If all goes well, you already know that whole grains should be preferred over refined grains. A new study once again shows why choosing whole grains is wise. We’ll conveniently list 3 reasons for you.
Whole grains vs. refined grains
Because it’s handy not to confuse refined grains with refined sugars, first a brief explanation.
Refined grains are grains that have been filtered of everything except the starch. If you grind a grain kernel whole into flour and bake bread, you can call this whole grain bread. If you only grind the inner part of the kernel, the endosperm, and sift it, you make flour for white bread. Brown bread is made from flour with a mix of both.
This makes a big difference in the nutrients we get. By removing everything from the grain kernel except the sugars, you have also removed a large part of the proteins, fibers, minerals, and vitamins. You are left mainly with starch, fortunately still a complex carbohydrate. Starch is composed of two different sugars that are then built up into thousands of chains of glucose. Your body needs to break down these chains before the glucose can be absorbed into the blood. However, this happens much faster than when there were still fibers to process as in whole grain bread. To process that glucose, certain vitamins and minerals are also needed. These must be ‘borrowed’ from your body itself if you have mostly filtered them out.
However, starch is very different from the refined sugars that are often added to bread, on average about one sugar cube per four slices of bread. For these refined sugars, other natural sugars such as sugar beets and sugar cane are used. Both yield after several steps of filtering pure sucrose, the well-known table sugar. Sucrose is not built up from thousands of chains like starch, but only two; glucose and fructose. This results in a different absorption in the body. To make the story even more confusing, I must note that this does not mean that the glucose from starch is absorbed less quickly than the glucose from these added sugars. That has to do with the fact that the fructose in sucrose must first be converted into glucose.
For now, it suffices to know that with refined grains, we mean something different than with refined sugars. In this article, we are talking about replacing refined grains with whole grains.
Researchers from the Technical University of Denmark conducted research on the effect of choosing to replace refined grains [1]. For example, by replacing white bread with whole grain bread and white pasta with whole grain pasta. They conducted the research in collaboration with the University of Copenhagen and DTU Bioinformatics and researchers from other universities and hospitals. The study involved 50 adults at increased risk of developing cardiovascular disease and type 2 diabetes.
The participants were randomly divided into two groups. One group followed a diet containing whole grains in all grain products for eight weeks. Then they followed their normal diet for 6 weeks before being put on a diet containing refined grains for eight weeks. This was done in reverse order for the other group.
1. Eating less and lower weight?
The study found that participants eating whole grains ate less, probably because whole grains lead to a feeling of satiety sooner. It also appeared that participants on the whole grain diet lost weight on average.
Similar results have been seen in previous studies, although this did not always reduce the total amount of energy consumed [2]. In the Danish study, this may have to do with the test group consisting of overweight individuals who were placed on this diet themselves (except for the 6 weeks in between).
In a study from 2008, the results of fifteen trials were compared, all of which looked at the relationship between whole grains, refined grains, BMI, waist circumference, and total energy intake [3]. In total, these trials represented 20 test groups consisting of almost 120,000 people. On average, BMI was 0.630 kg/m2 lower with a high intake of whole grains compared to a low intake of whole grains. Waist circumference was on average 2.7% smaller in the group with a high intake of whole grains.
A difference with the Danish study is that the ‘whole grain fans’ actually consumed more energy. However, this was not a selected group of overweight people. The people who ate a lot of whole grains in the fifteen compared trials were found to make healthier choices. They smoked less, ate less fat, and exercised more. The latter may explain the lower weight with an average higher intake of food/energy.
2. Lower risk of diabetes
Blood tests in the Danish study showed that participants had less inflammation in their bodies when they ate whole grains. Rye in particular was found to have a positive effect here. Inflammation is a natural response of the body to an infection. However, in some people, there are increased levels of inflammation (the so-called low-grade inflammation), even when there is no infection. This mainly occurs in overweight people. These unnecessary elevated levels of inflammation increase the risk of developing type 2 diabetes.
Interestingly, these effects were not accompanied by significant changes in gut bacteria. Most of us have heard of the importance of fiber for the gut flora. Although the researchers did not find these changes based on the examined stool, they took into account that this may be due to individual differences in gut flora and the response to fiber.
3. Lower risk of cardiovascular disease and longer life
In an earlier study from 2015, including researchers from Harvard, a lower risk of death was demonstrated when more whole grains were consumed [4].
The researchers used data from the Nurses’ Health Study (1984–2010) and the Health Professionals Follow-Up Study (1986–2010), two large prospective cohort studies. With this, they had insight into the dietary habits of over 74,000 women and nearly 44,000 men. For every 28 grams per day of whole grains eaten, the risk of death was 5 percent lower and the risk of cardiovascular disease was 9% lower.
Need more reasons?
References
- Henrik Munch Roager, Josef K Vogt, Mette Kristensen, Lea Benedicte S Hansen, Sabine Ibrügger, Rasmus B Mærkedahl, Martin Iain Bahl, Mads Vendelbo Lind, Rikke L Nielsen, Hanne Frøkiær, Rikke Juul Gøbel, Rikard Landberg, Alastair B Ross, Susanne Brix, Jesper Holck, Anne S Meyer, Morten H Sparholt, Anders F Christensen, Vera Carvalho, Jens Juul Holst, Jüri Johannes Rumessen, Allan Linneberg, Thomas Sicheritz-Pontén, Marlene D Dalgaard, Andreas Blennow, Henrik Lauritz Frandsen, Silas Villas-Bôas, Karsten Kristiansen, Henrik Vestergaard, Torben Hansen, Claus T Ekstrøm, Christian Ritz, Henrik Bjørn Nielsen, Oluf Borbye Pedersen, Ramneek Gupta, Lotte Lauritzen, Tine Rask Licht. Whole grain-rich diet reduces body weight and systemic low-grade inflammation without inducing major changes of the gut microbiome: a randomised cross-over trial. Gut, 2017; gutjnl-2017-314786 DOI: 10.1136/gutjnl-2017-314786
- Cooper DN, Martin RJ, Keim NL. Does Whole Grain Consumption Alter Gut Microbiota and Satiety? Samman S, Darnton-Hill I, eds. Healthcare. 2015;3(2):364-392. doi:10.3390/healthcare3020364.
- Wu H, Flint AJ, Qi Q, van Dam RM, Sampson LA, Rimm EB, Holmes MD, Willett WC, Hu FB, Sun Q. Association Between Dietary Whole Grain Intake and Risk of MortalityTwo Large Prospective Studies in US Men and Women. JAMA Intern Med. 2015;175(3):373–384. doi:10.1001/jamainternmed.2014.6283
- Wu H, Flint AJ, Qi Q, van Dam RM, Sampson LA, Rimm EB, Holmes MD, Willett WC, Hu FB, Sun Q. Association Between Dietary Whole Grain Intake and Risk of MortalityTwo Large Prospective Studies in US Men and Women. JAMA Intern Med. 2015;175(3):373–384. doi:10.1001/jamainternmed.2014.6283
