Before researching the subject, I was sure it was, but after reading it, I was confused. There are different versions on the internet.
For example, it is claimed that instant coffee is healthier than others in this source. The reason is that the soluble granules do not contain the harmful “fatty substances” found in freshly ground coffee. In this way, it does not pose a risk to cardiovascular health. it also contained 50% less caffeine than filter coffee. The interesting thing is that Turkish coffee is shown as the most harmful. Reason: it contains very high amounts of harmful cafestol and kahweol because it is not filtered.
This source confirms the fact that instant coffee contains less caffeine, but presents this as a risk. Since it contains less caffeine, the possibility of overconsumption of instant coffee increases. This causes irritability, mildness, and insomnia. In addition, instant coffee has a direct effect on iron absorption. Instant coffee consumed during meals or up to 1 hour after a meal significantly reduces iron absorption (proportional to how hard the coffee is). When taken 1 hour before a meal, it has no effect on iron absorption. During the processing of instant coffee, a chemical compound called acrylamide emerges. This is a chemical that occurs when foods are heated above 120 degrees. It was discovered in 2002. this has also been revealed in animal tests to be carcinogenic and associated with neurotoxicity. There are also findings that it increases the risk of ovarian and endometrial cancer in women. instant coffee also contains an organic acid called oxalates. this is very harmful to hyperoxaluria patients.