Updated: Nov 5, 2020
· Brains preferred energy source is glucose
· Water vs. Wine
· Beware over-dependence of a “Western diet”
· Pillars of a happy diet: Variety, wholefoods, B-vitamins, a happy microbiome, omega-3s
The Coronavirus outbreak has impacted everyone in some way. Fears for our health and that of our loved ones and financial worries are just some of the uncertainties the virus has brought with it. A U.K. survey recently revealed that the number of adults experiencing some form of depression, almost doubled from about 1 in 10 adults pre-Coronavirus, to 1 in 5 (1).
It is largely accepted that you can eat well to support your physical health e.g. most people know that calcium is good for bone health and vitamin C can support immune health. But can you eat well to support your mental health? The science is not fully there yet for treating or preventing poor mental health, but to support it, yes you can!
RESTATING THE BASICS
Maintaining blood glucose levels within the normal range means our bodies and brains have enough fuel for peak functioning. Eating regular meals that contain some carbohydrate (which breaks down into glucose) will help achieve this. Choose good quality carbohydrates e.g. wholegrains, potatoes/sweet potatoes, fruits and vegetables, legumes and some dairy too (2).
Our body is made up of >50% water. Dehydration can poorly affect mood and concentration (3). Aim for 2 litres a day but note that water from soups, juices, fruit and vegetables, is within this. The quickest indicator that you are well-hydrated? Pale pee!
Keep alcohol intake to a minimum. Do you ever experience that feeling of relaxation after a drink? Alcohol is ‘switching off’ the part of our brain related to inhibition. Some people find that they are able to ‘let go’ and not be so self-conscious. This is great for a Friday night at the end of a week (especially in these strange times!) but heavy or more regular drinking in the longer term, can negatively affect our mental health and increase feelings of depression and anxiety (4).
Now for the slightly heavier bit but bear with me...
Quality of a Diet
We do not consume single foods or nutrients in isolation so a lot of research is now focusing on dietary patterns. The field of Nutritional psychiatry studies the relationship between ‘overall diet quality’ and mental health.
What does a ‘higher’ quality diet look like?
A high consumption of fruits and vegetables, wholegrains (brown bread/pasta/rice), legumes, nuts and seeds i.e. predominantly plant-based foods, but with moderate amounts of fish, meat, dairy and alcohol. The Mediterranean diet is the classic example of a high quality diet but specifically includes unsaturated fats (olive oil) and a moderate consumption of fish, poultry and dairy. A ‘lower’ quality diet is a more Western diet (yep that includes the U.K.) i.e. a higher consumption of saturated fats (processed foods, meat and bakery products) and sugar.
What does the evidence say about diet quality and mental health?
Research largely focuses on depression. Numerous studies show that the Mediterranean diet (or equivalent e.g. a traditional-Japanese diet which is rich in fruits and vegetables + soybean products) is associated with a lower risk of depression and depressive symptoms i.e. compared to a Western diet. Results are the same from studies all over the globe including the U.K., USA, France, Spain, Greece and Iran (5). These are human observational studies so can only show that there is a relationship between a diet and a condition. Two recent well-designed Australian human randomised control trials (intervention studies), support these findings (6,7). This type of study can show that one thing causes another to occur i.e. those consuming a higher quality diet had a lower risk of depression.
Nutritional psychiatry is less than 10 years old so this research is still very new but there is convincing evidence that a higher quality diet can benefit our mental health. BUT there is not enough of it. More human intervention studies are needed before governments can publish dietary recommendations for mental health.
B-vitamins play a role in producing the chemicals required by our brain for cognition and mood regulation. The beauty of a higher quality diet is that it is rich in B-vitamins (found in wholegrains, green vegetables, beans, lentils, nuts and seeds). Note: B12 is only found in animal products (meat, fish, eggs, dairy) so if you are following a vegan diet you may need to supplement - check with a qualified health professional.
Our ‘second brain’…
There is an extensive network of nerves and hormones that connect our brain to both our intestines and our gut microbiome - the trillions of friendly bacteria living there. This is known as the ‘gut-brain axis’ or our ‘second brain’. The brain sends messages to our gut telling it how to behave e.g. a hunger or stress signal. Our microbiome may be sending messages back to the brain, telling it how to behave. A microbiome with higher levels of friendly bacteria has been linked to lower risk of cardiovascular disease, type 2 diabetes and inflammatory bowel disease.
A microbiome high in ‘friendly’ bacteria can be achieved by consuming a higher quality diet. How? Because this type of diet is high in fibre and what do our microbiome eat? Fibre!
More recently, the microbiome has been linked to mental health.
A number of studies have shown that people with depression have a different gut microbiome to people without depression - and yes, they found out by studying participants’ poo samples. People with depression have less ‘friendly’ gut bacteria (8)(9). These are observational studies so it is difficult to say whether depression altered participants’ microbiome or if their microbiome, caused their depression.
When animals receive probiotics (just another name for friendly gut bacteria) in intervention studies, there is an increase in GABA (a brain neurotransmitter) and serotonin (the happy hormone). These are both known to be reduced in people with depression. It is not clear yet whether probiotics – naturally occurring in the largest amounts in yoghurt and kefir - can help improve mental health in humans. Even though some human intervention studies (yep the type with the most scientific clout!) show the administration of probiotics reduces the risk of low mood when compared to a placebo, other studies find no difference. A recent review of 10 studies concluded that probiotics made no improvements to mood. BUT these studies all involved different doses of probiotics and different combinations of bacteria strains so it is difficult to make a meaningful conclusion (10). Studies looking at human mental health and probiotics / the microbiome, are still quite limited. Nevertheless, it is proving to be an exciting area of research so watch this space.
The inclusion of omega-3 fats in our diet is essential because our body cannot make them by itself. The causes of depression are complex and not fully understood yet, however, it has been linked to inflammation. Omega-3’s - EPA and DHA in particular - have anti-inflammatory properties.
U.K. dietary guidelines recommend we consume two portions of fish a week, one of which is oily – this is where you’ll obtain the omega-3's EPA and DHA that have been shown to provide the most health benefits to our brain and gut. Examples of oily fish are salmon, mackerel, kippers, sardines, herring and trout. You can get omega-3s from non-oily fish, just in much lower amounts. Certain plant products such as chia seeds and walnuts to name a few also contain them, see more details here.
What does the evidence say?
There is overwhelming evidence that diets high in fish are associated with a lower risk of depression, particularly in women. Supplementation of omega-3's (rather than fish) can reduce incidence of depression. These are all observational studies but there are now a number of human intervention studies that support this ‘antidepressant effect’ of omega-3’s.
One Australian intervention study gave the intervention group omega-3 fish oils for 6 months – along with food hampers based on a Mediterranean-style diet and cooking classes. The control group attended social groups so researchers could exclude the social-interaction of the cooking classes, as a cause of any change in mental health that might be observed (6). At the end, the group receiving the intervention had improved mental health when compared to the control group. The question is whether it was the omega-3's that caused better mental health, or if it was the Mediterranean-style diet as a whole i.e. a higher quality diet.
Four studies on participants with depression, found participants who received daily omega-3 supplements alongside their normal antidepressant medications, experienced reduced depressive symptoms. This was compared to participants with depression who were given a placebo plus their normal antidepressant (11). This has led to omega-3 supplementation being used to treat major depressive disorder, within a clinical setting (12). The inclusion of omega-3 fats in our diet, appears to have beneficial effects on our mental health.
The take home message
Include a diverse range of foods and try to stick to a higher quality diet as a whole. This can help support not just your physical health but your mental health too.
Eating is not just about the nutritional value but it is there for pleasure too and this is just as important!! If you crave a bar of Dairy Milk – EAT ONE – but take a moment to enjoy and savour it (more on Intuitive eating here).
If you are looking for some general wellbeing tips, try here however, if you are experiencing low mood or anxiety, consider making an appointment with your GP or call 111 to discuss the options available to you. The sooner you reach out, the sooner you can begin your journey to recovery.
A big thanks to Jo for writing the blog this week. Jo is a recent graduate of King's College London where she completed a BSc in Nutrition. Jo shares “I began a career in insurance, but after working for a number of years in the City, I realised nutrition and health were my passion. I went back to ‘school' to retrain, completing an Access course before finishing my degree. I’m currently doing some training in Intuitive Eating and some volunteering for Foodcycle. I am particularly interested in Public Health and eating behaviours".
You can find Jo on:
Facebook business page: Josephine Bew
1. Coronavirus and depression in adults, Great Britain: June 2020. [Internet]. 2020. Office for National Statistics. Vizard, T., Davis, J., White, E., and Beynon, B. Available from: https://www.ons.gov.uk/peoplepopulationandcommunity/wellbeing/articles/coronavirusanddepressioninadultsgreatbritain/june2020
2. Food and mood: Food Fact Sheet. [Internet]. 2017. British Dietetics Association. Available from: https://www.bda.uk.com/resource/food-facts-food-and-mood.html
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