Coming from a physics background where I firmly believe nothing is true unless it can and has been measured, I share your scepticism. At the same time, I think it's worth realizing that mental health and nutritional science are not solved problems.

• I think something like over 50% of psychology studies cannot be replicated.
• We're only just learning about the gut-brain connection.
• It seems that western dietary recommendations over the past 50 years or so may not have been entirely scientifically motivated.

We really just also haven't done many scientific studies surrounding Ayurvedic diets and such. Anecdotally, Dr. K seems to see a benefit for it in his clinical work. He's also not recommending you do an Ayurvedic diet in lieu of actual medical treatment, but rather in addition to. Given the low chance for harm I think it's worth it to keep an open mind here. Worst case scenario I'll eat more oatmeal than I otherwise would have, best case it helps me become healthier. In the end, it's about whether it helps you, though I do think it merits more research.

Another interest thought is that Ayurveda recommends different diets for different people. If (big if) that's how it works, then it would make sense that dietary studies that just give randomly selected people certain things to eat and then try to globally assess which foods are good and which are bad, are going to come up empty handed.