@Blobbymatt is correct in saying that Huel has a moderate amount of purines due to the high oat and flax content.
Uric acid is a waste product produced from the breakdown of dietary purines and is an important antioxidant that helps to prevent free radical damage. However, chronically high blood levels of uric acid have been associated with gout.
It’s important to note that Project 100 involved participants who were consuming Huel for 100% of their diet, some of whom were having almost 3000 calories per day, not typical for most Huelers who usually have Huel for 1 or 2 meals per day. As such, their overall purine intake would have been high.
Interestingly, although participant 13 was not one of the core 4 participants, it is worth mentioning that he has been consuming Huel for the majority of his diet for 3 years and showed uric acid levels that were within optimal range. See the full trial report with a breakdown of results here.
Nevertheless, individuals who are susceptible to gout should take caution if they have a high-calorie requirement and are considering using Huel for 100% of their nutritional intake, and it would be preferential to limit Huel to one or two meals/snacks per day.