The Trouble with Fiber

by David Mendosa Patient Advocate

People with diabetes know that carbohydrates will raise our blood glucose levels. But we think that one form of carbohydrates -- fiber -- is benign.

It isn't.

Dr. Robert C. Atkins was a pioneer in seeing the benefits of a very low-carb diet in his books like his 1972 bestseller,
Dr. Atkins' New Diet Revolution. But the organization that he left behind, Atkins Nutritionals, sells all sorts of goodies packed with what it calls "Net Carbs." They say that we don't need to count the amount of fiber you eat:

"When you follow the Atkins Diet, aka the Atkins Nutrition Approach, you actually count grams of Net Carbs, which represent the total carbohydrate content of the food minus the fiber content. The Net Carbs number reflects the grams of carbohydrate that significantly impact your blood sugar level and therefore are the only carbs you need to count when you do Atkins."

But fiber does count. Depending on the source and type of fiber that it is, each gram of fiber provides us about 2 calories, which is about half the amount that non-fiber carbohydrates provides.

This is what the best source, the Institute of Medicine, indicates. This group and its parent organization, the National Academy of Sciences, are hybrid governmental-private organizations. The U.S. government created these private organizations to advise it on scientific and technological matters. "While it is still unclear as to the energy yield of fibers in humans, current data indicate that the yield is in the range of 1.5 to 2.5 kcal/g," the IOM says.

Still, the members of my Very Low Carb for Health Diabetes Support Group in Boulder, Colorado, wanted to check for ourselves. Chris Quemena at Quest Nutrition Inc. sent me a case of 12 Peanut Butter Supreme Quest Bars for us to test.

These bars have just 4 grams of non-fiber carbs. But they have 17 grams of fiber each, so they have a total carbohydrate count of 21.

Most of us liked the taste of the Quest Bars. But we didn't like how they impacted our blood glucose levels.

We met at our most recent Saturday morning time and followed this protocol: We ate breakfast before 8 a.m. and tested our blood glucose level at 10:30 a.m., the start of our meeting. Then, each of us ate one Quest Bar. At 11:30 a.m., which was one hour after the first bite, we tested again. Then, we tested once again at 12:30 p.m., the end of the meeting and two hours after the first bite -- the generally recommended time to test.

Ten of us attended the meeting and followed the protocol. Their average blood glucose level at 10:30 was 95; at 11:30 it was 147, and at 12:30 it was 146. That's an increase of 51 points in two hours.

However, two members of the group are type 1s and took insulin during the test. Excluding their numbers shows a greater jump after eating the Quest Bar from an average of 88 at 10:30 to 143 at 11:30 and 145 at 12:30. This is an increase in 57 points in two hours reaching a level that is too high for anyone who wants to manage his or her diabetes.

We hadn't expected such a big increase from the 4 grams of non-fiber carbs in the Quest Bar. "And they are all from nuts -- not sugar," Quest says. It is only true low carb bar on the market."

I don't mean this article as a condemnation of Quest Bars. What I intend is to show that fiber probably does have a significant impact on our blood glucose levels. Another consideration is that we can't always trust the carb counts on the Nutrition Facts label.

But the real trouble is that we are truly all individuals, meaning that different people react differently to what we eat. One of the main reasons is that we have different degrees of insulin resistance. For example, one of the members of the diabetes support group saw her blood glucose level rise 65 points in the two-hour period, while another tester experienced a 31 point drop.

With just 10 testers we don't claim that our numbers are statistically significant. They are illustrative, a warning that you may experience the same unwanted results.

We often say that Your Mileage May Vary. It means that all of us have to check out for ourselves the effect of what we eat. YMMV.

David Mendosa
Meet Our Writer
David Mendosa

David Mendosa was a journalist who learned in 1994 that he had type 2 diabetes, which he wrote about exclusively. He died in May 2017 after a short illness unrelated to diabetes. He wrote thousands of diabetes articles, two books about it, created one of the first diabetes websites, and published a monthly newsletter, “Diabetes Update.” His very low-carbohydrate diet, A1C level of 5.3, and BMI of 19.8 kept his diabetes in remission without any drugs until his death.