How Do You Do Fiber?

An article in the March/April 2009 issue of Diabetes Self-Management, entitled “Counting Carbohydrates Like a Pro” and written by Gary Scheiner, MS, CDE, has provoked a lot of comments and questions from readers. Many of the questions concern how to deal with fiber when counting the carbohydrate in a meal or snack.


In the article, Scheiner recommends subtracting all the grams of fiber from the total carbohydrate before calculating the carbohydrate grams (or “choices,” if you prefer) in a meal. But many readers have heard different advice on this, and they want to know why.

One reader, for example, said she thought the correct thing to do was to subtract half the grams of fiber. Another reader said that a dietitian had instructed him to subtract only the amount of fiber over 5 grams.

I decided to investigate.

I found that the 2007 edition of Choose Your Foods: Exchange Lists for Diabetes, published by the American Diabetes Association (ADA), recommends subtracting half the grams of fiber from the total carbohydrate when eating foods with more than 5 grams of fiber per serving. So if a serving of food contained 8 grams of fiber, you would subtract 4 grams. If the food contained fewer than 5 grams of fiber per serving, you would subtract none of them before calculating the carbohydrate grams or choices in your meal.

Another consumer guide, the American Dietetic Association Guide to Eating Right When You Have Diabetes, published in 2003, says that you can subtract all the fiber from the total carbohydrate but that doing so may only be necessary if your meal contains 5 or more grams of fiber. It goes on to say, “And it may only be necessary for those who are being precise with their carbohydrate intake and adjusting a rapid- or short-acting insulin based on how much carbohydrate they are eating.”

Similarly, the Joslin Guide to Diabetes, published in 2005, says that “most people can also ignore the dietary fiber amount,” but that those who “are trying to be very precise with the carbohydrate amount” can subtract all of the fiber if there’s more than 5 grams of it in the meal. It concludes, “Dietary fiber is not absorbed, but it is unlikely that 5 to 10 grams will have much effect on your blood glucose level unless you eat more than one serving.”

I don’t know where the dietitian who advised subtracting the amount of fiber over 5 grams got that information.

According to an ADA representative, the advice in Choose Your Foods is based on nutrition guidelines published by the Institute of Medicine, the medical arm of the National Academy of Sciences. Those guidelines state that some of the soluble fiber in food can be broken down by bacteria in the large intestine hours after the meal, making calories available to the body.

However, soluble fiber usually represents a small proportion of the total fiber in food, and the portion that is broken down becomes fatty acids, not glucose. You wouldn’t think that fatty acids would raise blood glucose, but according to nutrition experts Madelyn L. Wheeler, MS, RD, and Xavier Pi-Sunyer, MD, MPH, writing in the April 2008 Supplement to the Journal of the American Dietetic Association, one of the three types of fatty acids produced, called propionate, is gluconeogenic in human beings, meaning that it can be turned into glucose in the body.

The author of our article Counting Carbohydrates Like a Pro says he recommends subtracting all of the fiber, regardless of the total amount present in the food eaten, because he has seen no noticeable blood glucose rise from fiber, whether soluble or insoluble.

Given the small amount of fiber most Americans eat, subtracting half versus all may not make much of a difference for most people most of the time. However, it could lead to hypoglycemia (low blood glucose) if a person who was highly sensitive to insulin ate a high-fiber meal and took insulin to cover carbohydrates that weren’t, in fact, going to raise his blood glucose.

What have you been told to do about fiber when counting carbohydrate? And what do you actually do?

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  • amyt101869

    I was told by my Dietitian to subtract any amount of fiber that is over 5 grams. This is what I do and it seems to work for me.

  • Grandma Nei

    I was diagnosed as type 2 10 years ago and was taught to count carbs and the only fiber I could subtract is if it was 5 grams or more. This is what I have been doing for the past 10 years and it seems to be working along with the diet and exercise as I am not on any meds whatsoever.

  • radm2ph

    I was diagnosed as “Type 2 “Aug 2005. None of the oral meds worked and I was put on “insulin intensive” therapy Feb 2006. Eventually, my endo told me my pancreas was “essentially kaput”. I’m really sensitive to insulin and I count carbs, so I’m very careful to cover the carbs I eat. I take Novolog before meals and Lantus before bedtime. . How many carbs to count from the labels is an important bit of information. I use Gary Scheiner’s chart to compute. Thanks for all the information

  • aggie9391

    I was told t0 subtract fiber grams from carbohydrate grams and use that as carbohydrate grams for that particular food

  • Beckyjo

    I asked my RN/CDE and she said stick to the 5 grams of fiber per 15 carbs rule, meaning that for every 15 carbs, you can deduct 5 grams of fiber if there are that many. I mentioned the article and she read it. Her comment was that there is not a separate listing for soluble and non-soluble fiber on most nutritional information listings. She said the body does absorb the soluble fiber and turns it into glucose, whereas the body does not absorb the insoluble fiber. She felt the author should have discussed that. Because I am insulin dependent and very sensitive to it, I need to count the carbs exactly or I will have a hypoglycemic problem.

  • Ingrid Strauch, Editor


    To reiterate:

    “…soluble fiber usually represents a small proportion of the total fiber in food, and the portion that is broken down [in the large intestine] becomes fatty acids, not glucose. One of the three types of fatty acids produced, called propionate, is gluconeogenic in human beings, meaning that it can be turned into glucose in the body.”

  • Betty Ann

    Now I am more confused than ever. When I first wa diagnoses 3 years ago, my diabetic educator told me I could subtract fiber if it was over 5 grams, but the nutritionist (who worked for a endocrinologist) said I could not. I am not on insulin. It does make a difference if I am eating something (ex. part of an English muffin) before bed that should not be much more than 15 carbs. If the food is 20 carbs with 5 or 6 grams of fiber, where does that leave me?

  • sally smart

    People are always counting carbs against fibre in already made products, My question is if you add fibre like a fibre pill at meal time or just crushed flax seed and maybe other grains and maybe oats from a shaker to your food, does this help or not? I see most breads and pastas don’t have as much fibre as I would like and so I add fibre where possible like, hidden in a sandwich or a pasta dish. I am not sure how much the count for fibre would be then but it is obviously more then I would have if I did not do this. If it would work, why is it not stressed to do so more in diabetes informational write ups and studies and specific diabetic diet suggestions?

    I used to add bee pollen in sandwiches, Not sure it has that much fibre in it but it was a trick that a boyfriend of mine at the time tought me as a way of eating bee pollen each day without noticing it is there, He was a real health nut. It worked but I have forgotten to do it for quite some time, possibly because I have been doing the fibre instead.

    Just wondering because people seem to be relying so much on how much fibre is already in the product, so why would adding not fix at least half of the problem? I have found I can add fibre into almost anything, hot cereal, sandwich, soups, pasta dinners and even stir frys and it is not that noticable. I am doing it to help put more fibre in everyones diet without them noticing when they eat their meals. I have even thought that oats crushed into the fibre mixture (shaker bottle) might be a way of making sure there is more oats in the day even if a person will not eat hot oat cerial in the morning, like my hubby.

  • Peter Mead

    I am type 1 (for 2 years now) and I haven’t found subtracting makes a lot of difference to me. There are so many other variables that are more significant: The true value of the carb, often not what the label says; my current metabolism; my planned activity after eating; how much fat and protein I am eating with the carb; other food combining; the time of the day.

  • kobi

    How do you handle a situation where the fiber content exceeds the carbs? I recently bought a snack,fried soybeans, which contained 5g carbohydrate and 25g fiber. What does this mean in terms of carb intake?

  • Ingrid Strauch, Editor


    That sounds like a mislabeling. On foods sold in the United States, the total carbohydrate listed in the Nutrition Facts panel includes the dietary fiber. Half a cup of roasted soybeans has about 29 grams of carbohydrate and 15 grams of fiber.

  • buckigirl

    I, too, was told by a dietition, who was an instructor at my diabetes awareness classes, to only count carbs above 5 grams. She seemed to feel very sure about this.

  • kathy calfee

    if i add fiber such as, benifiber, to my food do i still subtract that from the carbohydrate total?

  • Ingrid Strauch


    A two-teaspoon serving of Benefiber powder has 4 grams of carbohydrate, 3 of which are fiber. That being the case, I wouldn’t think you’d need to add or subtract anything to your carbohydrate total for the meal, even if you added more than one serving of Benefiber.

  • Donna

    My nutritionist and RN/Diabetes educator told me to disregard the subtraction bit. I’m a type II, diagnosed 1 year ago. By counting the carbs and sticking to the meal plan I was given I’ve decreased my A1C from the 12’s to the 5’s, lost 65 lbs and have less neuropathic pain. I don’t care what the “current thinking” is, following their plan has made life a lot better for me, and I’m sticking to it!

  • ruth

    Hi! For a diet-controlled Type 2 diabetic who wants to eat lots of fibre-containing foods, like beans, i want to be able to subtract the fibre, so i have less carbohydrate and eat more food. From reading these articles and blogs, i still don’t know, should i subtract ALL the fibre or HALF the fibre? I’m hoping i can subtract all the fibre so i can eat more. ūüôā

  • Joy

    I take insultin and a friend told me to substract my fiber from the carbs. Is this wise? My blood sugar can go from 60 to 270 depending on what I eat. This is my life, I don’t want to play food games. What do I do?

  • mandi

    I do not have diabetes, but I am watching my carbs. So are you suggesting to subtarct soluble, insoluble, and ALL fiber from carbohydrates?

  • Dee

    I’ve been advised to subtract the fiber amount from the carb amount if the fiber was more than 5 grams.

    Currently I avod the carb that I tend to overdose on. I used the Adkins app on my smarrtphone to track my intake daily. it counts all the carbs in the foods that i didnt know had carbs lol. it is hard to not hace carbs as i am type 2 diabetic anyways…

  • Andy Pober

    First of all, discuss any planned fiber-related dietary changes with a nutritionist unless your BG is well controlled, in which case a change may be unnecessary.

    When soluble and insoluble fiber are listed on a nutrition label, soluble fiber tends to be much lower than insoluble. As stated above, part of the insoluble fiber can be converted to a fatty acid, propionate ,as the result of fiber fermentation in the lower gut. Propionate is gluconeogenic and can be a precursor to glucose production in the liver. The problem with trying to calculate insulin dosage based on fiber is that the possible production of glucose due to fiber in the diet is neither directly related to the total fiber eaten nor the time at which it is eaten. If you are using Novalog or any other fast-acting insulin it’s effects will have passed long before the fiber-related glucose hits your bloodstream.

    Since the efficacy of fast-acting insulin replacements is strongly related to the absorption rate of dietary carbohydrates insulin taken before a meal is unlikely to act on food that has passed beyond the duodenum (between the stomach and small intestine) where most carbohydrates are broken down and absorbed.

  • Lessie Spindle

    I subtract all fiber if is more than 5 g. as Joslin guide recommends. Lately I have been told not to subtract added fiber. Should I subtract added fiber or not? I have diabetes, treated by insulin.

  • Caroline

    As a T1D, I’ve been advised to subtract insoluble fiber to get net carbs. Usually insoluble is negligible but if more than a few grams, I’ll subtract half. Same goes for sugar alcohols.