## The epigenome can also be influenced positively

Diet can also have a positive effect on the epigenome – for example, positive effects have been observed in colon cancer cells after administration of cruciferous vegetables. Broccoli, Brussel sprouts, and cabbage contain a high concentration of a sulfphur-containing compound called sulphoraphane. This compound was found to affect histone acetylation, which alters the packaging of DNA into chromatin and thus regulates gene expression. In tumour cells, increased activation of genes that can suppress tumour growth was observed after sulphoraphane administration. It is not an isolated case that a substance contained in vegetables shows a positive effect in the form of donors of chemical groups for epigenetic modification. DNA methylation can be influenced by the intake of folic acid (vitamin B9, folate), which is contained in leafy vegetables, legumes, broccoli, and eggs. The intake of folic acid is important especially before and during the first months of pregnancy, where it also serves to prevent foetal spina bifida.

Just as gene expression is affected by a negative factor (electroshock associated with the smell of acetophenone, smoking, or a traumatic experience), some scientific teams have focused on studying a positive emotion - laughter. The researchers used young rats as a model, exposing them to tactile stimulation, namely tickling, which triggered their positive emotions. Gene expression was compared in the hypothalamus of the tickled and non-tickled (control) groups. After four weeks of tickling the rats, 321 out of 41,012 genes showed a change in expression. Of these, the expression of 136 genes was increased more than 1.5-fold and 185 genes were expressed less. The genes with altered expression were mainly involved in neuronal signalling and behaviour related to the feeding process.

The effect of laughter on the epigenetic state of cells was later observed in humans. Type II diabetes is a chronic metabolic syndrome in which the body is less sensitive to insulin due to insulin resistance, resulting in high blood glucose levels. In one study participants with type II diabetes were divided into two groups - one listened to a lecture, the other to a humorous skit. An hour and a half after the lecture or skit, samples were taken to compare gene expression. Of the 18,716 genes analysed, the group that had listened to the humorous skit was found to have a change in the expression of 23 genes, 8 of which were expressed more strongly and 15 less strongly. The change occurred in genes involved in immune processes, cell division, or programmed cell death. Another study examining the effect of laughter on diabetics showed that the expression of the gene encoding the protein which is responsible for the occurrence of complications in diabetes, was reduced in laughing patients. In addition, an increase in the expression of 15 genes involved in the immune system was found, 14 of which are related to the natural killer cells of the immune system. These genes were further researched in mice, where it was shown that these genes could reduce glucose resistance.