cukier czy fruktoza? pyt. do Joggera

[Gość: tita]

Joggerze, pomóż proszę....
Mam problem ze słodzeniem herbaty. Zaczełam używać fruktozy, ale czy przy
odchudzaniu rzeczywiście jest lepsza od cukru? Nie cierpię chemicznego smaku
słodzików, zreszta przeczytałam w postach że aspartam nie jest taki genialny.
Nie moge się oduczyć słodzenia herbaty, czym mogę słodzić gdy chce schudnąć
kilka kilogramów i pozbyć sie części tłuszczyku na biodrach. Ćwiczę na
siłowni, widzę efekty wszędzie ale nie w rejonie bioder.

[jogger]

O fruktozie czytałem, że potrafi sprytnie omijać enzymy trawiące, i w wątrobie
jest bezpośrednio metabolizowana do postaci tłuszczu. To już chyba zwykły
cukier jest lepszy. Ja przerzuciłem się już dawno na herbaty ziołowe, zieloną,
yer-vitę itp. wynalazki, które niesłodzone smakują lepiej. Natomiast na lokalny
tłuszczyk - tylko lokalne ćwiczenia przegrzewające, np. na biodra - na
zakończenie sesji na siłowni 30 min twistera non-stop.

[Gość: dan]

Mam nadzieje, ze ponizszy artykul rozwieje wiele mitow wokol frukntozy. Autor-
Lyle McDonald jest obecnie najbardziej cenionym przez kulturystow dietetykiem.

FRUCTOSE
by Lyle McDonald

As with so many other aspects of nutrition, especially bodybuilding and sports
nutrition, beliefs about the sugar fructose (more commonly known as fruit
sugar) vary widely. On the one hand, because of its low glycemic index (GI) and
general lack of insulin response, many people consider fructose an ideal sugar,
that should be used to replace other sugars especially for diabetics (1). There
is also some indication that fructose may blunt appetite and affect food choice
(2,3). Finally, because of the low insulin response, it's been suggested that
fructose before or during exercise might allow increased fat utilization during
exercise, while still maintaining blood glucose levels (4).

At the other end of the spectrum, because of differences in its metabolism
compared to other sugars, and the known effect of fructose on blood
triglyceride (fat) levels, many nutritional authorities (most notably John
Parillo) consider fructose and fruit a sort of nutritional satan that will only
make you fat and that should be eliminated from the diets of bodybuilders

What Is Fructose, How Much Do We Get and
Where Is It Found In the Diet?

Fructose is one of three monosaccharides (single sugar molecules, the other two
are glucose and galactose) that occurs naturally in foods. Sucrose (table
sugar, a disaccharide) is also 1/2 fructose. However, free fructose only occurs
naturally in a few foods, notably some fruits (hence its common name of 'fruit
sugar') and honey with the majority of our dietary fructose coming from the
ingestion of sucrose. Fructose is also found in small amounts in a few
vegetables.

In recent years, the amount of fructose being consumed has increased
significantly. One large scale analysis puts average daily amounts in the range
of 90-100 grams (8) which is a significant increase over the last 2 decades.
This increase has been caused not only by an overall increase in the
consumption of sugars, but also because of increased use of high fructose corn
syrup (HFS). HFS contains can contain 42% or 55% free fructose, with the
remainder being glucose. So, on top of an overall increase in fructose
consumption, the use of HFS has caused a significant increase in the
consumption of free fructose (8,9).

Additionally, many health-food stores also sell crystalline fructose powder as
a sweetener and both crystalline fructose and HFS are used in many commercially
produced food products (10).

Fructose Digestion and Metabolism

During digestion in the stomach and small intestines, all dietary carbohydrates
are eventually broken down to the monosaccharides glucose, fructose and
galactose (found in milk in lactose). These are absorbed via specific
transporters in the small intestine, bringing them into the portal vein, next
stop the liver.

While the small intestine seems to have an essentially unlimited (estimated
around 5000 grams per day) capacity to absorb glucose and galactose, the
absorption of fructose is a very different story. The consumption of as little
as 35-50 grams of free fructose at once causes gastric upset, gas, bloating and
diarrhea in a majority (60% or more) of people (11). However, the addition of
glucose to the free fructose prevents the problem. And the ingestion of large
amounts of sucrose (again, 1/2 fructose, 1/2 glucose) causes no such problem.
It thus appears that our guts have evolved to absorb fructose only in the
presence of other sugars and that large amounts of free fructose in the diet
are non-physiological for humans. Since HFS also contains a significant amount
of glucose, the malabsorption issue may not be a huge one for most processed
foods. However, anyone considering using crystalline fructose as a sweetener
should consider the potential problems with large amounts of free fructose. I
should also mention that some individuals suffer from a hereditary fructose
malabsorption syndrome (12), but this is typically identified at a very young
age. Fructose free diets can be developed for these individuals.

After digestion, fructose goes to the liver like all sugars, which is where the
bulk of its metabolism occurs. This is also where fructose metabolism differs
significantly from glucose metabolism, and is the source of much of the debate
over the relative 'goodness' of fructose.

Liver Metabolism of Sugars

Although they share many intermediate steps in their metabolism, dietary
glucose and fructose follow two distinct pathways in the liver. In fact, it has
been known for quite some time that most dietary glucose goes straight through
the liver with only minimal metabolism (13) while the majority of fructose is
metabolized in the liver (14).

This is part of the reason for the low glycemic index (GI) of fructose. Since
it is metabolized almost exclusively in the liver, it has only a very small
effect on blood glucose levels. Additionally, and also unlike glucose, the
uptake of fructose into liver cells doesn't require insulin. Hence there is no
need for the body to secrete insulin in response to dietary fructose ingestion.
This is the basis for the claims that fructose is a superior carbohydrate
source compared to glucose or sucrose (which recall is half glucose),
especially for diabetics (1) who have poor control over blood glucose and
insulin levels.

At the same time, because of its extensive metabolism, and the pathways that it
follows, in the liver, fructose can have negative effects on the overall
metabolism of the body. So first let's compare and contrast the metabolism of
glucose and fructose in the liver, and then look at some of the potential
negatives of fructose (especially excess fructose) intake.

But Just How Much Are We Talking About?

A cursory examination of the research into fructose feedings in terms of the
production of metabolites such as lactate, uric acid and especially VLDL
triglycerides has shown distinctly varying results. For example, while some
research has clearly shown an increase in VLDL triglyceride levels with
fructose feedings (18-23), other research has not (24-28). Why the discrepancy?

As with so many aspects of nutrition, it really comes down to two things: how
much fructose they gave, and what population they gave it to. Let's get the
population dynamic out of the way first. Studies have examined the effects of
fructose in essentially 4 different groups: individuals with normal insulin and
triglyceride levels, individuals with normal insulin but high triglyceride
levels, individuals with high insulin and normal triglyceride levels, and
people with high insulin and triglyceride levels. Different groups show a
different susceptibility to the negative effects of fructose (and that still
has to take amount into account).

Overall, the last group, those with high insulin and high triglyceride levels
tends to be the most sensitive to the negative effects of fructose in terms of
increasing VLDL triglyceride levels (3). The other three groups show a
distinctly less pronounced effect. This makes some sense as such individuals
would normally have skewed physiology to begin with. I should point out that
hyperinsulinemic/hypertriglyceridemic folks aren't very indicative of the
average lean athlete consuming a healthy bodybuilding/sports oriented diet.

But that brings us back to dose. Even in otherwise healthy individuals,
fructose has been found to increase VLDL triglyceride levels so the potential
for fat synthesis from fructose is apparently there. Again, looking at the
studies as a whole, both negative and positive results are typically found.
It's when you start looking at the

[Gość: dan]

It's when you start looking at the amounts given, that a pattern starts to
develop. First, a select group of studies has used absurd and non-physiological
amounts of fructose (200-500 grams per day, more than any human is probably
capable of consuming under all but the most forced conditions) and invariably
found increased triglyceride levels. Keep in mind that the average American
diet only contains about 30-40 grams of fructose per day so we can pretty
safely ignore those studies.

Looking at the other studies which gave more reasonable amounts of fructose, as
a recent review has done (29), we see a fairly standard pattern: at reasonable
amounts of fructose (30-60 grams per day depending on the study), there is no
negative effect on VLDL or triglyceride levels. At amounts higher than that (in
the range of 80-90+ grams per day), there tend to be an increase in VLDL and
triglyceride levels suggesting fat synthesis. This would tend to suggest a
distinct cutoff point somewhere between those two values as an approximate
maximum of fructose that can be consumed without causing significant
triglyceride synthesis.

In contrast, one study comparing 75 grams of fructose to 75 grams of glucose,
found that, over 4 hours of study, while there was a small amount of de novo
lipogenesis from the fructose, the net effect was that the body burned more fat
than it produced (30). The fructose group also showed a higher thermic effect
(meaning more calories were wasted as heat), most likely because of the high
amount of metabolic processing that went on. However, and perhaps more
importantly, despite very little fat synthesis in the fructose group, there was
less fat burning in that same group. This occurred with an increased burning of
carbohydrate in the fructose group.

So it may be that, while fructose at moderate ((50 g/day or so) amounts doesn't
increase fat synthesis per se significantly, it may slow fat loss by decreasing
fat burning in the liver. That is, to a degree, the end result may be the same:
whether the fructose is causing more fat synthesis, or less fat burning, the
net effect on fat loss (which is determined by fat burning - fat intake) may be
similar.

As I mentioned above, the metabolic fate of fructose appears to depend on the
metabolic state of the liver and the dieter. In the fasted state (as occurs
while dieting), fructose will be used for energy and fat synthesis will be
negligible, if it occurs at all. Fat burning may be decreased however. In the
fed state (as occurs when not dieting), excess fructose can be converted to
VLDL TG, increasing heart disease risk and bodyfat.

Fructose Feeding and Exercise Performance

Finishing up, I want to touch on the idea of fructose feeding during exercise.
To my knowledge, no studies have examined the consumption of different types of
carbohydrates prior to weight training, and all of the research done to date
has been in endurance athletes. From a theoretical standpoint (including the
low GI/insulin response), there are some good reasons to think that fructose
feedings might be superior to glucose during endurance exercise. However, the
research to date has not supported the theory. Fructose feeding before or
during has been found to be either no better, or in fact worse in terms of
performance of endurance exercise (3). As well, there is the issue of gastric
upset with high amounts of fructose that limits how much can be given in the
first place.

As a final comment, there is the issue of post-workout carbohydrate and
recovery. At this point, it should be no surprise to readers that the post-
workout consumption of carbs and protein improves recovery, performance and
protein synthesis (32,33). Studies examining different types of carbohydrate
intake post workout have invariably found that glucose and glucose polymers
refill muscle glycogen ideally, while fructose preferentially refills liver
glycogen. In that refilling liver glycogen can be important from the standpoint
of overall recovery and growth (the details are outside of the scope of this
article), consuming a small amount of fructose (10% of the total carbohydrate
content or roughly 10-20 grams) in the post-workout shake may be beneficial.
But the majority of carbohydrates consumed should come from glucose and glucose
polymers.

Summing Up and Practical Recommendations

Ok, an article like this wouldn't be worth much without some actual
recommendations and real world application. First and foremost, it should be
clear that in large enough amounts, fructose can certainly be detrimental both
to health, by raising VLDL cholesterol and triglycerides and possibly to
bodyfat levels for the same reason. However, at moderate intakes of fructose,
in the range of 50-60 grams per day, fructose appears to pose little problem
and certainly is not going to make or break a diet.

For an athlete to avoid all sources of fructose, especially fruit, seems a bit
silly and extreme (see below regarding pre-contest bodybuilding prep for a
possible exception). However, there is probably a good reason to avoid high
fructose corn syrup as much as is reasonably possible. Readers should realize
that many sports food companies are using fructose and HFS in their products,
so it's possible that athletes are being exposed to larger than normal amounts
of fructose in their diets. Athletes and bodybuilders are encouraged to become
avid label readers to see if HFS is listed as a primary ingredient.

Individuals who are hyperinsulinemic or have high triglycerides to begin with
may question whether using fructose in large amounts is beneficial and should
consult with their doctor before making major nutritional changes. The majority
of athletes, bodybuilders and otherwise healthy individuals are unlikely to
have problems with either hyperinsulinemia or hypertriglyceridemia although it
is a possibility.

So, back to the ~50 g/day value. Noting that the average American diet may
contain at least double that already, we might assume that athletes shouldn't
be adding more fructose or fruit to their diet. But, we really have to ask
whether or not that applies to bodybuilders and athletes, who typically avoid
the commercial foods which most commonly containing fructose (meaning those
containing high fructose corn syrup).

Most bodybuilders and other athletes already avoid the majority of such foods
and I would expect that their daily fructose intake is somewhat below the
American average. Once again, note that many commercial products aimed at
athletes, such as food bars and even some meal replacement powders, are
increasing their use of fructose and HFS as a sweetener so it is possible that
athletes are getting more fructose or HFS than they're aware of. How much is up
to debate and speculation.

So let's address the important question: What about fruit? Can it be part of a
healthy bodybuilding/athletic diet, or should it be avoided as Parillo claims?
To answer this we really need to look at the amount of fructose found in
typical fruits.

On average, fruits such as cherries, pears, bananas, grapes and apples contain
anywhere from 5 to 7 grams of fructose in an average sized piece of fruit.
Fruits such as strawberries, blueberries, oranges and grapefruit contain 2-3
grams of fructose per 100 gram serving. Honey is an exception, containing 40
grams of fructose per 100 gram serving, but its extreme sweetness would make
eating a lot of it difficult. The point being that fruit is actually not a very
large source of fructose in the first place. To get 50 grams of fructose per
day from fruit alone would require an intake of approximately 10 pieces per
day, far more than all but the most extreme intake would provide.


So, summing up, like most aspects of bodybu

[jogger]

Super wyciąg, nie znam za bardzo McDonalda, czytywałem tylko właśnie w/w
Parillo i Aceto. Czy nie znalazłbyś jeszcze opinii nt. kazeiny? Wg. mnie mleko
ze względu na b. dużą zawartość kazeiny jest dobre do tuczu zwierząt, a nie dla
ludzi. Dlatego dla 'uzależnionych' od mleka najlepsze byłoby humanizowane mleko
w proszku dla dzieci:
'
Proteiny z mleka mieszają się z kwasem żołądkowym podczas trawienia i tworzą
grudki z kazeiny i wapnia. Ponieważ mleko kobiece ma małą zawartość kazeiny,
tworzy miękkie i łatwostrawne grudki w żołądku. Duża zawartość kazeiny w krowim
mleku powoduje tworzenie się twardych i ciężkostrawnych grudek. Mleka w proszku
oparte na białku serwatkowym są lekkostrawne, gdyż imitują proporcje protein w
mleku kobiecym.
'
Stąd zresztą populaność białka z serwatki (whey protein).

[Gość: dan]

No tak ale dzieki gorszej przyswajalnosci kazeina ma wieksze dzialanie
antykataboliczne co jak sie okazuje ma w sumie istotniejsze znaczenie niz lepsze
wlasciowosci anaboliczne serwatki i w konsekwenji skutkuje wyzszym bilansem
azotowym.
Z tym ze dla kulturystow lepsza jest serwatka bo przyjmuja ja czesto i w duzych
ilosciach, co zapewnia rownie wysoki wskaźnik antykataboliczny, a dzieki lepszym
wlasciwosciom anabolicznym daje to jeszcze wyzszy bilans niz w przypadku kazeiny.

Wiecej szczegolow znajdziesz tutaj:
ajpendo.physiology.org/cgi/content/full/280/2/E340

[Gość: dan]

So, summing up, like most aspects of bodybuilding and athletic nutrition, there
are few absolutes. While there is no doubt that large amounts of fructose are
both non-physiological and potentially harmful, it certainly appears that low
to moderate amounts of fructose, and yes fruit, can be included in a
bodybuilding or athletic diet. From the standpoint of liver glycogen and
maintaining an anabolic state, small amounts of fructose probably should be
included in the diet. Considering the other nutrients (fiber, vitamins and
minerals) present in fruit, it seems silly to exclude them from the diet based
on the rather small amount of fructose present

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4a. Web article at: www.parrillo.com/sng/tsb_det...946114869&id=45

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