(Why) can't blood sugar spikes be countered by consuming fiber generally?

Question

Excessive sugar consumption is a widely-acknowledged problem in the modern Western diet. One of the specific problems often stated is that the quick consumption of highly sugar-laden foods leads to spikes in blood sugar, the corresponding burden placed on the pancreas to produce a sufficient amount of insulin, etc.

But these same warnings on the ills of sugar always give a pass to fruit, and the justification is usually that the fiber in fruit slows down the processing of the sugar in the blood, thereby avoiding the spikes in blood sugar levels.

This is just one example of an article articulating what I've summarized above about blood sugar spikes, fruit, and fiber, but the same has been described in an innumerable number of articles: https://www.johnson.k-state.edu/health-food-safety/agents-articles/should-you-avoid-sugars-in-fruit-and-milk-for-weight-loss.html

In my mind, this then raises the question: can the blood sugar spikes caused by all sugar consumption be avoided by consuming a compensatory amount of fiber?
E.g. can a person mitigate the blood sugar spikes from eating an ice cream or cheesecake by eating Metamucil, or some other such fiber supplement?

An obvious response might be: if it was that simple, everyone would do it, which implies that the short answer is "no" -- but if so, I'd like to learn why it isn't that simple: if blood sugar spikes from sugar in fruit is mitigated by its inherent fiber, why can't blood sugar spikes from added-sugar in human-made food be mitigated by consuming some "compensatory" amount of fiber?

Answer 1

Yes, adding fiber to diet can reduce the "spikes" in blood sugar. Just a couple references I found quickly, I have not reviewed them closely so I'm not sure of their quality and there may be better examples, just want to demonstrate that these things are commonly studied:

Cassidy, Y. M., McSorley, E. M., & Allsopp, P. J. (2018). Effect of soluble dietary fibre on postprandial blood glucose response and its potential as a functional food ingredient. Journal of Functional Foods, 46, 423-439.

Pastors, J. G., Blaisdell, P. W., Balm, T. K., Asplin, C. M., & Pohl, S. L. (1991). Psyllium fiber reduces rise in postprandial glucose and insulin concentrations in patients with non-insulin-dependent diabetes. The American journal of clinical nutrition, 53(6), 1431-1435.

Sharma, R. D. (1986). Effect of fenugreek seeds and leaves on blood glucose and serum insulin responses in human subjects. Nutrition Research, 6(12), 1353-1364.

Torsdottir, I., Alpsten, M., Holm, G., Sandberg, A. S., & Tölli, J. (1991). A small dose of soluble alginate-fiber affects postprandial glycemia and gastric emptying in humans with diabetes. The Journal of nutrition, 121(6), 795-799.

However, the proposed mechanisms are mostly based on impacts on the digestive system and how quickly sugars are taken up. This mechanism has an obvious ceiling in that slowing digestion indefinitely is not going to be a good feeling. So, while you could certainly extract the fiber of an apple and pair it with some apple-equivalent amount of sugar, you're going to get a result comparable (though quite a bit less convenient) to just eating an apple, but there's no algebraic "canceling" of sugar and fiber, just a modest delay in uptake. While adding fiber may always reduce blood glucose peaks compared to no fiber, that doesn't mean you can add more and more fiber to compensate for any amount of sugar.

Answer 2

Prof. Dr. Robert Lustig says that both soluble and insoluble fibers are needed to avoid sugar spikes. Excerpts:

The fiber in real food is of two kinds: soluble, which is globular (e.g. beta-glucan, pectin, inulin, etc.); and insoluble, which is stringy (e.g. psyllium, cellulose, chitin, etc.). You need both, as they do different jobs. The insoluble fiber forms a latticework (like a fishing net) in the duodenum, and the soluble fiber plugs the holes in that latticework.

Psyllium is an insoluble fiber. Alone It could form the latticework, but not plug the holes.

One can further assume that the mixing of the sugar into the soluble and insoluble fibers has to take place before consumption in a way that makes the sugar stick to the fiber. This is apparently not done immediately.