Loren Cordain wrote:

>      I agree that that carbohydrate mixed with fat generally results
>in a lower glycemic (blood glucose) response.   My point here was that
>the insulin response to fat + carbohydrate is greater than to
>carbohydrate alone because of the stimulatory effect of fat ingestion
>upon glucose-dependent insulino-tropic polypeptide (GIP) (5).
>
>5.      Collier GR et al.  The acute effect of fat on insulin secretion.
>J Clin Endocrionol 1988;66:323-26.

I would like to point out what I think is an inaccuracy in the last statement. I
looked up in the articles published by Collier et al. (1,2,3), and the results
were:

From (1):
The effects of co-ingestion of 50 g fat (butter) with 50 g carbohydrate
(potato) compared with potato alone: markedly decreased glucose, very
slightly decreased insulin, markedly increased GIP.

From (2):
Similar experiments and results with 75 g carbohydrate (438 g potato or
121 g lentils) with or without 37.5 g fat (46.5 g butter). Of course, all
the effects are more important with the rapidly absorbed carbohydrate
(potato) than with the slowly absorbed carbohydrate (lentils).

From (3):
The aim of that article was to test the conjecture that the rate of rise
of GIP, rather than the steady state level achieved, stimulates insulin
secretion when fat and carbohydrate are ingested together. To do that, the
authors administered a 5 g iv bolus dose of glucose 15 minutes after the
meal, when the RATE of rise of GIP was highest but the level still LOW,
and observed the insulin response. It appears that the peak insulin after
the mixed meal was 60% higher than after the carbohydrate meal. That seems
to confirm their hypothesis.

It should be noted that, in a practical situation, nobody will inject you
some glucose after lunch, so, that the insulin peak is higher after such a
practice following a mixed meal shouldn't be of concern.

So, in summary, 50 grams of carbohydrates+50 grams of fat is much "better" on
the blood glucose point of view, and only slightly "better" on the insulin point
of view than 50 grams of carbohydrates alone.

Now, in a practical situation, a man would have the choice between:

A) 50 grams carb. at breakfast, 50 grams fat at lunch
B) 50 grams carb and 50 grams fat at breakfast, no lunch
C) 25 grams carb and 25 grams fat at each meal

Obviously, from the preceding, B is "better" than A, and I think most people
will agree that C is better than B.

So, that's in favor of mixed meals. Now, the problem is, fat is often
co-ingested with protein. The effect of carbohydrate+protein has been studied by
Westphal et al. (4), but Westphal's findings contradict earlier findings (5,6).

So, I realize it's not clear, but the effect of mixed meals on blood glucose
nevertheless shouldn't be underestimated, since it is thought that high blood
glucose can cause insulin resistance or exacerbate an underlying insulin
resistance state (7-14).


Best wishes,

Jean-Louis Tu
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REFERENCES

1. Collier et al., The effect of co-ingestion of fat on the glucose, insulin
and gastric inhibitory polypeptide responses to carbohydrate and protein,
Am J Clin Nutr 37:941

2. Collier et al., Effect of co-ingestion of fat on the metabolic responses
to slowly and rapidly absorbed carbohydrates, Diabetologia 26:50-54

3. Collier et al., The acute effect of fat on insulin secretion, J Clin
Endocrin. Metabolism 66:323 (1988)

4. Westphal et al., Metabolic response to glucose ingested with
various amounts of protein, Am J Clin Nutr 1990 (62):267-272

5. Spiller et al., Effect of protein dose on serum glucose
and insulin response to sugars, Am J Clin Nutr 1987 (46):474-80

6. Rabinowitz D, et al., Patterns of hormonal release after glucose, protein,
and glucose plus protein, Lancet. 1966 Aug 27; 2(7461): 454-456

7. Yki-Jarvinen H. Acute and chronic effects of hyperglycemia on glucose
metabolism, Diabetologia 1990(33):579-585

8. Yki-Jarvinen H. Glucose toxicity, Endocrine Rev. 1992(13):415-431

9. Anderson CM et al., Relative expression of insulin receptor isoforms does not
differ in lean, obese and NIDDM subjects, J Clin Endocrinol Metab
1993(80):1037-1044

10. Rossetti L et al., Effect of chronic hyperglycemia on in vivo insulin
secretion in partially pancreatomized rats, J Clin Invest 1987(80):1037-1044

11. Rossetti L et al., Correlation of hyperglycemia with phlorizin normalizes
tissue sensitivity to insulin in diabetic rats, J Clin Invest 1987(79):1510-1515

12. Garvey WT et al., The effects of insulin treatment on insulin secretion and
action is type II diabetes mellitus, Diabetes 1985(34):222-234

13. Henry RR et al., Diabetes 1986(35):990

14. Kolterman OG et al., The acute and chronic effects of sulfonylurea therapy
in type II diabetics, Diabetes 1984(33):346