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12 Side Effects of Eating Oatmeal Every Day, Say Dietitians

Is oatmeal good for you? We asked the experts.
FACT CHECKED BY Samantha Boesch

It feels like everyone is singing the praises of oatmeal lately. It can do wonders for your body, can help you live longer, and overall tastes delicious—especially when you make this peanut butter overnight oat recipe. But is oatmeal healthy? Are all of the side effects of eating oatmeal actually positive? Are there negative side effects we should know about, as well?

We turned to a few registered dietitians and doctors to get the low-down on the good, the bad, and the ugly when it comes to oatmeal. While the side effects of eating oatmeal are mostly good, there are a couple of potential negative effects to be mindful of when enjoying a hearty bowl of this warm cereal.

Here's what our experts had to say on the side effects of eating oatmeal—and for more dietitian-supported healthy eating tips, be sure to check out Eating Habits to Lose Abdominal Fat As You Age, Say Dietitians.

It's a great source of fiber

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"Oatmeal is one of the healthiest breakfast choices you can make, namely because oats are a great source of fiber," says Brenda Braslow, MS, RD for MyNetDiary. "One cup of old-fashioned oats offers around 8 grams fiber and it's mainly soluble fiber, which is the type of fiber that has been shown to lower LDL (bad) cholesterol and blood sugar. Old-fashioned oatmeal helps keep your digestive system functioning well and fiber is also great for keeping you satisfied longer and can therefore help with weight management and loss."

It's a great protein source

"Oats also offer a decent amount of protein with just one cup of old-fashioned oats containing approximately 10 grams of protein," says Braslow. "Protein, along with fiber, can keep you full longer. Oatmeal is a nutrient-dense food, offering other vitamins and minerals, such as iron, calcium, and magnesium."

Getting enough protein throughout your day can benefit your health in numerous ways. In a report published in Nutrients, protein was found to help adults over the age of 40 regulate their appetite, as well as help improve muscle mass and strength.

Another study published in the American Journal of Clinical Nutrition found that people who were considered overweight were able to lose weight after increasing their protein intake to be 30% of their daily calories. Oatmeal, although it isn't enough protein to last throughout the day, can be a great place to start in the morning when you need a boost of protein.

Oatmeal can help you lose weight

"Oatmeal's fiber and nutrients have also been connected with weight loss. These characteristics keep the consumer feeling full, which can prevent overeating on calories throughout the day," says Trista Best, MPH, RD, LD,  a registered dietitian and consultant at Balance One Supplements. "It is easy to add antioxidant-rich ingredients into your diet when you eat oatmeal regularly. Dried fruit, nuts and seeds, and nut butters are rich in micronutrients that support most health and wellness goals."

It can help you feel full

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In the question of "is oatmeal good for you," many of the positive effects come from its fiber content.

"Oatmeal is a whole grain that is high in fiber, especially soluble fiber," says Emily Danckers, MS, RD. "When you eat soluble fiber, your digestion is slowed down, which can also increase feelings of fullness."

"Consistently eating a high-fiber breakfast food like oatmeal, especially when pairing it with a protein and/or fat like nuts, often keeps people full for hours," says Rachel Paul, PhD, RD, CDN. "They can then concentrate on their work and other items, before thinking about the next meal. Having a go-to, filling breakfast option like oatmeal creates consistency in one's life."

It can lower 'bad' cholesterol

"By eating oatmeal every day, you can lower your total cholesterol level, reduce the 'bad' LDL cholesterol, and increase your 'good' HDL cholesterol levels," says Megan Byrd, RD.

In fact, there's a specific type of fiber found in oats called beta glucan, which can also be found in barley and rye. According to Frontiers in Nutrition, beta glucan can help lower cholesterol levels through helping to improve the healthy of your gut microbiome.

You can enjoy oatmeal as is, but Byrd also recommends adding oatmeal to your treats, like her favored Oatmeal Protein Cookies recipe.

It can help you in the bathroom

"Oatmeal's fiber content contributes to positive gastrointestinal health, including having regular bowel movements," says Amy Goodson, MS, RD, CSSD, LD, and author of The Sports Nutrition Playbook. "It's important to increase your fluid intake as you increase your daily fiber intake."

It can help you control your blood sugar

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"Eating oatmeal every day can also help control your blood sugar because it's so high in that fiber," says Byrd. "It helps to slow down the speed at which the carbohydrates in your diet reach your bloodstream, making your blood sugar levels more even during the day. Oatmeal really is a superfood, and one that definitely can be eaten every day!"

It's great for your heart health

"Oats are an ingredient that has been in the heart-health spotlight for a while," says Mackenzie Burgess, registered dietitian nutritionist and recipe developer at Cheerful Choices. "Research continues to show cholesterol-lowering effects from regularly consuming this fiber-rich food. More specifically, the soluble fiber in oatmeal may help reduce our LDL cholesterol. Try mixing up your typical oats routine and soak them overnight with different flavor additions or combine them into easy energy bites."

RELATED: 51 Healthy Overnight Oats Recipes for Weight Loss

It provides helpful nutrients

"Oats are popular grains loved for their nutritional and medicinal value," says Edie Reads, RD, and chief editor at Health Advise. "Despite the normal fear of carbs, oatmeal is good for you. Unlike ordinary cereals, oats are not only filled with carbs and fiber but multiple vitamins and minerals, too."

It can help improve skin conditions

"Colloidal oatmeal is also known to help with dirty and dry skin. It proceeds to further help with such skin conditions as eczema," says Reads.

Is oatmeal bad for you?

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Oatmeal brings many positive benefits to your health. With side effects like better digestion, potential weight loss, better heart health, and greater feelings of fullness, it's hard to deny that oatmeal is healthy.

However, it's also important to look at a few of the ways oatmeal can deliver some unwanted side effects, too.

Oatmeal may cause some belly bloat

"If you are new to oats, they may cause bloating, so it's best to start with a small portion," says Lisa Young, PhD, RDN and author of Finally Full, Finally Slim.

"Whole grains such as wheat and oats contain high fiber, glucose, and starch," says Shannon Henry, RD, at EZCare Clinic. "All of them are consumed by bacteria in the gut or large intestine, which leads to gas and bloating in a few people. To lessen the side effects, start with a small quantity and increase gradually to the chosen amount. When you start eating oat bran, the harmful outcomes from your body will probably disappear."

RELATED: 24 Ways To Get Rid of Bloating in Less Than 24 Hours

It may cause weight gain

"Finally, eating a jumbo serving of oatmeal can lead to weight gain," says Young. "And watch the toppings—a tablespoon or two of crushed walnuts or flaxseeds is great, but too much butter or sugar isn't."

"People typically want their oatmeal to be sweeter so as not to eat a boring meal," says Dr. Gan Eng Cern. "They achieve this by adding sugar, chocolate chips, and other sweet food items, which ultimately decrease oatmeal's overall nutritional value as these additions throw in extra calories, fat, sugar, carbs."

A previous version of this story was published on April 17, 2022. It has been updated to include additional copy and proofreading revisions, corrections to any irrelevant or broken links, and additional research.

Kiersten Hickman
Kiersten Hickman is a freelance health and nutrition journalist. Read more about Kiersten
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