Oats

Health Benefits
(Source: World's Healthiest Foods, George Mateljan)

Oat's Digestive Support

Once foods are eaten, not all of them have an equally supportive impact on our digestive tract. For example, when eaten in large amounts, food with disproportional amounts of fat can slow down our digestive process excessively, including the rate of that foods pass out of our stomach (known as the rate of emptying). Foods that contain disproportional amounts of simple sugars and simple starches can work in the opposite direction, speeding up the digestive process and challenging our blood sugar regulation. By contrast, oats are a food that seems to provide us with unusually helpful digestive support.

A key focus in studies on oats and digestive support has been the unique fibers known as beta-glucans. Water-soluble fibers, beta-glucans support our digestion in two basic ways.

First, beta-glucans increase the "viscosity" of our food contents when they are present in our upper digestive tract. While "viscosity" is a measurement that generally refers to thickness, the idea of viscosity actually involves more than just thickness. When a substance is "viscous" it is not only thick but it is also resistant to flow. Honey and molasses are examples of viscous fluids that take time to pour out of a bottle or jar. Compared to non-viscous fluids like water, these viscous fluids take much longer to pour out and be emptied from the container in which they reside. The beta-glucans in oats appear to have this same type of effect in our small intestine. They allow our food to keep moving through our digestive tract, but they also help regulate the pace by slowing it down and allowing more time for nutrient digestion and absorption.

The increased viscosity of our GI contents may also be accompanied by more engagement of the smooth muscles that surround our small intestine, as well as by the release of digestion-related hormones. This hormone release may include peptide YY and glucagon-like peptide-1 (GLF-1), which are associated with increased feelings of fullness and satisfaction with food. So as you can see, there are a variety of factors that fall into this "digestive support" category when oats are present in the upper portion of our GI tract.

The digestive tract support provided by oats extends to our lower GI tract as well. In our large intestine (colon), oats—including their beta-glucans—get fermented by intestinal bacteria. This fermentability of oat fibers like beta-glucans not only helps maintain healthy bacterial populations in our large intestine, but it also provides the release of short chain fatty acids from these fibers that can provide energy for our intestinal cells.

Researchers have linked both aspects of digestive tract support—increased viscosity in the small intestine and fermentability in the large intestine—to better regulation of insulin, blood sugar, and cholesterol. While these health benefits have sometimes been associated with particular amounts of beta-glucan in oats, there remains a good bit of debate about the exact amount of beta-glucan that is needed. Most studies suggest that 1-2 grams of beta-glucan per serving of oats is not sufficient to provide optimal benefits, and that a more desirable range for beta-glucan intake falls between 3-6 grams per serving. Unfortunately, however, more research is needed before a firm conclusion can be reached about these beta-glucan amounts. More research is also needed about specific varieties of oats and variations in beta-glucan content. Still, the overall research is very clear about the digestive support provided by this unique grain.

Blood Sugar Support Provided by Oats

Although mentioned earlier in this profile, it's worth singling out blood sugar support as a special health benefit provided by oats. Of course, healthy regulation of blood sugar would be expected from most any whole food that provided us with a substantial amount of protein and fiber. Both of these macronutrients can be helpful in stabilizing our blood sugar because both help moderate the passage of food through our GI tract and engage our digestive processes in a balanced way. Interestingly, you will not find oats in our Top 25 WHFoods for either protein or fiber; therefore, they are not an especially concentrated source of either macronutrient. Yet, they are a significant and balanced source, with ¼ cup of dry unprocessed oats typically providing us with 6-7 grams of protein and 4-5 grams of fiber. Importantly, the fiber in oats is split between soluble and insoluble, providing us with digestive benefits from both fiber types. And equally important, the soluble fiber in oats includes their beta-glucans.

Researchers are not entirely clear about all of the connections that exist between oat intake and blood sugar regulation. All studies point to an important role played by the soluble fiber found in this grain and the beta-glucans that are contained within this soluble fiber component. Also involved may be minerals like manganese (oats are the number 2 source of manganese at WHFoods), the B vitamins they contain (as they play a role in glucose metabolism), and oat saponins, including avenacoside A,1 and B,2. Perhaps it is the unique combination of all these factors in oats that result in the blood sugar support seen in research studies. Intake of oats and oatmeal has repeatedly been shown to improve after-meal (postprandial) blood sugar and insulin levels. In addition, healthy levels of hemoglobin A1C have been associated with intake of both oats and oatmeal. (Hemomglobin A1C is a form of the key protein in our red blood cells—hemoglobin—in which the protein gets linked up with a sugar molecule through a process called glycosylation. If an overly high percentage of our hemoglobin proteins begin to take this form, healthcare providers begin to suspect problems in glucose and insulin metabolism. Since our red blood cells live for approximately three months, hemoglobin A1C levels are viewed as representing the degree of blood sugar stability over a three-month period. In persons at risk for blood sugar problems, intake of both oats and oatmeal have been associated with healthier levels of hemoglobin A1C—which researchers consider evidence of blood sugar support provided by the intake of this grain.

One final issue that we would like to address regarding oats and blood sugar is glycemic index (GI). Although you will find a more detailed description of this issue in the Description section of this profile, we think that it is important to point out that the GI values that we have seen for old-fashioned rolled oats and steel cut oats are significantly lower than the values that we have seen for instant oats. The overall GI range for old-fashioned rolled oats and steel cut oats is 55–70. By contrast, the overall GI range for instant appears to be much closer to 70–80. At WHFoods, we treat 55 or below as "low GI;" 56–69 as "medium GI;" and 70 or above as "high GI." So you can see that old-fashioned rolled oats and steel cut oats fall into the low or medium GI range, while instant oats fall into the high range. For this reason, old-fashioned or steel cut oats (versus instant oats) would be expected to provide you with better blood sugar support than instant oats.

Oats' Cardiovascular Support

Strong intake of fiber—including both soluble and insoluble fiber—has long been associated with decreased risk of cardiovascular problems. While the focus in many cardiovascular studies has remained on soluble fiber, research has shown cardiovascular benefits for both fiber types. Soluble fiber—just like its name suggests—is especially "friendly" toward water. Soluble fibers can take on water, swell, and hold water. This characteristic of soluble fiber can lead to improved viscosity in our small intestine contents as described earlier in this profile. As a result of this improved viscosity, we get improved digestion and absorption of nutrients, including some of the key cardiovascular-support nutrients present in oats. These nutrients include multiple B vitamins, as well as the minerals magnesium and zinc. Within the soluble fiber portion of oats are found beta-glucans, and intake of these unique polysaccharide fibers has been associated with decreased levels of total and LDL cholesterol.

In a very large scale study in Denmark involving over 50,000 adults between the ages of 50–64 years, intake of oats has been associated with decreased risk of heart attack (also known as myocardial infarct, or MI). Researchers conducting this study pointed to potential roles for both soluble and insoluble fibers in producing the study results. Some more complicated metabolic processes may also be involved in the cardiovascular benefits related to intake of oats. In particular, researchers have been interested in the ability of oat intake to lessen the risk of excessive inflammation in the blood vessels. The series of events in this area of research has sometimes focused on some unique phenolic, nitrogen-containing molecules in oats called avenathramides. Also of interest have been the oat saponins—primarily avenacoside A,1 and avenacoside B,2. These sugar-related (glycoside) molecules are found primarily in the bran portion of the oat, and like beta-glucan, their intake has been associated with decreased levels of LDL and total cholesterol.

It's important not to lose the forest through the trees, however, when looking at the cardiovascular benefits of oats and oatmeal. In multiple studies, consumption of this grain has been associated with decreased risk of metabolic syndrome, decreased risk of obesity, lower waist circumference, and lower body mass index (BMI). These findings all point in the direction of cardiovascular support following routine intake of this unique grain. Also worth mentioning in this context are the findings from an analysis of the data from the Nutrition Health and Examination Surveys (NHANES) between 2001—2010 in the U.S. In these analyses, children who ate oatmeal on a regular basis were found to have decreased risk of "central adiposity", which is the accumulation of excessive body fat in the general abdominal area.

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