A popular book, Grain Brain by Dr. David Perlmutter, claims that carbohydrates are "destroying your brain". He says that "even healthy ones like whole grains can cause dementia, ADHD, anxiety, chronic headaches, depression, and much more". A similar book, Wheat Belly, makes many of the same claims. Most of these authors' arguments against eating carbohydrates are based on data about refined carbohydrates and excess calories.
Refined carbohydrates are different from whole grains and other healthful sources of carbohydrates: vegetables, fruits, beans and seeds. The authors would be correct if they warned you to avoid refined carbohydrates. They should not condemn the healthful carbohydrates, which protect your brain and prolong life by helping to prevent diabetes (Am J Clin Nutr, August 2002;76(2):390-398), heart attacks (Am J Clin Nutr, September 1999;70(3):412-419; Eur J Clin Nutr, 2006 Oct;60(10):1145-59), and premature death (J of Am College of Nutrition, 2000;19(3):326S-330S).
Pre-Diabetics Improve by Eating Whole Grains Just 12 weeks on a whole-grain cereal-based diet lowered blood sugar, insulin and triglycerides in pre-diabetics (Nutr Metab Cardiovasc Dis, 2014 Aug;24(8):837-44). When blood sugar rises too high, the pancreas releases huge amounts of insulin. Insulin converts the extra sugar into triglycerides so triglycerides are a measure of the harmful effects of high blood sugar levels. Feeding diabetics refined carbohydrates caused:
• blood sugar levels to rise very high to increase cell damage,
• blood insulin levels to rise very high which increases risk for heart attacks, and
• triglycerides to rise very high which makes people fat and worsens diabetes. On the other hand, feeding unrefined whole grain cereals lowered blood sugar, insulin and triglycerides, which help to prevent and treat diabetes.
Understanding Carbohydrates Carbohydrates are chains of sugar molecules. They are found in all plants and all foods made from plants. Carbohydrates can be a single sugar, or two, three or more sugars bound together. Thousands of sugars bound together are called starch, and millions of sugars bound together so tightly that you cannot break them down are called fiber.
Only single sugars can pass from your intestines into your bloodstream. When you eat, food that contains starch enters your intestines where enzymes knock off each end sugar consecutively and each end sugar is absorbed immediately. All simple sugars and starches that are broken down rapidly go into the bloodstream rapidly, which causes blood sugar to rise.
Fiber and other resistant starches contain long chains of sugars that cannot release their end sugars, so they are not absorbed. They pass to the colon where bacteria convert them into fatty acids that help prevent colon cancer and heart attacks. You want to eat carbohydrates that release their sugars slowly, and restrict carbohydrates that release sugars rapidly. The easier it is to break carbohydrates down into single sugars, the higher your blood sugar level rises and the more insulin you produce.
The Difference Between Whole Grains and Refined Carbohydrates A whole grain is a seed that is covered with a thick fiber coating like a capsule. When you eat whole grains, this capsule prevents sugar from being released and blood sugar levels do not rise very much. On the other hand, when whole grain is ground into a powder to make flour, it loses its protective capsule that keeps it from being broken down so quickly. You get a high rise in blood sugar that calls out large amounts of insulin. Eating a lot of foods made from flour increases your chances of gaining weight and becoming diabetic.
The most healthful carbohydrates are those left with fiber where nature puts them: in whole grains, beans, nuts and other seeds, vegetables and fruits. The most harmful carbohydrates are foods made from refined carbohydrates : flour, white rice or milled corn, fruit juices and all extracted sugars.
Flour is Like Sugar If you think sugar-free cookies, cakes and pastries will help you lose weight or control diabetes, you’ve gotten the wrong message. Flour makes your blood sugar rise almost as much as table sugar. Most recipes for baked goods use about six cups of flour for every cup of sugar. Eliminating the sugar does virtually nothing to slow the rise in blood sugar that you get when you eat most bakery products. Rice flour, corn flour or corn meal, and other "gluten-free" flours are just as harmful as flours that contain gluten.
Slowly Digested Carbohydrates Refined carbohydrates are absorbed in the upper intestinal tract to increase risk for obesity and diabetes. On the other hand, slowly digested or non-absorbable carbohydrates that are absorbed in the colon help to lower cholesterol and prevent diabetes, heart attacks and premature death (American Journal of Clinical Nutrition. 2000;72(6):1461-1468). If you are diabetic or trying to lose weight, you don’t need to avoid all carbohydrates. You need to avoid only carbohydrates that cause a high rise in blood sugar. More on slowly digested carbohydrates
Who Needs to Avoid Gluten? The only people who need to avoid gluten are those with a relatively uncommon condition called celiac disease. Your doctor can order a blood test called "celiac panel" to see if you make antibodies against a component of wheat called gluten. If that test is positive, you may benefit from avoiding wheat, rye and barley, which contain gluten, and oats because oats are stored in silos that are commonly used to store wheat also. Otherwise, most of the scientific community agrees that you should eat whole grains and restrict the refined carbohydrates that can make you fat and diabetic and cause heart attacks. People who are gluten-intolerant can still eat whole grains such as wild rice, brown rice, corn and quinoa.
My Recommendations A healthful diet for everyone includes plenty of vegetables, fruits, whole grains, beans and other seeds. If you are trying to lose weight or are diabetic, you should restrict all foods that cause a high rise in blood sugar:
• foods made from flour (bakery products and pastas),
• all drinks with sugar in them including fruit juices, and
• all foods that contain added sugars. Even if you are not trying to lose weight, I recommend limiting these foods to keep from gaining the ten pounds or more that most people add with each passing decade.
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