Oats are a whole-grain cereal, known scientifically as Avena sativa. They are mainly grown in North America and Europe.
They are a very good source of fiber, especially beta-glucan, and are high in vitamins, minerals and antioxidants.
Whole oats are the only source of a unique group of antioxidants called avenanthramides, believed to have protective effects against heart disease.
Oats are most commonly rolled or crushed, and can be consumed as oatmeal (porridge), in baked goods, bread, muesli and granola.
Whole grain oats are called oat groats.
The oat groats are most commonly rolled or crushed into flat flakes and lightly toasted to produce oatmeal.
Quick, or instant oatmeal is made up of more thinly rolled or cut oats that absorb water much more easily and therefore cook faster.
The oat bran (the fiber-rich outer layer of the grain) is often consumed separately as a cereal, with muesli or in breads.
To produce infant oatmeal, oats are often further processed into powder that becomes a thick porridge when mixed with water.
Oats have a well-balanced nutritional composition, and one serving (30 grams) of oats contains 117 calories.
By weight, raw oats are 66% carbohydrates, 17% protein, 7% fat and 11% fiber.
The table below contains detailed information on the nutrients in oats (5):
Carbs make up 66% of oats.
Oats are very low in sugar, with only 1% coming from sucrose.
About 11% of the carbs are fiber, and 85% consists of starch.
Starch is the single biggest component of oats, made up of long chains of glucose molecules.
Three types of starches are found in oats, classified with respect to digestibility (9).
The main starches in oats are:
- Rapidly digested starch (7%), which is quickly broken down and absorbed as glucose.
- Slowly digested starch (22%), that is broken down and absorbed more slowly (10).
- Resistant starch (25%), which functions like a type of fiber. It escapes digestion and improves gut health by feeding the friendly gut bacteria (11).
Oats contain almost 11% fiber, and porridge contains 1.7% fiber.
The majority of the fiber in oats is soluble, mostly a fiber called beta-glucan.
Oats also contain insoluble fibers, including lignin, cellulose and hemicellulose (12).
Beta-glucans are unique among fibers, as they can form a viscous (gel-like) solution at a relatively low concentration.
Beta-glucans are known to lower cholesterol levels and increase excretion of bile acids. They are also believed to cause a reduction in blood sugar and insulin levels after a carbohydrate-rich meal (17, 18, 19, 20).
Daily consumption of beta-glucans has been shown to lower cholesterol, especially LDL (the "bad") cholesterol, and may therefore decrease the risk of heart disease (21).
Bottom line: The carbs in oats are mostly made up of starches and fiber. Oats are a good source of a unique type of fiber called beta-glucan, which is associated with a range of health benefits.
The major protein in oats is called avenalin (80%), which is not found in any other grain, but is similar to legume proteins.
A minor protein is a prolamin called avenin, which is related to gluten in wheat (23).
However, pure oats are considered safe for most people with gluten intolerance (24).
Whole oats contain more fat than most other grains, ranging from 5-9%. It consists mostly of unsaturated fatty acids (3).
Bottom line: Oats contain more protein and fat than most other grains. Pure oats are gluten-free.
Oats are high in many vitamins and minerals. The main ones are listed below.
- Manganese: Typically found in high amounts in whole grains, this trace mineral is important for development, growth and metabolism (25).
- Phosphorus: An important mineral for bone health and tissue maintenance (26).
- Copper: An antioxidant mineral that is often lacking in the Western diet. It is considered important for heart health (27).
- Vitamin B1: Also known as thiamine, this vitamin is found in many foods, including grains, beans, nuts and meat.
- Iron: As a component of hemoglobin, a protein responsible for transporting oxygen in the blood, iron is absolutely essential in the human diet.
- Selenium: An antioxidant, important for various processes in the body. Low selenium status has been associated with increased risk of premature death, and impaired immune and mental function (28).
- Magnesium: Often lacking in the diet, this mineral is important for numerous processes in the body (29).
- Zinc: A mineral that participates in many chemical reactions in the body and is important for overall health (30).
Bottom line: Oats contain high amounts of many vitamins and minerals, such as manganese, phosphorus, copper, B-vitamins, iron, selenium, magnesium and zinc.
The main plant compounds are listed below.
- Avenathramides: Only found in oats, avenathramides are a family of powerful antioxidants. They may reduce arterial inflammation and regulate blood pressure (34, 35, 36).
- Ferulic Acid: The most common polyphenol antioxidant in oats and other cereal grains (12, 37).
- Phytic Acid: Most abundant in the bran, phytic acid is an antioxidant that can impair the absorption of minerals, such as iron and zinc (12, 38).
Bottom line: Oats are the only dietary source of powerful antioxidants called avenathramides. They also contain ferulic acid and phytic acid.
Listed below are the main health benefits of oats and oat bran.
Oats Can Lower Cholesterol
Heart disease is the leading cause of death worldwide (49).
Two suggested mechanisms for these cholesterol-lowering effects have been proposed.
First, beta-glucan may slow the absorption of fats and cholesterol by increasing the viscosity of the digestive contents (56).
Second, beta-glucan binds with cholesterol-rich bile acids in the intestine, produced by the liver to aid digestion. Beta-glucan then carries them down the digestive tract and eventually out of the body.
Normally, bile acids are recycled (re-absorbed) in the digestive system, but beta-glucan inhibits this recycling process, leading to reduced levels of cholesterol in the body (57).
Authorities have approved the health claim that foods containing at least 3 grams of beta-glucan per day may lower the risk of heart disease (58).
Bottom line: Oats contain high amounts of beta-glucans, which are very effective at reducing blood cholesterol levels.
Oats and Type 2 Diabetes
The prevalence of type 2 diabetes has increased dramatically in recent years and decades.
Type 2 diabetes is characterized by the abnormal regulation of blood sugar, usually as a result of decreased sensitivity to the hormone insulin.
In patients with type 2 diabetes and severe insulin resistance, a 4-week dietary intervention with oatmeal resulted in a 40% reduction in the insulin dosage needed for stabilizing blood sugar levels (64).
Studies suggest that beta-glucans may favorably alter insulin sensitivity, delaying or preventing the onset of type 2 diabetes (65, 66, 67, 68), but a recent review study concludes that the evidence is inconsistent (54).
Bottom line: Oats may reduce blood sugar and insulin responses following carbohydrate-rich meals. This makes them particularly beneficial for diabetics.
Oats and Increased Satiety
Satiety plays an important role in energy balance. It stops eating and prevents us from eating again until hunger returns (72).
In a study ranking the satiety effect of 38 common foods, porridge (cooked oatmeal) ranked 3rd overall, and 1st among breakfast foods (75).
Human trials have shown that oatmeal, rich in beta-glucans, may increase satiety and reduce appetite when compared to a ready-to-eat breakfast cereal and other types of dietary fiber (13, 14, 79, 80).
In addition to being highly satiating, oats, eaten as porridge, are low in calories and contain plenty of fiber and other healthy nutrients, making them an excellent addition to an effective weight loss diet.
Bottom line: Porridge (cooked oatmeal) is low in calories, is very filling and may decrease appetite, compared to other breakfast foods.
Oats and Gluten-Free Diets
A gluten-free diet is the only solution for individuals who suffer from celiac disease, as well as for many individuals with gluten sensitivity.
Oats do not contain gluten, but they contain a similar type of protein, called avenin.
Oats have been shown to enhance the nutritional value of gluten-free diets, increasing both mineral and fiber intakes, and individuals usually prefer to include oats in their gluten-free diets (87, 88).
Therefore, it is important for celiac patients to only eat oats that have been certified as "pure" or "gluten-free."
Bottom line: Oats are naturally gluten-free, but they are often contaminated with wheat. Individuals sensitive to gluten should only consume oats that are certified as "pure" or "gluten-free".
Other Health Benefits of Oats
Oats are being extensively studied in many other areas, such as in cancer research, which is still in its early stages.
There are a few other benefits that deserve mentioning.
Feeding oats to young infants, before they reach an age of 6 months, has been associated with decreased risk of developing childhood asthma (91).
A few studies indicate that oats may boost the immune system, enhancing the body's ability to fight bacteria, viruses, fungi and parasites (92).
Bottom line: Oats have been associated with all sorts of benefits, including decreased risk of childhood asthma, enhanced immune system and decreased need for laxatives in the elderly.
Oats are usually well tolerated, with no adverse effects in healthy individuals.
It is important for individuals allergic or intolerant to wheat, or other grain types, to buy only oats that are certified as pure from contamination.
Bottom line: Oats are usually well tolerated, but they may be contaminated with gluten. Individuals who are sensitive to gluten should only consume "pure" and non-contaminated oats.
Oats are among the world's healthiest grains.
They are a good source of many vitamins, minerals and unique plant compounds.
Oats also contain large amounts of unique soluble fibers called beta-glucans, which provide numerous health benefits.
These include lower cholesterol, reduced blood sugar and insulin responses, relieved constipation and improved immune function.
In addition to all this, oats are also very filling, and may reduce appetite and help you eat fewer calories.