Cereal grains, such as wheat, rice, and corn, are some of the most commonly consumed foods in the world.
Despite widespread consumption, many people remain unsure whether grains support health. Some think they are an essential component of a healthy diet, while others believe that they cause harm.
The truth is, whole grains in particular are linked to numerous health benefits and are mostly considered very nutritious. Yet, some folks claim that refined grains are too high in carbohydrates, impede any intentional weight loss, and spike blood sugar (
This article reviews grains — both whole and refined — and their potential benefits and downsides, according to scientific evidence.
Grains are small, hard, and edible dry seeds that grow on grass-like plants called cereals.
They are a staple food in most countries and have played a major role in human history. Wheat was one of the first crops to be domesticated — about 10,000 years ago in the area now known as the Middle East (
Today, grain-based foods supply roughly half of the world’s calories (
A few of the commonly produced and consumed grains are corn (or maize), rice, and wheat. Other popular grains include barley, oats, millet, sorghum, and rye.
There are also foods that are prepared and consumed like grains but are technically “pseudo-cereals,” such as quinoa and buckwheat.
Foods made from grains include breads, pasta, breakfast cereals, oatmeal, tortillas, pastries, cookies, chips, and crackers. Grains are also used to make sweeteners, such as high fructose corn syrup and rice syrup, that are added to many packaged foods.
Grains are edible dry seeds from plants called cereals. They provide about half of the world’s food energy. Some commonly consumed grains are corn (maize), rice, and wheat.
Grains can be classified as either whole or refined.
A whole grain consists of three main parts (
- Bran: The hard outer layer of the grain, it contains fiber, minerals, and antioxidants.
- Germ: The nutrient-rich core contains carbs, fats, proteins, vitamins, minerals, antioxidants, and various phytonutrients. The germ is the embryo of the plant — the part that gives rise to a new plant.
- Endosperm: The biggest part of the grain, it contains mostly carbs (in the form of starch) and protein.
A refined grain has the bran and germ removed, leaving just the endosperm. As a result, refined grains have less fiber — an essential nutrient for healthy digestion and other functions — and fewer nutrients than whole grains (
However, in the United States, refined grains are often enriched. Enriched grains have nutrients that were lost during the refining process, such as B vitamins and iron, added back to them (7, 8).
Still, fiber is typically not added back to refined grains.
Some grains, like oats and brown rice, are usually eaten whole. Others are generally eaten refined.
Many grains are mostly consumed after they are processed to remove the bran and germ and/or milled into flour.
Some examples are foods with white flour made from refined wheat, like pasta, white bread, and flour tortillas. White rice, which has the bran and germ removed, is also popular; it’s the refined version of whole grain brown rice.
A whole grain contains the bran and germ of the grain, which provide fiber and important nutrients. Refined grains have these parts removed, leaving only the high-carb endosperm.
The possible benefits of grains are mostly discussed in the context of whole grains.
Since whole grains have not been processed to remove the bran and germ, they tend to be higher in certain minerals, beneficial compounds, and fiber than refined and even enriched grains.
For example, whole wheat flour is higher in protein, fiber, zinc, manganese, and phosphorus than enriched white flour. However, enriched white flour tends to have higher levels of B vitamins (
Whole grains also contain more phenolic acids — a category of phytochemicals (plant compounds) — than refined grains.
In particular, the bran of whole grains like wheat is loaded with phenolic acids that act as antioxidants and may exhibit anti-inflammatory and anticancer effects, among other benefits (
The higher fiber and phenolic acid contents of whole grains are the main reasons they are considered healthier than refined grains and are likely responsible for their associated health benefits (
Studies on whole grains and health
Numerous studies link whole grain consumption with the following potential health benefits (
- Longevity: Large observational studies have found that with each serving of whole grains consumed, there was a 9% lower risk of death from heart disease over the course of the study (
- Weight: Eating more whole grains is linked to lower body weights. That could be because the fiber in whole grains may help reduce hunger and increase satiety, leading to decreased energy (calorie) intake (
- Type 2 diabetes: People who eat more whole grains appear to have a lower risk of developing type 2 diabetes (
- Heart disease: Whole grains may help protect the heart. A review of 45 studies found that 3 servings (90 grams) of whole grain intake per day is associated with a 22% reduction in heart disease risk and 12% reduction in stroke risk (
- Colorectal cancer: In one large observational study, the group with highest intake of whole grains had a 16% lower incidence of colorectal cancer compared to the group with the lowest intake (
Keep in mind that most of these studies are observational, meaning that they show a link between whole grains and better health but cannot prove that eating whole grains is definitely the cause of these benefits.
That being said, there are also randomized controlled trials — which may be more accurate — that also show the benefits of whole grains.
These trials have found that whole grains may improve many other potential health markers, including inflammation levels, heart disease risk, and body fat levels (
Whole grains are linked to many health benefits. For example, adequate intake may protect against heart disease, diabetes, and colorectal cancer. These beneficial effects likely come from fiber and phenolic acids in whole grains.
Grains may also come with some downsides. These are typically attributed to refined grains, not whole ones.
Refined grains have been mostly stripped of fiber. Plus, they do not have the beneficial phenolic acids that whole grains provide (
Even though refined grains are often enriched with B vitamins and iron, they lack other micronutrients found in whole grains (
Keep in mind that many foods with refined grains — like cakes, cookies, or highly processed crackers and snack foods — are also high in other nutrients that may negatively affect health when consumed in excess, such as added sugar, sodium, and saturated fat.
As a result, refined grains are not linked to the same benefits as whole grains. In fact, they are often linked to poor health outcomes instead, though more research is needed to confirm those associations.
Studies on refined grains and health
Many studies have found associations between refined grains and negative health effects, including:
- Obesity: High refined grain consumption has been linked to weight gain and an increased risk of obesity. The exact connection between refined grains and weight is unclear, but one idea is that refined grains drive spikes in blood sugar followed by increased cravings, overeating, and subsequent weight gain (
- Blood sugar: Without much fiber, refined grains tend to be digested quickly and can therefore lead to spikes in blood sugar. That may be one of the reasons that refined grain consumption is associated with poor blood sugar management (
25, 26, 27).
- Inflammation: Eating a lot of refined grains may increase markers of inflammation in the body, such as C-reactive protein. Low-grade inflammation has been linked with heart disease and type 2 diabetes, among other health problems (
- Heart disease: One study found that eating 7 or more servings (about 350 grams) of refined grains per day was linked to a higher risk of major heart disease events like stroke compared to eating fewer than 50 grams per day (
While these studies suggest a link between refined grains and poor health, most of the research has been observational. There is a clear need for high-quality studies and randomized controlled trials.
In addition, some studies offer inconclusive results or have found no link between refined grains and health problems (
One explanation for the mixed results is that the definition and amounts of refined grains may vary across studies.
Overall, the amount of refined grains you eat and the quality of the rest of your diet likely makes a big difference in their effects (
Refined grains lack the levels of fiber and plant compounds responsible for the benefits of whole grains. They may also be linked to issues like obesity, heart disease, and inflammation, but we need more research into those relationships.
Some grains contain gluten, a protein found in wheat, spelt, rye, and barley.
Many people are intolerant to gluten, including people with celiac disease — a serious and chronic autoimmune condition — as well as people with gluten sensitivity (
Some grains, especially wheat, are also high in FODMAPs (fermentable oligosaccharides, disaccharides, monosaccharides, and polyols). FODMAPS are a group of carbs that can cause digestive distress in some people (
For these reasons, some individuals may need to limit or avoid grains depending on their needs.
However, just because gluten and FODMAPs may cause problems for some people, this does not mean all grains should be avoided or that everyone needs to limit grains.
Many whole grain foods, such as brown rice, quinoa, and corn, are gluten-free and can be enjoyed on gluten-free diets.
Lastly, some people are concerned about antinutrients in grains.
Antinutrients are substances in foods, especially plants, that may interfere with digestion and absorption of other nutrients. They include phytic acid, lectins, and others (
However, it’s important to keep in mind that antinutrients are not specific to grains. They are also found in all sorts of healthy foods, including nuts, seeds, legumes, tubers, and even some fruits and vegetables.
Antinutrients like phytic acid can also be degraded (broken down) by preparation methods like soaking, sprouting, and fermenting (
Even if grains are not prepared with these methods, however, antinutrients likely do not pose any meaningful health risks to people who eat whole grains in normal amounts as part of a varied diet (
Plus, cooking grains (and other plant foods) generally reduces any effects of antinutrients, and most people don’t eat raw grains.
Gluten, a protein found in several grains, can cause problems for people who are sensitive to it. Some people are also concerned about antinutrients in grains, but these concerns are generally unwarranted.
Grains may offer potential benefits, though there are some potential downsides for certain groups of people.
Whole grains are high in fiber and have been linked to health benefits, such as lower risks of heart disease, colorectal cancer, and type 2 diabetes.
Too many refined grains, on the other hand, are thought to contribute to health problems. Plus, people who need to avoid gluten cannot consume certain grains.
At the end of the day, the overall quality of your diet has more of an effect on health than any one food or food group. Whether or not grains can fit into your diet depends on your individual needs and concerns.
But for most people, whole grains can — and even should — be included as part of a balanced diet.
Just one thing
Try this today: Did you know that popcorn counts as a whole grain? For a healthy snack, pop kernels in an air popper and toss with olive oil, fresh herbs, and parmesan cheese.