How Much Carbohydrate Do You Need to Eat Per Day?

How Much Carbohydrate Do You Need to Eat Per Day?

By | May 18, 2011 at 3:19 pm | 96 comments | Low Carb, Nutrition, Weight Loss | Tags: , , , ,

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We’ve all grown up equating sugar to energy, but new research suggests our bodies are engineered to run on fat…

I recently attended a fascinating series of meetings in Baltimore, MD accompanied by the top physiology and weight loss specialists in the country. Although I’d long known sugar was dangerous and advised limiting all carbs to 50-100gm per day, going into the meeting I’d assumed we needed some. Specifically, I thought our brain cells required glucose because that’s what I learned from biochemistry books, physiology books, and other medical texts.

Your body requires ZERO grams of dietary carb. What little glucose your body requires (30gm) you can generate yourself from an ounce of protein


During the meeting, however, I became convinced by the abundance of newer lab and clinical data showing that brain cells, and the vast majority of other cells in the body, actually prefer a product of fat metabolism, called ketone bodies. The power plants of the cell that burn oxygen to produce energy in the form of ATP, called mitochondria, function poorly in the presence of another chemical, called malonyl-coA, which comes from the breakdown of glucose. Forcing mitochondria to deal with malonyl-coA overwhelmes their ability to control the high-energy electrons used in the making of ATP, and the result is a release of free radicals. Free radicals can cause DNA mutations as well as enzymatic destruction.

A minority of cell types actually do require glucose, specifically a few types of cells in the liver and cells without mitochondria (e.g., red blood cells). All other cells work perfectly well burning fat and special kinds of fat-breakdown molecules called ketone bodies. According to world-renowned metabolism expert Dr. Mary Vernon, we need 30 gm (2 Tbsp) of glucose per day to keep those cells that prefer glucose running properly. That small amount can readily be supplied by the conversion of protein to glucose in a metabolic process carried out through a cooperation between the liver and kidney, called gluconeogenesis.

What about Adrenal “Burn-Out”?

Somebody got the idea circulating that low-carb diets might cause adrenal “burn out,” and a few readers have asked about this. I’ve looked everywhere and I can’t find any data supporting the theory. I do find a physiologically plausible mechanism by which carb consumption may cause adrenal gland problems. Take a look at the diagram I’ve adapted here (below) from a lecture presented by Dr. Jeff Volek. It illustrates the mechanism by which high carb diets produce energy swings.

High blood sugar causes excessive insulin release which leads to low blood sugar and a ‘panic’ reaction from the adrenal gland

It’s important to consider that, if you have a metabolism that’s been running on glucose for decades, your metabolism is not in a healthy state and therefore will need some time to realign itself with the input of proper nutrition. You’ll need to give your body some time to adapt to the new fat-burning state. A whole new set of enzymes will need to be re-manufactured, which can take a few weeks to accomplish. For those with metabolisms in serious trouble, I typically advise going low-carb one meal at a time giving each mealime two weeks.

Bottom line: All the latest science contradicts the assertion that we need carbs—any carbs—in our diets. This isn’t to suggest that everyone needs to remove carbohydrates entirely from their diets. Indeed, there may be some as-yet undiscovered benefit to dietary sugar. Today’s article is not meant to suggest that we’d all be better off with zero carbs in our diet. It is, however, meant to point out that very few of our cells need dietary sugars for energy, and therefore the old idea that we need to include carbs in our diets or we’ll feel tired all the time, is running on empty.

ADDENDUM: Thanks to Paul Jaminet, Matt Stone, Cheeseslave and others, there has been a much-needed awareness-raising of the fact that we can overdo every good thing. Since originally posting, I’ve added the following caveat:

I believe that just as we enjoy a change of pace from time to time, so does our metabolism. There may be benefits from consuming enough carb to kick you out of ketosis (50-120 gm per day) on occasion. I suspect our ancestors enjoyed seasonal fruit binges from time to time, for example, and a rare (emphasise RARE) infusion of simple carbohydrate may flood your body with a variety of different sugar molecules in ways that aid fertility, and support tissues that require sugar molecules for structural purposes (like tear and mucuous production by the eyes and digestive system).  Just remember, whatever as-yet unexplained benefit carb-flooding may offer, it may also temporarily stall weight loss .

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96 Comments

  1. Hilda (1 year ago)

    Dr. Cate I’ve used the no Carb Diet before but lost tons of hair for limiting my carbs that much is there anything I can do, But lost lots of weight on the low carb diet.

  2. Craig Bird (1 year ago)

    Dr Cate – I have implemented a low carb diet, for long term health and energy reasons. I have always had an extremely high metabolism and have a hard time not being skin and bones. My BMI was 21 and dropped to 20 after going low carb. I didn’t think I could get any skinnier. My question is, I want to gain weight and muscle so what will that take on my low carb diet with my hummingbird metabolism?

    • Greg (1 year ago)

      Dr. Cate, you should check out this website:

      http://weightology.net/weightologyweekly/?page_id=319

      @Craig: Don’t do it man! I used to have a BMI of 22; I was 5’10″ and weighed ~145 lbs. I was very healthy. I then got totally deluded by the “science” of nutrition and went low carb, high protein/high fat. Guess what??? I lost 20-25 lbs. My family freaked out…I felt tired and weak. I looked emaciated and pale all the time. Worst several months of my life. I almost ended up in the hospital. Please don’t make the same mistake I did. Most of this low carb “science” is a joke. It’s just theory. It’s not been proven either in the lab, or empirically over many decades. Low carb diets will make you lose weight (Atkins). This is why some people who are overweight report shedding pounds and “feeling great” after doing low carb for a while, but for us skinny people with fast metabolisms, nothing could be worse. If you want to gain weight, here’s how to do it: High carb, some fat, not too much animal flesh. Eat a burrito bowl for breakfast every day: rice, beans, salsa, veggies, guacamole, some sour cream…that will make you gain weight. Add some chicken once in a while. Plus it’s much better than trying to ram a whole steak or a stick of butter down your throat.

      If you still don’t believe me, think about what every major ancient civilization has generally eaten for thousands of years. China: Rice is the bedrock of every meal. Same in India, SE Asia and Mexico. In Africa people eat some form of cereals. In Europe, bread has been considered the staff of life for hundreds of years. Roman legionnaires would sometimes refuse to fight if they didn’t have grain. Honestly, what are the chances that all of those people over thousands of years/hundreds of generations were completely deluded about what to eat, and now that we finally have nutrition “science” WE (read a few scientists and doctors in just one generation in the US only) have discovered that “low carb is better?” Come on…seriously…what are the chances? It’s impossible. If low carb were indeed a better choice and led to superior metabolism, growth, and health, we would have discovered this thousands of years ago and left grains in the past. But we haven’t. Every generation of human beings has eaten grains as their staple because they work extraordinarily well for us. Civilization would not have been possible otherwise. I could go on all day long, but I wrote a post about this to Dr. Cate:

      http://drcate.com/five-reasons-a-healthy-fat-diet-is-good-for-you/#comments

      My long post is toward the bottom…Best of luck to you man…I know that was a bit long-winded but I just felt like I had to write something…Hope you feel better…

      • Craig Bird (1 year ago)

        Greg – I have never felt better. The carbohydrates I was eating were causing huge swings in my blood sugar levels with peaks and valleys, causing fatigue periods followed by quick onsets of shakiness/hunger. Keep in mind that I have never been a sweet tooth. I enjoyed occasional candy/cakes etc., but in very small doses and not every day. I drank no soda or caffeine. I had lots of excess gas(as my wife would attest to). My fatigue caused lots of fogginess and difficulty in concentration.

        I decided to try and go gluten free. I started studying various diets and had a friend who was strict paleo. I settled in with a Paleo + sweet potatoes + rice. I really wouldn’t even consider my diet Paleo as I have swung more towards Dr. Cate’s philosophy.

        The first two weeks sucked from a digestive point of view. Lots of diarrhea. I stuck it out when I learned what a diet heavy in grains does to your digestive enzymes/bacteria. Lots of yoghurt, fermented pickles and lightly rinsed and unpeeled veggies fixed up the digestive tract and soon all the good fats and meat protein where doing exactly what they do best – give me lots of energy without the wild blood sugar swings.

        I am not withering away at all. All my symptoms have disappeared. I have lost 5 lbs switching to my current diet, but that was my floor – I am not losing anymore. I have always been skinny, so my natural psyche wants me to gain weight when I lose 5 lbs. My body actually looks more muscular now and I lost the little belly pouch I had before. I don’t mind the extra 5 lbs off, but I was looking for a way to put some weight on within the diet I have chosen as I do not want to increase my grain intake. Unfortunately, if I want to do that without the negative effects coming back, it means I just have to eat more of my current foods. Its just hard to do with a busy lifestyle so I will probably just be at my current weight, which is fine by me.

        As far as “civilization”, I prefer to look at the survival of our species over 2 million years rather than 10,000. Just because grains became more convenient, doesn’t mean they are superior. Today’s grains are also a far cry from ancient grains and not in a good way(other than yield and profitability). I still love bread with a passion, I am just not going to eat it after my own experience and self-education.

        Thats all opinion of course, which I know you will disagree with and offer your view. That doesn’t really matter, since the way I feel being off grains and on lots of good fats/proteins will dictate how I move forward.

        • Greg (1 year ago)

          If it works for you, that’s what counts. Personally, I think balance and diversity are key. Today’s grains are not bad for you compared to ancient grains (soil quality has suffered, but the quality of the grain is still good because humans are still around), and mainstream medicine (tens of thousands of peer reviewed articles) is of the consensus that a diet high in animal products, specifically meat and milk, is linked to heart disease. These can form between 10-20% of a diet that is otherwise composed of grain, legumes, veggies, nuts, seeds, and fruit. Olive oil and flax seed oil are also good, but it may be you had wild blood sugar swings because you ate too many carbs at each meal instead of having enough of the other stuff…

          • Craig Bird (1 year ago)

            The fact that “humans are still around” is very bad reasoning for passing judgement on the effects of grain on the human body. We can eat things that are very convenient but not necessarily good for our health, and still still survive as a species. We can live with disease.

            A recent meta-analysis in the American Journal of Clinical Nutrition pooled together data from 21 unique studies that included almost 350,000 people, about 11,000 of whom developed cardiovascular disease (CVD), tracked for an average of 14 years, and concluded that there is no relationship between the intake of saturated fat and the incidence of heart disease or stroke. In fact, the “risk ratio” for the development of CVD as intake of saturated fat increased was 1.0, meaning that people who ate more saturated fat were no more or less likely to develop CVD.

            The problem is smaller studies are more prone to error and more likely to show an association between saturated fat intake and CVD than larger studies less prone to error. The need to have bold results that are in line with “mainstream medicine” in order to not get swept under the rug. The study suggests that that many small studies went unpublished or otherwise lost down the memory hole if they found no association or a negative association between intake of saturated fat and risk of CVD.

            Low fat, high carb is what is shoved down our throats by the establishment that includes many powerful companies that would be very damaged by a shift in the American diet. The same companies that provide the funding for “mainstream medicine” research.

          • Greg (1 year ago)

            Craig, eventually you’re going to realize as I did that grains work. They have worked for thousands of years, and if you really want to condemn them as being “not necessarily good for our health” and “survival” food, you’re going to have to explain why some of the longest-lived communities on the planet are grain eaters. I’m sure you’ve heard of the “blue zones.” Everyone in those zones eats grains. None of them have a high intake of saturated fat. Sure, we all know people who have lived to a ripe old age and have eaten plenty of saturated fat, but I think you should stop cherry-picking the studies and just accept mainstream medical research.

            While the USDA food pyramid is certainly influenced by industry, and they include a lot of items on the “acceptable” diet list that are clearly not ideal, the idea that “low-fat, high carb” is a giant conspiracy by the “establishment” (don’t know who you are referring to here) to mainly publish scientific research that benefits large companies is preposterous. I’m not even advocating that people should eat tons of carbs, I’m only pointing out what should be obvious to anyone who looks at the overall body of medical research: Getting the majority of daily calories from fat is not recommended. The research on low carb, high fat is still too young at this point. While saturated fat may not be the evil that everyone thought it was, it should still be consumed in small quantities as part of a balanced diet.

            When I first posted, I was just trying to be helpful. I’ve tried this high fat diet, and it doesn’t work for me. Not even close. The fear of grains is totally unjustified, and if you want to gain weight, eat more rice and beans, not more steak and fat!

  3. Michal (2 years ago)

    Cultures such as the Kitavans and the Okinawans maintain a high carb intake (90% of their calory intake), but they aren’t eating cereals. Almost all of their carb calories come from glucose and maltose in the form of sweet potatoes, yams, cassava, and other tubers. On high carb diets like those, they are free of disease of affluence and have high level of longevity. What do you think about this?

  4. Bob Falco (2 years ago)

    Hello Dr. Cate, it was two years ago today I picked up Deep Nutrition when I visited you in your NH office. I am still thoroughly enjoying the diet eating real food and it’s benefits. Still at my nadir weight, from when I had initially lost 20 pounds of fat.

    I feel like I am 18 again, oh for your readers, I am 53, but feel certain I am in the best physical shape, and the strongest I’ve ever been.

    I have to say, it’s been an ego boost as well. On multiple occasions people have made positive remarks on my physique. I am not super muscle bound by any stretch of the imagination — maybe it’s just that I am not carrying the typical 30 plus pounds of fat of a 50+ year old. One of my wife’s girlfriends impulsively squeezed my arm while remarking “dude you’re buff.”

    As I said, I an not super muscle bound. I have just really latched onto the Mark Sisson philosophy of exercise. Which is to do it in support of your other life goals and have fun with it.

    For me it boils down to getting plenty of quality animal fats & protein (I have been under 50 gms carb for almost a year), lots of sunshine, variable exercise as described by Mark, plenty of romance with my wife, enjoying family time, fulfilling work and a couple of hobbys — not necessarily in that order.

    Thank you for creating the foundation of transformation via Deep Nutrition.

  5. Liz (2 years ago)

    There is something that just doesnt seem right about blaming carbs. Frutarians/vegans for example. Those people, if they got any skinnier they would die. No body fat, theiy tend to look old and bony. And those people try to ingest at least 2000 to 3000 calories in fruit and vegetables. A LOAD of carbs. No fat. Can you explain this to me. If its carbs that make you gain weight, why are they so skinny? Maybe its the combination of high fat and high carb toegether with processed and modified food intake. I would love to understand this further.

  6. Paleo For Women | Two Happenings: AHS Starch Panel Recaps and the Forthcoming Birth Control Series (2 years ago)

    [...] Dr. Cate Shanahan’s take (from 2011). [...]

  7. Blakely Page (2 years ago)

    Dr. Cate,
    I just finished Deep Nutrition and LOVE it. I am a RD who is basically in nutrition rehab :) but progressing nicely I feel.

    I have been LC (50-100g) for about 4 months now and as you noted in comments above, have had constipation. I increased potato, rice and water this week and all is well. However I’m waiting to see if it will affect my wt loss. What do you suggest if incr carbs decrs wt losss but VLC results in constipation? (taking probiotics & eating fresh ferment)

    • Dr. Cate

      Dr. Cate (2 years ago)

      Try Flax, 2tbsp ground, stirred into hot water. More troubleshooting tips on low-carb issues will be coming out in future posts and of course, Page, if you share this post you will be helping other low-carbers find this site and they may add their own tips!

  8. Imogene (2 years ago)

    Dr Cate-
    I have been working on going low-carb for a few months. Eliminating processed foods, soy, corn, grains. I read your 100gr/day limit in Deep Nutrition. Do I count carbs from all the veggies I eat? I eat carby veggies (b-nut squash, sweet pototoe) right after exercise. Do these carb grams also count against the 100gr? I do not use dairy (eczema)

    What do you recommend for intestinal upset (indigestion, bloating)? I tried NOW Super Enzymes, but seemed ineffective.

    Thanks!

    • Dr. Cate

      Dr. Cate (2 years ago)

      Carbs from every source do count. The solution to intestinal upset depends on the cause! But one thing that may help is to eat something acidic before the meals that bother you–like a (fermented) pickle or q/2 tsp vinegar.

  9. Marco (2 years ago)

    @ANN: you wrote about the china study, well…in the china study as far as i remember the only kind of milk that was taken into account was pastourized milk, do try the raw milk version from a safe place, you will find out that most of the people that you know to have issues with pastourized/boiled milk will probably don’t on a raw milk trial.. :P

    Catey thanks for the great info on carbs, another nice clear up =)

    Marco – Italy

  10. tam (2 years ago)

    @Greg: You should read Paul’s blogs on the dangers of zero carb diets, like no mucous production:

    http://perfecthealthdiet.com/?p=1077

  11. Greg (2 years ago)

    Experimented with ZC for a few weeks. Very bad results. Heart constantly pounding in chest, felt wired/nervous/anxious/physically stressed out all the time. trouble falling asleep at night/had to drink at least 2-3 liters of water just to not feel dehydrated. Went to see a Traditional Chinese Medicine physician, who told me that eating only meat/fat/dairy/eggs with veggies and fruit had totally imbalanced my internal organs. Went back to eating white rice/veggies/little meat Now feel much better

    • Dr. Cate

      Dr. Cate (2 years ago)

      The experience you describe is common, and of the reasons I wrote up this post: http://drcate.com/going-low-carb-too-fast-may-trigger-thyroid-troubles-and-hormone-imbalance/

      While I never advise forcing your body to follow a program that makes you feel bad, nor do I feel Zero Carb is necessary, it’s important to understand why you feel that way. One common observation from my clinic is that people who feel bad from cutting carbs quickly almost all have prediabetes and I use a fasting blood glucose above 90 as a cut off to diagnose this.

      • Greg (2 years ago)

        My current hypothesis is that while human beings may have evolved to eat a low carb kind of diet aka plenty of fat/moderate protein/minor amounts of fruits and tubers and veggies; modern/civilized human beings probably should not be eating such a diet because our lifestyle and environment is much different from that of the paleolithic. Traditional Chinese Medicine dietetics are tried and true over a large land area with a diverse and varied climate. Plant based with supp protein/fat is the way

  12. izzy (2 years ago)

    im 12 years old and im trying to lose weight im doing more sports but im not sure how much carberhydrates i should have and i just lost
    HELP ME PLEASE !!!!!!!!!

  13. Bob Falco (2 years ago)

    Hello Dr. Cate
    You may remember me as a patient of yours in NH. I am still enjoying the diet, and have reduced my carb intake in stages to my current under 30 per day. I’ll be 53 next week, & I have never felt better, or been in better physical shape. Yesterday I did my first IF, skipped breakfast, and I can’t believe the energy boost. If I had done this before I would’ve had the low blood sugar shakes, but I was better than fine. Does this indicate my FBG has dropped & that I am ketogenic?

    • Dr. Cate

      Dr. Cate (2 years ago)

      Yes and Welcome to the club! So nice to hear from you. Do you have before/after photos?

      • Bob Falco (2 years ago)

        Dr. Cate, Unfortunately I didn’t take any before photo, or have anything that would be useful. I started the diet to get my BP under control, and the weight loss was a surprise. I started at 162 lbs with a tight 34 waist jean, today I am at 146 lbs with a loose 30 waist jean. I am 5’11” and consider myself to be small framed. I started the diet Oct 2010 at ~100 gms carbs and was 142 lbs by March 2011. I have seen significant improvements at the gym. Today I am at 30 gms. carbs with IF 3x week

  14. Lizzie McCormick (2 years ago)

    Hi Dr. Cate!!!!

    As you know, I have been very committed to lower-carb paleo-style living in general, but I have been wary of maintaining a low a level of carb intake (or doing any intermittant fasting) during pregnancy and during breastfeeding. The Paleo-sphere has variable advice about carbohydrate intake and breast-feeding: “We reproduced during the Ice Age so low-carb is fine” or “People waited for the right season to reproduce so be moderate (100g).” Love to hear your take on it!

    • Dr. Cate

      Dr. Cate (2 years ago)

      Consider this: Gestational diabetes is now being diagnosed at a FBG of 90 or higher. The treatment? Low carb diet.

  15. tam (2 years ago)

    You need a certain amount of glucose for mucous production and immune function, whether directly from starches or converted from protein. If you have a dry mouth or eyes, you have a problem. Cutting carbs can be risky if you don’t know what you’re doing.

    • Dr. Cate

      Dr. Cate (2 years ago)

      Thank you for pointing out that changing diet is something that can have health consequences that a specially trained heatlh provider should help you sort out. It is also important to point out that while dry mouth and eyes CAN be due to problems w/ glucose metabolism they can of course be due to other issues ie inflammation or prior infection/trauma.

  16. GiGi Eats Celebrities (2 years ago)

    I eat marginally carbs. I only eat them from vegetables. I have never had more energy or felt better before in my life. I have not eaten any other source of carbohydrate for the past 10 years. It’s a phenomenal way of life and I recommend it to anyone.