Do you need supplements? Some food for thought.


Vitamins, minerals and trace elements are essential nutrients that your body needs in small amounts. The actual amounts you need vary. This will depend on your age, the amount of physical activity you take, your medical history, gender and for women whether you are pregnant or breast-feeding. Do you need supplements? Here is some food for thought for healthy adults.

Many clients come to me with questions about vitamins, minerals and trace elements and whether they need supplements. Some even come with bags full of all the different supplements they take. Nutritional supplements are not regulated in the same way as medicines so you cannot assume that it is safe to take whatever you find on sale. Most healthy adults who are not planning a pregnancy, pregnant or breastfeeding do not need to take any supplements at all, with one exception.

The exception to the rule

Current advice in the UK is that we should all consider taking a 10 microgram supplement of vitamin D each day. This is because we don’t make enough from the effect of sunlight on our skin in our dull and cloudy part of the world and it’s hard to get enough from our diets.

Risks of supplements

Other supplements may just be making your urine more expensive. This is because our kidneys just flush out small excesses of vitamins and minerals. Worse still supplements can cause unpleasant symptoms and can even be harmful for health. Furthermore an excess of one nutrient can stop your body absorbing enough of another. This means that supplements can upset the body’s natural balance.


There are two main groups of vitamins:

Fat-soluble vitamins – A, D, E and K are found mainly in oils, dairy foods, eggs, liver, oily fish and butter. You don’t need to eat foods containing fat-soluble vitamins everyday because your body stores them. This is useful because you can draw on these stores when you need them. However if you consume more than you can store then fat-soluble vitamins can be harmful.

Pregnant women should not take supplements containing vitamin A as too much can harm the developing foetus.

Water-soluble vitamins –  C, the B group and folic acid are not stored in the body, so you need to have them more frequently. They are found in a wide range of foods including fruits, vegetables, grains and dairy foods.

Pregnant women (up to 12 weeks) and women who are trying to conceive should take folic acid as a supplement daily to reduce the risk of neural tube defects such as spina bifida. For most women, the dose is 400 micrograms (0.4 mg) a day. If you have a higher risk of having a child with a spinal cord problem then the dose is 5 mg a day. You need a prescription for this higher dose. Talk to your doctor if you:

  1. Have a spinal cord defect,
  2. Have had a previously affected pregnancy,
  3. Or your partner have a family history of spinal cord defects
  4. Have a body mass index over 30
  5. Are taking medication for epilepsy
  6. Have diabetes, coeliac disease, sickle cell anaemia or thalassemia.

Very large doses of water-soluble vitamins can be harmful but generally if you have too much your kidneys will just flush out the excess.

Water-soluble vitamins are destroyed by heat and exposure to air and they can be lost in cooking water. To conserve as much as possible:

  • Eat them whole and raw or
  • Chop them into large chunks rather than small pieces before cooking/eating.
  • Steam, grill or microwave rather than boiling and
  • Use cooking water to make gravy, soup and sauces.

What about vitamin C and colds?

Thorough reviews of the research evidence have concluded that there is little evidence that vitamin C supplementation is beneficial in terms of preventing infection. However high doses of vitamin C (1g per day or more) seem to reduce the duration of colds. Sadly the difference is marginal (an 8% reduction in adults and 13% in children.) Given that the average cold lasts about a week that’s a reduction of about half a day for adults and just under a day for children.

Large doses of vitamin C may cause nausea, diarrhoea and stomach cramps so given the small potential benefit you may decide that supplementation is not worth the risk.


Calcium, iron and fluoride are minerals that clients frequently ask about.

Calcium is essential for healthy bones and teeth, ensuring normal blood clotting and regulating muscle contraction including your heart muscle. Most people get all the calcium they need from their diet. Good sources of calcium include:

  • Milk, cheese and other dairy foods
  • Green leafy vegetables – but not spinach because it contains other chemicals that reduce its availability
  • Soya beans
  • Calcium set tofu
  • Soya products with added calcium
  • Nuts
  • Bread or other baked products made with calcium fortified flour
  • Fish such as sardines and pilchards if you eat the bones

Iron helps make red blood cells, which transport oxygen around the body. Again most people will get everything they need from a balanced diet. Good dietary sources include

  • Liver (don’t eat this if you are pregnant as it contains a lot of vitamin A, which may harm the developing baby.)
  • Meat
  • Beans and pulses eg kidney beans, chick peas, lentils etc
  • Nuts
  • Dried fruit
  • Wholegrains
  • Fortified breakfast cereals
  • Soybean flour
  • Most dark-green leafy vegetables

If you rely on plant sources for iron then you should have foods high in vitamin C at the same time to increase absorption. Something as simple as a small glass of fruit juice or an orange is perfectly adequate.

Fluoride is a naturally occurring mineral found in water in varying amounts, depending on where you live. It can help to prevent tooth decay, which is why it’s added to toothpaste, mouthwash and, in some areas, to the water supply. Scientific reviews have shown that fluoridation of water is safe and helpful in reducing tooth decay. Even if you water locally is not fluoridated natural levels of fluoride may be high enough. Taking dietary supplements is not recommended due to the risk of dental fluorosis. This can be seen as very fine pearly white lines or flecking on the surface of the teeth. Severe fluorosis can cause the tooth’s enamel to become pitted or discoloured.

Sulphur, magnesium, phosphorous, potassium and silicon are other minerals essential for health. A varied diet will provide enough of them all. Sodium and Chloride are also minerals that are essential for health. Together as sodium chloride they form salt. Salt is essential for health in very small amounts to keep our fluid levels balanced. However most of us have too much salt in our diets. This is associated with raised blood pressure, heart disease and stroke. You should have no more than 6g salt/day. Fizzy vitamin supplements or painkillers can contain up to a gram of salt per tablet so these are best avoided. To keep your salt intake down:

  • Check food labels and look for foods with 0.3g salt/100g or less
  • If you use tinned vegetables and pulses look for varieties with no added salt
  • Limit your use of soy sauce, brown sauce, ketchup and mayonnaise and choose reduced salt versions where possible
  • Have unsalted nuts and fruit instead of salty snacks like crisps, salted nuts and savoury biscuits
  • Think about your intake of salty foods such as bacon, cheese, pickles and smoked fish and cut back if you have these foods frequently or in large amounts
  • Avoid adding salt when cooking or at the table – there are plenty of healthy ways to add flavor such as using herbs and spices
  • Choose low-salt stock cubes, or make your own stock without adding salt

Trace elements

These are needed for health but only in really tiny amounts. Iodine and zinc are the trace elements I am asked about most often.

Iodine helps to make thyroid hormones, which are essential for regulating our metabolism. Good food sources include sea fish and shellfish. Iodine is also found in plant foods, such as cereals and grains, but the levels vary, depending on the amount of iodine in the soil where the plants are grown. You should be able to get what you need from your diet. Taking supplements can be dangerous as large doses of iodine taken over a long period can affect your thyroid gland and metabolism causing weight gain. If you are worried about your iodine intake check with your Dietitian.

Zinc helps us process foods that provide us with energy. It is also essential for making new cells and enzymes and for healing wounds Good food sources of zinc include:

  • Meat
  • Shellfish
  • Dairy foods
  • Bread
  • Wheat germ

We can get all the zinc we need from our diets and high doses such as the amounts you might get from supplements can reduce the amount of copper and iron we absorb leading to deficiencies of these nutrients.

But what about zinc for preventing colds?

A recent review found that taking zinc lozenges or syrup within 24 hours of cold symptoms starting reduced the duration of a cold by about a day. The severity of the symptoms also seemed to be reduced. The same review also showed that people who took zinc supplements for at least five months were protected against catching colds. It’s hard to say what dose you should take because the studies included in the review looked at different populations using different doses for different durations. Whether or not you take zinc over the winter months to protect you from colds is a personal choice. If you do decide to give it a try then use a supplement that contains no more than the “recommended daily allowance” and check that it also contains copper and iron to help reduce the risk of these nutrients becoming deficient.

Boron, chromium, cobalt, copper, manganese, molybdenum, nickel and selenium are also essential trace elements. These are required in very tiny amounts and our diets provide more than enough.

A word about antioxidants

Antioxidants can prevent or delay cell damage and so there has been significant interest in their benefits for health. Antioxidants can be obtained from the diet particularly from eating a wide variety of grains and fruits and vegetables from all the colours of the rainbow. Examples of antioxidants include:

  • Beta-carotene (gives foods their yellow/orange colour and is converted by the body into vitamin A)
  • Lutein
  • Lycopene
  • Zeaxanthin
  • Selenium
  • Retinol (vitamin A)
  • Vitamin C
  • Vitamin E

Antioxidant supplements appear to have no beneficial effects on chronic disease prevention in the general population and have limited effects on disease progression. Furthermore evidence from some clinical trials suggests that beta-carotene, vitamin A and vitamin E either alone or in combination may increase risk of cancer and death. Therefore the use of the antioxidant supplements is not recommended. Antioxidants in foods have not been shown to have any harmful effects and may be beneficial. The advice based on current science is to eat a varied diet and in particular to have 5 or more portions of different coloured fruit/vegetables every day.

Take home message

Most healthy adults can get all the vitamins, minerals and trace elements they need from a varied and balanced diet without the need for the additional expense of supplements. If you are concerned that your diet is not varied enough for whatever reason or if you need advice about a specific medical condition make an appointment with a Dietitian. See the link below for more information about my services.

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