It is not bad. Phenylalanine is an essential amino acid and safe for everyone except those who have a condition called phenylketonuria, or PKU. This amino acid, combined with another amino acid called aspartic acid, forms the artificial sweetener aspartame. While the U.S. Food and Drug Administration has classified aspartame as safe up to a certain level, some people have reported side effects after consuming it. It is safe for adults to take aspartame at a dose of 40 mg / kg per day, and it has no effect on blood glucose in diabetic patients.
Phenylalanine in beverages mostly function as sweeteners. For patients with diabetes, it is recommended to reduce consumption of sweet beverages. Moreover, drinking too much beverages is also not good for your congestive heart failure. However, phenylalanine should not be blamed for your jitteriness.