Today’s topic was proposed by Lisa, who called in on the Nutrition Diva Listener line with this great question:

“Hey Monica, I have a question about whether too much fiber causes nutrient deficiencies. I read that an excessive amount of fiber binds with minerals including calcium, magnesium, zinc, and iron preventing them from being absorbed by the body. Is there validity to these claims? What can we consider to be excessive fiber?”

How Much Fiber Do You Need?

The recommended daily allowance for fiber is around 30 grams per day. The average intake in the U.S. is somewhere in the neighborhood of 15 grams per day. So the typical American would need to double their fiber intake to meet the recommended amount. But is the recommended amount of fiber too low?

The Recommended Daily Allowance for fiber was set decades ago and was based on research showing that fiber was beneficial for digestive health, weight management, and can also play a role in moderating cholesterol levels. 

How Fiber Supports Health

Fiber from foods absorbs water and takes up a lot of space. This helps with weight management by filling up the stomach and making us feel more full on fewer calories. Fiber also binds to certain food elements, such as cholesterol. That means that as the food moves through the small intestine, less of the cholesterol is absorbed into the bloodstream. As it continues through the digestive tract, fiber also helps move waste matter through the large intestine, which prevents constipation and reduces our risk of colon cancer.

However, in recent years we’ve become aware of another important way that fiber supports our health: by supporting the health of our gut bacteria. The greater the amount and variety of plant fiber we include in our diet, the more varied and robust that population of beneficial bacteria becomes. Studies have shown that increasing fiber to 50 grams a day positively changed the composition of the gut microbiome in a surprisingly short period of time. 

But Lisa raises an interesting question: Is there any danger of consuming too much fiber? 

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