If you’re like me and you’re watching this video you’ve probably heard such conflicting things on what is healthy to eat, and may never have even considered that our diet might affect our mental health… There are so many different diets and foods marketed these days, often with no evidence behind them that it can almost feel like an impossible task to eat in a way that supports us to feel our best. 

Resources on Eating Your Way to Happiness: (rest of transcript and references continued below)

This Guide is Plant-Based 101 from the T. Colin Campbell Centre for Nutrition Studies and has everything you need to know about a plant based diet, and all the support you need on transitioning your diet to one that will support your mental and physical health in the best way!

The good thing is there is a lot of compelling evidence that our diet can have a massive impact on how we feel, and we can use that knowledge to help us feel amazing and move through our lives more happily and confidently. In this video let’s take a look at what the scientific evidence says about the relationship between diet and mental health.

It’s not something that I considered until relatively recently, but this is something I’m super interested in and something that can potentially have a very positive effect on your life when put into practise!

Let’s begin with a look at the shape of mental health in our modern world.

Depression, anxiety and similar mood conditions are at very high rates, and have been steadily increasing over the past 100 years. It is estimated that mental health disorders affect over 792 million people globally – more than 10% of the world’s population1. Anxiety is also incredibly common affecting more than 284 million people worldwide1

Depression affects more than 264 million people worldwide, making it the second leading cause behind heart disease of healthy years of life lost2.

Antidepressant and anti-anxiety medications are commonly prescribed for these conditions. In many countries around the world antidepressant prescriptions have risen hugely in the last few decades. With many developed countries having more than 1 in 10 people on antidepressants, with rates further increasing each year3

Antidepressants appear to be more effective than placebo when looking at all of the published studies4, but what about when published and unpublished studies are considered? Pharmaceutical companies actively suppress studies that don’t show the drugs are effective. In one meta analysis researchers applied under the freedom of information act to the FDA to have access not just to the published studies but the ones the pharmaceutical companies chose not to publish, and when the published and unpublished studies were combined they failed to show a clinically significant advantage for antidepressant medication over placebo5. This may be largely because they only treat the symptoms of depression and don’t address the underlying causes of the issue. So antidepressants, in many cases, may be no more effective than a sugar pill, but also have a whole host of negative side effects including fatigue, insomnia, loss of sex drive and sexual dysfunction, weight gain and many more5.

Many of us may consider taking antidepressants, anti-anxiety, or other medications or just think there’s something wrong with us without looking at an incredibly important factor in our wellbeing – our diet.

So how can our diet affect our mental health? Let’s find out.

A study of over 300,000 Canadians over 9 years found that higher fruit and vegetable consumption was associated with lower levels of depression, psychological distress and mood and anxiety disorders6.

There are many similar studies to this on populations all around the world, in Korea, Chile, Iran, the UK, USA and Japan and they have all found the same. Higher intake of fruit and vegetables made people more likely to be happier and have greater life satisfaction7,8,9,10,11,12

Does any of this sound familiar? Many of us keep hearing that it’s good to eat more fruits and vegetables but why is that? There is a lot of evidence to suggest that it may be due to the high antioxidant levels in fruit and vegetables.

In a study on 2000 US adults they found that higher levels of antioxidants called carotenoids (the most known one being lycopene in tomatoes) in the blood were associated with lower likelihood of experiencing depression. They also found a dose-response relationship, meaning the higher people’s antioxidant levels were, the better they would feel11.

So how can antioxidants help with depression?

We know people who are depressed have higher amounts of inflammation than people who arent and inflammatory diseases are associated with higher rates of depression, in fact you can even induce depression by inducing inflammation in the body1,13. There is a lot of evidence suggesting that depression is an inflammatory condition13, 14

In a study 43,000 women without depression were followed for 12 years and they found that women that ate a more inflammatory diet pattern (characterised by more soda, refined grains and meat) became more depressed. Further supporting the evidence that chronic inflammation may underlie the association between diet and depression14

So what’s causing the inflammation? Free radicals. They can come from metabolic processes in the body, from environmental pollutants or certain foods in our diet, largely processed grains, dairy, meat and oils. Free radicals are highly reactive and can change the chemical structure of certain natural compounds in our body through oxidation, causing our immune system to detect them as dangerous and attack them – causing an inflammatory response. The cure to the oxidation? Antioxidants, they dampen the effect of these free radicals15.

If you’re wanting to get the most out of your diet and reduce your risk of depression, the best antiinflammatory diet is a plant-based diet which, in some studies, can cut inflammation levels by 30% in just 2 weeks, in part due to the large quantities of antioxidants consumed and also due to the fact that your cutting out many foods that contain high levels of free radicals16.

Higher fruit and vegetable intake has been shown to lead to better cognitive test scores, fewer depressive symptoms and lower risk of developing depression. But if it’s just antioxidants, can’t we just take an antioxidant pill? In this study they found that it was only antioxidants from whole food sources that had the positive effect, not antioxidants from supplements17.

In another study on diet and depression almost 3500 people were followed for 5 years. People that ate a processed diet high in sweetened desserts, fried food, processed meat, refined grains and high-fat dairy products had increased risk of depression 5 years later, whereas people that ate a whole food diet high in fruit and vegetables and low in processed foods and meats had a significantly reduced risk of depression 5 years later18

This may be, as we discussed earlier due to the high antioxidant content of a whole food diet but it could also be due to the significantly increased folate (vitamin B9) intake as well. Studies have shown increased rates of depression in people not getting enough folate19.

In a study of 2300 Finnish men, researchers found that low folate levels are a risk factor for depression, with low levels leading to a 3 times higher risk of experiencing depression. Again they also found that the beneficial effect was from folate consumed from whole food sources and that supplements made negligible impact19. Which whole food sources have the most folate? Legumes, beans and dark leafy greens (including kale, chard, broccoli and spinach).

A meta analysis on all of the studies considering the relationship between diet and depression was published in 2014. The authors concluded that a healthy diet including high intakes of fruit, vegetables, fish, and whole grains could be associated with a reduced depression risk20.

Fish? What about meat in general, what effect might the consumption of meat have on our mental health? There have been two randomized control trials directly looking at this effect, both with a similar setup, They randomised a sample of omnivores into three groups, one consuming their normal diet, one excluding all meat except for fish and another excluding all meat together. They found that after 2 weeks the moods for the omnivore and fish eating groups were unchanged, but the mood scores for the vegetarian group significantly improved21,22.

The authors suggest that this may be due to the high concentrations of arachidonic acid in meats – it’s especially high in chicken and eggs and also found in significant concentrations in beef, pork, fish, other meats and other animal products including cheese and cream22.

Arachidonic acid is an inflammatory omega-6 fatty acid, and it’s consumption has been shown to cause inflammation in the brain. As we’ve already covered, inflammation in the body is linked to depression. The brain inflammation from arachidonic acid consumption has been directly linked to mood disorders including depression, anxiety and even increased suicide risk23. When you restrict consumption of meats and animal products you can completely eliminate preformed arachidonic acid from the diet and further boost your mental and physical health. In fact vegans and vegetarians have been shown to have negligible levels of arachidonic acid in their bloods compared to omnivores24.

Many people think that Omega 3 fatty acids, like what are found in fish, or fish oil can help negate the inflammatory effects of Omega 6 fatty acids (like arachadonic acid). Well, in these studies they found that the fish group certainly did increase their Omega 3 intake, but it didn’t appear to have any protective effect on mood22. It is important to note though, Omega 3s do have other important effects in the body beyond mood, but you can skip the arachidonic acid and other pollutants from fish and fish oil and get them straight from plant sources such as flax seed, chia seed, hemp seeds and walnuts.

Where else does inflammation come from in our diet? Endotoxins. These toxins are found in certain bacteria in animal products. In a study, participants were injected with endotoxin and within just a few hours inflammation in the body greatly increased, as well as feelings of depression and social disconnection25.

It’s cool to know that if you’re experiencing these feelings, it’s may not be that there’s something wrong with you, it may just be time to eat more fruits and vegetables and cut down on the meat!

In a study of over 80,000 british people researchers found that the more fruit and vegetables people consumed, the more life satisfaction and happiness they reported – with the most being at 7-8 servings of fruit and vegetables a day10.

Another interesting study of 405 participants didn’t just look at improvements in depression or happiness but also looked at greater measures of wellbeing (called eudaemonic wellbeing). They found that those who ate more fruit and vegetables had increased self-reported curiosity and creativity. So there may be more benefits to eating more fruit and vegetables than just feeling good, they may also help with overall wellbeing including greater curiosity and creativity26.

One important question though. Is this actually cause and effect, or is it that people who were feeling happier, healthier, more curious and creative were because they were eating more fruit and vegetables or were they eating more fruit and vegetables because they were feeling good?

Well they did a study on just that, they found that increased fruit and vegetable consumption predicted good mood the next day, but good mood did not predict fruit and vegetable consumption the next day. They found that on days participants ate more fruit and vegetables they reported feeling calmer, happier and more energetic than normal. They also felt more positive the next day. The authors concluded that eating fruit and vegetables may really promote emotional health and wellbeing. We know exercise can elevate mood, why not the same with healthy food. Note – in this study the amounts of fruit and vegetable consumption was 7.2 servings or fruit or 8.2 servings of vegetables to have a noticeable effect on mood positivity27.

What about other dietary approaches that people think are healthy? A popular one at the moment is the ketogenic diet (or a high fat and very low carb diet, often including significant amounts of meat, cheese, high fat dairy, eggs, oils, some vegetables and small amounts of fruit) which is becoming popular for weight loss. We’ve just learned about the benefits of eating more fruits and vegetables. What effect might restricting them have on mood?

In a study comparing a very low-carb (or ketogenic) diet to a low-fat diet for weight loss 118 overweight but healthy individuals were randomized to either a low-carb (ketogenic) diet or a low-fat diet. They were followed for one year and they found that participants on the low-fat diet’s mood significantly improved over the year and they maintained this positive effect on their mood throughout the whole study. 

Participants on the low-carb (or keto) group appeared to have an improvement in the first 8 weeks but over time their mood returned towards the negative baseline levels they were feeling in the beginning of the study – which is worrying because they did lose a significant amount of weight (about the same as participants in the low-fat group), which normally has a positive effect on mood. Suggesting that ketogenic diets might be no more effective than other approaches for losing weight, but also may have a significant negative effect on mood over time28

This change in mood may be because higher-carbohydrate intake can increase serotonin synthesis, whereas high fat and protein intakes reduce serotonin concentrations in the brain28.

The authors concluded the sustained improvements in mood in the LF group compared with the LC group are consistent with results from epidemiological studies showing that diets high in carbohydrate and low in fat and protein are associated with lower levels of anxiety and depression and have beneficial effects on psychological well-being28. There are many more reasons and studies on why low-carb (or keto) diets may have a negative effect on mood, and on overall health… but that is a topic for another video!

Let’s close this video out by looking at a couple of very interesting studies. Now we have an understanding of how increased fruit and vegetable intake can improve our mood and mental health in many positive ways. We also have an understanding of how consumption of meats and animal products may have a detrimental effect on our mood and mental health. These studies put it to the test.

The first study compared vegan whole food plant based nutrition to a control group in a workplace. Employees were assigned to two groups, one received weekly instruction on a whole food plant based vegan diet and the other group received no instruction and continued their regular diet. The study lasted 5.5 months, neither group counted calories or had any change in exercise frequency. The vegan group ate no meat, eggs, dairy, oil or other processed junk food yet reported greater dietary satisfaction than the group that received no instruction and ate their normal diet. The vegan group also reported improved digestion, increased energy and better sleep than the control. They also reported a significant increase in physical functioning, general health, vitality, mental health and experienced a clinically significant improvement in the quality of their lives. They also had significant improvements in work productivity compared to the control group. Which makes sense if you’re feeling that much better in every aspect of your life29!

They concluded that a Vegan diet improves quality of life and productivity29

Now all we need is to confirm these findings with a larger randomized trial… Enter the next study. It had the same setup as the last one where people were either assigned to a group with weekly instruction and support on a vegan whole food plant based diet or a group that received no instruction and continued their normal diet. This study had a much larger sample size of 292 individuals across 10 corporate offices of a large company in America. What did they find? Participants in the whole food plant based vegan group reported significant improvements in depression, anxiety, fatigue, emotional and overall well-being and work productivity30.

Part of the reason why plant-based diets are so successful in improving mental and physical health is because they are a lifestyle intervention. There are many diets that claim to promote weight loss etc, but they are often incredibly unsustainable and unhealthy in the long-term28. People eating plant-based often report this increased dietary satisfaction and enjoy eating this way once they realise they can eat many amazing, tasty foods and experience all the benefits that come with it for mental and physical health30. This makes it a sustainable lifestyle to promote lifelong physical and mental health. As the study above puts it – lifestyle interventions have an increasingly apparent role in physical and mental health, and among the most effective of these is the use of plant-based diets30.

It’s amazing the evidence that is out there on the effect of diet on mental health. We don’t need to think there’s something wrong with us if we aren’t feeling our best – it might just be time to take a look at what foods we’re putting in our bodies. From the understanding of the link between increased inflammation and depression and the powerful anti-inflammatory effect of antioxidants in fruit, vegetables and other whole plant foods to support our mood. As well as the inflammatory effect of endotoxins and arachidonic acid found in meats and animal products that cause inflammation in the brain and body and detrimentally impact our mental health. There is some amazing evidence supporting a whole food plant based diet as the optimal way to eat, not just for mental health, but for increased physical health, better sleep, less anxiety and depression, and overall improved quality of life. 

So if you take one thing away from this video – eat more fruits and vegetables, but now you actually know why!

If you’re interested about learning more about a plant-based diet and experiencing all the benefits that come with it check out the link in the description for more resources on living an awesome healthy life eating delicious healthy food!

If you’ve enjoyed this video please give it a like as it helps me out in the YouTube algorithms. Check out my channel for more evidence-based wellness videos as well as plant-based recipes, lifestyle videos and guided practises to support your mental, physical and overall wellbeing.

For a full transcript of this video and all of the references cited check out the link in the description.

References:

  1. Hannah Ritchie and Max Roser (2018) – “Mental Health”. Published online at OurWorldInData.org. Retrieved from: ‘https://ourworldindata.org/mental-health
  2. Madeeh Hashmi, A., Awais Aftab, M., Mazhar, N., Umair, M., & Butt, Z. (2013). The fiery landscape of depression: A review of the inflammatory hypothesis. Pakistan journal of medical sciences, 29(3), 877–884. https://doi.org/10.12669/pjms.293.3357
  3. OECD (2018), Pharmaceutical Consumption, Antidepressants, OECD accessed on 17/9/20
  4. Cipriani, A., Furukawa, T. A., Salanti, G., Chaimani, A., Atkinson, L. Z., Ogawa, Y., Leucht, S., Ruhe, H. G., Turner, E. H., Higgins, J., Egger, M., Takeshima, N., Hayasaka, Y., Imai, H., Shinohara, K., Tajika, A., Ioannidis, J., & Geddes, J. R. (2018). Comparative Efficacy and Acceptability of 21 Antidepressant Drugs for the Acute Treatment of Adults With Major Depressive Disorder: A Systematic Review and Network Meta-Analysis. Focus (American Psychiatric Publishing), 16(4), 420–429. https://doi.org/10.1176/appi.focus.16407
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  19. Gilbody, S., Lightfoot, T., & Sheldon, T. (2007). Is low folate a risk factor for depression? A meta-analysis and exploration of heterogeneity. Journal of epidemiology and community health, 61(7), 631–637. https://doi.org/10.1136/jech.2006.050385
  20. Lai, J. S., Hiles, S., Bisquera, A., Hure, A. J., McEvoy, M., & Attia, J. (2014). A systematic review and meta-analysis of dietary patterns and depression in community-dwelling adults. The American journal of clinical nutrition, 99(1), 181–197. https://doi.org/10.3945/ajcn.113.069880
  21. Beezhold, Bonnie & Johnston, Carol & Daigle, Deanna. (2009). Preliminary evidence that vegetarian diet improves mood. 
  22. Beezhold, B. L., & Johnston, C. S. (2012). Restriction of meat, fish, and poultry in omnivores improves mood: a pilot randomized controlled trial. Nutrition journal, 11, 9. https://doi.org/10.1186/1475-2891-11-9
  23. Vaz, J. S., Kac, G., Nardi, A. E., & Hibbeln, J. R. (2014). Omega-6 fatty acids and greater likelihood of suicide risk and major depression in early pregnancy. Journal of affective disorders, 152-154, 76–82. https://doi.org/10.1016/j.jad.2013.04.045
  24. Fisher, M., Levine, P. H., Weiner, B., Ockene, I. S., Johnson, B., Johnson, M. H., Natale, A. M., Vaudreuil, C. H., & Hoogasian, J. (1986). The effect of vegetarian diets on plasma lipid and platelet levels. Archives of internal medicine, 146(6), 1193–1197.
  25. DellaGioia, N., & Hannestad, J. (2010). A critical review of human endotoxin administration as an experimental paradigm of depression. Neuroscience and biobehavioral reviews, 34(1), 130–143. https://doi.org/10.1016/j.neubiorev.2009.07.014
  26. Conner, T. S., Brookie, K. L., Richardson, A. C., & Polak, M. A. (2015). On carrots and curiosity: eating fruit and vegetables is associated with greater flourishing in daily life. British journal of health psychology, 20(2), 413–427. https://doi.org/10.1111/bjhp.12113
  27. White, B. A., Horwath, C. C., & Conner, T. S. (2013). Many apples a day keep the blues away–daily experiences of negative and positive affect and food consumption in young adults. British journal of health psychology, 18(4), 782–798. https://doi.org/10.1111/bjhp.12021
  28. Brinkworth, G. D., Buckley, J. D., Noakes, M., Clifton, P. M., & Wilson, C. J. (2009). Long-term effects of a very low-carbohydrate diet and a low-fat diet on mood and cognitive function. Archives of internal medicine, 169(20), 1873–1880. https://doi.org/10.1001/archinternmed.2009.329
  29. Katcher, H. I., Ferdowsian, H. R., Hoover, V. J., Cohen, J. L., & Barnard, N. D. (2010). A worksite vegan nutrition program is well-accepted and improves health-related quality of life and work productivity. Annals of nutrition & metabolism, 56(4), 245–252. https://doi.org/10.1159/000288281
  30. Agarwal, U., Mishra, S., Xu, J., Levin, S., Gonzales, J., & Barnard, N. D. (2015). A multicenter randomized controlled trial of a nutrition intervention program in a multiethnic adult population in the corporate setting reduces depression and anxiety and improves quality of life: the GEICO study. American journal of health promotion : AJHP, 29(4), 245–254. https://doi.org/10.4278/ajhp.130218-QUAN-72