Tuesday, October 22, 2013

Fructose in fruits may be good for you, especially if you are low in glycogen

Too much nutritional fructose has been revealed to cause an unhealthy elevation in serum triglycerides. This and other relevant variables are hypothesized to have a causative result on the onset of the metabolic syndrome. Considering that fructose is found in fruits (see desk underneath, from Wikipedia simply click to enlarge), there has been some problem that taking in fruit could cause the metabolic syndrome.

Veggies also have fructose. Sweet onions, for example, have more free of charge fructose than peaches, on a gram-modified basis. Sweet potatoes have more sucrose than grapes (but significantly less general sugar), and sucrose is a disaccharide derived from glucose and fructose. Sucrose is damaged down to fructose and glucose in the human digestive tract.

Dr. Robert Lustig has provided a presentation indicting fructose as the main lead to of the metabolic syndrome, weight problems, and related conditions. Yet, even he pointed out that the fructose in fruits is quite harmless. This is backed up by empirical analysis.

The issue is above-use of fructose in sodas, juices, desk sugar, and other industrial food items with additional sugar. Table sugar is a concentrated type of sucrose. In these foodstuff the fructose content is unnaturally high and it comes in an simply digestible form, with no any fiber or health-promoting micronutrients (vitamins and minerals).

Dr. Lustig’s presentation is available from this put up by Alan Aragon. At the time of this producing, there were in excess of 450 feedback in response to Aragon’s submit. If you read through the feedback you will recognize that they are considerably argumentative, as if Lustig and Aragon ended up in deep disagreement with one particular other. The actuality is that they agree on a variety of problems, like that the fructose located in fruits is usually healthful.

Fruits are amid the really few all-natural plant foodstuff that have been evolved to be eaten by animals, to facilitate the dispersion of the plants’ seeds. Normally and metaphorically speaking, vegetation do not “want” animals to try to eat their leaves, seeds, or roots. But they “want” animals to consume their fruits. They do not “want” one particular solitary animal to take in all of their fruits, which would compromise seed dispersion and is possibly why fruits are not as addictive as doughnuts.

From an evolutionary standpoint, the idea that fruits can be harmful is relatively counterintuitive. Presented that fruits are manufactured to be eaten, and that useless animals do not try to eat, it is affordable to count on that fruits must be good for some thing in animals, at the very least in a single crucial well being-associated process. If yes, what is it?

Well, it turns out that fructose, blended with glucose, is a far better gasoline for glycogen replenishment than glucose by itself in the liver and possibly in muscle, at the very least in accordance to a review by Parniak and Kalant (1988). A draw back of this review is that it was conduced with isolated rat liver tissue this is a draw back in phrases of the findings’ generalization to people, but served the scientists unveil some exciting results. The total reference and a link to the total-text edition are at the stop of this post.

The Parniak and Kalant (1988) research also suggests that glycogen synthesis dependent on fructose will take precedence over triglyceride formation. Glycogen synthesis occurs when glycogen reserves are depleted. The liver of an adult human shops about one hundred g of glycogen, and muscle tissue retailer about 500 g. An intense 30-minute excess weight coaching session may use up about sixty three g of glycogen, not a lot but sufficient to trigger some of the responses linked with glycogen depletion, this sort of as an acute boost in adrenaline and development hormone secretion.

Liver glycogen is replenished in a couple of hours. Muscle glycogen takes days. Glycogen synthesis is discussed at some duration in this exceptional e-book by Jack H. Wilmore, David L. Costill, and W. Larry Kenney. That discussion normally assumes no blood sugar metabolic rate impairment (e.g., diabetes), as does this post.

If one’s liver glycogen tank is shut to empty, consuming a pair of apples will have little to no result on body fat formation. This will be so even however two apples have close to thirty g of carbohydrates, more than 20 g of which becoming from sugars. The liver will grab every thing for itself, to replenish its a hundred g glycogen tank.

In the Parniak and Kalant (1988) research, when glucose and fructose ended up administered simultaneously, glycogen synthesis primarily based on glucose was enhanced by more than two hundred per cent. Glycogen synthesis based on fructose was enhanced by about fifty percent. In fruits, fructose and glucose occur together. Again, this was an in vitro research, with liver cells attained right after glycogen depletion (the rats were fasting).

What leads to glycogen depletion in individuals? Exercising does, equally cardio and anaerobic. So does intermittent fasting.

What takes place when we eat abnormal fructose from sodas, juices, and table sugar? The additional fructose, not used for glycogen replenishment, is transformed into excess fat by the liver. That fat is packaged in the type of triglycerides, which are then speedily secreted by the liver as tiny VLDL particles. The VLDL particles supply their material to muscle and body body fat tissue, contributing to physique body fat accumulation. Soon after delivering their cargo, modest VLDL particles eventually turn out to be tiny-dense LDL particles the types that can perhaps lead to atherosclerosis.


Parniak, M.A. and Kalant, N. (1988). Improvement of glycogen concentrations in major cultures of rat hepatocytes uncovered to glucose and fructose. Biochemical Journal, 251(3), 795–802.
Title: Fructose in fruits may be good for you, especially if you are low in glycogen
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