What’s the maximum safe dose of fiber? What’s too much?

There hasn’t been established an upper safe dose of fiber. Though the recommended intake is up to 36 g a day, consuming even extremely high doses of 70 g a day is rather unlikely to cause any adverse effect.

Health benefits of fiber

A diet high in fiber is essential for good health. Fiber has been linked to significantly lower risk of developing coronary heart disease, stroke, hypertension, diabetes, obesity, and certain gastrointestinal diseases.

In fact, consuming high amounts of fiber may lower elevated blood pressure and serum cholesterol levels. Additionally, fiber may improve insulin sensitivity and glucose levels, enhance immune function, help lose weight, and maintain a healthy body weight.[1]

Furthermore, fiber contributes to healthy gut microbiota, which is crucial for good health as well. Gut microbiota protects the body from chronic inflammations, improves metabolic processes, and promotes weight loss, due to regulation of appetite![2]

Moreover, following a diet high in vegetables may reduce the risk of certain cancers like colon cancer. Colon cancer is rarely seen in rural communities consuming a high fiber diet of 50 g a day.[3,4]

Actually, high fiber intake significantly decreases the risk of mortality. Especially, if we consume many fruits, beans, and vegetables.[5]

How much fiber do we need a day?

As a rule of thumb, we should consume at least 14 g of dietary fiber per 1,000 calories.

Thus, women who consume 2,000 calories a day should consume at least 28 g of fiber. The recommended daily intake of fiber for men, who consume about 2,600 calories a day, is at least 36 g.

But, we could consume much higher doses as well. Actually, more fiber consumption is better. Most people should benefit from consuming 20 g of fiber per 1,000 calories a day.

Unfortunately, most people who follow the standard Western diet fail to meet the daily recommended intake of fiber. Dietary fiber is naturally present only in plants. Refined foods contain negligible amounts of fiber, while animal products contain no fiber whatsoever. For instance, whole-grain bread contains about 3 times more fiber than white bread!

It’s estimated that 90% of the US population doesn’t consume the recommended daily intake of fiber. Actually, most Americans consume only 15 g of fiber a day. This dose is only half of the recommended daily intake.[5]

Children should consume adequate amounts of fiber as well. The recommended daily fiber intake for children older than 2 years of age is child’s age plus 5 g of fiber a day.[6]

What’s the maximum dose of fiber a day?

There hasn’t been established an official upper safe dose for dietary fiber. As a rule of thumb, a dose up to 50 g of fiber a day is considered a pretty safe and well tolerable.

But, there are many traditional diets around the world which are particularly high in dietary fiber, without causing any significant side effect.

For instance, Ugandan diet is particularly high in fiber, as it consists mainly of vegetables. People get up to 100 g of fiber per 2,000 calories, without experiencing any side effect. Most noteworthy, they get adequate amounts of nutrients.[7]

Consuming too much fiber may cause discomfort, though. It isn’t suitable for general population. The maximum safe fiber intake for most people is 70 g a day.

Certainly, you should consult your physician before changing your diet habits.

The maximum safe fiber intake for children is child’s age plus 10 g of fiber per day.

Too much fiber may cause adverse effects

First, it’s believed that too much fiber may cause mineral deficiencies because fiber binds to them, inhibiting their absorption. So, it is a common false belief that too much fiber may cause calcium, magnesium, zinc, or iron deficiency. This isn’t true, though.

Healthy adults and children who consume a well-balanced diet have normal serum vitamin and mineral concentrations. Actually, a moderate increase in fiber is more likely to be more healthful than harmful. A high-fiber diet has a small impact on mineral balance. In any case, a daily fiber dose up to 50 g won’t cause any nutrient deficiency.[8,9]

Though fiber is good for health, eating too much could cause side effects such as bloating, a sense of fullness, discomfort, gas, cramping, diarrhea, constipation, as well as other gastrointestinal distresses.[10]

Bacteria in the colon produce gas by breaking down and fermenting fibers. So, fiber may cause bloating or other gastrointestinal distresses, as it may impair gas transition and promote gas retention.

Therefore, we should gradually increase fiber intake. You want to give healthy bacteria time to grow in population. For instance, if you consumed only 15 g of fiber a day for years, even consuming the recommended daily intake could be too much for you. Let alone, much higher doses of 50 g.

But, if you used to consume 38 g of fiber a day, consuming higher doses of 50 g are rather unlikely to cause any side effects.

Can I get too much fiber from supplements?

In most cases, following a healthy, well-balanced diet and gradually increase fiber intake won’t cause any adverse effects. It’s more likely to experience side effects after excessive use of fiber supplements, though.

You better increase fiber intake through diet. Most fiber supplements contain fiber from only one source. Also, most of them lack the physical characteristics of fiber naturally present in food. Hence, they probably aren’t as beneficial as eating foods high in fiber.[11]

But, if you really need to boost your fiber intake, you’ll find a wide variety of fiber supplements on iHerb.

Always consult your physician before taking any supplement.

Common foods high in fiber

Following a whole-food plant-based diet is the easiest way to get high amounts of fiber. Plants are the only foods containing fiber. Vegetables, fruits, whole-grains, seeds, and nuts are excellent dietary sources of fiber.

Even many favorite foods, like popcorn, sweet potatoes, potatoespasta, and chocolate, are particularly high in fiber.

But, if you really want to boost your fiber intake, you should start eating beans and legumes. Beans are the richest foods in fiber. For instance, a serving of lentils provides more than 50% of the daily required dose of fiber!

Beans and legumes are beneficial for good health and help you maintain a healthy body weight.

Last, but not least, you better avoid fruit juices and highly processed products, such as vegetable oils. They’re high in calories and contain no fiber.