good sources of magnesium

Magnesium is found in a range of foods, including:

  • green leafy vegetables
  • wholegrains
  • nuts

How much magnesium do I need?

The RDA of magnesium in adults is:

  • men: 300mg
  • women: 270mg

Magnesium deficiency signs

The following may be signs of magnesium deficiency:

  • muscle spasms
  • also associated with heart disease, diabetes, high blood pressure and weak bones

What happens if I take too much magnesium?

High doses can cause diarrhoea, other effects are unknown.

Zinc

Zinc is good for:

  • immune system
  • the breakdown of protein, fat and carbohydrate
  • wound healing

Good sources of zinc

Zinc is found in a range of foods, including:

  • meat
  • shellfish
  • milk
  • brown rice
  • wholegrains

How much zinc do I need?

The RDA of zinc in adults is:

  • men: 9.5mg
  • women: 7.0mg

Zinc deficiency signs

The following may be signs of zinc deficiency:

  • lesions on skin, eyes and in throat
  • loss of taste and smell
  • hair loss
  • diarrhoea
  • slow healing of wounds
  • growth problems in children

What happens if I take too much zinc?

High doses can lead to stomach cramps, nausea and vomiting. High levels of zinc can reduce the amount of copper the body absorbs.

Medical Xpress

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