Myth Busting: Your Brain and That "Required" 130 Grams of Carbohydrate

My email has been filed this past week with emails from people with diabetes whose doctors or nutritionists have told them that it is dangerous to eat less than 130 grams of carbohydrates a day.

It isn't true. In fact, for most people with diabetes the opposite is true: eating more than 130 grams of carbs a day guarantees blood sugars that are so high they raise your risk of blindness, amputation, kidney failure and heart attack.

The old wives tale that you must eat 130 grams of carbohydrate a day has no basis in science. Is is one of those factoids that has been passed from teacher to student in the health profession for generations--long after anyone remembers where it originally came from. As it turns out, it came from two sources, one was ignorance of how the body works and the other a problem common 25 years ago that has been solved by medical progress.

Let's look at the origins of the damaging myth that you have to eat 130 grams of carbohydrate every day:

1. Though the brain requires carbs, you don't need to eat carbs to provide your brain with carbs.

The brain is unique among organs in its need for glucose. All your other organs can run on ketones or free fatty acids, both the byproducts of the metabolizing fat--but your brain does does require a certain amount of glucose to keep functioning--somewhere around 120 grams.

But before you rush off to eat a bagel for breakfast, you need to know while your brain needs glucose, you do not need to EAT glucose to provide your brain with the glucose that it needs. That is because your liver has the remarkable ability to transform the protein that you eat into glucose. This process is called "gluconeogenesis."

You liver can transform 58% of every gram of protein you eat into glucose, so any deficit created by eating less than 130 grams of carbohydrate can be made up by eating enough extra protein to supply the liver with the raw material to make some carbohydrate on its own.

But (as they say on the infomercials) that's not all! After a period of prolonged glucose "starvation" the brain's requirement for glucose drops. It becomes far more efficient and is able to run largely on the ketones produced by metabolizing fat. At that point, the brain's requirement drops to a mere 40 grams of glucose. If you ate no carbohydrate at all, you could can easily get that 40 grams of glucose from eating 69 grams of protein, or slightly over ten ounces of a protein-containing food like meat, cheese, or eggs. If, like most of us who limit our carbohydrates to control our blood sugars, you eat 45 to 100 grams a day, you will already be eating enough glucose to keep your brain happy.

This ability of the liver to make glucose from protein and its ability to adapt to burning ketones has been known for a long time. You can find it discussed in complex scientific language on pages 279 and 282 of the textbook, "Understanding the Brain and Its Development." Though the chapter assumes that a lowering of carbohydrate would be caused by "malnutrition" the same mechanisms occur when you lower carbohydrate and eat enough protein and fat to avoid malnutrition.

With this information, you can see that a person with diabetes who is eating 40-80 grams of carbohydrate a day can easily meet their brain's need for carbohydrates by eating a slightly higher protein intake for three weeks and then dropping it to a moderate amount--no more than 12 ounces a day for many people.

I have put together a calculator which will let you figure out exactly how much protein you need to eat to give your body both enough glucose to run your brain and additional protein to repair your muscles: Protein Need Calculator. Check out your current diet and see whether you are getting enough protein.

In case you might worry that your brain might still suffer if you make this adaptation to glucose "starvation" you might find it interesting to know that, far from it being dangerous, neurologists have found that eliminating all carbohydrates from the diet and providing high quality protein and fat often cures forms of childhood epilepsy that are otherwise untreatable with any drug or surgery, often permanently. Many parents also report improvements in their children's behavior when they are placed on these extreme low carb diets. (NOTE: The epilespy extreme low carb diet also severely limits fluids, which is not the case with the diabetes mildly lower carb diet.)

It is worth noting that the authors two of the best-regarded and bestselling books about diabetes, Dr. Bernstein and Gretchen Becker, both eat considerably less than 130 grams of carbohydrate a day. So, for that matter, do I. Perhaps another side effect of limiting carbohydrates is uncontrollable bibliographia*.

2. Low carb diets posed some danger to people using insulin and insulin-stimulating drugs before blood sugar meters came into use.

There is another reason why many doctors and nutritionists were trained to believe that a diet of less than 130-140 g of carbohydrate a day was dangerous. It is because, until the middle 1990s, few people with diabetes had access to blood sugar meters. At the same time, their diabetes was usually treated with sulfonylurea drugs that stimulate uncontrolled insulin production or with antique insulin regimens that involved taking one or two large shots of mixed insulins each day.

Because these people could not check their blood sugar in real time and had large, often unknown doses of insulin coursing through their bloodstream, there was always the fear that they might get too much insulin and have a life-threatening attack of hypoglycemia.

Back in these bad old days the only way people with diabetes could test their blood sugar at home was by dipping test strips in urine. These strips changed color when the concentration of glucose in the urine rose. Since most people don't spill glucose into urine until their blood sugar has been quite high for several hours, the lowest blood sugar that could be identified with these strip was one somewhere between 160 and 180 mg/dl (8.9 mmol/L and 10 mmol/L). If a person's blood sugar dropped below this level, it was impossible to tell what it was. It might be a normal 130 or a near-fatal 32 mg/dl (6.7 or 1.8 mmol/L). Not only that, but the "blood sugar" reading you saw on a urine test lagged several hours behind your blood sugar at the moment of testing so they told you what your blood sugar had been an hour or two before, not at the time of the test.

Given that situation, doctors and nutritionists urged people with diabetes to eat a lot of carbohydrate, enough to make sure they wouldn't suffer dangerous hypos no matter how much insulin was in their blood stream. To make it possible to check their blood sugar with urine test strips, many were urged to eat enough carbohydrate to keep their blood sugar above the 160 mg/dl level that showed up on urine test strips--which most people with diabetes can do if they eat at least 130 grams of carbohydrate a day.

But we have blood sugar meters now that can tell us exactly what our blood sugar is, any time we fear it might be dropping. We also have drugs for Type 2 diabetes that do not cause dangerous hypos, and much more controllable insulin regimens available to those of us who need to use insulin.

So for many of us hypos are not even an issue, and even for those of us using insulin, they are no where near the threat they used to be. That is why there is no longer any reason for anyone to ever eat a diet intended to push their blood sugar up over the high end of the normal range, which is 140 mg/dl (7.7 mmol/L). Doing so raises your likelihood of developing complications.


Bottom line: There is no reason to eat any set amount of carbohydrates. The best carbohydrate intake level is the one that keeps your blood sugar at a safe and normal level. This flyer will explain to you what that level is and how to reach those safe and normal blood sugar levels. http://bloodsugar101.com/flyer.pdf. If you live in a part of the world that uses the mmol/L measurements, download this version: http://www.bloodsugar101.com/flyer-mmol.pdf.

Even the American Diabetes Association--notorious for its hyper-conservative stance on diet--has stated in its 2008 practice recommendations that the low carb diet appears to be safe for people with diabetes.

If you are still battling a doctor or nutritionist whose last education about diet and diabetes took place decades ago, bring them some of the research studies proving the safety of low carb diets you'll find at HERE.

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Bibliographia: medical term for writing books.