How Much Carbohydrate is Essential in the Diet?

INTRODUCTION: I was asked a question recently on social media as to what is our body’s essential daily requirement for carbohydrate. This is a very good question – so much so, that I decided to answer it in the form of a short article. If you are considering a low carb high fat lifestyle, this is important to understand.


Our body has an absolute requirement for specific essential nutrients; nutrients that we must take in our diet because we can’t synthesize them. What these nutrients are and how much we require depends on our age and stage of life, our gender and other factors and are listed in several volumes called the Dietary Reference Intakes (DRIs), published by National Academies Press.

There are Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein and Amino Acids (2005), Dietary Reference Intakes for Calcium and Vitamin D (2011), Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium, and Carotenoids (2000), Dietary Reference Intakes for Calcium, Phosphorus, Magnesium, Vitamin D, and Fluoride (1997), Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate (2005), Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline (1998), Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc (2001).

In these texts are listed the essential amino acids (histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, valine) that must be supplied in the different kinds of protein that we eat.

These texts also establish that there are two essential fatty acids, linoleic (an omega 6 fat) and alpha-linolenic (an omega 3 fat) that can’t be synthesized by the body and must be obtained in the diet.

There are 13 essential vitamins (vitamin A, vitamin B1 (thiamine), B2 (riboflavin), B3 (niacin), B5 (pantothenic acid), B6 (pyrodoxine), B12 (cyanocobalamine), biotin, vitamin C (ascorbic acid), choline, vitamin D (cholecalciferol), vitamin E (tocopherol) and  folate) listed and essential minerals, including major minerals (calcium, phosphorus, potassium, sodium, chloride and magnesium) and minor minerals (chromium, cobalt, copper, fluorine, iodine, iron, manganese, molybdenum, selenium, silicon, sulfur and zinc).

But is there “essential carbohydrate?

In Chapter 6 of the Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein and Amino Acids (2005) is the chapter titled “Dietary Carbohydrates: Sugars and Starches” (pg. 265), which indicates that the  Recommended Dietary Allowance (RDA) for carbohydrate,  considered to be the average minimum amount of glucose needed by the brain, is set at 130 g / day for adults and children.

Recommended Dietary Allowance (RDA) for carbohydrate

It is important to note that the Recommended Dietary Allowance (RDA) for carbohydrate is at 130 g / day based on the average minimum amount of glucose needed by the brain – with no consideration that the body can manufacture this glucose from both FAT and PROTEIN.

Just 10 pages later, in the same chapter of the Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein and Amino Acids (2005) it reads;

The lower limit of dietary carbohydrate compatible with life apparently is zero, provided that adequate amounts of protein and fat are consumed. 

The lower limit of dietary carbohydrate

That is, there is no essential need for dietary carbohydrate, provided that “adequate amounts of protein and fat are consumed”.

The text goes on to say that there are traditional civilizations such as the Masai, the Greenland and Alaskan Inuit and Pampas indigenous people that survive on a “minimal amount of carbohydrate for extended periods of time with no apparent effect on health or longevity“, and that white people (Caucasians) eating an essentially carbohydrate-free diet resembling that of the Greenland natives were able to do so for a year, without issue.

That is, the minimum amount of dietary carbohydrate required is zero provided that adequate amounts of protein and fat are consumed. Phrased another way, the “minimum amount of glucose needed by the brain of 130 g / day is made by the body from protein and fat provided they are eaten in adequate amounts.

In the absence of carbohydrate, de novo synthesis of glucose

On the next page (pg. 276) of the Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein and Amino Acids (2005) it explains the process;

“In the absence of dietary carbohydrate, de novo synthesis of glucose requires amino acids derived from the hydrolysis of endogenous or dietary protein or glycerol derived from fat. Therefore, the marginal amount of carbohydrate required in the diet in an energy-balanced state is conditional and dependent upon the remaining composition of the diet.”

That is, even when minimal amounts of carbohydrate is eaten (not something I promote), the body will synthesize the glucose needed by the brain from the protein taken in through the diet (provided it is in adequate amounts) or from glycerol which is formed when fat is broken down. If the protein in the diet (exogenous protein) is inadequate however, the body’s own protein (endogenous protein) will be used.

So, no, there isn’t any “essential carbohydrate” requirement.

Even when a person is completely fasting (religious reasons, medically supervised, etc.) the 130 g / day of glucose needed by the brain is made from endogenous protein and fat.

When people are “fasting” the 12 hour period from the end of supper the night before until breakfast (“break the fast”) the next day, their brain is supplied with essential glucose! Otherwise, sleeping could be dangerous.

In previous articles reviewing long-term studies of low carbohydrate diets, safety and efficacy has been established with intakes as low as 20 gm of carbs for 12 weeks and 35 gm of carbohydrate per day for extended periods of time, provided adequate protein and fat is eaten.

I am of the opinion that in order to have a diet with the essential vitaminsminerals, amino acids and fatty acids, that a wide range of healthy foods with some carbohydrate content is required.  I encourage people to consume low carb fruit and dairy products and nuts and seeds, along with a wide range of meat, fish and poultry, eggs and even tofu, if desired. I design each person’s Meal Plan to meet their individual requirements, lifestyle as well as the foods they like and take into consideration whether they like to cook or prefer meals with the minimum of preparation required.

Have questions?

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Note: Everyone's results following a LCHF lifestyle will differ as there is no one-size-fits-all approach and everybody's nutritional needs and health status is different. If you want to adopt this kind of lifestyle, please discuss it with your doctor, first.

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Author: Joy Kiddie, MSc, RD

Joy Y Kiddie MSc., RD - I'm a Registered Dietitian in private practice in British Columbia, Canada that provides low carb and ketogenic services in-person in my Coquitlam office, as well as by Distance Consultation (using Skype / telephone).