> They didn’t test caffeine in isolation

But they did test both caffeinated and uncaffeinated coffee, and found the same effects in both, indicating that the effect is caused by something in coffee other than the caffeine

Doesn't decaf also contain caffeine, just a lot less of it?

Typical extraction yield is 18-20%. For a 20g dose that's 4g of material consumed, or about 30 individual beans.

I wonder if you could find similar effects with 4g or broccoli sprouts, or garlic, or ginger, or cumin seed, shiitake mushroom, seaweed, soursop leaf, or...