Does the Brain Require 130g of Carbs to Survive? What is the evidence?
Jul 11, 2023If you are a parent of a child diagnosed with Type 1 diabetes who has been told that your child’s brain requires a minimum of 130g of carbohydrates to function properly, or you are a medical professional who has advised your patients and clients of this recommendation, then this video is for you!
In this post, we are going to explore the questions:
Where did the guideline that we must eat 130 grams of carbs daily originate?
And is this recommendation well-founded?
As parents, it can be challenging to navigate the world of nutrition and make informed decisions about what to feed our kids. As parents of a child diagnosed with Type 1 diabetes, the challenge is amplified. And one of the most confusing topics is carbohydrate consumption.
In a previous post, we challenged the widely held view that carbs are essential for human survival. If you haven’t yet watched that video, you may wish to visit my last post title "Are Carbs Essential for Human Survive?" and start there.
If you already understand why carbs are not essential for humans, you’re ready for this video & post.
Let’s investigate where the recommended minimum carb intake of 130 grams per day comes from and whether it’s valid.
1. The Origin of the 130g of Carb Guideline - Unearthing the Historical Context
First, some context. In the 1930’s and ‘40’s, the American and Canadian governments began to develop dietary standards. Initially, these targeted food relief efforts during wartime and economic depression.
In the decades following, government nutrition guidance evolved to address whether citizens were properly nourished, what info should be included on food labels, and how foods can be fortified to make the population healthier.
2. The Institute of Medicine's Role - Dietary Reference Intakes (DRI) Unveiled
These dietary standards eventually came to be called the Dietary Reference Intakes (DRI), and since 1998, the Institute of Medicine has issued eight large DRI publications. These outline reference values for the nutrients we eat.
Reference values for carbohydrate is covered in a volume originally published in 2002. It’s 1359 pages long - as thick as a Bible - with an entire chapter dedicated to dietary carbohydrate.
It was in this DRI document that the Institute of Medicine first set out a standard for daily carb consumption, and it recommended healthy people eat a minimum of 130g of carbs per day.
3. Decoding the 130g of Carb Recommendation - What Justifies the 130g Carb Daily Minimum?
It was this recommendation that advised medical and nutrition professionals that all people, one year of age and older, must consume a minimum of 130 grams of carbs per day.
To explore the origin of this dietary standard, we are going to focus on 3 questions:
- Why did the Institute of Medicine recommend people consume a minimum of 130 grams of carbs per day?
- What evidence was considered for estimating the average requirement for carbohydrate?
- Does this recommendation make sense?
Let’s dig in!
The second line in the Chapter on carbs states:
The Recommended Dietary Allowance (RDA) for carbohydrate is 130 g/d for adults and children based on the average minimum amount of glucose utilized by the brain.
This says healthy people are required to eat foods containing this many carbs daily to meet the brain’s energy requirements.
4. Analyzing the Evidence - The Tug of War in DRI's Carb Chapter
What evidence was considered for estimating the average requirement for carbs?
First, it’s important to know that this DRI publication opens with a preface that notifies the reader that,
“Although all reference values are based on data, available data were often sparse or drawn from studies with significant limitations in addressing various questions confronted by the panel and subcommittees.
Thus, although governed by scientific rationales, informed judgments were often required in setting reference values.”
Next, let’s turn to a section in the DRI chapter on carbs about the evidence used specific to carbs. It states:
“Long-term data in Westernized populations, which could determine the minimal amount of carbohydrate compatible with metabolic requirements and for optimization of health, are not available.”
We are told here by the panel that there is no data they can use to determine the minimal amount of carbs we should eat to meet the body’s metabolic requirements and optimize health.
The very next sentence states:
‘Therefore, it is provisionally suggested that an Estimated Average Requirement (EAR) for carbohydrate ingestion … be based on an amount of digestible carbohydrate that would provide the brain (i.e., central nervous system) with an adequate supply of glucose fuel without the requirement for additional glucose production from ingested protein or triacylglycerols.” DRI pg 285
We see that the panel has narrowed its focus for carb consumption. They’ve related it to what they feel the BRAIN requires.
The dietary standard for carbs is based on a suggestion – that the brain should be solely fuelled by the carbohydrate one eats. Discounting the brain’s ability to use glucose produced by the liver or other fuel sources derived from fat, the estimation for carbs centres on providing glucose for the brain.
I will talk more about this in a minute.
But I want to stick with our 2nd question - how did they estimate the average amount of glucose the brain requires to function?
The DRI document discusses multiple methods that can be used to determine glucose utilization by the brain. These study methods had limitations related to their accuracy, and indirect methods of measurement and indirect estimations were used, such as the correlation between the weight of the brain and the weight of the body in order to calculate brain glucose utilization.
Based on these direct and indirect methods, the panel suggested that the Estimated Average Requirement for total carbohydrate be set to 100g per day. The panel stated this amount should be sufficient to fuel the central nervous system solely through glucose coming from dietary carbohydrate.
The Panel then added an extra 30% on to this Estimated Average Requirement for total carbs to account for “variation in brain glucose utilization”. When you add 30% to the 100-gram Estimated Average Requirement, you get 130 grams of carbohydrate, and that’s how they came up with the 130!
THIS became what is known as the Recommended Dietary Allowance (RDA) for all humans aged 1 year and above.
5. Challenging the Recommendation - Does 130g of Carbs Daily Make Sense?
Here’s a key problem with setting a guideline that says everyone should eat at least 130 grams of carbs per day. The evidence considered in estimating the requirement is based on:
GLUCOSE utilization by the brain
GLUCOSE utilization, not CARB utilization!
And we know from our last video/post (Are Carbohydrates Essential for Human Survival?), the liver can produce glucose to fulfill the body’s needs by breaking down glucose or making new glucose for the body and brain to use.
Plus, the body can also take fatty acids and turn their components into fuel the body and brain can use.
Dr. Jason Fung, a physician and metabolic health expert, explains this clearly. He says,
“The best lies have a grain of truth. And what they mean is that the brain requires some glucose to function, but it doesn’t require you to eat glucose to function and that’s the distinction.”
But don’t worry, because even the DRI document acknowledges that carbs are not essential and that the brain can function without them. In fact, the whole chapter 6 on carbs reads like a tug of war between “we need carbs” and “we don’t need carbs”.
In the very same chapter where a RDA of 130 grams per day is set out, the document states:
“The lower limit of dietary carbohydrate compatible with life apparently is zero, provided that adequate amounts of protein and fat are consumed.” (p. 275)
And this point is important, because all humans need adequate amounts of food, adequate amounts of energy for the cells to do their work, regardless of the amount of carbs, proteins or fats consumed.
I think this point gets overlooked and lost within the many pages of this thick document.
They state that the requirement for dietary carbohydrate is zero, and they also mention that the body can make glucose for the brain and other glucose-requiring cells such as red blood cells, but then… they insist that every person must eat 130 grams of carbs each day, and they tie it to the phrase, “based on the average minimum amount of glucose utilized by the brain.”
It's senseless. The phrase, ”the brain is the only true carbohydrate-dependent organ”, which makes us think the brain relies on us to eat carbs, is followed later in the same paragraph with, “the brain can adapt to a carbohydrate-free, energy-sufficient diet, or to starvation.”
This tug of war is confusing! On the one hand, the document provides a RDA with a minimum amount of carbs needed, which it says is for the brain being able to have enough glucose from the carbs it eats to function, and the document also confirms that carbs are not essential for life and that the body and the brain can survive on a carbohydrate-free diet.
And we are back to what we learned in our last video (Are Carbohydrates Essential for Human Survival?):
As long as you eat enough protein and fat, dietary carbohydrate is not required in the diet. The liver can produce glucose for the body to use, if required.
And the American Diabetes Association confirmed this in their 2019 Consensus report on Nutrition Therapy for Adults with Diabetes:
“The amount of carbohydrate intake required for optimal health in humans is unknown.
Although the recommended dietary allowance for carbohydrate for adults without diabetes is 130 grams per day and is determined in part by the brain’s requirement for glucose, this energy requirement can be fulfilled by the body’s metabolic processes, which include glycogenolysis, gluconeogenesis and ketogenesis…”
The American Diabetes Association reassures us that the body’s, including the brain’s requirement, for glucose can be fulfilled by its own metabolic processes.
So, if the evidence confirms that the human body doesn’t require carbs to survive, why are parents of children diagnosed with Type 1 diabetes told that kids need carbs to grow and need carbs for their brains to function properly?
I can’t be certain, but my guess is there are a number of reasons.
For one, health care professionals are busy - they do not have time to delve into the DRI document to evaluate the recommendation and the evidence which underpins it.
The DRI are over 1300 pages long, and many health care professionals will refer only to the DRI Summary Tables, a quick and easy reference guide, trusting that the evidence and science underpinning the recommendation is solid. Unfortunately, this is not the case.
And the recommendations and phrasing that have come out of the DRI for carbohydrate ends up in our nutrition textbooks, with statements that guide nutrition professionals to learn that a minimum of 130 grams of carbs are necessary for the brain to function.
In my graduate nutrition program, we are taught and had to memorize the dietary standards for all nutrients, including the carbohydrate RDA of a minimum of 130 grams.
6. Conclusion
My aim is not to demonize carbohydrates. There are many excellent carbohydrate foods that are nutrient-dense and support health.
My aim in this post is to help set the record straight.
Despite what you may have been told or what may have been included in your education curriculum, carbohydrates are not essential for human survival and brain function, and we don’t need to consume a minimum intake of carbohydrates daily, provided we are consuming enough food, enough energy.
I hope you found this information useful.
If you would like to watch a presentation by another health care professional who discusses Type 1 diabetes and carbohydrate consumption, I encourage you to view a talk by endocrinologist Dr. Jake Kushner. Dr. Kusher also talks about the Dietary Reference Intakes, and I’ve included the URL for this talk in the reference section below.
If you have not already read or watched my previous post on (Are Carbohydrates Essential for Human Survival?), I strongly recommend that you check it out: https://www.t1dnutrition.com/blog/are-carbs-essential
For more information on how to safely achieve normal, non-diabetic blood sugar levels, manage Type 1 diabetes with more confidence and protect your child's future health, please visit:
T1D Nutrition: https://www.t1dnutrition.com/
Follow T1D Nutrition via:
Blog: https://www.t1dnutrition.com/blog
Facebook: https://www.facebook.com/t1dnutrition/
YouTube: https://www.youtube.com/@t1dnutrition
References:
Institute of Medicine. 2005. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. Washington, DC: The National Academies Press. https://doi.org/10.17226/10490.
Evert, A. B., Dennison, M., Gardner, C. D., Garvey, W. T., Lau, K. H. K., MacLeod, J., Mitri, J., Pereira, R. F., Rawlings, K., Robinson, S., Saslow, L., Uelmen, S., Urbanski, P. B., & Yancy, W. S., Jr (2019). Nutrition Therapy for Adults With Diabetes or Prediabetes: A Consensus Report. Diabetes care, 42(5), 731–754. https://doi.org/10.2337/dci19-0014
Dr. Jake Kushner - 'Low Carbohydrate Nutrition For Type 1 diabetes: A Practical Guide' https://www.youtube.com/watch?v=4t8_wvnlaNM&t=889s
(Discussion about the DRI at ~14:30)
#T1DNutrition #Type1diabetes #AreCarbsEssential #NormalBloodSugars #TheNutritionEffect #doesthebrainrequirecarbstofunction
