Depending on the dosage, it’s been found that black pepper oil can, oddly enough, have either spasmodic or antispasmodic effects. Antispasmodic oils can help to calm tense muscles and spasms in the body, helping to reduce painful cramps, while spasmodic oils can stimulate the muscles into action. This means that not only can black pepper help to relieve gut pain by relaxing tense muscles, but in a different dosage, it can help with the uncomfortable feelings of constipation. Black pepper oil can also have antidiarrheal effects. All the digestion-soothing abilities of black pepper can be attributed to the presence of the compound piperine. A study in 2013 found that rats with IBS and severe symptoms of low mood showed a significant improvement in both conditions after being given piperine. There is evidence that serotonin plays a role in the abnormal brain-gut signalling that may cause IBS, explaining why the two conditions are often linked. The fact that piperine can apparently help treat both is a very exciting discovery.