“Fiber matters more than almost anything else in your diet.”
Moderate confidence because a large series of systematic reviews found consistent health benefits from higher dietary-fiber intake and WHO recommends adequate fiber as part of a healthy diet. Neither source compares fiber with every other feature of diet, so the superlative claim is not established.
Fiber matters, but saying it matters more than almost anything else goes beyond the evidence. Higher intake is consistently linked with better health, while a healthy diet also depends on overall food quality, energy balance and other nutrients.
Health comes from your overall eating pattern, not one food or ingredient in isolation.
Fiber is healthy, but increasing it too fast can cause gas and bloating. Add it gradually if your current intake is low.
Can fiber support long-term health?
Higher-fiber diets support bowel function and are associated with lower risks of cardiovascular disease, type 2 diabetes and colorectal cancer. Trials also show modest improvements in weight, blood pressure and cholesterol.
Fiber is worth paying attention to as one part of a healthy eating pattern. Evidence does not rank it above almost every other dietary factor.
Add one high-fiber food daily, such as beans, lentils, fruit, vegetables or whole grains, and increase gradually if you are not used to it.