Should People With Diabetes Restrict Carbohydrates?

MB900402413Dr. John Rollo (a surgeon in the British Royal Artillery) in 1797 published a book, An Account of Two Cases of the Diabetes Mellitus. He discussed his experience treating a diabetic Army officer, Captain Meredith, with a high-fat, high-meat, low-carbohydrate diet. Mind you, this was an era devoid of effective drug therapies for diabetes.

The soldier apparently had type 2 diabetes rather than type 1.

Rollo’s diet led to loss of excess weight (original weight 232 pounds or 105 kg), elimination of symptoms such as frequent urination, and reversal of elevated blood and urine sugars.

This makes Dr. Rollo the original low-carb diabetic diet doctor. Many of the leading proponents of low-carb eating over the last two centuries—whether for diabetes or weight loss—have been physicians.

But is carbohydrate restriction a reasonable approach to diabetes, whether type 1 or type 2?

What’s the Basic Problem in Diabetes?

Diabetes and prediabetes always involve impaired carbohydrate metabolism: ingested carbs are not handled by the body in a healthy fashion, leading to high blood sugars and, eventually, poisonous complications.  In type 1 diabetes, the cause is a lack of insulin from the pancreas.  In type 2, the problem is usually a combination of insulin resistance and ineffective insulin production.

Elevated blood pressure is one component of metabolic syndrome

Elevated blood pressure is one component of metabolic syndrome

A cousin of type 2 diabetes is “metabolic syndrome.”  It’s a constellation of clinical factors that are associated with increased future risk of type 2 diabetes and atherosclerotic complications such as heart attack and stroke. One in six Americans has metabolic syndrome. Diagnosis requires at least three of the following five conditions:

■  high blood pressure (130/85 or higher, or using a high blood pressure medication)

■  low HDL cholesterol:  under 40 mg/dl (1.03 mmol/l) in a man, under 50 mg/dl (1.28 mmol/l) in a women (or either sex taking a cholesterol-lowering drug)

■  triglycerides over 150 mg/dl (1.70 mmol/l) (or taking a cholesterol-lowering drug)

■  abdominal fat:  waist circumference 40 inches (102 cm) or greater in a man, 35 inches (89 cm) or greater in a woman

■  fasting blood glucose over 100 mg/dl (5.55 mmol/l)

Metabolic syndrome and simple obesity often involve impaired carbohydrate metabolism. Over time, excessive carbohydrate consumption can turn obesity and metabolic syndrome into prediabetes, then type 2 diabetes.

Carbohydrate restriction directly addresses impaired carbohydrate metabolism naturally.

Carbohydrate Intolerance

Diabetics and prediabetics—plus many folks with metabolic syndrome—must remember that their bodies do not, and cannot, handle dietary carbohydrates in a normal, healthy fashion. In a way, carbs are toxic to them. Toxicity may lead to amputations, blindness, kidney failure, nerve damage, poor circulation, frequent infections, premature heart attacks and death, among other things.

Diabetics and prediabetics simply don’t tolerate carbs in the diet like other people. If you don’t tolerate something, you have to give it up, or at least cut way back on it. Lactose-intolerant individuals give up milk and other lactose sources. Celiac disease patients don’t tolerate gluten, so they give up wheat and other sources of gluten. One of every five high blood pressure patients can’t handle normal levels of salt in the diet; they have to cut back or their pressure’s too high. Patients with phenylketonuria don’t tolerate phenylalanine and have to restrict foods that contain it. If you’re allergic to penicillin, you have to give it up. If you don’t tolerate carbs, you have to give them up or cut way back. I’m sorry.

Carbohydrate restriction directly addresses impaired carbohydrate metabolism naturally.

But Doc, …?

1.  Why not just take more drugs to keep my blood sugars under control while eating all the carbs I want?

We have 12 classes of drugs to treat diabetes.  For most of these classes, we have little or no idea of the long-term consequences.  It’s a crap shoot.  The exceptions are insulin and metformin.  Several big-selling drugs have been taken off the market due to unforeseen side effects.  Others are sure to follow, but I can’t tell you which ones.  Adjusting insulin dose based on meal-time carb counting is popular.  Unfortunately, carb counts are not nearly as accurate as you might think; and the larger the carb amount, the larger the carb-counting and drug-dosing errors.

2.  If I reduce my carb consumption, won’t I be missing out on healthful nutrients from fruits and vegetables?

No.  Choosing low-carb fruits and vegetables will get you all the plant-based nutrients you need.  You may well end up eating more veggies and fruits than before you switched to low-carb eating.  Low-carb and paleo-style diets are unjustifiably criticized across-the-board as being meat-centric and deficient in plants.  Some are, but that’s not necessarily the case.

3.  Aren’t vegetarian and vegan diets just as good?

Maybe.  There’s some evidence that they’re better than standard diabetic diets.  My personal patients are rarely interested in vegetarian or vegan diets, so I’ve not studied them in much detail.  They tend to be rich in carbohydrates, so you may run into the drug and carb-counting issues in Question No. 1.

Steve Parker, M.D.

PS:  The American Diabetes Association recommends weight loss for all overweight diabetics. Its 2011 guidelines suggest three possible diets: “For weight loss, either low-carbohydrate [under 130 g/day], low-fat calorie-restricted, or Mediterranean diets may be effective in the short-term (up to two years).”  The average American adult eats 250–300 grams of carbohydrate daily.


Filed under Carbohydrate, Causes of Diabetes, Prediabetes

8 responses to “Should People With Diabetes Restrict Carbohydrates?

  1. Thank you Dr. Parker for providing such an excellent review of the type 2 diabetes issues as well as excellent historical perspective. SO far in all my reading of excellent sites as yours and other good blogs; one seems to end up at a low carb mediterranean diet and carefull restriction of carbs. And I would add using metfomrin to haul back the liver missignalling and over release of gluycose

  2. I had a client yesterday finally get diagnosed with Type II. She was required to go see the hospital RD and CDE. Now she is confused! They told her to eat 45-60 grams of carbs at eat each meal and to restrict her fat intake. 8 months of me teaching her to eat low carb for weight loss (and finally starting to see progress), then they screwed it up in two weeks! Grrr…

  3. Jan

    Hi Dr. Parker,
    I don’t think type 1 and type 2 diabetics have the same type of carbohydrate intolerance in that type 2’s require much more insulin for their carbs than a type 1. Type 1’s must inject insulin even without carbohydrate in their diet, and then of course use sugar to successfully use that exogenous insulin—to save themselves from the inevitable insulin shock/hypo.
    I know you know this, but it almost sounds as if you’re saying that a type 1 must give up or severely restrict carbs, when that is a tool that may help some achieve better control, but many achieve good control without carb restriction. And it is a tool that they cannot exclusively use without dying.

    • Jan, I agree with much of what you say. I appreciate your commenting. I’ve run across many type 1 diabetics who find it much easier to control blood sugars if they keep their total daily digestible carbs well under 100 grams a day. When I see an overweight or obese type 1, and I see many more now than I did two decades ago, I can fairly reliably predict they’re eating well over 100 g/day.


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  5. Jim Jozwiak

    Perhaps when communicating with the type 2 patient, instead of proposing that the patient can’t
    handle carbs in a healthy, normal way, might it be more effective to say something like “this
    {whatever diagnostic finding} suggests your distant ancestors ate very little starch or sugar
    and instead ate quite a lot of animal fat, and this was healthiest for them and now is healthiest for you.”