There hasn’t been established a maximum safe dose of fiber. Though the recommended daily intake of fiber is up to 36 grams, even consuming extremely high doses of 70 grams 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 following a high fiber diet of 50 grams 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 grams of dietary fiber per 1,000 calories.
Thus, women who consume 2,000 calories a day should consume at least 28 grams of fiber. The recommended daily intake of fiber for men, who consume about 2,600 calories a day, is 36 grams.
But, we could consume much higher doses. Actually, more fiber is better. Most people should benefit by consuming 20 grams of fiber per 1,000 calories a day.
Unfortunately, most people who follow the standard Western diet fail to meet the recommended daily 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 grams of fiber per day. This dose is only half of the recommended daily intake.[6]
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 grams of fiber a day.[7]
What’s the maximum dose of fiber a day?
There hasn’t been established an official maximum safe dose of fiber. As a rule of thumb, a dose up to 50 grams of fiber a day is considered pretty safe and well tolerable.
In fact, there are many traditional fiber-rich diets around the world which don’t cause any significant side effect.
For instance, Ugandan diet is particularly high in fiber, as it consists mainly of vegetables. People consume up to 100 grams of fiber per 2,000 calories, without experiencing any side effect. Most noteworthy, they get adequate amounts of nutrients.[8]
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 grams a day.
The maximum safe fiber intake for children is child’s age plus 10 grams of fiber per day.
Certainly, you should consult your physician before changing your diet habits.
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 healthful than harmful. A high-fiber diet has a small impact on mineral balance. In any case, a daily fiber dose up to 50 grams won’t cause any nutrient deficiency.[9,10]
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.[11]
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, it’s important to gradually increase fiber intake. You want to give healthy bacteria time to grow in population. For instance, if you used to consume only 15 grams of fiber a day for years, even consuming the recommended daily intake could be too much for you. Let alone, much higher doses.
But, if you used to consume 38 grams of fiber a day, consuming higher doses of 50 grams 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 increasing 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.[12]
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, potatoes, pasta, 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!
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.
