Artificial sweeteners

Please share your experiences, successes, and failures in using non-drug therapies for RLS/WED (methods of relief that don't involve swallowing or injecting anything), including compression, heat, light, stretches, acupuncture, etc. Also under this heading, medical interventions that don't involve the administration of a medicine to the body (eg. varicose-vein operations, deep-brain stimulation). [This forum contains Topics started prior to 2009 that deal with Non-prescription Medicines, Supplements, & Diet.]
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Artificial sweeteners

Post by Robin-Whittle »

Does anyone find that their symptoms get worse after ingesting the
artificial sweetener Aspartame?

It is widely known that caffeine makes RLS worse, but I think there is
a theoretical reason why just the Aspartame - as found in Diet Coke,
Diet Pepsi, Equal, NutraSweet etc. - would contribute to the RLS

Aspartame is a widely used artificial sweetener - a billion dollar industry
according to some sources. It is composed of two amino acids -
Aspartic Acid and Phenylalanine - plus a small methyl group: ... tameh.html

Aspartame breaks down quickly and goes into the bloodstream as these
two amino acids. Normally, humans eat proteins which contain these
amino acids and many or all of the 18 others. There is no precedent in
Nature for a "food" which gives us just one or both these amino acids.

Amino acid levels in the blood fluctuate hour-by-hour according to what
has been recently ingested. There is are several transport systems which
take amino acids through the blood-brain barrier into the brain, and
presumably the spine and Cerebro-Spinal Fluid (CSF) as well.

The brain is carefully protected from most things in the blood, and there is
a specific transport system (which is still not properly understood) for a
subset of amino acids called the "Large Neutral Amino Acids" - LNAA. The
main amino acids of interest which use this LNAA Transporter are
Tryptophan, Tyrosine and Phenylalanine. This transporter system has a
limited capacity, and the amino acids compete with each other to be
carried into the brain (and presumably the spine and CSF). If all three are
present at the same concentration in the blood, they are all transported at
about the same rate. But if there is a lot more of one, then this will
diminish the quantities of the others which are carried into the brain.

It is well known that Tryptophan levels in the brain have a direct affect on
the ability of neurons to produce the neurotransmitter Serotonin, because
Tryptophan is converted into 5-HTP and then 5-HTP is converted to
Serotonin in the neurons which need Serotonin. (Consequently Selective
Serotonin Re-uptake Inhibitor drugs like Prozac are used to make the
most of the limited quantity of Serotonin in patients with depression, and
supplements of Tryptophan, or 5-HTP, can be used to help the neurons
produce more Serotonin.)

Most RLS drug treatments (which, I understand, all have various
problems) involve drugs which make the most use of available Dopamine.
So clearly RLS involves some problem in neurons which produce or sense
Dopamine as a neurotransmitter.

Neurons which produce Dopamine must take in Tyrosine from the fluid
between the cells. This is converted with an iron-dependent enzyme into
DOPA, which is then converted with another generally reliable enzyme
into Dopamine.

It seems to me that if RLS involves, to some extent, difficulties in
producing enough Dopamine, then a cause could be lower than ideal
levels of Tyrosine in the brain (and probably the spine and CSF).

We would expect that eating or drinking Aspartame (Diet Coke etc. etc.)
would lower Tyrosine levels in the brain, due to Aspartame being digested
into high levels of Phenylalanine which reduces the amount of Tyrosine
which is carried into the brain by the LNAA transporter.

So people with RLS and/or Depression have good theoretical reasons not
to drink or eat Aspartame!

The test of this theory would be to drink Aspartame sweetened
non-caffeinated drinks for a few days to see if this makes RLS worse.
Alternatively, if an RLS suffer usually drinks or eats Aspartame, then to cut
it out entirely, and see if this improves their condition.

Googling Aspartame leads to all sorts of critiques, not least:

I haven't considered all the other arguments against Aspartame, but it
seems clear that it would reduce Tyrosine levels in the brain, and so
presumably the spinal cord and CSF.

The material at:

on amino acid digestion and transport into the brain seems correct to me,
based on what I have been reading in various neuroscience books and
papers. However, as far as I know, the exact nature of the LNAA
transport mechanism has not been discovered.

- Robin

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WOW, Robin

Post by jumpyowl »

You sure sound like a neuroscientist yourself! Welcome aboard! :)

You have several good points, one is against "collective" guilt. Caffeine could still be involved of course, and one could take caffein citrate only to test the hypothesis.

I would love to know or learn more about the biochemistry of the brain function. What you are saying about the kinetics of amino acid transport across barriers is sure making sense.
Jumpy Owl


Re: artificial sweeteners

Post by Anonymous »

Interesting concept! Aspartame and other artificial sweeteners have been blamed for everything from causing multiple schlerosis to warts. OK, maybe not warts.

It seems to me that if RLS involves, to some extent, difficulties in
producing enough Dopamine, then a cause could be lower than ideal
levels of Tyrosine in the brain (and probably the spine and CSF).

This is a logical enough deduction, but there are a couple of problems with it.

1. First, you get a LOT of tyrosine from the foods you eat. There would not be a measureable reduction of tyrosine in the brain from ingestion of aspartame, unless you were a diet-cola drinking anorexic, then you'd have a whole 'nuther set of problems, anyway.

2. Neurons use tyrosine as a precursor, so why isn't that given as a Parkinson's / RLS treatment? The reason is because it would take absolutely mammoth doses to get any into the brain (hard to get those LNAAs in), and secondly, from a kinetic standpoint, it is a much longer process to convert tyrosine into l-dopa than to convert l-dopa into dopamine. That's why L-dopa and carbidopa work so well.

As an aside, you bring up serotonin reuptake inhibitors. They block reuptake into the pre- or post-synaptic cell so that the same serotonin molecule can bind to receptors again and again. You might well ask the same question of RLS treatment. That is, if RLS patients don't have enough dopamine in the synapse, why won't a dopamine uptake inhibitor work? The problem is that the dopamine system is very much involved in pleasure, and so far, all dopamine uptake inhibitors are addictive, and subject to abuse. Cocaine is a good example. Anyway, just thought you might be interested.

The bottom line, of course, is use whatever works for you! You suggested a very good experiment, to document RLS symptoms under a variety of caffeinated / sweetened conditions. Right now, I believe I'd pass on the caffeine! Eeeeek.

Good luck,


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Joined: Sat Mar 27, 2004 2:59 pm
Location: Yantis, TX


Post by jumpyowl »

Mighty interesting! Keep it up ladies (and gents). :D I truly enjoy these "insights."
Jumpy Owl

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Post by sugbrendas »

I'm not sure what all of the scientific things mean but as for me,I wasn't using ANY artifical sweeteners when mine began..I began using them afterward (not too long) when I was diagnosed with reactive hypoglycemia about the time I began gaining weight..Right now i'm not sure if the wt. gain came from lack of sleep or hypoglycemia.
Finally able to sleep on average 9 hours a night!

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Joined: Fri Jun 03, 2005 5:15 pm

Post by Kris »

I had a lot of problems with RLS when I used to drink a lot of diet Mt. Dew.

When I went on Atkins - before I went on atkins - I took a week to come off sodas first.

The first week was hard with the caffiene withdrawal, but I knew that should be quick. The RLS was very annoying. It never did get painful back then, just very annoying and kept me from sleeping.

Well, i had 3 weeks that were all heck. RLS bad, twitching, palpable, and then of all things, tremors - like a drunk going through DT's - terribly tremors that would start and I would shake something fierce.

well I got on line and figured out it was the nutrasweet withdrawal doing it. It got better after a whole month. I've not drank a soda since! It was sickening. I'm convinced Nutrasweet is addictive poison.

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Post by captgenefl »

I had a Doctor tell me the phosphoric acid in soda can make a lot of illnesses worse. Oh well I guess I can give up soda for a month just to see if it helps. Somehow I feel like if I live to be 80 years old I'll be on a rice and water and a hand full of pills ,diet. This getting old thing stinks.
When the doc's tell me I'm going die , the heck with health foods I'm going to guzzle a 12 pac of Budweiser!

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Post by notch »

What about Splenda?

Anyone have any information on the effects of this product related to RLS?

I think that the aspartame in the drinks I drink (Coke Zero, Diet Pepsi, Diet Mt Dew, etc) contribute to my RLS but I know that they now make Diet Coke WITHOUT aspartame and with Splenda instead (same as Diet Rite).

Again, any information on RLS & Splenda?
"War is cruelty. There's no use trying to reform it, the crueler it is the sooner it will be over." -- William Tecumseh Sherman

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Post by Sadiegirl »

I switched from diet coke back to regular coke (caffeine free) because I thought the artificial sweetner of diet coke was making my RLS worse. But I am now experimenting with regular coke. I think caffeine free regular coke is not any better for my RLS then diet coke. But, I am still experimenting.

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