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Too much of a good thing? Supplement cautions.

ClaireB_VegWe are all aware that we’re eating too much sugar, saturates and salt as a nation – but how are we doing on the vitamins and minerals front? Should we take a supplement? Can you have too much of a seemingly good thing?  Read on to sort the myths from the sensible advice.

Many product labels display claims that they provide a source of various vitamins and minerals and that these can benefit health.  For example, foods providing a source of calcium can support bone and muscle health; foods rich in iron can help maintain the function of the immune system or help prevent fatigue.  These claims are regulated and food and supplement manufacturers are not permitted to make misleading statements.  However, as a nation are we truly deficient in certain nutrients or are those taking supplements or eating fortified foods simply the worried well?

Every year the National Diet and Nutrition Survey analyses the diet of a thousand people in the UK aged 18 months and upwards.  Headline findings of the last report, published in 2015 showed that for the most part, we obtain sufficient vitamins and minerals from our diet, with the exception of vitamin D (for some adults and children, particularly in winter) and iron (in women under 50 and teenage girls).  Some children and adults were also low in vitamin B2 (riboflavin).

Should everyone be taking a multivitamin and mineral supplement?  Surely it can’t hurt and is just a safety net for times when we don’t eat as well as we should?  Here’s why supplements can never replace a varied, balanced diet and in some cases might be harmful:

  • Not all supplements are eliminated from the body if too much is taken. For example, high doses of vitamin A can build up over time and weaken bones, increasing the risk of fractures in later life.  It can also cause damage to unborn babies if taken in excess during pregnancy.
  • Certain nutrients can affect the absorption of others. For example, calcium can reduce iron absorption (taking iron with tea, coffee or wholegrain foods does the same thing) so it’s best to avoid taking the 2 minerals together. Instead take iron with a source of vitamin C (which helps the body to absorb this mineral) and take calcium separately, ideally with a source of vitamin D – see, it’s getting complicated already!
  • Some herbal supplements can interfere with prescription medicines: ginkgo biloba can interact with medications that slow blood clotting, like Warfarin and may cause bruising and bleeding; St John’s wort can reduce the effectiveness of some anti-depressant medications.
  • Some supplements have been found to INCREASE the risk of some diseases in clinical trials. For example, while foods containing beta-carotene (such as carrots) are linked to a reduced risk of lung cancer, taking beta-carotene supplements appears to slightly increase the risk of lung cancer in smokers.


What’s the best approach?  There is no contest between a healthy, varied diet without supplements and an unhealthy one that includes supplements.  There are nutrients in foods that may have as yet unidentified benefits and overdosing on a vitamin or mineral from food is highly unlikely compared with taking a supplement.  Furthermore, a diet based upon natural, minimally processed whole foods is far more enjoyable than a lifetime of pills and powders!  The only exception is vitamin D, which has few dietary sources and is made in the body when the skin is exposed to sunlight in the summer months.  A supplement may be necessary for those individuals who don’t get enough sun.  Other than this, most people should be able to get everything they need from a varied and balanced diet.

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