Whether it's from a bowl of creamy oats or a perfectly plump asparagus spear, the dietary fiber in plant foods provides a host of health benefits.
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You might reach for something fibrous when you're feeling constipated, but really, you should be considering the nutrient for much more: A high-fiber diet is associated with cholesterol management, blood sugar control and gut health, too.
There are two main types of fiber: soluble and insoluble. These are what form the structure in our plant foods — fruits, vegetables and whole grains. While they serve different functions for our bodies, they're both beneficial.
- Soluble fiber dissolves in water, forming a gel that helps slow the passage of food from our stomach to our intestine, keeping us fuller longer. This type of fiber also helps control cholesterol and blood sugars.
- Insoluble fiber (aka roughage) helps create softer, bulkier stool for improved bowel movements.
In addition to these two types of fiber, there's also prebiotic fibers — resistant starches found in foods such as oats, wheat, asparagus, Jerusalem artichokes, onions and garlic, per a January 2018 study in Current Developments in Nutrition. These starches help fuel probiotics for maintaining a healthy gut.
How much fiber do you need? We should aim to get 14 grams of fiber per every 1,000 calories we eat, according to the 2020-2025 Dietary Guidelines for Americans. This guideline follows previous recommendations of 25 to 35 grams of fiber per day.
But before you start feasting on bran cereal, know that it's important to build up your fiber intake gradually and be wary of other common mistakes, Jana Mowrer, RDN, says. Here are some typical ways people can go wrong with fiber, along with how to add fiber to your diet the right way.
1. You Don't Get Fiber from Whole Foods
When it comes to fiber, you should aim to meet daily recommendations. But it's just as important that you choose wholesome foods and get a good balance of insoluble fiber, soluble fiber and resistant starches.
"We must get fiber in both soluble and insoluble forms, as well as resistant starches, that act similar to a fiber, but are often gentler on the stomach and selectively feed the good gut bacteria, which assists with more well-rounded health benefits," Kara Landau, RD and founder of Uplift Food, tells LIVESTRONG.com.
While you may reach for a fiber bar to meet your daily nutrient goals, know that whole, plant-based foods are a better bet. Whole foods provide a synergy of nutrients that bring about more benefit than convenient packaged foods, which are either deficient in nutrients or loaded with added sugars and non-nutritive additives.
The fix: Eat fiber-rich whole foods — such as wheat bran, beans and legumes, pears, soybeans, chia seeds and raspberries — to reap all the benefits that fiber can provide, Landau says.
"Look for those that contain a blend of insoluble, soluble and resistant starch, so that you can reap benefits and avoid any negative side effects," she says.
2. You Pack in Too Much
While it isn't likely you'll get too much fiber in one day, you should be wary of the consequences of being overzealous with the nutrient.
"In general, over 40 grams per day is above the recommended range, but the side effects won't be seen in all individuals," says Madathupalayam Madhankumar, MD, a family physician who specializes in surgical gastroenterology. "As per guidelines, more than 70 grams of fiber intake per day is considered out of range."
Dr. Madhankumar explains that too much fiber negatively affects the digestive system and can result in constipation, stomach bloating and stomach pain. He also warns that eating too much fiber can result in nutritional deficiencies. "Excess fiber will bond with certain minerals like calcium, iron and zinc and prevent its absorption," he says.
The fix: "Establish a baseline of how much fiber you are taking in initially, then increase by 5 grams of fiber per week until the goal of 25 to 35 grams of fiber per day is met," Mowrer says.
3. You Avoid Fiber and Prebiotics Because of IBS
Landau says that avoiding fiber and prebiotic foods is a common misconception among people with Irritable Bowel Syndrome (IBS) and Irritable Bowel Disease (IBD).
"But refraining from consuming fiber and prebiotics, unfortunately, leads to degradation of the gut and gut lining which makes negative symptoms associated with these conditions worsen," she warns.
You'll want to build up your tolerance to those fiber-rich foods you're avoiding. "Many actually find consuming prebiotic fibers can support an increased tolerance to many foods they previously felt they needed to avoid thanks to a strengthened gut lining as their microbiome strengthens," Landau says.
As far as managing your IBS, be mindful of foods that can trigger your issues. "Tomato, broccoli, leafy vegetables should be avoided while having diarrhea, as this may trigger bowel movements. Apples and berries should be avoided when you have constipation as this may reduce further reduce the speed of digestion," Dr. Madhankumar says.
The fix: Increase your tolerance to fiber-rich foods gradually. And be sure to include prebiotic foods.
4. You're Not Drinking Enough Water
When you increase your fiber intake, you should also be upping the amount of water you drink. "Increased fiber intake plus increased water intake helps ease GI symptoms as well as create bowel movements," Mowrer says.
Drinking enough fluids — that's at least 64 ounces or eight 8-ounce glasses per day, per the Cleveland Clinic — will prevent your stool from clogging up. If you are taking any fiber supplements, like Metamucil, drink at least 8 ounces of water with your supplement.
Again, Mowrer recommends getting your fiber from your whole foods as much as possible (rather than relying on supplements). "Use a food-first approach when increasing fiber. If that doesn't help, only then consider a supplement such as Metamucil. We want your gut to keep working and breaking down real food helps with that," she says.
The fix: Drink an additional 8-ounces of water for every additional 5 grams of fiber you eat, Mowrer says.
5. You're Eating Too Much Fiber at Dinnertime
Meeting your fiber goals is important if you want to stay regular, but it's best to spread your intake throughout your day, rather than eating the bulk of your fiber in one meal. In fact, you may not want to go overboard with fiber at dinnertime specifically, Landau says.
"When you sleep, a lot of your energy does go toward digestion, [so] you may find going to the toilet [is] smoother in the morning," Landau says. But, she warns, if you eat too much fiber at dinner, you run the risk of feeling uncomfortable or bloated, and this can get in the way of a good night's sleep.
The fix: Aim for 5 to 7 grams of fiber at dinner, and try to stay under 13 grams. To meet your fiber goals, spread your fiber intake evenly throughout the day.
- Cleveland Clinic: "Improving Your Health with Fiber"
- Current Developments in Nutrition: "Health Effects and Sources of Prebiotic Dietary Fiber"
- Nutrients: "Utra-processed Foods are Not "Real Food" But Really Affect Your Health"
- BMJ: "Ultra-processed Food Intake and Risk of Cardiovascular Disease: Prospective Cohort Study (NutriNet-Santé)"