A recent meta-analysis showed fiber reduces overall mortality by 23%. Surprisingly enough, this isn't just due to the effect on cardiovascular disease via cholesterol -- fiber actually reduced risk of cancer by 22%.

Interesting article!

We always talk about the Mediterranean diet as being one of the best for reducing mortality - interestingly a typical Mediterranean diet would have approximately "14g of vegetable fiber for every 1,000 kcal per day, which is more than double what is consumed every day in many industrialized countries" (https://pmc.ncbi.nlm.nih.gov/articles/PMC7190876/). Aside from its healthy fats, omega 3s, etc. there may be a big role here for the fiber in this dietary approach.