You should eat lots of unrefined whole grains because they promote the growth of healthful colon bacteria that help to prevent death and heart disease, particularly if you are overweight or have high blood sugar levels.  A study from Iran found that people who ate lots of refined grains were at increased risk for suffering blocked arteries leading to the heart, while those who ate more whole grains were at reduced risk (Am Coll of Cardiol Middle East, 13th Emirates Cardiac Society Congress in Dubai, United Arab Emirates, October 7, 2022). Doctors recruited people who had X-ray imaging of the blood vessels leading to their hearts, and had them complete questionnaires detailing how much whole grains or refined grains they were eating. Of the 2537 participants, 1,168 had healthy, unblocked arteries and 1,369 had 50-75 percent more blockage by plaques in at least one heart artery. Those who had the highest intake of refined grains were one and a half times more likely to have blocked arteries leading to their hearts as the group that took the least amount, while those who had the highest intake of whole grains had only one half the chance of having blocked heart arteries.

This study agrees with the earlier PURE study (Prospective Urban and Rural Epidemiological study), which showed that people who eat a lot of refined grains – foods made from flour – are at increased risk for dying of heart attacks (Nutrients, Dec 4, 2018;10(12):1912). The researchers followed 148,858 people in 21 countries, ages 35 to 70 and with no heart disease, for 9.4 years (BMJ, Feb 3, 2021;372:m4948). They found that those who ate the most refined grains (>350 g per day) had a 33 percent higher risk of serious heart disease and high blood pressure, and a 27 percent higher risk of death, compared to those with the lowest intake (<50 g per day). These increased rates of heart disease and death were not found in those who ate unrefined whole grains

The Healthful Whole Grains
Unrefined whole grains promote the growth of healthful colon bacteria that form short chain fatty acids (SCFAs), which help to prevent heart disease.  Whole grains are the seeds of grasses that look like little pebbles and have a fiber coat that cannot by broken down by your intestinal enzymes. Common whole grains include oats, wheat, barley, brown rice, wild rice, quinoa and dried corn.

Grains are refined by rubbing off the outer coat (fiber), grinding the seeds into flour, or both. When the outer capsule of the grain is removed or ground up, your intestinal enzymes can easily break down the carbohydrates into simple sugars that are readily absorbed from your upper intestines into your bloodstream. If you eat lots of bread, pasta, most dry breakfast cereals, bakery products, and other sources of refined carbohydrates, you are likely to have high rises in blood sugar that can damage cells throughout your body, raise your cholesterol and blood pressure, and increase your risk for obesity, diabetes, heart attacks and certain cancers (J Am Coll Cardiol, 2015;66:1590-614).

Studies on Benefits of Whole Grains
We have strong evidence that eating whole grains instead of refined grains is associated with the reduced risk for heart disease and premature death (Lancet, 2019;393:434-45).
• A review of 20 studies, with 2,282,603 participants and 191,979 deaths during the study periods, found that greater intake of whole grains was significantly associated with lower risk of all-cause mortality (Adv Nutr, November 2016;7:1052-1065). Each additional three servings of whole grains per day was associated with a 25 percent lower risk of death from cardiovascular disease.
• Researchers followed 54,871 Danish adults, aged 50-64, for almost 15 years and found that those who ate a lot of whole grains, particularly rye and oats, had far fewer heart attacks (Am J Clin Nutr, Feb 17, 2016). Eating whole grain breads was not associated with reduced heart attack risk.
• Whole grains lowered total cholesterol and the bad LDL cholesterol (Am J Clin Nutr, Sept 2015;102(3):556-72).
• In a study that followed 108,000 Danish, Swedish, and Norwegian participants for 11 years, those who ate more whole grains had a significantly lower risk for colorectal cancer (Cancer Causes Control, July 2013;24(7):1363-74).
• 120,010 adults, ages 30-64, were followed for 10 years and those who ate lots of whole grain oats, rye and wheat lived longer than those who ate less (Br J Nutr, August 28, 2015;114(4):608-23).
• A survey of studies published between 1965 and 2010 showed a reduced risk for overweight, diabetes and heart attacks with high intake of whole grain cereals or mixtures of whole grains and bran (Am J Clin Nutr, Aug 2013;98(2):594-619).
• A review of 29 articles showed that people who ate whole grains had a 20 to 40 percent reduced risk for heart attacks and diabetes (Curr Atheroscler Rep, Nov 2004;6(6):415-23).
• The Physicians Study followed 86,190 male doctors, aged 40-84, for 5.5 years. Those who ate whole-grain breakfast cereals lived longer and had fewer heart attack deaths than those who ate refined-grain breakfast cereals (Am J Clin Nutr, March 2003;77(3):594-9).

My Recommendations
Virtually every North American adult should limit refined carbohydrates in bakery products, snack foods, pastas, many dry breakfast cereals and so forth. These foods commonly cause high rises in blood sugar, add unwanted pounds and have little nutritional value.
• If you are overweight or if you can pinch more than three inches of fat underneath the skin over your belly, or if you have diabetes or heart trouble, you should severely restrict all refined carbohydrates. Eat carbohydrates as nature packages them: in whole fruits, vegetables, whole grains, beans and other seeds. Also avoid sugared drinks including fruit juices and all sugar-added foods. See Hidden Sugars
• Realize that the term “whole grain” on the package label does not guarantee that a food actually contains all of the parts of the grains. The only way to know that you are getting whole grains is to eat the seeds themselves. See Is it Really Whole Grain?
• Whole grains are easy to cook and can be used wherever you formerly used pasta or white rice. See Diana’s simple instructions for cooking whole grains and her many delicious, easy recipes.

Fiber from Grains Linked to Reduced Heart Attack Risk