In some recent posts, I’ve mentioned the net carb counts of some foods I like. True Primal soup has 11 net carbs per serving, lentil pasta has 24 net carbs per two ounces, etc. In case you’re wondering, yes, I’m aware that net carbs has become somewhat controversial, and that some low-carb gurus suggest counting all carbs, period. I beg to differ. I still think it makes sense to subtract fiber from the total carb count.
The concept of net carbs got a bad reputation because it was abused by the makers of low-carb junk foods. They’d put 25 grams of sugar alcohol in a dessert bar, then subtract those grams and claim 5 NET CARBS! on the label. Sugar alcohols raise glucose levels in many people, so yeah, I say go ahead and count them as carbs. (Better yet, just skip those food-like products altogether and eat real food.)
But I think it’s a mistake to count fiber as carbohydrate. If you are 1) restricting carbohydrates to VLC or ketogenic levels and 2) counting fiber grams as carbs, you’ll likely end up restricting your fiber intake to little or nothing. Bad idea.
Fiber got a Nyaaaa, who needs it? reputation in the low-carb community because the (ahem) “experts” told us we need to eat our hearthealthywholegrains! to make sure we get enough fiber. I’m pretty sure our Paleolithic ancestors didn’t start their day with bowls of All Bran, and yet the experts insisted we need grain fibers to avoid everything from heart disease to colon cancer. That of course turned out not to be true. Gary Taubes devoted an entire chapter in Good Calories, Bad Calories to the subject.
But grain fibers are the wrong kinds of fibers. As Dr. William Davis explains in this post, the fibers in hearthealthywholegrains! are mostly cellulose, a constituent of wood. Humans have no biological need to eat wood. Yes, those “whole grain” fibers promote regularity, but at a cost:
The poop-bulking effect of cellulose can fool you into thinking that you have achieved bowel health. In the case of wheat and grains, for instance, wheat germ agglutinin and gliadin peptide fragments are highly toxic to the intestinal wall, block gallbladder and pancreatic function, and induce alterations in bowel flora. Cellulose and phytates bind minerals, such as iron and zinc, and make them unavailable to you. But the cellulose provides the appearance of bulky stools despite the toxic damage incurred, causing you to believe that you’ve had a healthy BM.
We certainly don’t need cellulose fibers, which unfortunately led to the belief that we don’t need fiber at all. But we do, because plant fibers feed the good gut bacteria.
When we adopt a low-carb diet, what are our goals? What do we hope to achieve? To lose weight, sure, but also to keep our glucose levels under control and reap the benefits of short-chain fatty acids like butyrate. There’s plenty of research out there suggesting that plant fibers help us achieve both goals, including a study with the rather obvious title of Short-chain fatty acids produced by microbial fermentation of plant fibers improve glucose regulation.
If you’re onboard with the idea that mimicking the diets that kept our ancestors healthy is a good idea, then fibers should be part of your paleo or primal diet. Fossilized stool samples show that Paleo Man ate rather a lot of fiber from plant foods. Here are some quotes from another post by Dr. Davis:
Yes, consuming such fibers is evolutionarily appropriate, as it dates back well over 8000 generations of human existence, predating even the appearance of the Homo species, even predating carnivory, as it was practiced by pre-Homo hominids, Australopithecus (especially “robust” strains). It is therefore deeply instilled into the adaptive physiology of our species.
We evolved on diets that fed our good gut bateria. Here are some quotes from an article by Chris Kresser:
When we eat the soluble fibers found in whole plant foods, the bacteria in our gut ferment these fibers into short-chain fatty acids like butyrate, proprionate, and acetate, and greater amounts of fiber consumed will lead to greater short-chain fatty acid production. In this case, naturally occurring soluble fibers are very important for feeding the friendly bacteria that live in our guts.
One of the risks of long term very low-carbohydrate (VLC) diets, in my view, is the potentially harmful effect they can have on beneficial gut flora. VLC diets starve both bad and good gut bacteria, which means these diets can have therapeutic effects on gut infections in the short term, but may actually contribute to insufficiency of beneficial strains of gut bacteria over the long term. Providing adequate levels of carbohydrate and soluble fiber to feed friendly bacteria is important for optimizing digestive health and maintaining the integrity of the gut lining through the production of short-chain fatty acids.
I don’t count fiber grams as carbs because in my experience, fiber doesn’t raise blood sugar at all. If anything, it seems to blunt the effects of non-fiber carbs. As I’ve mentioned, if I include three ounces of lentil pasta in a meal, I’m getting 36 net carbs. But my blood sugar only rises to 125 or so, probably because of the 10-12 grams of soluble fiber in the pasta.
If you’re not convinced, then I’d suggest conducting a few n=1 experiments. Get out the glucose meter and see how you react to carbs that are high in soluble fibers vs. non-fiber carbs.
Even if you decide to forget the net carb concept entirely and count all carbs, please make sure you get some beneficial fibers into your diet. I know I just posted this video back in August, but it’s worth another look. Here’s Dr. Davis on why you don’t want to skip beneficial fibers on a low-carb or ketogenic diet:
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