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Category: Nutrition


Making Sense of “Net Carbs”

Now that the low-carbohydrate dietary recommendations have really taken hold, we are beginning to see quite a bit more information about nutrition labeling that not only describes total carbohydrate content of a particular food, but also indicates “net carbs.” Depending on the type of food, there may, in fact, actually be a significant difference between these two numbers.

So let’s break it down as it is actually very straightforward.

The term net carbs simply describes the number of grams of total carbohydrates in a portion of food minus the grams of fiber. Fiber, it turns out, is a form of carbohydrate, but is not a carbohydrate that has any effect on blood sugar or insulin response. Therefore, the idea of focusing on net carbs, meaning the carbs that are left over when the fiber is removed from the equation, does make a lot of sense because it is these residual carbohydrates that strongly influence blood sugar and, consequently, insulin response.

Let’s look at an example. One half cup of baby carrots contains approximately 6 grams of total carbohydrate. But there is a fair amount of fiber in whole carrots, amounting to about 2 or 3 grams in this case. So the net carbs would be about 3 or 4 grams.

An important place where this understanding comes into play is in looking at, for example, fruit juices. A one cup serving of regular orange juice provides of 25.8 grams of total carbs and only 0.5 grams of fiber, so the net carbs are about 25.3 grams. That’s enough to have a significant effect on blood sugar and insulin response.

Another way of looking at this calculation reveals that a larger difference between the total carbs and the net carbs is a good indication of the fiber content. The larger the difference, the better food.

  • Lynn Dell

    Very important distinction, especially for those who need to lower their blood sugars and for those who want to be in a state of ketosis. Many vegetables appear to have more carbs than one would want, but they don’t, once the fiber is subtracted.

  • TechnoTriticale

    Is net carbs starting to show up on product labels more often? I’ve only seen it rarely.

    Net carbs is just a rule of thumb; the glucose meter is the final authority. But NC is a very useful approximation, and easy to calculate from the required FDA Nutrition Facts elements.

    Fermented foods, for example, often overstate total carbs (and thus net carbs) if they are reporting sugars prior to fermentation, rather than at point of consumption.

    After fixing that, the next step would be for the label to break down the “fiber” carbs into prebiotic/resistant/fermentable and insoluble/roughage. Right now, one must resort to various internet sources, many of which disagree.

  • Sandy

    So should we consume 60 to 80 grams of net carbs to keep the risk of developing Alzheimer’s low?

    • TechnoTriticale

      Actually, I’d like to see Dr. Perlmutter publish his current target(s) for either total or net carb, as daily, meal or time-period numbers. The original Grain Brain had a TC target of 60 grams per day (p230), but I don’t quickly find similar specificity in the later books.

      • David Perlmutter

        Continuing with 60-80g/day of net carbs.

        • TechnoTriticale

          Thanks for the response. That would also seem to be consistent with an HbA1c target of 5.2%.

          • john wallin

            Many nutritionists dispel the idea of net carbs especially with sugar alcohols found in nutrition bars like Adkins or Quest bars. BEWARE!

          • Jim

            I agree…since ALL carbs eventually turn to sugar, it’s best not to rely too heavily on NET carbs! 🙂

  • Dr. Perlmutter, What low-carb dietary guidelines are you referring to? I’m a lawyer who is looking to explore the FDA’s (and other agencies’) food regulations and analyze these regulations in the context of eating healthy–primarily, low-carb, organic, grass-fed, non-gmo, and additive free. Thanks.

    • ron

      Great to hear somethings being done, there’s so much fraud out there and it’s on websites, books, confusing those of us looking for the truth.
      Good luck.

      • Thank you. I’m essentially going to look at the regulations and other agency-produced guidelines and strip them down to their bare bones and explain what they really say. The next step would be to illustrate how companies can use these regulations to make deceptive–albeit profitable–claims and confuse consumers or lead them astray of what the consumer actually wants. Lastly, I’ll try and bring in the scientific literature that describes the harmful effect these substances can have on our bodies–relying on the work of Dr. Perlmutter, Mark Hyman, and others who have already synthesized the research.

        Best of luck on your quest to prosperity, longevity, and vibrant health Ron.

  • Joseph Hoffman

    Does the net carb concept play into the glycemic index? From my understanding carrots are noted as high on the glycemic index, but if you factor in the fiber, could be considerably lower?

  • Jane Jewell

    Should add that this only applies in some countries, like the USA.
    In UK, the carbs on the nutrition label ARE the net carbs. In other words, they have already subtracted the fiber.
    If you don’t realise this, you can end up subtracting the fiber again and end up with a negative number for net carbs! So always check where the product came from first.
    Somewhere on the internet there is a list of which countries do which system. Of course I can’t find it now!

  • beatrice nordberg

    thank you again, Dr. Perlmutter for this important information, you are keeping us healthy.

    • David Perlmutter

      Thanks for following along Beatrice!

  • Sharon

    Dr Perlmutter, I have a question on this – So the fibre is a carb that has no influence directly on our blood sugar, but as a fibre does it not then influence the way the body is then dealing with the other carbs and affecting our blood sugar? So if we have a high net carb and high fibre, will that fibre then slow down the uptake of the sugars? thinking I guess about home made juices(fruit or veggie). Some of the juicers take out the fibres and some leave them in. So are we just drinking a sugary drink or are we drinking easily absorbed high nutrition when the fibre is left in???? Specially for very ill/cancer people.
    Would love some feed back.


  • AnnieLaurie Burke

    Where do “resistant carbs” fit in? They are not necessarily fiber.

    • Kevin Halls

      They are right next to unnecessary fiber in the health index.

  • janeyt

    hi there, i was thinking; if fiber is form of carbohydrate can fiber itself have an affect on ketosis? there are advocates of ketosis who believe that fiber plays a role in keeping you out of ketosis. is there any shred of truth to this? thanks. janet

    • Bellagirl105

      For me, it does hurt ketosis. I think it depends on an individual’s sensitivity to carbohydrates, as I am one of the extremely sensitive cases. Another point is that labels cannot be trusted in many cases. I always count total carbs in my daily diet and keep them to a minimum.

  • Brad Fuller

    Hi Dr. Perlmutter. Watched you on YouTube with Mike of High Intensity Health and really enjoyed the conversation and the chance to learn more about my newly adopted diet, the Keto diet. My question has to do with your grass-fed beef comment. Since it’s not always possible to get grass-fed meat, cheese, and uncured meats, does organic, nitrate/nitrite, hormone and anti-biotic free suffice with a omega 3 supplement for good measure? Also what is your recommendation on supplements in general, which should we take? Thanks much! Just ordered two of your books.

    • David Perlmutter

      This blog post should be of help Brad: drperlmutter.com/grain-brain-seven-super-supplements

      • Brad Fuller

        Thanks doc!!

  • John R Fish, MD

    Just read your new book and now I’m having to take three new supplements, also, looks like some of the recommendations to the diet boosts the carb levels to way over the 75 gram original recommendations. Am I misinterpreting this new information?

    • David Perlmutter

      I advise 60-80g/carbs/day for most people, 80-100 for those engaging in regular exercise.

  • Diane

    Hi, new to all of this. A previous pharmaceutical rep and married to a doctor who went to med school at UF. He is practicing ER physician in Jax., Fla. Zero nutritional classes in med school so we are blown away right now. We are runners and tennis players, we don’t know how many carbs to shoot for daily with all the sports going on in this heat. A couple girls on my tennis teams have ended up in hospitals from dehydration. We never knew high carbs could cause all of these problems. Look forward to hearing back. Thank You!!!

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