Since the time I adopted a low carbohydrate approach, I've heard a frequent concern of people that they don't want to give up their fiber. This sentiment is further heightened by the frequent admonition by "conventional wisdom" that you need "healthy whole grains" and that they are an excellent source of fiber. That doesn't really seem to add up in my mind when you think of things like so many of the vegetables and other foods that are perfectly suitable in a low carbohydrate approach.
After hearing this again several times over the last week as part of a couple presentations I've given on the Primal Blueprint, I decided I would see if I could do a real comparison of what you give up when you give up "healthy whole grains" and replace that with other real foods that don't contain a lot of digestible carbohydrates.
[Note that when I talk about carbohydrates, generally I am talking about those carbohydrates that don't include fiber. When you look at the total carbohydrates on a nutrition label, it includes fiber which is pretty much indigestible and doesn't have the same impact on insulin. So, when I mention the amount of carbohydrates, I mean the total minus the fiber. In other words, I don't count the fiber.)
To look into this, I first chose a slice of whole wheat bread and a single serving of oatmeal to see how much fiber they really contain. A slice of whole wheat bread only contains about 2.8 gms. of fiber and a serving of oatmeal contains about 4 gms. of fiber.
Interested in seeing if we can really adequately replace the fiber in "healthy whole grains" with the fiber in better food choices, I then looked up a few non-high-carbohydrate foods, to see what fiber content they have. I chose 1/4 avocado, 1 serving of almonds, 1 serving of macadamia nuts, 1 serving of celery, 1 serving of carrots, and 1 serving of broccoli. It turns out that there's not much agreement when searching on the web for a standard serving size so I just did the best I could. For example there really wasn't anything for a serving size of avocado but I picked 1/4, even though I generally eat 1/2 at a time when I'm having some, but 1/4 still has plenty of fiber. For a serving of nuts, I used 1 oz. (28 gms.) which seems to be pretty consistent and is only about a small handful, and is probably less than I might typically consume in a day.
From the numbers I found (and you're welcome to look up numbers for what you think is a serving size) the amount of fiber in these foods can easily replace the fiber in the so called "healthy whole grains." I conclude that there really is no reason to eat grains to get the fiber you need.
I graphed the numbers I found for fiber below. I think it makes it clear that there are obviously variations in the amount of fiber in different foods, but these low carb foods are still a substantial source of fiber in the diet. Very much on par with the whole grain foods.
I also looked at what the carbohydrate content (not including fiber) is of these foods. I've graphed those numbers below as well. Note that the highest of the "low carb" foods doesn't even have half the net carbs of the whole wheat bread.
That made me think that I could calculate a "fiber density index" of sorts by dividing the fiber content by the net carbohydrate content. In other words, this would be a measure of how much good fiber you get from a serving of food as compared to how much of the carbohydrate that you don't want. I graphed such a calculation for that selection of foods as well. Interestingly it shows how much more effective these low carb foods I selected are at providing good fiber without adding all those carbs, versus the whole grain foods. This shows as a proportion of total carbs, whole grains are really not very good at providing fiber without the penalty of taking in those digestible carbs.
So the next time you think you need to get more fiber, you don't need to resort to eating whole grains that are going to generate insulin spikes that are probably not good for you. Instead try an avocado, some nuts, or some non-starchy vegetables. I think that's a much better choice.