I have been doing some research into foods that boost mood recently, and in particular foods affecting certain medical conditions such as ADHD. It is a fascinating field of research which has been prompted in part by the recurrent articles about how a mental health crisis is ensuing as a direct result of the Covid-19 pandemic.
However, my curiosity was also piqued by the fact that the winter months are also known to negatively impact mood. Seasonal Affective Disorder (SAD), just one type of depression, reportedly affects over 10 million people in the USA alone. This does not take into account other forms of depression or the fact that medical health professionals have experienced a surge in demand for help over the past year. Lockdowns and working from home haven’t helped.
(I have examined the theme of happiness before, from another perspective which you can read here).
Non-food contributors to low mood
Asides from the following:
- lack of physical exercise, which is hard if you cannot leave your home for extended periods (exercise releases endorphins as well as increasing dopamine levels);
- lack of sunshine, associated with dropping Vitamin D levels, which in turn are directly linked to reduced serotonin activity;
- lack of sunlight in general (think of places like Alaska or Denmark during the autumn and winter months with reduced daylight hours), which contribute to feeling blue due to decreased dopamine levels;
- lack of (restful) sleep, brought on by increased anxiety and stress due to external circumstances (the constant uncertainty we live in) disrupts the release of hormones in you body altering their balance;
- eating while under stress, distracted or even while watching distressing news or images (yes, studies do show there is a huge impact on digestive functions);
- and lack of social interactions, which studies have clearly linked to a higher incidence of depression;
physiological and chemical imbalances can also play their part in regulating your mood.
The important role of food therapy
Assuming you are already doing everything else, I am a great believer in “every little bit helps”, and in “prevention is the best cure”. As TCM says
He that takes medicine and neglects to diet himself wastes the skill of the physician.
Proverbs and sayings aside, diet is important for health for one simple reason I will never get tired of repeating: the largest part of your immune system resides in your intestines. A healthy microbiota (intestinal flora) is the key to health. Neglect your diet at your own peril. This is as true for healthy body as it is for a healthy mind. Let’s explore this in more depth.
The four “happy hormones”
In previous blog posts you read how hormonal imbalances can lead to depression especially during the peri-menopausal and menopausal years for women. ( read more here ). These changes in hormones also affect men in later life. Although not as clearly defined as the female transitions, men go through their own version of menopause, called Andropause. But it isn’t only the reproductive hormones which are involved in mood and depression. In fact there are four hormones specifically implicated in regulating feelings of happiness or pleasure.
1. Serotonin
The queen of Happy Hormones. Serotonin acts as a mood stabiliser, promotes wellbeing and feelings of happiness. It is estimated that between 90 to 95% of serotonin is produced in the gut, when microbial cells in the colon stimulate the cells which make serotonin.
2. Dopamine
Also referred to as the “pleasure hormone”, dopamine is responsible for feelings of pleasure, motivation and reward. It is estimated that between 50% and 60% of dopamine is produced in the gut. The human digestive system makes dopamine from foods which contain the precursors needed, such as the precursor Levodopa which is abundant in fava beans and other legumes. Dopamine is also the hormone which is linked to addictions. Studies have shown that you do not need to eat the food for the dopamine to increase, just the anticipation of the food brings this about. In light of this, the expression “food porn” takes a new meaning (something to think about!).
3. Oxytocin
This hormone is responsible for feelings of bonding, love and trust, which is why it is commonly called the “cuddle hormone”. Need any more reasons to cuddle your partner or dog?
4. Endorphins
These are hormones involved in pain relief and relaxation. They have been dubbed the “runner’s hormone” because exercise releases endorphins, which results in post workout feelings of euphoria.
Serotonin and Dopamine as Neurotransmitters
Serotonin and Dopamine are not just hormones, they are also neurotransmitters. In layman’s terms, neurotransmitters are chemical messengers which connect your brain to the rest of your body, sending signals through neurons, or specialised cells, which transmit nerve impulses.
Whilst Happy Hormones act throughout the body and travel through the bloodstream to the various organs and tissues, Happy Neurotransmitters only occur in the brain and Central Nervous System (CNS) where they communicate via neurons.
Serotonin and Dopamine are part of a group of neurotransmitters which can directly affect mood. Research has clearly shown that there is a direct link between Serotonin, Dopamine and other dietary neurotransmitters and your mental health, in the broadest sense of the word. But before we look at these, let’s look at the connection between the brain and your digestive system.
The Brain-Gut connection and the BBB
Scientists are only just discovering the extent to which there is a direct link between the brain and the gut which has been called the Gut-Brain connection. This is not a new concept: Mens sana in corpore sano (loosely translated as ‘a Healthy Mind in a Healthy body’) said the Roman poet Juvenal as far back as the first century A.D.!!
If you are skeptical about this connection just think about what happens when you take medications. Research done in Harvard shows that medications used to treat depression and other mood disorders (and not only) directly affect the digestive system and its functions. Just think, how many times have you taken an aspirin or other pill only to experience problems with your digestion, constipation or diarrhoea?
Since dopamine and serotonin are made mainly in the digestive system, but affect the brain, it becomes apparent that the food you consume and the state of your gut flora will have a direct effect on your mood. How much these foods, be they of animal origin, plant origin or roots, influence your mood will depend on many factors. Environment, diet, exercise, intestinal flora, and the state of your relationships will all factor in, as well as the BBB.
The Blood Brain Barrier (BBB)
To start with, not all chemicals or molecules, including amino acids, can actually get past the structure that separates the brain from the bloodstream and its contents. This structure, called the Blood Brain Barrier (BBB), serves to protect the brain, in order to maintain homeostasis ie a healthy mind and body. This is a complex part of the human body which I will not attempt to go into. Suffice to say, some foods are better than others if you want them to go across this barrier and lift your mood.
You may be excused by thinking that only healthy substances are allowed through, unfortunately this isn’t the case. For example, alcohol, nicotine and caffeine all manage to get across, whilst penicillin struggles. The permeability of the BBB is even less effective at keeping enemies at bay when inflammation is involved. This is yet another reason why your diet should be as healthy as possible.
Instead of reaching for the chocolate, or the sweets or even the pasta next time you are feeling low there are some better alternatives….So, what foods should you be (not) eating?
Dietary Neurotransmitters and which foods to eat
The most important dietary neurotransmitters are as follows:
1. Acetylcholine (ACh) – Acetylcholine is the chief neurotransmitter of the parasympathetic nervous system. It is involved in contracting muscles, dilating blood vessels, and slowing heart rate. Studies have found high levels of ACh in depressed people. Contrastingly, low levels of ACh have been found in Alzheimers’ sufferers and it has been suggested an ACh-rich diet could help. Foods rich in ACh include:
- squash (Curcubita pepo L.)
- aubergines
- spinach
The seeds of peas, mung beans, the common bean (Phaseolus vulgaris), bitter orange, wild strawberry and radish, also contain ACh.
2. Glutamate (Glutamic Acid)- a non essential amino acid, it is the most important excitatory NT in the brain and is involved in memory and learning. Dietary glutamic acid is transformed into glutamate in the body. Low levels of glutamate have been linked to depression.
Good dietary sources of glutamic acid include:
- fish sauces
- tomato sauce products
- mushrooms
- spinach
- miso
- caviar
- seaweed
- Parmigiano Reggiano cheese
A diet free of glutamate is used to treat coeliac disease and some believe it could also benefit epilepsy and migraine sufferers.
3. Gamma Aminobutyric Acid (GABA) – an inhibitory NT of the nervous system. It has analgesic effects and helps reduce anxiety as well as to lower blood pressure. It is found in many plants and foods including:
- raw spinach (the highest levels found in any food)
- potatoes
- sweet potatoes
- cruciferous vegetables (e.g. broccoli, kale)
- mushrooms (shiitake)
- chestnuts
- the sprouts of adzuki beans, soybeans, the common bean and the common pea
As well as oat, wheat, barley (Hordoeum vulgare L.), rice (black, brown, red and white), buckwheat and tomatoes.
In drinks, the highest level of GABA has been detected in white tea. It can also be found in valerian, wild celery and St John’s Wort.
If you suffer from insomnia and anxiety you may benefit from a GABA-rich diet.
4. Biogenic Amines Dopamine (DA) or Dopamine– has an essential role in coordinating body movements, in attention, as well as in motivation and reward. Low levels of DA are considered to be responsible for many of the symptoms of ADHD.
The top two foods that help to naturally increase dopamine levels are:
- banana
- avocado
Lower levels of dopamine can be obtained from eating:
- oranges
- forest apples
- tomatoes
- aubergines
- spinach
- peas
- the common bean
The amino acid Tryosine, made from Phenylalanine and found in proteins, is used by the body to make dopamine. Sources of this amino acid are:
- turkey
- beef
- eggs
- diary
- soy
- legumes
Parkinson’s disease sufferers as well as people affected by ADHD could benefit from a Dopamine-rich diet.
5. Serotonin (5-HT)- This NT has a dual role. In the Central Nervous System it modulates behaviours, eating and sleeping. In the gut, it is involved in regulating gastrointestinal motility. Feeling constipated? Add more serotonin-rich foods to your diet! But beware, too much Serotonin can lead to the other extreme, and diarrhoea. In fact, an imbalance of serotonin levels have been linked to IBS (which might help explain the pendulum effect of the symptoms).
Major dietary sources of Serotonin are fruits, vegetables and seeds. The top ranked include:
- bananas, especially before ripening,
- bell peppers
- Chinese cabbage
- coffee
- hazelnuts
- kiwis
- paprika
Other foods which can help increase serotonin levels are:
- papaya
- plantain
- passion fruit
- pineapple
- plums
- velvet beans
- spinach
- tomatoes
- wild rice
- nettle
- green onions
- lettuce
- potatoes
You can also find lower dosages in pomegranate, strawberry and chicory.
6. Histamine (His)- which can be found in nearly all the regions of the brain, is involved in mediating arousal, attention and reactivity. High levels of histamine in food can lead to histamine poisoning, and are associated with a higher risk of depression. This is why, although it is needed in the food processing industry to get the characteristic flavours and textures of many processed foods (aged cheeses, red, white and dessert wines, Champagne and Sherry – which all contain significant amounts of histamine), they try to keep the levels as low as possible to prevent histamine poisoning.
Histamine can be found in processed foods such as:
- fish
- ham
- other cured dry meat products
- sauerkraut
- in cheeses such as Cheddar, Gruyere and Gouda
Other sources include:
- dairy (aged cheeses, yoghurt, sweet and sour cream, UHT milk, pasteurised milk, fresh milk)
- fish (tuna, mackerel, bonito, sardines, anchovies, herrings)
- soybean products eg fermented soy, tempeh, soy sauce, soya bean milk, tofu and natto
- dandelion
If you suffer from migraine and cluster headaches you may want to try a histamine-free diet for a while.
It is worth noting that availability of dietary Neurotransmitters depends on many factors: ripening time, preservation methods, cooking methods and microbial activity. So eating a ripe banana as opposed to a green banana will not have the same effect on your mood.
The take home message
The importance of having a healthy intestinal flora cannot be emphasised enough. You can eat all the right foods but if your digestive system is not healthy, it will do little to improve your depression. A healthy digestive tract depends on a healthy diet, as well as your level of stress, among other things. Besides, even if you are the healthiest person alive, how positive and happy can you be when you have an upset stomach?
Since 90-95% of Serotonin is produced in the gut, as is 50-60% of Dopamine, you may want to start paying attention to the foods (and drinks!) that you put into your system to promote not just health but at the same time improve your mood!
An ounce of prevention is worth a pound of cure.
Stay safe, eat healthy, stay positive!
Further reading
Dietary Neurotransmitters:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5986471/
SAD: https://www.nimh.nih.gov/health/publications/seasonal-affective-disorder/index.shtml
Histamine poisoning:
Histamine poisoning (scombroid fish poisoning): an allergy-like intoxication - PubMed (nih.gov)
