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There are thousands of vitamin supplements on the market. Many promote themselves as wonder pills that can cure tiredness, boost your brain and enhance your immune system.
Manufacturers are able to make these claims with very little hard scientific evidence because they qualify as ‘food products’ rather than medicines — making it difficult for the average person to discern what is true.
A study earlier this year found vitamins and mineral supplements give such little benefit to the vast majority, making them a waste of money for healthy people. Researchers said most people get almost all of the nutrients they need from a healthy and balanced diet.
However, that doesn’t mean they are all snake oil.
For example, there is a wealth of evidence that taking vitamins maintains good health and may even slash your risk of some illnesses. And for people with deficiencies, the supplements can be life changing.
Health chiefs advise everyone to take certain tablets, while some groups need to take vitamins in specific doses and at different points of life — such as during the menopause.
Everyone in the UK is advised to take supplements of the so-called ‘sunshine vitamin’ daily for half of the year, while vegetarians and vegans may need daily doses of vital minerals missing from their diets.
MailOnline’s handy guide sets out what vitamins and minerals you may need and when:
Vitamin D
How much do I need? 10 micrograms per day
Who should take the supplement? Everyone
When should it be taken? October to April
Most Britons get enough of the ‘sunshine vitamin’ from April to September, as the weather improves and more time is spent outdoors. When the sun hits the skin, it triggers a chemical reaction that creates vitamin D.
But as the days get shorter, the weather gets colder and people cover up when they’re outside, Britons need to consume vitamin D in other ways.
The vitamin is essential for regulating calcium and phosphate in the body, which are needed to keep bones, teeth and muscles healthy. Not getting enough raises the risk of rickets (soft bones) in children and bone pain in adults.
Oily fish, red meat and egg yolks are rich sources. But medics say nearly a fifth of adults don’t get enough vitamin D and note that it is difficult to consume it in sufficient amounts through food.
Instead, they recommend taking supplements, which cost around 3p per pill.
While all Britons are told to take vitamin D in the colder months, some groups should take a daily tablet all-year round, including breastfed babies, children aged one to four and those who are not exposed to sunlight — such as those who are bed bound or live in a care home.
All groups are advised to take 10 micrograms of vitamin D. Consistently exceeding this amount can cause too much calcium to build up in the bones, which can damage the heart and kidneys.
The health service last month issued a fresh warning over overdosing on vitamins, after a middle-aged man on a health kick was hospitalised after his kidneys stopped working.
He was taking 375-times more vitamin D than recommended, along with a too high dose of 19 other over-the-counter supplements.
But a swath of studies suggest set out that those taking the correct dose can reap health benefits.
Research published in the British Medical Journal earlier this year set out that those who took daily vitamin D supplements were a fifth less likely to suffer from an autoimmune disease, such as arthritis and psoriasis.
And a team at the University of South Australia Cancer Research Institute this month found had sufficient vitamin D levels were less likely to suffer diabetes and heart disease.
However, other studies have found no sign that vitamin D supplements prevent poor health.
Iron
How much do I need? 8.7 micrograms per day for adult men and women over 50; 14.8 micrograms for women aged 19 to 50
Who should take the supplement? Women with heavy periods and some vegetarians and vegans
When should it be taken? Daily among those who need them
Iron produces haemoglobin — an essential ingredient in red blood cells, which carry oxygen from the lungs around the body.
Liver, red meat, beans, nuts and dried fruit are good sources and most people get enough iron through their diet.
But those who don’t are at risk of developing anaemia, where the body is not producing enough red blood cells to carry oxygen around the body. Breathlessness, feeling tired and a lack of energy are the main symptoms.
Those with heavy periods lose more iron than the average woman, so may need to take a supplement.
And dozens of studies have shown that there are higher rates of anaemia among those following a plant-based diet, compared to those who eat meat. One showed that a third of vegetarians were iron deficient, compared to no one who ate meat.
Meanwhile, other research has found that three-weeks of iron tablets can slash tiredness by 50 per cent.
But people should check with their doctor before turning to a supplement.
Dr Duane Mellor, a dietitian at Aston Medical School in Birmingham, told MailOnline: ‘Generally, unless someone has been diagnosed with iron deficiency anaemia or has a specific medical condition iron supplements are not generally recommended.’
Those who already get enough of the mineral are at risk of over-dosing. Consuming more than 20μg of iron per day can cause constipation, nausea and can even be fatal. But taking a supplement that has 17μg of iron or less per day is unlikely to cause harm, experts say.
Those advised to take the supplements, which cost around 5p per pill, should take them an hour before eating, as food stops as much from being absorbed in the gut.
Vitamin B12
How much do I need? 1.5 micrograms per day
Who should take a supplement? Vegetarians and vegans
When should it be taken? Daily among those who need it
Vitamin B12 is essential for making red blood cells, keeping the nervous system healthy and reduces tiredness.
Meat, fish, milk, cheese and eggs are good sources. So those who eat these animal products should easily get enough — 1.5μg per day — of this vitamin from their diet.
But it is not naturally found in plant-based food, such as fruit, vegetables and grains — although some products are fortified with the vitamin, such as cereal.
Those who don’t get enough may suffer from severe tiredness, low energy, breathlessness, feeling faint and headaches.
Dr Mellor said some evidence suggests that those following a plant-based diet should consider taking B12 supplements, which cost 5p per tablet.
He added: ‘It is important to note, for most people supplements of other vitamins and minerals are not necessary and it is better to eat a varied diet based on vegetables, fruit and wholegrain with some meat and dairy (or alternatives).’
There’s not enough research into the effects of taking high doses of vitamin B12, so it is unclear whether people can have too much.
Calcium
How much do I need? 700 micrograms per day
Who should take a supplement? Some oesteoporosis and coeliac disease sufferers, breastfeeding mothers and post-menopausal women — but talk to your doctor first
When should it be taken? Daily among those who need it
Calcium is vital for healthy bones, teeth and muscles. The body then stores almost all of its calcium supply in the bones, with the rest being spread between the blood, muscle and tissue.
Dairy products, such as milk, yoghurt and cheese, are rich in the mineral.
Green leafy vegetables, such as kale, products made with fortified flour, including some bread, and fish where the bones are eaten, such as sardines and pilchards, are also good sources of calcium.
As with other vitamins, most adults should get enough calcium from their diet. But those who consistently don’t meet the 700μg daily target may be advised to take a supplement, which cost 3p per tablet.
Studies have shown that calcium supplements can boost bone mineral density and may reduce the risk of risk of fracture.
Those following a dairy-free diet, have osteoporosis or coeliac disease are most at risk of a calcium deficiency, as are women who are breastfeeding or have gone through menopause, so may be told to take a calcium supplement by their doctor.
Women going through the menopause are also at risk of osteoporosis, caused by lower levels of oestrogen, so may be encouraged to take calcium, as well as vitamin D.
Not getting enough calcium increases the risk of osteoporosis (weak bones), rickets (soft bones) and breaking a bone from a fall.
Those who have too much — more than 1,500μg per day — may suffer stomach pain and diarrhoea. But those taking a supplement of 1,500μg or less per day are unlikely to do any harm, experts say.
Folic acid
How much do I need? 200 micrograms per day
Who should take a supplement? Women trying to get pregnant and expectant mothers in the first trimester
When should it be taken? Between once a day and once a week — depending on doctor recommendations
Also known as folate and vitamin B9, folic acid is a vitamin found in small amounts of a variety of food, including broccoli, leafy green vegetables and chickpeas.
It helps the body make healthy red blood cells and is important to maintain an unborn baby’s health — helping its brain, skull and spinal cord develop properly in pregnancy. Studies have shown the vitamin reduces the risk of spina bifida and premature birth.
Women are advised to take a 400 microgram folic acid supplement daily for three months before they begin trying for a baby and during the first three months of pregnancy.
Folic acid supplements are also used to prevent and treat folate-deficiency anaemia, which can be caused by not eating enough folate-rich foods, drinking too much alcohol, celiac disease, cancer and pregnancy.
Health chiefs say the supplements are safe and taking too much is unlikely to cause any harm.
Iodine
How much do I need? 140 micrograms per day
Who should take a supplement? Some vegetarians, vegans and those who do not eat fish
When should it be taken? Daily for those who need it
Iodine helps make thyroid hormones. These keep cells and the metabolic rate — the speed at which chemical reactions take place in the body — healthy.
Milk, eggs and other dairy products, along with fish and shellfish contain plenty iodine. The mineral may also be found in cereals and grains but the amount depends on where the plants are grown.
As with most other minerals, most people should be able to get all the iodine they need from their diet. But those following a strict vegan diet and do not eat fish, eggs or dairy should consider iodine supplements, the NHS says.
Not getting enough can lead the thyroid to increase in size, which will make the neck look swollen. And those with an iodine deficiency during pregnancy may have a child with a low IQ or reading ability. Studies have shown the supplement boost children’s brain development.
However, taking too much can change the way the thyroid gland works, which can lead to weight gain.