Caffeine. This can irritate the gastrointestinal tract (which is why we often need to go to the toilet after drinking coffee or tea).

Sugar. Highly concentrated sugar solutions – such as sports drinks – can cause GI distress in some people. That’s why it’s vital you experiment in training with sports drinks that have different sugar concentrations, to see what works for you.

Fibrous foods. Prior to a race or training run is one of the rare times when you shouldn’t opt for fibrous foods, as they take a long time to digest and absorb a lot of water, making you feel bloated and heavy.

Dairy products. Some people find dairy products hard to digest.

Fruit. The high acid content can cause stomach cramping.

Aspirin and ibuprofen. Non-steroidal anti-inflammatories can cause stomach upsets and even bleeding if taken too often, or when taken on an empty stomach.

Stitches
Although there can be few runners who aren’t familiar with the pain of a stitch, the science bods still don’t really know what causes it. Some experts believe that the pain is caused by the jolting of the diaphragm and the internal organs connected to it by ligaments, while others argue that if this were the case then cyclists and swimmers wouldn’t suffer from stitches (which they do).

Another theory relates to the outer sheath of the diaphragm muscle becoming fatigued and rubbing on the outside of the abdominal wall. If this is correct, then strengthening the ‘core muscles’ may help. Regardless of the cause, researchers from the University of Newcastle in Australia suggest you avoid big meals prior to running – particularly foods that are high in fat and sugar – and warm up thoroughly. If you do get a stitch, then slowing down or stopping and kneading the painful area is the simplest solution.