Serotonin in the Gut
But what you probably don’t know is that about 80% to 90% of the human body’s total serotonin is found in specialized cells in our guts, not in our brains. In fact, serotonin was tied to food long before it became an important mood hormone. In many species, its directly tied to appetite – deplete serotonin, and they act like they are starving. They hunt for food, put off mating and egg laying, and generally do whatever they can to find another bite to eat.
In many species, including us, serotonin is key in the functioning of gut muscles, causing contraction of our intestines. As it turns out, our digestive system has its own neural network and largely controls itself without any input from our brains whatsoever. In fact, if you were to cut the main nerve that connects the two, the gut would continue to function independently. In part, that is where serotonin comes in. It is the key in the control our digestive muscles during digestion. Serotonin acts on gut nerves, which signals pain, nausea and other gut problems.
Stomach, up close
For example, if you eat something that upsets some of your stomach cells, they release copious amounts of serotonin. This flood of neurotransmitter causes the gut to empty, leading to diarrhoea. But if the serotonin overflows the gut’s management system, it leaks into the blood, where it stimulates 5HT3 receptors in the brain which induces vomiting. So depending on how bad the insult to your stomach, serotonin levels control how your body reacts. Because of this, some of those anti-depressants, particularly the SSRIs, frequently trigger nausea and vomiting as a side effect.
Our gut uses so much more serotonin than our brains its amazing. In fact, so much serotonin enters our stomachs every day that if it were injected into the body in general it would be lethal. Luckily for us, there are certain gut cells which contain a lot of serotonin transporters which keep the serotonin in our stomachs and out of the rest of our bodies. (Watch the following video if you REALLY want to know the science behind serotonin in the gut):
LINK:
http://www.dailymotion.com/video/x22xdz_exploring-serotonin-in-the-gi-tract_news?start=13
There’s even rising evidence that serotonin is important in our hunger signalling, particularly in feelings of fullness. Injecting low serotonin doses into the body has caused rats to
eat less even though they’re hungry, an effect enhanced by those same MAOIs that increase serotonin levels. Overall, more and more research suggests that
serotonin is somehow modulating food intake – but we’re not sure exactly how… yet.
Serotonin and Nutrition
Since it has so many diverse and important roles in the body, serotonin levels are key to health mentally and physically. Because its so common in all kinds of animals, serotonin can be found in a variety of foods. The highest concentrations are found in:
· walnuts
· plantains
· pineapples
· bananas
· kiwis
· plums
· tomatoes
These foods can boost serotonin levels in the gut, ensuring rapid communication between gut cells. But because serotonin in its complete form cannot pass through the blood-brain barrier, we have to do more than include serotonin-rich foods in our diets: we have to include its building blocks.
In fact, our bodies naturally understand this, and cause us to crave foods rich in tryptophan, an amino acid key to serotonin production in our brains when serotonin levels are low. What foods are high in tryptophan, you might ask? Carbohydrates. All of a sudden those calorie-rich, carbohydrate-packed comfort foods make a whole lot of sense. It’s logical, then, that
sad people tend to eat more junk food even when a more nutritious option is available. When we’re depressed or upset, we want higher levels of serotonin to feel better, and packing in as much tryptophan as possible is our body’s way of trying to cope. Studies have shown that
ingesting carbohydrates boosts serotonin synthesis and levels. Particularly tryptophan-rich foods include:
· turkey
· bananas
· milk
· yogurt
· eggs
· meat
· nuts
· beans
· fish
· a variety of cheeses including Swiss and Cheddar
The irony is that not only does mood affect how we eat, but how we eat affects our mood. It’s a two way street. Research has shown that dieters tend to become depressed about two weeks into a diet, about the time their serotonin levels have dropped due to decreased carbohydrate intake. Cutting calories has been shown to
reduce tryptophan levels in rats, leading to less serotonin , and even
decreases the number of receptors in their brains, so they’re less responsive to the serotonin they have.
Watch out ladies...
Of course, just because that’s how the world seems to work, women have to be even more careful than men when it comes to dieting and serotonin. In women,
calorie reduction has a dramatic impact on serotonin and tryptophan levels – an effect not nearly as strong in men. This strange double standard
is suggested to be a part of why women are so much more prone to eating disorders. The obvious recourse when it comes to dieting, logically, is that by cutting calories we make ourselves more depressed, which in turn makes our bodies want more carbohydrates and calories to boost our moods. It’s yet another reason our weight tends to yo-yo when we try to diet, especially when carbs are cut, and
helping keep serotonin levels in check might just be the solution. For example, cheat. Giving yourself a carb-rich treat every so often can help you maintain higher serotonin levels and keep you in a better mood where you can curb your cravings to eat calorie-craving comfort foods during the rest of the week.
But its not just tryptophan that’s important. It turns out that vitamin levels in our diets can have a dramatic impact on serotonin systems. One of the most important vitamins key to serotonin function is thiamine, one of the components of Vitamin B Complex. Simply altering the levels of thiamine in our diets and ensuring enough intake can have amazing effects. One study, for example, found that
supplemental vitamins for a year significantly boosted women’s moods and overall well-being, particularly due to levels of thiamine.
Another Vitamin-B compound, folic acid, is also strongly linked with serotonin levels. Boosting folate levels in older people, who are generally deficient compared to younger adults,
has been found to improve their mood and cognitive function. Even in healthy adults
higher levels of serum foliate have been linked to fewer mood swings and negative moods. And even more impressively, high folate levels can improve other depression treatments,
particularly with how well anti-depressants work. Exactly how folate relates to serotonin is unclear, though it appears to act through an intermediate compound called
S-adenosylmethionine (SAM). SAM increases serotonin levels, but it requires folic acid. Folic acid deficiency leads to low levels of SAM, and subsequently reduced serotonin.
Serotonin and Behaviour
One way in which we can help our bodies have healthy serotonin levels is by good behaviour. Things we do, behaviourally, have a major impact on serotonin levels. For example,
stressing, feeding, and exercise have been shown to have marked affects on serotonin levels in rats. It turns out that sleep and exercise are particularly strongly tied to serotonin. After all, one of serotonin’s major actions in our bodies is as a sedative, so its not shocking that it has close ties with how we regulate our energy.
Exercise to increase serotonin (credit, Frederic de Villamil, flickr)
It’s well established that
exercise can boost our moods and make us feel better. One way in which this occurs is by increasing serotonin. Exercise is a cheap and dirty way to
boost blood and brain serotonin levels immediately, making it a good alternative to other ways of dealing with stress and depression. But exercise does even more: it helps regenerate neurons. Unlike we’re told when we’re young, our brain cells can and do regenerate, albeit slowly. Increased levels of exercise have been shown to
increase neuron production, giving out brains better ability to utilize the serotonin boosts and improve our moods. Exercise also
allows our brains cells to function better by making them more flexible, leading to better responses to all neurotransmitters, including serotonin.
Sleep, however, is even more important when it comes to serotonin. People have been studying the connection between serotonin and sleeping behaviors for over 50 years. We know that changes in serotonin levels have marked impact on sleeping, with
decreases in serotonin leading to apnea or other sleep problems. But only recently have we realized the opposite is true, too. Lack of sleeping
negatively affects our brains neuronal signalling, including how it responds to serotonin.
Sleep deprivation has been shown to desensitize serotonin pathways, meaning that consistent lack of sleep has a negative impact on our brain’s response to serotonin in general. This means that consistent healthy sleeping patterns are key to maintaining healthy serotonin signaling in our brains and likely our bodies in general.
Go Outside and Be Happy! Light triggers serotonin...
Another, simple way to increase serotonin production is to get outside. Scientists discovered the connection between light and serotonin almost accidentally. They looked at levels of serotonin in recently-dead people, and found
higher concentrations of serotonin in those who died in the summer instead of the winter. That got doctors thinking. It was already known that many people have seasonal changes in mood, with more depression occurring during the cold, dark winter than the warm, sunny summer. It had even been found that
increasing light levels helped treat non-seasonal depression. Could light be having an impact on serotonin levels? Research suggests yes. They’ve since found that
serotonin levels in healthy men are directly correlated to the amount of sunlight in the day, with marked increases as the seasons changed and the sun’s intensity rose, and other research has found
strong connections between light and serotonin function. Taken together, these suggest that a walk in the sun or getting away on vacation to somewhere tropical and sunny during the darker months might be able to naturally boost serotonin levels.
There are other behavioral ways to change serotonin levels, too.
Rising evidence suggests that our own emotions and moods affect serotonin levels. In other words, trying to boost our moods or rosy our outlooks can help raise serotonin levels. Things you can try:
· Meditation
· Relaxation Techniques
· Talking to Friends
· Counseling
All these mood-boosting behaviors might just help raise overall serotonin levels, allowing us to keep out of those bad moods later on.
In The End…
Of course, like anything else, it’s balance that counts. Over-eating of carbohydrates and sugars can lead to decreased sensitivity to serotonin, leading to negative mood and physical side effects like obesity. Eating lots of protein can help balance serotonin levels. As it turns out, eating protein before carbs curbs the usual spike in serotonin. And, the truth is, we want to cut down our serotonin sometimes. It is a mild sedative, and eating serotonin-boosting foods in the middle of the day can make us drowsy and less focused. A protein-rich snack instead will help increase energy and keep you going when you need it most.
Even worse, eating too many serotonin-boosting foods, while it might feel good for a short time, can lead to a worse crash later on. That’s why a candy bar or a soda are so much worse for us – the sugary energy-upping effect is only temporary, and we’re left with sleep-inducing increases in serotonin instead, leading to a much harder crash. Proper nutritional balance is required for sustained energy throughout the day and a balanced mood. And if you do want a snack with a pick-me-up in terms of mood, try something with less sugar or caffeine but plenty of tryptophan, like nuts – plus
nuts are packed with other brain-boosting goodies, too.
In general, though, people don’t get enough of the healthy serotonin boosters in our diets – leading to a lot of grumpiness and overall blah-feelings. We are outside less than we should be, sleeping odd or too few hours, exercising less, and generally eating poorer. All of these are causing our bodies serotonin levels to get out of whack. Understanding the impacts of our actions and what we eat on this important system can help us improve our moods and gut health dramatically without resorting to anti-depressants or other drugs and their side effects, allowing a natural way for us to feel great more often.
You may want to check out the first part of the series if you enjoyed this amazing article: Leptin, The Fullness Hormone
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