Article at a Glance
- Carbs are addictive because high carbohydrate meals spike insulin which allows tryptophan to enter the brain and make serotonin, the feel good neurotransmitter.
Pasta, mashed potatoes, pizza, oatmeal, crunchy sourdough bread with butter. Yum. Maybe not great for you all the time, but so tasty. Some would even say addictive. I can only speak for myself, but if I get rolling on a pizza, you’re looking at a runaway freight train that can easily put back a whole pie and then some. I feel great for about 45 minutes, then not so much.
What drives this process? Is there a scientific reason I (we) eat carbs with reckless abandon?
Why are carbs so addictive?
Of course, researchers don’t agree on this topic, and to be fair, there are probably a number of reasons why a person could have trouble stopping once they’ve gotten rolling on a plate of pasta, some of which are related to the state of the microbiome, some of which are related to emotion, but there is also a biochemical process at play.
And that is exactly what I want to talk about in this blog post.
Carbs make us happy, literally
People get addicted to carbs because eating carbs sets off a metabolic chain of events that literally makes us happy. Carbs light up our brain’s pleasure centers.
Carbohydrate rich meals spike insulin levels, which helps our brains make serotonin, the feel good neurotransmitter responsible for sleep, mood, and even sex drive.
I wrote a post recently titled: Boosting serotonin with food: what you need to know.
When I sat down to do the research, I expected to find that a diet high in animal protein is what gives us the greatest boost in serotonin because animal protein, and famously turkey, is very high in tryptophan, which is the amino acid precursor to serotonin.
Indeed, our bodies need tryptophan to make serotonin, it’s just that the level of tryptophan circulating in the blood does not dictate the amount of tryptophan that makes its way into our brains where we can use it to actually make serotonin. High protein meals raise our blood levels of tryptophan, but not serotonin, in fact, they lower serotonin.
How is this possible?
Because amino acids work in concert with their other amino acid friends. They’re not all guaranteed a place in the brain where they can do their thing.
Carbs help tryptophan reach the brain
Tyrosine, methionine, tryptophan and others, compete for uptake into the brain, and as it turns out, tryptophan is perpetually in last place.
On a level playing field, other amino acids, such as the amino acids we get from eating animal protein, will win out against tryptophan. But tryptophan has a trick up its sleeve. Where other amino acids are neutralized by spikes in insulin, serotonin binds to a substance called albumin when insulin levels spike, as they do when we eat delicious carbohydrates. Binding to albumin preserves tryptophan so it can journey into the brain and make serotonin, which makes us feel good.
Boom, we eat carbs, and our brains become better at making serotonin. In this way, eating crabs lights up the brain’s pleasure centers, and has the potential to be addictive for some people.
Consider this quote from Richard J. Wurtman’s paper titled the Effect of Nutrients on Neurotransmitter Release:
Thus, the ability of circulating tryptophan molecules to enter the brain is increased when plasma levels of the other LNAAs fall (as occurs after insulin is secreted) and is diminished when the plasma levels of the other LNAAs rise, even if plasma tryptophan levels remain unchanged. Since all dietary proteins are considerably richer in the other LNAAs than in tryptophan (only 1.0–1.5 percent of most proteins), consumption of a protein-rich meal decreases the plasma/tryptophan ratio (the ratio of the plasma tryptophan concentration to the summed concentrations of its major circulating competitors for brain uptake, principally, tyrosine; phenylalanine; the branched-chain amino acids leucine, isoleucine, and valine; and methionine). This, in turn, decreases tryptophan’s transport into the brain and slows its conversion to serotonin.
So, load up on the carbs?
Not necessarily. While never eating carbs isn’t healthy, eating a high glycemic diet isn’t a good idea either and, especially for some genotypes, can be associated with type 2 diabetes.
Excess insulin can and will cause inflammation in the body. (R)
As a general rule, staying away from refined carbohydrates is a good idea for most people, and lots of our readers will have issues with grains as well.
The main thing I wanted to draw attention to in this post is the happy place our carb favorites take us to, at least for a time.