In most cases, taking too many vitamins is simply a waste of time and money. Many vitamins are water-soluble, so your body excretes any excess once it’s taken what it needs. Meaning all the money you spent on then ends up in the loo.
But sometimes overdosing on vitamins – even water-soluble ones - can lead to problems. Taking too much Vitamin C, for example (over 1000mg), can lead to stomach pain and wind, while too many B Vitamins could lead to a rash and in some cases they could interfere with prescription medicines.
You need to take special care with vitamins that are fat soluble because your body has a harder time getting rid of the excess. Vitamins A, D, E and K are all fat-soluble. In rare cases, excess levels of Vitamin D have been known to lead to high levels of calcium in the blood, although this has only been seen in people taking 40,000iu, 100 times the current recommended upper limit in the UK, for two months or more. And taking too much Vitamin A – more than 1.5mg over a number of years - has been linked with a higher risk of osteoporosis. Minerals, too, can cause problems: “Iron supplements aren’t necessary unless you actually have low iron levels, and too much can cause problems including constipation,” says Sharon Morey, nutritionist at Quest Vitamins.
So how can you be sure you’re not overdoing it? “Choose a trusted brand and follow the suggested dose on the label,” says Sharon. “But you also need to avoid doubling up if you’re taking several vitamin products.” So, for example, if you’re taking a multivitamin, be careful about adding a single vitamin supplement on top of it – check how much is contained in the multivitamin and don’t go over the suggested maximum intake for the day. “And be aware that cod liver oil is high in vitamin A, and a multivitamin will also contain it,” points out Sharon. Similarly, while you don’t generally need to worry about your diet in combination with vitamin supplements, if you eat liver or pate once a week, you should avoid taking extra vitamin A, either in single supplement form or in fish liver oil.
If you’re taking medicine or you have a medical condition, always check with your doctor before you take vitamins. Some supplements can interact with your medicine and stop it working in the way it should, so it’s worth asking your GP or your pharmacist if a supplement is safe for you.