Sunday, July 31, 2011

High-Protein Diet Worse For Insulin Sensitivity Compared To High-Cereal-Fiber Diet

High-protein and high-fat diets have been shown to increase insulin resistance, setting the stage for diabetes. These diets are typically low-carb. Yet supporters of low-carb diets claim the converse, that they lower diabetes risk. Which is true?

If you take two overweight people with metabolic syndrome (at increased risk for diabetes), give them the same number of calories, except one eats a high-protein diet, the other eats a lower-protein diet with more carbs and fiber, which one will experience better insulin sensitivity?

This new study out of Germany did just that and found:1
"Insulin sensitivity was 25% higher* after 6 weeks of the high-cereal-fiber diet than after 6 weeks of the high-protein diet."

* Measured by euglycemic-hyperinsulinemic clamp
Group assignment:
  • The high-protein group was eating 28% protein, 43% carbohydrate, and 13 g cereal fiber.
  • The lower-protein, higher-carb, higher-fiber group was eating 17% protein, 52% carbohydrate, 43 g cereal fiber.
For a 2000 calorie diet:
  • This high-protein diet provided about 140 g protein and 215 g carb.
  • This lower-protein/higher-fiber diet provided about 85 g protein, 260 g carb.
Not only did the cereal-fiber group eat less protein, but they absorbed less of the protein they did eat owing to interference from increased fiber. This lower protein may have contributed to improved insulin sensitivity:
"High-protein intake was associated with a tendency to increased protein expression in adipose tissue of the translation initiation factor serine-kinase-6-1, which is known to mediate amino acid–induced insulin resistance."
Anecdotally, I've noticed that people who eat more meat, and so more protein and fat, have a harder time clearing glucose from their blood.

This isn't the first time fiber was found to improve insulin sensitivity. This study found:2
"Increased insoluble dietary fiber intake* for 3 days significantly improved whole-body insulin sensitivity. These data suggest a potential mechanism linking cereal fiber intake and reduced risk of type 2 diabetes."

* 31 grams insoluble fiber daily. (Wheat bran is about 90% insoluble, where as oat bran is only about 50-60% insoluble)
A take-away message for me ... keep fiber intake up; watch protein/meat intake.
1 Effects Of Supplemented Isoenergetic Diets Differing In Cereal Fiber And Protein Content On Insulin Sensitivity In Overweight Humans, American Journal of Clinical Nutrition, August, 2011
2 Cereal Fiber Improves Whole-Body Insulin Sensitivity In Overweight And Obese Women, Diabetes Care, 2006


virginia said...

And, the take-away message for labels more carefully, and keep a calculator handy.

Thank you, this was helpful.

RB said...

I also heard that animal protein takes calcium to metabolize and can lead to osteoporosis. Osteoporosis is more common in societies that eat a lot of meat and dairy products. So a diet with just the needed protein (50 to 70 grams) can also reduce osteoporosis.

Basically for diabetes and osteoporosis, it all come down to eating less meat (no more than 4 oz. a day) and eating more plants. Like Michail Pollan says "Eat food, mostly plants, not too much."

Anonymous said...

But was the 13g fibre (43g) part of,
or additional to the 215g carbs. (260g)?
(I cannot find it clearly stated.)

Assuming fibre was not included in the carb. figures, then I would really have liked to see the effects of the two other possible combinations also, i.e. 28% protein, 43% carbs, 43g fibre, and 17% protein, 52% carbs, 13g fibre.


Anonymous said...

Regarding my previous comment, I guess they thought the control group was enough for comparison. (They had quite similar fibre intake to the high-protein group.)

Still, ...

pronutritionist said...

Interesting study, especially as it is done with clamp technique (gold standard in insulin sensitivity). However, there was no significant difference between groups at 18 weeks. It's noteworthy that fat was not modified in the study. Thus, it was solely supplemented protein vs. fiber, and cannot be extrapolated directly to Low Carb Diets. In any case, these results are intriguing as high protein diets have been linked to increased incidence of type 2 diabetes/CVD. I wonder how Mr. Protein Power will comment ;-)

Another study by Kirk et al. 2009, also clamp study, showed that Low Carb Diet may attenuate liver insulin resistance in short term "Our results refute our original hypothesis that a LC diet will cause insulin resistance because of increased adipose tissue lipolytic rates and excessive FFA release into the bloodstream.". This was a real Low Carb Diet trial.

Let's see what other studies will suggest.

Reijo Laatikainen, dietitian, Finland

Laurie Endicott Thomas said...

A diet high in animal protein and especially a diet high in calcium does promote osteoporosis.

Ben P. DaSalt said...

The low-carb advocate would respond that the low carbohydrate diet in the study was not low carbohydrate at all, that the outcome is unsurprising, and the comparison to true low-carb diets is void.

Many low-carb proponents state that the ideal carbohydrate consumption (or certain foods like grains) should be (near) zero but permit a minimal allowance out of real world practice. A 43% carbohydrate ratio is too high to be considered low-carb by most proponents.

Bix Weber said...

I think you're right, Ben.

I will say this ... I've seen how some people translate the low-carb message - they eat their regular diet and just add in more meat. I'm not sure if this is benefiting them.

Since Dr. Eades of Protein Power was mentioned ... It reminded me of a video I saw where he and his wife were promoting the sous vide cooker. His wife admitted that his diet was expensive and time-consuming. Maybe that's why people do it just a little (as above), instead of following it rigorously? I don't know.

Grok said...

@RB Laurie already pointed to some stuff, but here is another by Denise Minger on animal protein an bones using Campbell's own research:

"people who eat more meat, and so more protein and fat, have a harder time clearing glucose from their blood."

I agree

Laurie Endicott Thomas said...

Denise Minger has no scientific training whatsoever. She's been trying to "debunk" the China study, even though she evidently hasn't taken even an introductory course in statistics. She's been quite obnoxious to Dr. Campbell, and he has been patient and polite in response.

Bix Weber said...

I agree with Laurie here. If you want to discuss bone health, you need to discuss renal acid load, as Laurie did. Diets high in animal proteins are very acid-forming. They push body fluids down to a lower, more acidic pH. The body draws from minerals in bone to neutralize acid.

North Alaskan Eskimos, whose diets are high in animal protein, have low bone density and high rates of osteoporosis.

Anonymous said...

Re. Ben's comment, low-carb advocates
could also simply point out that the differences went away at 18 wks (as Reijo mentions above). It could be that negative effects are just transient.

Not a very helpful study.

Cris Barrows said...

43% carb is not a low carb regimen. There would be no meaningful ketogenic effects with such a proportion. The entire principle of LC is a majority of energy from fat, not glucose. The correct designation should be LCHF see the Swedish revolution as a good example.

The conclusions of these studies are meaningless - a 43% carb ratio as low carb is a strawman fallacy.