I know there's alot of negative things being tossed around about diet drinks, most of which don't seem to be extremely conclusive. However, I've been researching aspartame biochemistry and it turns out aspartame breaks down into phenylalanine (and methanol), which competes with tryptophan, the precursor for serotonin, for the same channel through the blood-brain barrier into the central nervous system. Excessive consumption of aspartame (isolated phenylalanine in big doses, unnaturally) is now being shown to reduce serotonin levels leading to depression, anxiety and sleep disorders (serotonin -> melatonin).
Anyone notice similar problems with diet soda consumption or after quitting? I used to be a 2L/day guy on Diet Cokes and sugar free sodas. I've dropped it recently in medical school and I seem to see improvement but I'll need a few weeks to re-confirm. Share your thoughts!
Also, reduced serotonin leads to carb/sugar binging and cravings. Do you that's why people who drink diet cokes tend to eat unhealthy foods? Maybe it's not simply because they think they can cheat more with a zero calorie drink
Edit: For a long time, I knew that aspartame breaks down into phenylalanine, and since Phe is an amino acid I figured its all-natural. Not so fast after I did some more digging. Phe competes with tryptophan through the same channel into the brain. However, it turns out that tryptophan (precursor to serotonin) is mostly bound by albumin proteins in the blood whereas the other 19 amino acids are more free in plasma. During a meal, insulin is secreted and drives the rest of the amino acids into body/muscle cells leaving tryptophan alone in the blood, because it remains bound to albumin. This selectively increases tryptophan delivery into the brain with no competition from other amino acids (being bound to albumin has no effect on tryptophan delivery into brain, unlike to muscle cells). Hence this is why we all know carbs to selectively raise serotonin levels: as other AA's are cleared from blood into muscle cells, tryptophan can cross the blood brain barrier more readily.
The problem with diet soda is you not only get a giant bolus of phenylalanine into the blood, but diet soda triggers little insulin secretion (if any), allowing large amounts of isolated phenylalanine to stay in the plasma instead of going to muscle cells. It now can out compete tryptophan through their common channel into the brain, and causing low serotonin.
asked byDH (1074)
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on July 22, 2013
at 11:01 PM
This seems very unlikely.
A can of diet soda contains about 180mg of aspartame. Aspartame is a phenylalanine/aspartic acid dipeptide, so it will yield around 90mg of phenylalanine. According to cronometer, yesterday I ate 116g of protein from animal and dairy sources, and got a total of 5.2g of phenylalanine. Unless you have PKU, the amount naturally occurring in your diet is many times higher than what's in a soda.
Even if we assume that the phenylalanine from aspartame is released into your system more quickly than it is from real food, it's still a tiny amount. There's as much phenylalanine in one bite of hamburger as in an entire can of diet soda. (back-of-envelope calculation; I used 15g of 80% lean meat).
Finally, phenylalanine contributes to the production of dopamine and norepinephrine. For people with some types of depression, increases in those neurotransmitters are more helpful than an increase in serotonin.
on July 22, 2013
at 10:31 AM
Sounds like a nice vicious cycle which causes the victims of these products to be addicted to them, not in the same sense that caffeine is addictive, but in fooling them to keep buying the very thing that depleted their serotonin levels in the first place.
on December 21, 2013
at 04:18 PM
My experience is anecdotal, but powerful, at least for me.
I suffered from severe depression for twelve years (1997 - 2005). The last six years I was on antidepressants. In order, I tried prozac, zoloft, lexapro, and finally wellbutrin, always looking for option that had the least side effects (especially on libido).
I've always exercised frequently and began to notice that my knees would hurt terribly after 30 minutes on the stair stepper. I also developed bones spurs on both elbows. I thought it was probably age. Then I read an article that described how the phosphoric acid in diet drinks leaches calcium out of your bones. Since I was drinking 3 cans of diet coke per day, I thought I'd give it up to see if it made a difference. So, I gave up the diet cokes cold turkey. I had none of the supposed addiction withdrawals that some people claim.
A few months after I gave up the diet coke, I noticed that my depression was lifting. Six months post diet coke, I was off my meds completely, and I have not taken any meds for seven years, now. Also, my joint pain did go away and I exercise much more comfortably.
I am an evangelist against all soft drinks, especially the diet varieties. When I read the 2013 stories about diet soft drinks and depression, I was already there.
on July 23, 2013
at 02:32 PM
Would love to hear thoughts on aspartame and migraine. At the adivise of a doc in 1998, I quit all artificial sweeteners and have been migraine free ever since...except once after I had a mint with aspartame ONE TIME. I guess I am just on the low end of food/additive sensitive folks, tho.