Jane Symons

Millions of people take medicines such as cholesterol-lowering statins, metformin for diabetes and contraceptive pills. But these widely prescribed drugs can come with a hidden cost.

They are just a few of the life-saving and life-changing medicines which can disrupt nutrient absorption. And the more of them you take – and the longer you take them — the greater the risk of developing potentially dangerous nutrient deficiencies.

Michael Wakeman, a pharmacist and specialist in nutritional medicine, was alerted to the danger after spotting a scientific paper which was aptly titled: “Effects of widely used drugs on micro nutrients: a story rarely told.”

It led to five years of research, trawling medical journals and scientific papers, which he says “was like peeling an onion. The more you dig and the more layers you peel away, the more problems you discover.

“Some of the links – such as metformin and vitamin B12 – are quite well-known, but the more you look, the more you find.”

NHS dietitian Catherine Collins says: “Medications impact nutrient status in a number of ways. They reduce uptake by binding with the nutrient, or a co-factor needed for absorption; there can be issues with increased clearance; and there can be metabolic changes influencing absorption.”

In many cases, the impacts are quite subtle, so they are not listed as potential side effects. But taking several medicines, each with a small effect, can easily add up to a serious deficiency.

Problems are compounded by the fact that the number of medicines we take tends to increase as we get older, when our bodies are less efficient at absorbing nutrients. Dietary gaps and bad habits, such as smoking and drinking alcohol, add to the risk of shortfalls.

Catherine Collins says not to take nutrients in large doses, unless it is on medical advice, but adds: “A generic vitamin and mineral supplement can be useful to mop up micronutrient deficiencies.”

Just 20 medicines account for almost a third of prescriptions dispensed each year and Mr Wakeman says four out of five of them have some impact on nutrient status.

Metformin impairs uptake of vitamin B12, and this is flagged up as a “very rarely reported” side effect on information leaflets. However, one study warned as many as 30% of diabetics taking metformin for three or more years develop problems.

Eating a vegan or vegetarian diet and older age, also increase the risk of being low in vitamin B12. Shortfalls can cause muscle weakness and nerve damage, which is also a common complication of diabetes. Mr Wakeman suspects some cases of deficiency are being misdiagnosed as diabetic neuropathy. Metformin also reduces levels of folate, thiamine, magnesium and vitamin D — which is important for immunity.

Mr Wakeman says: “The last thing I want to do is scare anyone into stopping taking metformin, but it is important people are aware of the issue and, in my opin mul vita

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