You don’t have to, but if it works for you, do it. For one, it may help you remember what score to give yourself each day. For another thing, you may for the first time be witness to what you are actually putting in your body!
There is no food log requirement in the Whole Life Challenge. Some players thrive when they record everything they eat, others find it tedious and unnecessary, and still others obsess unhealthily over food logs. Choose what works best for you.