Medical Matters: Supplement your vitamin intake with a little caution

When Hippocrates, the Greek father of clinical medicine, said, “Let food be thy medicine,” he undoubtedly had natural food sources in mind. Packaged dietary supplements were a long way in the future. But he wouldn’t have been overly impressed by the latest research into the dangers of supplements to emerge from the Centres for Disease Prevention and Control (CDC) in the US.

Researchers estimated the number of emergency department (ED) visits for adverse events associated with dietary supplements in the US using 10 years of data (from January 1st, 2004 to December 31st, 2013) from 63 US hospitals. In a paper published in the New England Journal of Medicine they calculated that 23,000 visits to emergency departments every year involve adverse events from dietary supplements, leading to an estimated 2,154 hospitalisations annually. To put these figures in context, about half of adults in the US report taking a dietary supplement in the past month.

Most attendances involved either young adults, ages 20 to 34 (28 per cent), or unsupervised children (21 per cent). Children’s visits were often triggered by them gaining access to micronutrient products such as multivitamins and iron, as well as weight-loss supplements used by adults. Among older adults, ED visits mostly involved problems with swallowing, suggesting a need to limit tablet shape and size, the researchers said.

While we probably oversupplement with vitamins, the body needs them for various essential metabolic functions. Metabolism is the neverending chemical cycle of ingesting food, converting it to energy and eliminating waste products.

Catalysts Many of the body’s essential chemical reactions can take place only in the presence of vitamins. Basically, they act as catalysts, speeding up the natural process of cellular functioning. Vitamins A, D, E and K are fat-soluble. With the exception of K, the body can store fat-soluble vitamins for long periods. People taking supplements of these vitamins need to be careful, as high doses can be toxic.The B vitamin groups (a complex of different substances) and vitamin C are water soluble. In theory, the risk of toxic buildup is unlikely as any excess will be flushed out by the kidneys.

The good news from the research, if we exclude the risks to children from consuming large amounts of micronutrients that look like sweets, is the relatively innocuous side effects linked to vitamin consumption.

Adverse effects

The most common adverse effects from most micronutrients were mild-to-moderate allergic reactions and swallowing problems. Choking caused most emergency department visits involving calcium products, whereas abdominal symptoms such as nausea and abdominal pain were frequently associated with iron or potassium products.

It seems the moniker “horse tablets” lives on as vitamins and supplements are still combined into overly large tablets that exceed the recommended 22 mm size limit.

There are a couple of caveats that apply to the CDC paper. First, according to the authors, “the number of emergency department visits attributed to supplement- related adverse events that we identified is probably an underestimation, since supplement use is underreported by patients, and physicians may not identify adverse events associated with supplements as often as they do those associated with pharmaceuticals”. And doctors generally have more limited knowledge of interactions between prescription drugs and dietary supplements than they do interactions between prescription drugs.

Second, the regulatory regime surrounding dietary supplements in the US is far more lax than that operating in the EU. The Food Safety Authority of Ireland operates to a much tighter set of rules than does the US Food and Drug Administration.

Bon voyage and safe travels to everyone flying abroad this mid-term break. I hope you get some much- needed vitamin D, the natural way to make up for the dull skies of our Irish summer.

mhouston@irishtimes.com muirishouston.com