Nutrition science is incredibly complicated. However, woo-peddling dickheads on the internet would like you to believe otherwise. Let me give you an incredibly counter-intuitive example.

A null finding in nutrition research is not necessarily evidence of no effect. 1/4

Say we have a study testing the effects of fibre on colon cancer risk. Say one group is consuming 20g/day and the other group is consuming 40g/day. Suppose the results come up null. Does that mean there's no benefit of fibre for that endpoint? No, actually. Not at all. 2/4

For the sake of argument, let's also arbitrarily suppose that the maximal benefit of fibre in preventing colon cancer is around 15g/day. This would place both groups in the maximum benefit category. The effect would only be revealed if you were comparing <15g/day to >15g/day. 3/4

This is largely how cherry-pickers and diet gurus are able to cobble together persuasive narratives about diet and health. Some carnivore diet quack could very easily seize upon that null finding to make a point about how fibre doesn't matter. But, in reality it really does. 4/4