Instant coffee if more convenient to use compared to regular coffee but is no way different to the regular coffee. It has a good amount of caffeine and is equally harmful for the body. Thus it can lead to various complications further to the heart and other parts of the body. Caffeine as all know is a stimulant for the brain and reduces sleep. Having high amounts of coffee everyday also increases the serum lipid levels and increases the risk of cardio vascular disorders. Risks get reduced if it is a decaffeinated coffee but people don't like it much as it does not give that kick that a normal coffee does. So anything in excess is bad and you have to limit it to less tan 2 cups a day if you want to lower health risks.