Gold, like silver and copper (one above the other in the periodic table and with similar properties) are potent bactericides and fungicides. When Americans colonised the Wild West, they would drop a silver coin in their milk jar to prevent it from going bad. Koreans have traditionally used silver cutlery because it was said protects against food poisoning. Copper plays an important role in the immune system to kill bacteria (while zinc is more essential in fighting off viruses). Gold is very neutral for the human body and, in colloidal form, their nanoparticles may improve the connectivity of neurons.
So the bottom line is that eating fine gold leaves could make sense and isn't bad for the body, although in that form it is probably not very effective. The picture you posted is clearly intended as a decoration for haute cuisine. Gold is in fact commonly used for this purpose in French cuisine. It's also used to decorate Belgian pralines. It may look expensive but it's really not. It's just a few milligrams.