|"Fructose handles"? "Glucose handles"? "Saturated fat handles"? No, just the net result of a trashy diet.|
Enough of the rants, let's get to the facts!
I guess that's enough for the "ranty" introduction. Let's now have a look at what a group of researchers from the School of Medicine in Portland has in stock for us: It's a paper titled "Change in postprandial substrate oxidation after a highfructose meal is related to body mass index in healthy men" that's about to be published in one of the future installments of Nutrition Research. As you will by now probably have figured out, the Anne C. Smeraglio and her colleagues had two things in mind, when they came up with the protocol that involved
- What did the subjects eat? Participants were fed an egg omelet, bagel with cream cheese, and sweetened beverage breakfast consisting of one-third of their estimated daily caloric. The meal consisted of 30% fat, 15% protein, and 55% CHO (as % of energy). The CHO energy was further divided into complex and simple CHOs; 25% of the total calories were from complex CHOs and 30% of the calories were from either glucose or fructose added to the beverage.12 healthy men without diabetes, with a mean age of 25 (23-31) years and a BMI less than 30 kg/m²,
- 2 visits at their labs that were separated by at least 1 week, but less than 1 month,
- two meals that were high in glucose or fructose which were served in random order as a breakfast after an overnight fast, and
- fasting for 7h after the ingestion of the standardized breakfast (sitting around watching TV or performing other, non-exciting quiet activities without the propensity to produce a catecholamine response)
|Figure 1: Insulin and glucose levels, as well as non protein respiratory quotient (high = carb oxidation; low = fat oxidation) 0-7h after the fructose and glucose breakfasts (Smeraglio. 2013)|
"There must be a mistake here!? Fructose is bad for you!"
The scientists have really done their homework as they did even take into account whether or not the amount of protein in the meals would have been responsible for differences in the respiratory quotient. The latter was not the case, the "baseline RQs between the fructose and glucose study visits were equivalent (0.82 ± 0.08 and 0.81 ± 0.10, respectively) and the p-value, indicating that there was a difference even rose from 0.72 to 0.75, when "when protein use was accounted for by evaluating NPRQ [non-protein respiratory quotient]" (Smeraglio. 2013)Surprised? Well, I guess over all the lustig (=German for "funny") and unwarranted hoopla about how bad even small amounts of fructose are, you must have forgotten why scientists believed not too long ago that fructose could be the solution to, not the cause of the diabesity epidemic. After all, the paradigm of the mid to late 20th century was: Fructose does not spike glucose, so it should be the ideal sweetener for diabetics, because it is not necessary that your pancreas produces insulin to get rid of it.
I will not have to tell you, though that this assumption and the corresponding notion that totally replacing glucose with fructose would be a great idea is about as unwarranted, as the current fear of the "toxicity" of the small amounts fructose contained you'll be exposed to from a couple of pieces of fruit. I mean, let's take a peek at the data again.
Compared to the same amount of glucose, the consumption of the fructose equivalent of 5-6 medium sized (185g) apples (50-70g fructose, which is the amount of fructose the subjects in the study consumed) produces lower insulin levels and does not change either the leptin, triglyceride or glucose concentration in the blood or the ratio of glucose to fatty acid oxidation in healthy non-obese volunteers...
...apropos, non-obese, there was another thing to the headline wasn't there?
You are absolutely right, the research question involved (a) finding out what happens if you ingest a realistic breakfast where the carbohydrate content comes from (i) glucose or (ii) fructose and (b) determining whether the reaction would depend on the body weight / height² (BMI) ratio of the participants. So what about that, then? Let's see...
As the scientists rightly point out, this suggests that the postprandial fat oxidation after the fructose meal was less than the fat oxidation after the glucose meal only among subjects with a higher BMI, and that the correlation with body weight, but not the difference itself was statistical significant.
"Although the absolute values for fat and CHO oxidation were not different between the fructose and glucose study visits, we did find a correlation between BMI and change in fat oxidation as a result of consuming the high-fructose meal compared with the high-glucose meal. The difference in fat oxidation (fat oxidation after the fructose meal minus fat oxidation after the glucose meal) was negatively correlated with BMI at the 4- and 7-hour time-points (Fig. 3; r =−0.59 [P= .04] andr=−0.59 [P= .04] for 4- and 7-hour time points, respectively) but not the 1-hour time point (Fig. 3; r=−0.52, P< .09). Nonprotein RQ displayed these same trends but did not reach significance." (Smeraglio. 2013)
Did you know that there is a catalytic dose of ~40g of fructose per day (=6 normal size bananas) that will improve your glucose metabolism? (learn more)
And that's not just because it's simply too small, but also because the ratio of glucose to fatty acid oxidation, i.e. the respiratory quotient (RQ) is not determining whether you store or lose body fat - if it were, you'd better be training in the "fat burning zone" for the rest of your (in that case) miserable lives.
|Figure 3: Adding 7.5g of fructose ( to a 75g glucose load will improve not detoriate the glucose metabolism and that without increasing the amount of insulin that's released in response to the glucose load (Moore. 2000)|
On a related note, you are aware that small amounts of fructose, like the 7.5g of fructose scientists added to the 75 g of glucose their 11 healthy subjects ingested during an oral glucose tolerance test had an up to 31% lower glucose response (these were the values for the 6 subjects with the highest level on the regular test) in the absence of concomitant increases in insulin response (see figure 3; Moore. 2000)!? You did not know that? Well, I guess it was about time to take a mental note, then ;-)
- Moore MC, Cherrington AD, Mann SL, Davis SN. Acute fructose administration decreases the glycemic response to an oral glucose tolerance test in normal adults. J Clin Endocrinol Metab. 2000 Dec;85(12):4515-9.
- Smeraglio AC, et al. Change in postprandial substrate oxidation after a high-fructose meal is related to body mass index in healthy men. Nutr Res.2013 [epub ahead of print]