Tuesday, June 9, 2015

Reduced Fat Gain, Improved Glucose & Lipid Metabolism on Obesogenic Diet Make D-Xylose a Good Sugar-Replacement

If you are looking for sugar-replace-ments, D-Xylose may be the "new kid on the sugar-block" you may be interested in. It has a lower energy content than sugar, acts as a sugar blocker and has prebiotic effects.
"Xylose (cf. Greek ξύλον, xylon, "wood") is a sugar first isolated from wood, and named for it. Xylose is classified as a monosaccharide of the aldopentose type, which means that it contains five carbon atoms and includes a formyl functional group. It is derived from hemicellulose, one of the main constituents of biomass and is abundant in corn cobs, coconuts, seed hulls, and straw (Horton. 1995). Like most sugars, it can adopt several structures depending on conditions. With its free carbonyl group, it is a reducing sugar". That's what Wikipedia knows about a monsaccharide that has less than 70% the sweetness of regular sugar and Xylose contains the equivalent of 2.4 calories of energy per gram.

Now, in isolation, this probably doesn't sound very exciting. In conjunction with the results of a recent study from the Ewha Womans University however, the facts may look exciting enough for you to ask: "Where can I get this stuff?"
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Previous studies have already shown that D-Xylose,can reduce postprandial glucose levels. Its effect on lipid metabolism, however, has not been investigated, before.

Table 1: Composition of the exp. diets (Lim. 2015)
In their latest study, Eunjin Lima, Ji Ye Lima, Jae-Ho Shinb, and colleagues tested, whether D-xylose, when as an alternative sweetener, would suppress increases in body fat mass and yield improvements in lipid by regulating blood lipid profiles, blood glucose levels, and related gene expression in high-fat diet (HFD)-induced obese mice.

To test their hypothesis that replcing a decent amount of sugar / CHOs in an obesogenic high fat + high energy rodent diet (5% or 10% of the total sucrose content were replaced with D-xylose | Xylo 5 and Xylo 10 diets, respectively) would ameliorate if not block the weight gain and its ill metabolic consequences, the scientists conducted a 12 week study, during which they assessed weight gain, food intake, and serum lipid levels, as well as pathological changes of the liver sections and changes in gene expression related to adipogenesis and lipid metabolism in all four study groups, i.e. normal diet, high fat diet (HFD), HFD + 5% Xylose (Xylo 5) and HFD + 10% Xylose (Xylo 10).
D-piscose may be another interesting sugar-replacement, one that's derived from fructose, by the way | learn why it may still be good,
How does Xylose work? Well first of all, the energy content of D-Xylose is lower than that of regular sugar, but since this was compensated for by higher food intakes in the study at hand, it appears clear that it is rather the xylose-induced inhibition of of sucrase and thus its interference with the metabolism of sucrose into glucose and fructose that does the anti-diabetes / anti-obesity trick. Since it is also only partly absorbed by passive diffusion in the human duodenum and jejunum (60-70%) and the remainder is transported to the ileum and colon where it undergoes bacterial fermentation in the latter or is excreted, this effect may be promoted by SCFA formation as you'd see it with resistant starches.
Body weight gain, fasting blood glucose levels, weights of subcutaneous and visceral adipose tissues were significantly, but not earth-shatteringly lowered (see Figure 1) in the Xylo 5 and Xylo 10 groups.
Figure 1: Ok, there are sign. effects on body fat and weight, BUT the only thing that was completely reversed was the gain in liver weight - a true "weight loss wonder" looks sign. different (data expr. rel. to control | Lim. 2015).
What's more interesting, maybe, is that similar changes were observed for many serum biochemical markers, including total cholesterol (TC) and low-density lipoprotein-cholesterol (LDL-C), LDL/high-density lipoprotein (HDL), and TC/HDL, as well.
Figure 2: in contrast to the effects on body weight / composition, the effects on glucose & lipid metabolism were quite impressive; Xylose is thus rather a health than a fat loss supplement (data expr. rel. to control | Lim. 2015).
In that, it's also noteworthy that these changes were not an an effect of the reduced energy content of xylose vs. sucrose diet (look at the last column in Figure 1, the energy intake was identical in all HFD groups), but may also have been mediated by the D-xylose induced down-regulation of adipogenesis-related genes, including SREBP-1C, FAS, aP2, and C/EBPα in visceral adipose tissues, as well as the significantly reduced fat accumulation of fat and decreased expression of FAS and PPARγ in the liver.
SV Classic: "Resistant Starch Powered Health Bagels - High RS Bagel Consumption Improves Glycemia in T2DM Risk Patients" | read more
So what? In view of the fact the provision of D-Xylose also enhanced the rodents lipid oxidation by increasing expression the activity of corresponding enzymes (CPT-1A, CYP4A10, and ACO), there's little doubt that the authors rightly say that their "finding suggests that D-xylose may help prevent or attenuate the progression of obesity-related metabolic disorders by alleviating adipogenesis and dyslipidemia, and improving lipid oxidation" (Lim. 2015).

What Lim et al. do now have to do, though, is to confirm that similar effects can be seen in human beings. And what's more: They would also have to show that Xylose can do more than to inhibit fat gain on an adipogenic diet.

I mean, even when you're bulking, your diet is far from the fat- and carbohydrate laden fattening HFD chow the mice in the study received. To be relevant for athletes, we'd need a study where let's say the sugar in a meal replacement would be replaced and we'd see sign. reductions in body fat in one group vs. the other... ah, and no, I don't know if it is as diarrhea-prone as xylitol, since it is also used to test malabsorption and doesn't require enzymatic breakdown, it appears relatively unlikely that "normal" doses would give you the runs | Comment on Facebook!
References:
  • Horton, Tracy J., et al. "Fat and carbohydrate overfeeding in humans: different effects on energy storage." The American journal of clinical nutrition 62.1 (1995): 19-29.
  • Lim, Eunjin, et al. "D-Xylose suppresses adipogenesis and regulates lipid metabolism genes in high-fat diet-induced obese mice." Nutrition Research (2015).