Key Points.

1.        Processed food & mental health: Ultra-processed foods which are typically high in refined sugars, “unhealthy” fats and artificial additions are increasingly linked to mental health issues such as anxiety and depression. I have seen this in countless clients, myself, and further literature to come.

2.        Inflammation & Gut health: The majority of serotonin & dopamine is made in the gut, if one’s diet is rich in ultra-processed foods, this can lead to chronic inflammation, (which can already be present with severe trauma) only to be exacerbated by diet. This can disrupt the microbiome causing severe mental health issues and mood disorders.

3.        Blood Sugar & mood:
Processed foods typically have a high glycaemic index, which causes fluctuations in blood sugar levels leading to mood swings, irritability and increased risk of mental health issues.

4.        Nutritional Interventions: a whole food, nutrient-dense meal plan that includes a large spectrum of micronutrients, omega-3 fatty acids, antioxidants, and fibre-rich foods can help mitigate the negative effects of processed foods and ensure good mental health/wellness within people.

5.        The psychological benefits of a whole food diet that prioritises anti-inflammatory, nutrient-dense foods have been shown to support good mental health, mood regulation, reduced anxiety and overall improved mental health.

In Brief:

Processed foods are nearly unavoidable in common society due to both their affordability and convenience. Our supermarket aisles are lined with things wrapped in plastics, as well as numbers and names on packages that the majority of us don’t even recognise.

It is no coincidence that as processed foods increase in society, the presence of mental health disorders has also increased, most commonly anxiety & depression.

The 2 are travelling in parallel.

Processed foods are typically low in essential nutrients and high in refined sugars, unhealthy fats, and artificial additives.

This can influence brain function, mood regulation and overall mental well-being.

Below we will dive into the the biological mechanisms such as inflammation, blood sugar, and gut microbiome and highlight the importance of dietary interventions to mitigate ongoing mental health complications.

In-Depth:

Processed food & Mental health:

Most processed foods are very energy-dense and nutrient-poor, loaded with refined sugar, trans fats and preservatives, all of which can negatively impact physical and mental health.

More research comes out every year that these foods are not only linked to obesity, heart disease, and diabetes but also mental health conditions such as anxiety and depression (1) (2).

Inflammation & Mental health:

Research indicates that diets high in processed foods can promote systemic inflammation, which may impact brain function and contribute to mood disturbances (3). Additionally, higher intakes of ultra-processed foods is linked to depressive and anxiety symptoms (4). Another study found that individuals with higher levels of inflammatory markers such as CRP (C reactive protein) had a significantly greater risk of developing depression (5). Even more to this, a diet rich in processed foods has been shown to increase CRP levels, suggesting a link between diet and inflammatory processes that can affect mental health issues (6).

Gut health – and the gut-brain axis

The gut-brain axis refers to the communication between the gastrointestinal system and the brain, which can impact both your mood and behaviour.

The gut microbiome consists of trillions of microorganisms and bacteria. This plays a huge role in regulating this communication.

Ultra-processed food can disrupt this gut microbiome balance and therefore the communication.

The disruption in this balance can lead to dysbiosis (an imbalance of the gut bacteria)(7). Dysbiosis is linked to mood disorders like depression and anxiety due to neuroactive compounds from gut bacteria and inflammation from harmful microbes (8). Processed foods high in refined sugars and artificial additives cause gut inflammation and permeability, affecting the gut-brain connection (9).

Blood sugar fluctuations and mood regulation.

Processed foods, particularly those high in refined sugars and simple carbohydrates, have a high glycaemic index (GI). This means they cause rapid increases in blood sugar levels, leading to corresponding spikes in insulin levels, followed by swift drops in blood sugar. These fluctuations can result in irritability, fatigue, and mood instability, which may contribute to the development of anxiety and depression over time (10).

A 2010 study (10), found that a Western diet high in processed foods, refined grains, and sugar is linked to higher depression and anxiety risk in women. Poor diet quality may affect mood regulation and stress response. Similarly, a 2015 study in The American Journal of Clinical Nutrition by Gangwisch et al. found that high glycaemic index diets are associated with increased depression risk in postmenopausal women due to blood sugar fluctuations affecting brain function (10) (11).

NUTRITIONAL interventions to improve mental health.

Given the negative effects of processed foods on mental health, dietary interventions offer a promising approach to mitigating these impacts. By replacing processed foods with nutrient-dense, whole foods, individuals can reduce inflammation, promote gut health, and stabilise blood sugar levels—all of which can help improve mood and overall mental wellness.

Omega 3 Fatty Acids

Omega-3 fatty acids, found in fatty fish, flaxseeds, and walnuts, are essential for brain health. These fats have anti-inflammatory properties, help regulate neurotransmitters, and support serotonin and dopamine production, which are crucial for mood regulation (12).

Research has shown that omega-3 PUFAs can improve mental health, particularly depression and anxiety. One found that formulations with EPA at ≤1 gram per day are effective for reducing depressive symptoms (13).

A 2018 meta-analysis in JAMA Network Open reviewed the association between omega-3 PUFAs and anxiety symptoms. The findings indicate that omega-3 supplementation may reduce clinical anxiety symptoms, although the authors recommend further well-designed studies to confirm these effects (14).

Plant Food and High Fiber

A diet that includes a variety of plant-based foods—such as fruits, vegetables, whole grains, and legumes—contains essential vitamins, minerals, and antioxidants that are beneficial for brain health and can reduce inflammation. Studies show that plant-based dietary patterns, like the Mediterranean diet, which are high in polyphenols and anti-inflammatory compounds, have been linked to cognitive benefits and decreased inflammation (15). These diets are high in dietary fibre, which is essential for gut health. The gut microbiota ferments the fibre, producing short-chain fatty acids that support gut integrity and function (16)

Reducing refined sugars and processed carbs:

Reducing refined sugars and processed carbs can help manage mood swings from blood sugar imbalances. Whole grains, legumes, and vegetables provide complex carbs that stabilise blood sugar and reduce mood fluctuations. One study found high glycaemic index diets linked to depression in postmenopausal women, indicating low glycaemic foods may improve mental health (17).

Following a low glycaemic load diet is linked to improved cognitive function and a lower risk of cognitive decline. Research suggests that managing blood glucose through such diets may help prevent age-related cognitive decline(17)(18).

These findings suggest that diets high in complex carbohydrates and low in refined sugars can benefit mental health and cognitive function.

PROBIOTICS & Fermented food

Probiotics in foods like yogurt, kefir, sauerkraut, and kimchi may support gut health and improve mental health by affecting the gut-brain axis. A review in Frontiers in Psychiatry found that probiotics, prebiotics, synbiotics, and fermented foods could help treat psychiatric disorders by modulating this connection (19).

It is also suggested that microbiome-based therapies, like probiotics, might boost gut bacteria and improve mood via the gut-brain axis (20).

Another study examined the potential of probiotic therapies and fermented food diets in enhancing mental health, suggesting that individuals with psychiatric conditions could experience greater benefits from these interventions compared to healthy individuals (21).

These findings indicate that including fermented foods in one's diet may enhance mental and physical well-being by fostering a healthy gut microbiome and mitigating gut inflammation.

Conclusion

Processed food consumption is linked to anxiety, depression, and poor wellness. These foods cause inflammation, gut issues, and blood sugar spikes, which contribute to mood disorders. Eating whole foods rich in omega-3s, fibre, antioxidants, and probiotics can reduce these effects.

A nutrient-dense, anti-inflammatory diet improves physical and mental health, stabilising mood and lowering the risk of anxiety and depression. With rising mental health issues, these nutritional strategies could benefit public health significantly.

References:

1.        Coletro HN, Mendonça RD, Meireles AL, Machado-Coelho GL, Menezes MC. Ultra-processed and fresh food consumption and symptoms of anxiety and depression during the COVID-19 pandemic: COVID Inconfidentes. Clin Nutr ESPEN. 2022 Feb;47:206-214. doi: 10.1016/j.clnesp.2021.12.013. Epub 2021 Dec 20. PMID: 35063203.

2.        Lane MM, Gamage E, Travica N, Dissanayaka T, Ashtree DN, Gauci S, Lotfaliany M, O'Neil A, Jacka FN, Marx W. Ultra-processed food consumption and mental health: A systematic review and meta-analysis of observational studies. Nutrients. 2022 Jun 21;14(13):2568. doi: 10.3390/nu14132568. PMID: 35807749.

3.        González Olmo BM, Butler MJ, Barrientos RM. Evolution of the human diet and its impact on gut microbiota, immune responses, and brain health. Nutrients. 2021 Jan 10;13(1):196. doi: 10.3390/nu13010196. PMID: 33435203.

4.        Lane MM, Gamage E, Travica N, Dissanayaka T, Ashtree DN, Gauci S, et al. Ultra-Processed Food Consumption and Mental Health: A Systematic Review and Meta-Analysis of Observational Studies. Nutrients. 2022;14(13):2568. doi:10.3390/nu14132568.

5.        Kiecolt-Glaser JK, Derry HM, Fagundes CP. Inflammation: Depression fans the flames and feasts on the heat. Am J Psychiatry. 2015;172(11):1075–91. doi:10.1176/appi.ajp.2015.15020152.

6.        Dantzer R, O'Connor JC, Freund GG, Johnson RW, Kelley KW. From inflammation to sickness and depression: when the immune system subjugates the brain. Nat Rev Neurosci. 2008;9(1):46–56. doi:10.1038/nrn2297.

7.        Miller AH, Maletic V, Raison CL. Inflammation and its discontents: The role of cytokines in the pathophysiology of major depression. Biol Psychiatry. 2009;65(9):732–41. doi:10.1016/j.biopsych.2008.11.029.

8.        Chassaing B, Koren O, Goodrich JK, Poole AC, Srinivasan S, Ley RE, Gewirtz AT. Dietary emulsifiers impact the mouse gut microbiota promoting colitis and metabolic syndrome. Nature. 2015 Mar 5;519(7541):92-6. doi: 10.1038/nature14232. Epub 2015 Feb 25. PMID: 25731162.

9.        Whelan K, Bancil AS, Lindsay JO, Chassaing B. Ultra-processed foods and food additives in gut health and disease. Nat Rev Gastroenterol Hepatol. 2024 Jun;21(6):406-427. doi: 10.1038/s41575-024-00893-5. Epub 2024 Feb 22. PMID: 38388570.

10.  Gangwisch JE, Hale L, Garcia L, Malaspina D, Opler MG, Payne ME, et al. High glycemic index diet as a risk factor for depression: analyses from the Women's Health Initiative. Am J Clin Nutr. 2015;102(2):454–63. doi:10.3945/ajcn.114.103846.

11.  Raison CL, Capuron L, Miller AH. Cytokines sing the blues: inflammation and the pathogenesis of depression. Am J Psychiatry. 2006;163(6):861–70. doi:10.1176/appi.ajp.2009.09060881.

12.  Firth J, Gangwisch JE, Borsini A, Wootton RE, Mayer EA. Food and mood: how do diet and nutrition affect mental wellbeing? BMJ. 2020;369:m2382. doi:10.1136/bmj.m2382.

13.  Liao Y, Xie B, Zhang H, He Q, Guo L, Subramaniapillai M, et al. Efficacy of omega-3 PUFAs in depression: A meta-analysis. Transl Psychiatry. 2019 Aug 5;9(1):190. doi: 10.1038/s41398-019-0515-5.

14.  Lopresti AL, Hood SD, Drummond PD. A review of lifestyle factors that contribute to important pathways associated with major depression: diet, sleep and exercise. JAMA Netw Open. 2018;1(6):e182742. doi:10.1001/jamanetworkopen.2018.2742.

15.  Firth J, Marx W, Dash S, Carney R, Teasdale SB, Solmi M, et al. The effects of dietary improvement on symptoms of depression and anxiety: a meta-analysis of randomized controlled trials. Psychosom Med. 2019;81(3):265–80. doi:10.1097/PSY.0000000000000673.

16.  Marx W, Lane M, Hockey M, Aslam H, Raju K, Benassi-Evans B, et al. Ultra-processed food consumption and mental health: A systematic review and meta-analysis of observational studies. Eur J Nutr. 2023;62(4):1745–66. doi:10.1007/s00394-022-03013-5.

17.  Gangwisch JE, Hale L, Garcia L, Malaspina D, Opler MG, Payne ME, et al. High glycemic index diet as a risk factor for depression: analyses from the Women's Health Initiative. Am J Clin Nutr. 2015 Aug;102(2):454-63. doi: 10.3945/ajcn.114.103846.

18.  Seetharaman S, Andel R, McEvoy C, Dahl Aslan AK, Finkel D, Pedersen NL. Blood glucose, diet-based glycemic load and cognitive aging among dementia-free older adults. J Gerontol A Biol Sci Med Sci. 2015 Apr;70(4):471-9. doi: 10.1093/gerona/glu135.

19.  Ribera C, Sánchez-Ortí JV, Clarke G, Marx W, Mörkl S, Balanzá-Martínez V. Probiotic, prebiotic, synbiotic and fermented food supplementation in psychiatric disorders: A systematic review of clinical trials. Neurosci Biobehav Rev. 2024 Mar;158:105561. doi: 10.1016/j.neubiorev.2024.105561. Epub 2024 Jan 26.

20.  Mörkl S, Butler MI, Holl A, Cryan JF, Dinan TG. Probiotics and the Microbiota-Gut-Brain Axis: Focus on Psychiatry. Curr Nutr Rep. 2020 Sep;9(3):171-182. doi: 10.1007/s13668-020-00313-5.

21.  Karbownik MS, Mokros Ł, Kowalczyk E. Who Benefits from Fermented Food Consumption? A Comparative Analysis between Psychiatrically Ill and Psychiatrically Healthy Medical Students. Int J Environ Res Public Health. 2022 Mar 24;19(7):3861. doi: 10.3390/ijerph19073861.