Are Intact Whole Grains Better? What About Fruits and Veggies?

Fruits and vegetables are the most nutrient-dense foods on the planet, and dark green leafy vegetables lead the pack. Each of the top five so-called powerhouse fruits and vegetables are greens. If we blend them up in a smoothie, soup or sauce we’re taking food with the most nutrition and breaking cells and dumping that nutrition into the bloodstream.

Chewing is good, but blending is better in terms of digestive efficiency and nutrient absorption.

But, if we take in all that nutrition and it doesn’t all make it down to our colon, might we be starving our microbial selves? Why are intact grains, beans and nuts better than bread, hummus and nut butters?

No matter how well we chew, intact food particles make it down to the colon where they offer a smorgasbord for good bacteria. If grains, beans and nuts are finely ground into flour or paste, we may be leaving our gut flora high and dry. Would the same be true for fruits and vegetables?

There are special classes of phytonutrients that appear to protect against colon cancer. They can escape digestion and absorption in our stomach and small intestine and end up in our colon acting as prebiotics. No matter how much we chew, they stay attached to the fiber.

If we use a blender, might we prematurely detach these nutrients? No. Even if you blend in a high-speed blender for five minutes, the phytonutrients remain bound to the fiber for transport down to your colon bacteria.

Just as smaller particle size may improve digestive efficiency and gastrointestinal absorption of nutrients from fruits and vegetables, the same may be true for grains.

There is, however, a concern that this could boost starch availability and cause a blood sugar spike. In my video Are Green Smoothies Bad for You?, I show the rise and fall of blood sugar and insulin over four hours after eating a half-cup of brown rice compared with ground brown rice flour (like cream of brown rice hot cereal).

Consuming brown rice flour produces twice the blood sugar and twice the insulin spike compared to eating the rice intact. Same amount of food, just in a different form. This is why intact whole grains are better than even whole grain flour products.

Simply chewing really well can boost the glycemic and insulin response. If you chew rice really well compared to chewing it normally, the smaller rice particles empty out of your stomach faster, producing greater blood sugar and insulin responses. It’s ironic that there were health crusaders pushing people to chew more to digest their food better, but if what you’re chewing is a five cheese pizza, maybe it’s better not to digest so well.

What about blended beans like hummus? Unlike grains, blending legumes doesn’t affect their glycemic response. So, let’s circle back to the smoothie question: Is fruit more like grains or more like beans? If you liquefy fruit in a blender to make a smoothie, do you risk spiking your blood sugar too high? To find out, watch my Green Smoothies: What Does the Science Say? video.

My general take on beans is simple: the more beans, the better—however you get them. For more information, watch my videos Beans and the Second Meal Effect, The Hispanic Paradox: Why Do Latinos Live Longer?, and Canned Beans or Cooked Beans?

Want more on smoothies? Here it is:

Michael Greger, M.D., New York Times bestselling author and internationally recognized speaker on healthy eating, has produced hundreds of nutrition videos available at NutritionFacts.org. Follow Dr. Greger on Twitter

 

Michael Greger, M.D.

Author: Michael Greger, M.D.

Greger, MD, is a physician, author, and internationally recognized speaker on nutrition, food safety, and public health issues.   Dr Greger has lectured at the Conference on World Affairs, the International Bird Flu Summit and the National Institutes of Health. He has testified before Congress and was invited as an expert witness in the defense of Oprah Winfrey in the infamous "meat defamation" trial. Dr Greger is a graduate of Cornell University School of Agriculture and Tufts University School of Medicine. Currently, Dr. Greger serves as the Director of Public Health and Animal Agriculture at The Humane Society of the United States.