Guest blog by Vicky Ware,
It’s pretty well known now that eating the wrong foods can lead to ill-health in the long term but what about ill-feelings in the short term? Could your food be affecting your mood?
Over the centuries people have made false conclusions from the evidence in front of them; we thought Bubonic plague was caused by bad smells and even further back in history that the heart was where we did our thinking.
It’s starting to seem like modern people may have underestimated the function of the gut and the advice ‘trust your gut’ may be more literal than figurative.
There are three main pathways by which what you eat affects how you feel. The first is via the nervous system. A large nerve called the ‘vagus’ nerve travels directly from the complex nervous system in the gut to the brain. Artificial stimulation of the vagus nerve has been shown to treat chronic treatment resistant depression1. There are 500 million neurons in the gut, 200 times fewer than in your brain but still a significant number. It’s like a mini-brain. The gut can also secrete neurotransmitters which affect brain function — the gut produces 50% of the neurotransmitter dopamine in the body along with 95% of the serotonin, which regulates sleep, mood, appetite and pain2.
Secondly, the immune system is constantly sensing what is in your gut and reacting with different kinds of hormones based on what it senses — these hormones can then affect how you feel and promote or dampen down inflammation.
Thirdly, the bacteria in the gut can influence your cravings, moods and behaviours, more on this below.
Bioactive compounds are found in some foods and are also produced by the digestive process that breaks down foods into smaller parts. They’re tiny and can act directly on the immune and nervous systems, affecting how we feel3. It’s also thought that certain polyphenols in plants can directly act on bacteria in the gut, promoting so-called ‘good’ bacteria and inhibiting ‘bad’ bacteria, which in turn can impact how you feel4.
These gut bacteria are also able to ‘digest’ some foods that we’re not capable of digesting, meaning they can create bioactive compounds from our food that then affect the nervous and immune systems4.
Tea, coffee and dark chocolate are thought to be good for our health due to the polyphenols they contain5;6;7. Some bioactive compounds may even improve symptoms of depression and protect mental health in general8;9.
The type of bacteria in the gut can influence how we feel, some are directly linked with feelings of depression and anxiety10.
The most interesting (or horrifying) example of just how strong the influence of microbes can be on behaviour comes in the form of infection with a parasite called Toxoplasma in mice. The parasite needs to go from a mouse to a cat to complete its life cycle, so it wants the mouse it infects to get eaten by a cat. It therefore makes the mouse it infects unafraid of cats, increasing their likelihood of being eaten and therefore allowing their parasitic passengers to live on11.
There are no such extreme examples of tiny parasites affecting human behaviour, although intriguingly Toxoplasma infection in humans — originally thought to be asymptomatic — has now been associated with increased jealousy, suspiciousness and likelihood men will break rules, while infected women are more warm hearted, conscientious and were less likely to break rules12.
Although studies on bacteria in the gut are far from conclusive to date — it’s a complicated network taking a while to unravel — research does suggest that people who take probiotics feel less stressed, anxious and are generally feel more positive about the world than people who don’t take probiotics13.
One study even found that women who take a probiotic in the form of a fermented milk product for four weeks had less activity in regions of the brain relating to emotion and sensation while viewing images designed to provoke emotion14.
Bacteria in the gut are also responsible for producing a number of vitamins essential to mental health such as B12, more on micronutrients below4.
There are strong links between chronic inflammation and disease. Inflammation is the healing process but when it goes on for too long or is over zealous it causes damage. A body that is inflamed for a long time is more likely to develop mental health conditions such as depression, anxiety and even autism and schizophrenia15.
Research shows that people who eat a Mediterranean diet, which is associated with low inflammation, are around 30% less likely to suffer from depression than people who eat a ‘Western’ diet16. Foods that cause inflammation such as sugar and processed foods are associated with worse moods and even worsening of depression17.
While some mental health conditions are thought to be caused by brain inflammation specifically, it’s worth remembering the link between the gut and brain and how parts of the gut may act as a mini-brain, pumping out neurotransmitters than communicate directly with the sentient portions of our main-brain. If your gut is inflamed, this may also lead to anxiety. It’s also thought that ‘leaky gut’, where the gut wall allows small particles of food through into the blood stream causing inflammation, could lead to ‘leaky brain’ where the blood-brain-barrier also breaks down, causing inflammation in the brain18.
What you eat provides the building blocks to create your body, which is continually rejuvenated and developing. Without enough of the right building materials, your body must scavenge what it can from the foods you do eat to patch together alternatives to allow you to continue functioning — but these alternatives don’t work as well, and can even affect how you feel.
Omega-3 fatty acids are lacking in the Western diet. Without them, your body can’t produce the hormones necessary to calm an inflammatory response19. Large studies have shown that supplementing the diet with omega-3 fatty acids, and eicosapentaenoic acid (EPA in particular, can reduce symptoms of depression20;21). It’s not known exactly why EPA has this effect but it’s thought to be related to the production of hormones that affect inflammation and possibly also affects blood flow to the brain22. Some omega-3 fats can be found in land plants, but EPA is only found in the sea — in oily fish like herring, mackerel and salmon and also in some edible seaweeds.
Vitamin D is well known for its effect on mood — the ‘sunshine’ vitamin tends to be low in people living in the Northern hemisphere, especially during the autumn and winter months. Vitamin D is anti-inflammatory, one reason your skin produces it is to combat the inflammatory effect of radiation in the UV rays from the sun. It can be found in oily fish and eggs23.
Magnesium is the body’s ‘chill out’ mineral, where calcium acts in opposite to excite neurons. Too little magnesium in the diet can lead to anxiety and feeling ‘tired but wired’ when trying to get to sleep.
Vitamin B12 and folic acid also mood-boosting effects24;25, while whole foods containing antioxidants are another way to ensure good brain health. Oxidative stress causes inflammation and can result from eating too few foods that contain antioxidants. Vitamin A, C and E are antioxidants, lack of these in the diet appear to be linked to anxiety, depression, autism and bipolar disorder26.
Selenium another mood-affecting nutrient is also an antioxidant. In one study the lower the levels of selenium in the diet the more likely they were to suffer from depression, anxiety and tiredness — and these feelings decreased after only 5 weeks of taking a selenium supplement (100 mcg/day)27.
Larger nutrients also affect how you feel. Research that involved putting either fatty-acids or a saline solution directly into the gut led to a difference in the emotions of people viewing images designed to make them feel sad — those who’d been given fats felt less sad 28.This might explain why you reach for the chocolate rather than carrot sticks when you’re feeling glum.
How you feel can also affect what foods you choose to eat. People eat more calories the day after a bad night of sleep, probably due to changes in the hormones regulating appetite and stress causes sugar cravings as your body looks for a quick source of energy to deal with the fight or flight it thinks you’re about to do29;30. Too much sugar means your body needs to use more magnesium meaning you’re more likely to be deficient — leading to poor sleep. A vicious cycle.
What can you eat to ensure your food isn’t negatively affecting your mood?
What can you do to trial whether food is affecting your mood? Try changing your diet. Even a short period of time eating differently could make a big difference. Without a trial run of avoiding processed, sugary foods it’s difficult to believe the difference eating more healthfully could have on how you feel.
Before taking any kind of supplement, always try eating a healthy, balanced diet and then talk to your GP or health practitioner for their advice too.
Have you noticed a difference in how you feel when you’re eating more healthily? Let us know in the comments below!
Vicky has a degree in Biological Sciences with a focus on biochemistry and immunology and is currently studying for a MSc in Drug Discovery and Protein Biotechnology. She is also an endurance athlete.References
1. Corcoran (2006) Vagus nerve stimulation in chronic treatment-resistant depression
2. O’Mahoney (2015) Serotonin, tryptophan metabolism and the brain-gut-microbiome axis
8. Bahramsoltani (2015) Phytochemical constituents as future antidepressants: a comprehensive review.
9. Kumar (2012) Neuroprotective potential of phytochemicals
10. Foster (2013) Gut-brain axis: how the microbiome influences anxiety and depression
11. Barford (2013) Parasite makes mice lose fear of cats permanently
12. Flegr (2007) Effects of Toxoplasma on Human Behaviour
14. Tillisch (2013) Consumption of fermented milk product with probiotic modulates brain activity
15. Salim (2012) Inflammation in anxiety.
16. Skarupski (2013) Mediterranean diet and depressive symptoms among older adults over time
17. Jacka (2014) Dietary patterns and depressive symptoms over time
19. Calder (2010) Omega-3 Fatty Acids and Inflammatory Processes
20. Martins (2009) EPA but not DHA appears to be responsible for the efficacy of omega-3 long chain polyunsaturated fatty acid supplementation in depression: evidence from a meta-analysis of randomised controlled trials
22. Stahl (2008) The role of omega-3 fatty acids in mood disorders
23. Penckofer (2010) Vitamin D and Depression: Where is all the sunshine?
24. Coppen (2005) Treatment of depression: time to consider folic acid and vitamin B12
25. Young Lim (2016) Nutritional factors affecting mental health
27. Benton (1991) The impact of selenium supplementation on mood.
30. Yau (2014) Stress and eating behaviours
31. Mishra (2008) The effect of curcumin (turmeric) on Alzheimer’s disease: An overview
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