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The Science of Happiness Part 2: The Gut-Brain Axis

"Research demonstrates again and again that there is an actual connection between our brain health and our gut health."

Today’s live with Dr. Nancy Lin, PhD, is part 2 in her “science of happiness” series. This time she shares new research on how the health of our digestive system impacts brain function and plays a key role in determining happiness. Learn how the body absorbs and utilizes hormones from the gut — specifically serotonin, which is so vital to happiness. Check out this fascinating episode for tips critical to our health and happiness!

Video Highlights

  • 01:40: Recap of Part 1
  • 03:32: More Happiness Trivia
  • 11:03: A Helpful Happiness Hack
  • 12:39: What is Happiness?
  • 15:27: The Gut-Brain Connection
  • 17:29: The Enteric Nervous System
  • 20:13: Improving Gut Health for Stable Serotonin Levels
  • 34:05: More Happiness Hacks
  • 39:51: Wrap-Up

Inpart 1, we talked about what serotonin is, how it’s absorbed by your brain, and how it affects a range of emotions, including your happiness and sense of wellbeing.  We also talked quite a bit about tryptophan, the one essential amino acid that we need in order for our bodies to create serotonin, and Dr. Nancy demonstrated a few delicious, easy recipes that are loaded with tryptophan, vitamin B6,vitamin D, and omega-3 fatty acids — all essential for your body’s production of serotonin.

Today, we will dive deeper into the science of happiness, this time exploring the role of thebrain-gut connection — also called the brain-gut axis. Dr. Nancy will also go over some of her most effective methods of keeping your serotonin levels high by keeping yourdigestive system in tip-top shape. 

More Happiness Trivia

  • Bright colors go hand-in-hand with happiness! A recent medical study found that most happy people say their favorite color is yellow. On the other hand, the color gray is most closely associated with depression, sadness, and anxiety.
  • This one may be surprising, but people who get paid by the hour actually report being more happy than people who earn a salary. The reason? Researchers believe this is because people who are paid by the hour are better able to focus on the value of their time, which gives the sense of more control,less stress, and results in overall feeling more happy.
  • Similarly, people who experience more positive emotions, those associated with happiness; including joy, excitement, enthusiasm, and contentment, are less likely to experience pain than people who are depressed or who consider themselves sad.
  • You probably know this, but happiness is contagious — just being around positive, happy people releases serotonin that makes you happy too. Remember, we talked in part one about how serotonin improves mood and an improved mood increases serotonin — so hang out with happy people and notice how your own  mood improves!
  • Here’s another interesting fact: people who make phone calls, facetime, or video chats report being more happy than those who communicate by text or messaging alone. Researchers found that those who communicated via phone or webcam were more likely to feel emotionally supported by their significant other. Those who used text messages and instant messaging felt less of a connection.
  • A study of over 12,000 people found a strong correlation between eating fresh fruits and vegetables and increased levels of happiness! We know a healthy diet is important for good health, but turns out it’s also important for happiness too!
  • The same is true ofexercise. We need to exercise for our health, but research confirms that exercising for just 10 minutes in enough to lower stress, improve mood, and give you an overall sense of wellbeing!
  • Studies looking at the highest levels of emotional and physical wellbeing have found that where you live has a huge impact on your happiness. The happiest state in the US is Hawaii, followed by Utah, Minnesota, North Dakota, and California.
  • On the other side of the spectrum, West Virginia scores at the bottom of the happiness ranking. Hopefully all our West Virginia readers are exceptions to this, but if not, no worries! We are going to talk about improving your digestive health as a way to improve your serotonin and happiness in this article.

A Helpful Happiness Hack

Before we dive in, there’s one more interesting happiness fact — it’s actually a happiness hack you can do anytime and anywhere. Next time you are feeling down or are having negative thoughts, try writing them down on a piece of paper, crumple them up and physically throw them away. Research proves that doing that reduces negative feelings and actually improves happiness! And when you throw your negative thoughts out; take the opportunity to blow off some steam by really throwing them out! Really give it everything you’ve got.

What is Happiness?

Before we go into the science of creating more happiness, let’s take a minute to define what happiness is. Have you ever tried to define happiness? Most of us probably don’t need a formal definition of happiness; we know it when we feel it. We often use the term “happy” to describe a range of positive emotions, including joy, pride, contentment, and gratitude.  But what is happiness?

Happiness is difficult to define, mainly because it means something a little different to each of us. To measure happiness, researchers often use the term interchangeably with “subjective well-being,” which they measure by simply asking people to report how satisfied they feel with their own lives and how much positive and negative emotions they’re experiencing. So that’s one way to sum it up — “subjective, positive feeling of wellbeing”, being content, feeling joy, and an overall sense that your life is generally good and has meaning.

The Gut-Brain Connection

So, by now, you’ve got to be wondering, can thehealth of your gut and rest of your digestive system really impact your sense of wellbeing, and feelings of contentment and joy? 

The short answer is yes, absolutely.  This is where the gut-brain connection we mentioned earlier comes into play. There’s a reason the gut is often referred to as the body’s “second brain”. 

Research demonstrates again and again that there is an actual connection between our brain health and our gut health, which we call the gut-brain connection or the gut-brain axis (GBA). It consists of two-way communication between the central and theenteric nervous system, linking emotional and cognitive centers of the brain with peripheral intestinal functions.

That’s a really fancy way of saying the neurons, hormones, and neurotransmitters in your gut, including serotonin, are linked to your central nervous system and brain — creating a direct, two-way communication path between the two.

Think about it for a minute: have you ever had “butterflies” in your stomach, a “gut feeling” or a big knot in your stomach when nervous or stressed? That’s the gut-health axis at work.

The Enteric Nervous System

We mentioned the Enteric Nervous System above. The ENS is made up of two thin layers with more than 100 million nerve cells in them — more than the spinal cord. These cells line the gastrointestinal tract, controlling blood flow and secretions to help the GI tract digest food.  

Now our ENS, or Second Brain, doesn’t play a direct role in cognitive function or conscious decision-making, but it does have a significant impact on our emotions, including happiness. In fact, more and more scientists are discovering that our everyday emotions, including our perceived happiness — or depression, or anxiety — are being heavily influenced by the nerves in our gut. In fact, over 90% of the nerves in our vagus — the cranial nerve that connects our brain to our gut — carry information and neurotransmitters, including serotonin, from our guts to our brains (not from our brains to our guts). So, you can see the gut really is our second brain, or at least our emotional brain! 

The enteric nervous system has over 30 different neurotransmitters — the same amount as our actual brains — and 95% of your body's serotonin is found in your intestines and in your bowels. Scientists now know, without a doubt, that our gut controls most of our emotions, including how happy we feel.  

Research has found that any change in the balance between beneficial and disease-causing bacteria in your gut can alter production of serotonin, change your brain chemistry, and lead it to become either happy or moredepressed andanxious

Improving Gut Health for Stable Serotonin Levels

While we are still just starting to really understand this gut-brain connection, we do know that there are several steps that you can take to make sure you have a strong, healthy second brain, and to make sure that you are keeping serotonin levels at normal, stable levels. Let’s take a look at some of these:

Avoid Processed Foods

We know that processed foods contribute to all sorts of chronic health issues, including obesity,diabetes, andchronic inflammation; an unhealthy diet also really takes a toll on your gut health and your body’s ability to create and absorb serotonin. Unfortunately, over 60% of the average person's diet consists of processed foods — chips, cookies, white bread, refined sugars, fast foods, soda, and even foods that seem healthier. These foods really disrupt the overall health of our gut.

A diet based in whole foods and rich in fresh organic fruits and vegetables,lean proteins,healthy fats, and complex carbohydrates (which are known to be rich in tryptophan), is essential to ensuring a healthy brain-gut axis. Specifically, that means lower fructose fruits, like berries, citrus fruits, and pineapple; dark leafy greens and broccoli, lean proteins like turkey or salmon, healthy fats,vitamins andminerals found in almonds, walnuts, all different types of seeds, and of course, avocado!

Make it easy on yourself and just followDr. Nancy’s anti-inflammatory eating plan, a complete guide to eating a healthy, whole-food diet with a focus on reducing chronic inflammation in the body. Remember Dr. Nancy’s motto:

Less Inflammation In + More Inflammation Out = A Healthier You 

That means a healthier gut, and a healthier emotional state too, where more tryptophan is converted to serotonin and more serotonin is being absorbed into the blood and making its way to the brain. 

In addition to eating anti-inflammatory foods as a way to improve your gut-brain health, supplement your diet with a powerful, high-quality curcumin likeSmarter Curcumin. Curcumin, is the concentrated active ingredient inside turmeric. It only makes up about 2 - 3% of turmeric root, but when formulated properly it can have an amazing effect on your body. In fact, it’s a more potent ingredient to promote normal inflammation responses than mere turmeric itself.

But wait, there’s more… curcumin is really amazing stuff. It’s rare that a dietary ingredient can have such a broad spectrum of beneficial effects in the body. In nutritional science it’s called beingpleotropic, meaning it produces multiple health effects on biological systems throughout the body: including serotonin production and improving the gut-brain axis. Curcumin is one of the most highly pleotropic compounds on earth. Even pharmaceutical drugs can’t claim anything close to the many things it does.

Eat More Prebiotic And Probiotic Foods

There are a few more dietary steps you can take in order to improve your gut health and to improve your body’s ability to produce, absorb, and utilize serotonin, including incorporating more prebiotic andprobiotic foods.  

Probiotics are good bacteria that primarily line your gut and are responsible for nutrient absorption, supporting theimmune system. They even have a role in supporting your emotional wellbeing. 

Remember, probiotics in your gut are living organisms. Like any living organism, they need to be taken care of in order to function properly, and that means you need to feed them a healthy diet! Probiotics feed on complex carbohydrates andhigh-fiber foods commonly called prebiotics. This process encourages beneficial bacteria to multiply in the gut; they also ensure the bacteria are more resilient during changing environmental conditions, including changes in pH and temperature.

So what are the best sources of prebiotic foods?  

  • Asparagus
  • Bananas
  • Garlic
  • Onions
  • Whole grains
  • Apples
  • Leafy greens

Oh, andraw is always better — when possible feed your probiotics raw foods, not cooked.

Back to probiotics: it would be difficult to eat too many probiotic foods. These healthy bacteria are essential to balancing the good bacteria and bad bacteria in your gut, and have such a vital role in building a strong immune system, reducing inflammation, and supporting your emotional health, including the production of serotonin. That’s why we recommend that you get probiotics from whole food sources, like organic unpasteurized kimchi, sauerkraut, or pickled vegetables and kombucha. You should also take a natural, potent and high quality probiotic supplement, likeSmarter Nutrition’s Gut Health. It’s a soil-based formula containing three top clinically proven probiotic strains. Remember, you need to be consistent with a probiotic to see the affects on your body. 

Eat Healthy Fats, Nuts And Seeds

Eating healthy fats,nuts, and seeds is important not just for fighting the effects of inflammation, but also because they are great sources of omega-3 fatty acids and are rich in tryptophan or serotonin. Healthy fats, like olive oil or avocados, are essential for the health of your brain and contain powerfulantioxidants and help to improvememory and cognitive function. They also help improve mood. In order for the body to convert tryptophan into serotonin, it needs what are called cofactors. That means they require some assistance in order to be converted from tryptophan into serotonin — omega-3 fatty acids, vitamin B6, and Vitamin D found in healthy fats, avocados, walnuts, cashews, Brazil nuts, almonds, and pumpkin, chia, sesame, and hemp seeds (which are also rich in tryptophan) are perfect foods to provide the materials and supporting cofactors required to produce serotonin.

Head Into The Light 

We mentioned thevitamin D earlier — it’s an important cofactor required for serotonin production. Research has shown us again and again that our bodies’ serotonin levels are higher in summer and lower in the winter fall seasons — both of which are fast approaching! Spending time in the sun increases serotonin levels and improves happiness; 10 to 15 minutes of sunlight a day is all you need.  

Interestingly, you can also get your bright light fix from “fake sun”. If you live in a rainy climate, have a hard time getting outside, or have a high risk for skin cancer, research shows you can still increase serotonin with bright light exposure from a light therapy box. They are not too expensive and are really nice to have to make sure you are getting a healthy dose of vitamin D every day.


We discussed in part one how importantexercise is for triggering the release of tryptophan, the precursor of serotonin, into your blood. No need to belabor the point, but it is important to note that according to research, thetype of exercise you do matters when releasing tryptophan. While all types of exercise will help release tryptophan,aerobic exercise appears to be the best for this. So make sure you are exercising and really getting your heart rate pumping by swimming, dancing, jogging,brisk walks, bicycling — any type of aerobic or cardiovascular exercise!

Emotional Diversity

Let’s shift gears a bit and point out that improving serotonin levels isn’t just about happiness; it’s really about balancing our emotions. Happiness is great, but happiness alone just isn’t enough. We need a balanced “emodiversity” or a balanced feeling of various emotions. That includes happiness, trust, joy, and excitement, but those emotions should also be rounded out with others like fear, surprise, and even sadness. In fact, new research shows that people with high levels of emodiversity have higher levels of physical and mental health. The same study showed that the more value people place on happiness, the lonelier they felt. So, like everything else we talk about here, being happy is about being emotionally balanced. Making sure your body is producing plenty of serotonin is a great place to start. It can be tempting to apologize for how we feel, by saying things like “I’m sorry, I just feel a little down today.” Don’t apologize! We all have a whole spectrum of feelings, and that comes with being human. Give yourself a little compassion.

More Happiness Hacks

During this series, we have talked about several ways to improve our bodies’ production and absorption of serotonin. We talked about the importance of tryptophan and what foods to eat to improve serotonin levels, we looked at serotonin in both the brain and the gut, and we talked about steps you can take to have more available serotonin and more emotional stability. Before we wrap up, let’s look at a few more happiness hacks — little things that you can do when you need a quick emotional pick-me-up.

  1. Pet a dog! A recent study found that just petting a dog increases your levels of oxytocin, a hormone similar to serotonin, which makes you feel joy.
  2. Eat a clementine orange. Another recent study found that just the smell of clementine made participants feel really happy and mentally alert. Next time you are feeling down, reach for a clementine! You can also try diffusing some orange essential oil in the room.
  3. Color! Coloring is not only a great way to get back to our inner child, but research confirms that it’s a very effective way to relieve stress and increase your levels of happiness — plus it’s just fun! There are a million different adult coloring books, so grab your crayons and give it a shot.
  4. Say “Thank You” on a regular basis. Studies show that people who write down the things they are thankful for, or who express gratitude out loud on a regular basis, were 25% happier and more optimistic than those who did not. So what are you waiting for? Start counting your blessings and get happy.
  5. Laugh, Laugh, Laugh. It turns out that laughter really is one of the best medicines and people who use humor as a way to deal with tough situations are often more positive and report being happier overall.
  6. Do Yoga. It’s great for both physical andmental health! It’s also great for your emotional health, and studies actually show that it’s more effective at improving mood, lowering anxiety, and increasing happiness, than many other exercises. So give yoga a try; it’s just a great form of exercise for body and mind.


Remember, we all deserve to be happy and content in life — but that doesn’t mean that we are just going to wake up and feel happy. Science has demonstrated over and over that we need to take specific physical steps to ensure healthy emotions. This includes eating anti-inflammatory foods, taking probiotics, exercising, making sure we are not deficient in essential vitamins and minerals, and making sure we are taking time to destress — all essential steps that support our production of serotonin, and help us stay happy and healthy.

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