woman eating bowl of oats

Having oats for breakfast every day isn’t an uncommon choice for most folks. In fact, the results of a 2016 study suggest that about six percent of Americans regularly eat oatmeal. Whether you eat it plain or pile on the mix-ins, cook it on the stove, zap it in the microwave, or prepare it the night before and stick it in the fridge, there are endless ways to enjoy this humble breakfast food. And, to the confusion of many consumers, it seems like there’s an equally endless variety of oats to choose from.

According to the Oldways Whole Grains Council, the different types of oats correspond to different levels of processing. Oat groats, for instance, are the dehulled whole grain and take the longest to cook. Oat groats cut several times with a metal blade creates steel-cut oats. Scottish oatmeal is a stone-ground alternative to steel-cut oats. Old-fashioned rolled oats are made from steaming and rolling oat groats into flakes. This makes them more shelf-stable and faster-cooking. Instant oats are steamed longer and/or rolled into thinner flakes. These oats have a smoother texture than other varieties.

Oats are extremely healthy, but they do have some downsides. If oats are one of your breakfast staples, keep an eye out for these changes in your body.

You could lower your cholesterol

bowl of oatmeal with fruit

We usually think about staying regular when we think about the benefits of fiber. But not all fiber is the same. Per Medical News Today, insoluble fiber doesn’t break down as it travels through our digestive system. This type of fiber bulks up stool and helps fight constipation. Soluble fiber, on the other hand, turns into a gel-like substance as it moves through our intestines. It slows the digestion and absorption of certain nutrients. This can have numerous health benefits, including lowering cholesterol. Soluble fiber binds to LDL ("bad") cholesterol molecules in the intestines, "preventing them from entering your bloodstream" (via VeryWell Health).

About half the fiber in oats is soluble. In particular, oats contain a type of soluble fiber called beta-glucan, which has gained attention from health professionals for its cholesterol-lowering abilities. In one meta-analysis, published in 2014, researchers examined previously published studies to determine the effect of oat beta-glucan on cholesterol levels. They found that when individuals consumed at least three grams of oat beta-glucan a day, LDL cholesterol decreased by an average of 4.5 mg/dL, while total cholesterol was reduced by an average of 5.4 mg/dL.

You’ll keep your blood sugar levels under control

bowl of oatmeal

The soluble beta-glucan fiber in oats may also prevent post-meal blood sugar spikes and improve your body’s sensitivity to insulin. According to Healthline, the glycemic index (GI) measures how much a food raises blood sugar. Pure glucose is used as a reference point, with a value of 100. Anything 55 and below is considered a low-glycemic food and won’t cause a substantial or quick rise in blood sugar, while foods with a GI of 56–69 are medium-glycemic, and those above 70 are high-glycemic. Rolled oats score a 55.

A 2014 paper published in The British Journal of Nutrition found that the beta-glucan in oats may also improve how well the body uses insulin. Researchers found that individuals who consumed oats had a fasting insulin level significantly lower than the control group. Fasting glucose levels and hemoglobin A1C (a long-term marker for blood sugar issues) also improved, though not significantly. Per Springer Link, fasting insulin levels are used to gauge insulin sensitivity. High fasting insulin values are found in those developing type 2 diabetes. The pancreas is producing larger than normal amounts of insulin to compensate for the body’s inability to use insulin efficiently.

You’ll be doing your friendly gut bacteria a favor

raw oats in bowl

Although their soluble beta-glucan fiber gets a lot of attention (and rightfully so), oats also provide another important but undigestible nutrient: resistant starch. According to Clean Eating magazine, resistant starch "is a type of fermentable fiber" that has properties of both insoluble and soluble fiber. It passes undigested from the small intestine to the large intestine, but once there it becomes food for the beneficial bacteria that live in our colon. The bacteria produce butyric acid as they metabolize the resistant starch, and the cells lining our colon use this butyric acid as their main energy source. So the resistant starch provides food for our gut bacteria, which in turn provides the fuel our intestinal cells need to function properly.

In addition to oats, resistant starch is present in foods like potatoes, lentils, and unripe bananas. Per Healthline, a 3.5-ounce serving of oats contains approximately 3.6 grams of resistant starch. Interestingly, cooking and then cooling foods increases their resistant starch content. So you may want to consider making a big batch of oatmeal at the beginning of the week, storing leftovers in the fridge, and reheating your breakfast each morning.

You’ll build strong muscles

bowl of oatmeal with strawberries

If you’re looking for a protein-packed breakfast, oatmeal’s got you covered. A 3.5-ounce serving of oats contains 16.9 grams of protein. And, according to a paper published in Critical Reviews in Food Science and Nutrition, "oats … are distinct among cereals due to their considerably higher protein concentration. At the same time oats possess a protein quality of high nutritional value and a special protein composition." The majority of the proteins found in oats are from the globulin family, which are more bioavailable than the prolamin group of proteins found in large amounts in other grains. In fact, the protein makeup of oats resembles that of legumes.

We all know protein is essential for building and maintaining muscle, but it serves many other important functions as well. In an interview with Harvard Medical School, registered dietitian Nancy Rodriguez explained that protein is vital for making "hair, blood, connective tissue, antibodies, [and] enzymes." The recommended dietary allowance (RDA) for protein is expressed as a formula: 0.8 grams per kilogram of body weight. But Rodriguez and many other health professionals suggest that getting up to twice the RDA is a "safe and good range to aim for."

You’ll feel full longer

woman eating bowl of oatmeal

You may be able to skip your mid-morning snack if you regularly eat oats for breakfast. That’s because oats are incredibly filling. In a study published in the European Journal of Clinical Nutrition, researchers gave participants 240-calorie servings of 38 common foods and then tracked how satiated individuals felt. The researchers ranked the foods, using white bread as a reference point. Oatmeal came in third and was calculated to be 209 percent more filling than white bread. In another study published in 2013, researchers compared oatmeal to a ready-to-eat breakfast cereal. They found that, compared to the cereal eaters, participants who consumed oatmeal felt fuller, had greater reduction in hunger later on, and a lower desire to eat for up to four hours after consuming oats.

But what gives oatmeal its staying power? According to The Cooper Institute, how full (satiated) you feel after eating something depends on the macronutrient content of that meal. While food that takes up a lot of space in your stomach may trigger signals to stop eating, protein and fiber have the biggest role to play in controlling when you’ll be hungry again. Oatmeal is packed with both.

You’ll beef up your blood

oats and other grains in pantry cabinet

Eating oatmeal for breakfast is a great way to add more iron to your diet. According to Healthline, "A cup of cooked oats contains around 3.4 mg of iron — 19% of the [recommended dietary allowance] RDI."

Per the National Institutes of Health, iron is important for good health because it’s needed to create hemoglobin, the protein on red blood cells that allows them to carry oxygen throughout the body. Having low iron levels (either because you’re not eating enough, not absorbing it well, or losing too much blood) can lead to iron-deficiency anemia, a condition marked by low hemoglobin and red blood cell counts (via Mayo Clinic). Because their cells aren’t getting the oxygen they need to function properly, individuals with anemia can experience a number of symptoms, including extreme fatigue, shortness of breath, weakness, and chest pain. If left untreated, anemia can cause serious heart problems, because the heart has to work harder to make up for low oxygen levels in the blood.

Iron-deficiency anemia is extremely common, affecting approximately 20 percent of nonpregnant women, 50 percent of pregnant women, and 3 percent of men.

Your immune system will get a boost

Oats splashing into container of milk

Orange juice isn’t the only breakfast staple that can strengthen your immune system. Oatmeal is an excellent source of zinc, which has many immune-boosting properties. A paper published in Molecular Medicine noted that, in addition to having powerful antioxidant and anti-inflammatory properties, zinc is essential for many types of immune cells. It’s needed for the development and function of the cells that control our innate immune system, including neutrophils and natural killer cells. Zinc has been shown to reduce the frequency and length of lower respiratory tract infections, urinary tract infections, and gastrointestinal tract infections. Zinc deficiency negatively affects the growth and function of T cells and B cells, part of our adaptive immune response. Deficiency also hinders phagocytosis, the process by which immune cells "eat" harmful invaders and damaged cells.

According to MyProtein, a "half cup of oats contains 3.10mg of zinc." The recommended dietary allowance (RDA) for women is 8 mg, while the RDA for men of 11 mg. Research conducted by Oregon State University found that 11.7 percent of American adults don’t get enough zinc.

You’ll be loading up on all sorts of vitamins and minerals

man eating oatmeal

Oatmeal has a lot more to offer in terms of micronutrients than just iron and zinc. According to Healthline, "Oats are high in many vitamins and minerals," such as thiamin, manganese, magnesium, and folate.

Thiamin (vitamin B1) helps the body extract energy from food and therefore plays a critical role in the growth and function of cells. Folate (vitamin B9) is required for a number of important processes, including the synthesis of DNA and RNA and cell division. It’s especially critical during times of rapid cell division and growth, such as pregnancy, early childhood, and adolescence. Folate deficiency during pregnancy can lead to neural tube defects in the baby such as spina bifida.

Manganese is a trace mineral needed for a number of enzymes that assist with the metabolism of proteins, carbohydrates, and dietary cholesterol. It also plays roles in the immune and reproductive systems, bone formation, and blood clotting. Magnesium is involved in over 300 bodily processes, including blood pressure regulation, blood sugar control, and muscle and nerve function.

You’ll get a big helping of antioxidants

hands holding bowl of oatmeal with fruit

Oatmeal contains several powerful antioxidants, most notably avenanthramides. Per ScienceDirect, avenanthramides are a group of plant compounds found only in oats. Oat grain contains between 4 and 13 mg of avenanthramides per 100 g, while oat bran contains 1.3–12.5 mg per 100 g. A paper published in Nutrition Reviews noted that there are more than 20 avenanthramide compounds in oats, and in addition to serving as antioxidants, they may also prevent cancer cells from multiplying.

But what exactly are antioxidants? Antioxidants are chemicals that protect the body against damage from free radicals. According to LiveScience, free radicals are highly unstable atoms of oxygen that try to "steal" electrons from other molecules in the body. This destabilizes the molecules and creates a chain reaction that leads to damage throughout the body in a process known as oxidative damage or oxidative stress. Substances that produce free radicals can be found in food and in our environment, and free radicals are also created as the byproduct of natural chemical processes in the body. Antioxidants are able to give free radicals the electrons they want without becoming destabilized themselves.

You’ll keep inflammation under control

oats falling on spoon

In addition to serving as powerful antioxidants, avenanthramides also appear to have anti-inflammatory properties. A 2019 study published in the Journal of Sport and Health Science found that avenanthramides reduced levels of pro-inflammatory cytokines, a type of immune cell.

But you don’t need to eat oats to get these anti-inflammatory benefits. Ever wonder why oatmeal is often used in masks and other skin treatments? As it turns out, avenanthramides applied topically in concentrations as low as 1 parts per billion can prevent inflammation and itchiness at a cellular level by inhibiting certain enzymes and biological processes.

We tend to think of inflammation as a universally bad thing that should always be avoided, but that’s not the case. As the Harvard Medical School explained, acute inflammation occurs immediately after an injury and produces warmth, redness, swelling, and pain. Although unpleasant, this process brings white blood cells to the area, where they can begin the healing process. But if the inflammatory response becomes chronic, the body can get confused and begin attacking healthy tissue. Chronic, low-grade inflammation is believed to cause or worsen a number of conditions, including heart disease and diabetes.

You may have difficulty absorbing certain minerals

oatmeal and apple

Despite their many health benefits, oats do have a few downsides. One of these is their high phytate content. According to Healthline, phytate (phytic acid) is a substance found in the seeds of plants that provides a stored source of the mineral phosphorus, which the seed will need when it begins to grow. When eaten by humans, however, phytate can impair the absorption of minerals such as iron, zinc, and calcium and may lead to mineral deficiencies.

A study published in the Journal of Food Science and Technology found that oats contained between 0.42 and 1.16 grams of phytate per 100 grams of dry oats. Fortunately, there are a few simple things you can do to reduce the phytate content of your morning bowl of oats. As Healthline explained, soaking phytate-rich foods removes a significant amount of the anti-nutrient, so consider soaking your oats overnight before cooking them. Sprouting (allowing the seed to germinate) also reduces phytate content. If you don’t feel like spending the extra money to buy sprouted rolled oats, you can easily sprout oat groats at home.

You may be getting way more sugar than you think

boxes of Quaker oatmeal

Plain oats contain no simple sugars, but if you prefer the flavored kind or tend to pile on sugary mix-ins, your breakfast may not be as healthy as you think. Original (unflavored) Quaker instant oatmeal, for instance, contains 0 grams of sugar, natural or added. The apples and cinnamon flavor, however, contains 8 grams of added sugar, while the maple and brown sugar variety contains 12 grams of added sugar.

Because of its link to obesity, cavities, and chronic diseases like diabetes and heart disease, health professionals suggest limiting your intake of added sugar as much as possible. The 2015–2020 Dietary Guidelines for Americans recommends keeping added sugar consumption to no more than 10 percent of total calories. On a 2,000-calorie diet, that’s 200 calories. The average American, however, consumes about 17 teaspoons per day.

Some organizations suggest even stricter limits. The American Heart Association (AHA), for instance, advises "limiting the amount of added sugars you consume to no more than half of your daily discretionary calories allowance." The AHA considers this 100 calories (25 grams, 6.25 teaspoons) for women and 150 calories (37.5 grams, 9.3 teaspoons) for men.

If you’re staying away from gluten, you’ll need to be extra careful about your oats

oats arranged in snowflake pattern

Oats are innately gluten-free, so if you’re avoiding gluten because you have celiac disease, a non-celiac gluten sensitivity, or a wheat allergy you should technically be safe. But, according to Healthline, oats are often contaminated with wheat, rye, or barley (all of which contain gluten). This contamination can occur when the seeds are planted, when the oats are harvested, or in the facility where they’re processed. Cross-contaminated oats can contain as much as 10 times the amount of gluten needed to cause an adverse reaction in someone who’s gluten intolerant. In addition, avenin, a protein in oats, has a very similar chemical structure to gluten, so it may cause a reaction in some sensitive individuals.

While an allergy to oats is rare, it can happen. In an interview with Allergic Living, Dr. Scott Sicherer explained that individuals who are allergic to one grain (such as wheat) have a 20 percent chance of being allergic to another grain (such as oats).

If you’re sensitive to gluten and find yourself having negative reactions to oats, give certified gluten-free oats a try before you swear off this healthy breakfast option entirely.

Your oats may contain high levels of toxic herbicides

sad man eating oatmeal

What do you like to mix into your oatmeal? Nuts? Raisins? Fruit? How about the chemical herbicide glyphosate? According to an article in Health, "glyphosate is the most widely used herbicide in the world, and is used in hundreds of weed-killing products." In theory, foods like oats that are contaminated with glyphosate residue don’t contain enough of the chemical to be harmful to humans. But not everyone agrees on what, exactly, a safe level is. The Environmental Protection Agency (EPA) has set a daily tolerable limit of 30 parts per million (ppm). The Environmental Working Group (EWG), however, has set a limit that’s more than 60 times lower than the EPA’s. The EWG cautioned that "legal is not the same as safe" and opted for the stricter guideline to account for the fact that children may be more sensitive to the effects of glyphosate.

In 2018, the EWG tested 45 regular (non-organic) and 16 organic oat products. They found that 43 of the regular products and 5 of the organic products had detectable levels of glyphosate. Of those, 31 of the regular products contained levels higher than the EWG’s limit of 160 parts per billion (ppb).