Few nutrients are as important as protein. If you don’t get enough through your diet, your health and body composition suffer.

https://www.healthline.com/nutrition/how-much-protein-per-day

Protein deficiency can occur when you’re not eating enough protein to maintain normal body function. … Not consuming enough protein can also cause muscle cramping, weakness, and soreness. Your body will take protein from muscle tissue and use it as energy to support other vital body functions when protein is low.

https://www.verywellfit.com/what-are-the-effects-of-protein-deficiency-4160404

US Adults do not consume enough protein, study warns

10 Reasons to Eat More Protein

You need more protein as you get older