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Obsessive-Compulsive Disorder (OCD)

About Obsessive-Compulsive Disorder (OCD)

OCD has been classified by the World Health Organisation (WHO) as one of the top ten mental health disorders negatively affecting quality of life1. It is characterized by persistent, unwanted thoughts and compulsions, significant enough to disrupt normal social function and which may cause problems in relationships of affected individuals. OCD can present as either obsessions or compulsions and sometimes both2. Obsessions are the persistent, repetitive, intrusive, and unwanted thoughts while compulsions are the repetitive behaviours and rituals performed to make the individual feel better. Compulsions are, however, not helpful as they only provide short term relief before the anxious thoughts begin again, thereby keeping affected individuals in a vicious cycle.

Prevalence of OCD in the UK

OCD, once thought to be rare, is now more prevalent. It is currently estimated that 1% to 2% of the UK population have OCD2 and it can occur in any age group regardless of the gender, ethnicity, social and economic circumstances3. The risk of OCD is, however, higher in women than in men4

Causes of OCD

Though the cause of OCD remains uncertain, there are factors that have been attributed to its incidence. There is an increased risk for individuals with a family history of OCD due to genetic factors5,6. Environmental, behavioural, and cognitive factors also contribute to the cause of OCD. These include past trauma, neglect, emotional and sexual abuse, parental influence7,8. Substance abuse, history of phobia and loss of employment can also contribute to the occurrence of OCD in some people9

Symptoms of OCD

Persistent, unwanted thoughts causing distress and compulsive behaviour to reduce anxiety underlie There are many types of OCD triggered by fears and concerns about important people or things. For example, excessive washing and cleaning may be driven by the fear of being contaminated. Table below shows OCD themes as well as related obsessions, and compulsions.





Fear of germs and dirt

Excessive showering, washing, and cleaning


Harm-related fears and concerns

Constant checking


Concerns about disorder

Straightening, ordering, counting

Intrusive thoughts

Fears concerning religion, relationships, sexuality


Nutrition and OCD

Cognitive Behaviour Therapy (CBT) is the recommended treatment option for people with OCD, in conjunction with selective serotonin reuptake inhibitors (SSRIs) in severe cases2. However, nutrition has been observed to play a significant role in OCD outcomes. 

The Western diet, high in sugar and processed foods, does not contain adequate nutrition required to manage OCD and support individuals experiencing symptoms. Research has shown that nutritional deficiencies are present in patients with mental disorders such as OCD10. It has also been observed that specific nutrients have reduced patients’ symptoms effectively11. It is important however, to consult your GP if you are experiencing OCD to discuss further, before taking any supplements.

Increase consumption of foods high in Vitamin B12

Patients with OCD have been observed to have low levels of Vitamin B1212. The adequacy of Vitamin B12 is important to brain health because it is involved in the metabolism of homocysteine, a metabolite, which, when raised can increase risk of developing some mental health conditions, including serotonin and dopamine13. These neurotransmitters are important to prevent anxiety, depression and stress which are all indicators of OCD. There is an inverse relationship between homocysteine and Vitamin B12 in that homocysteine levels rise as the Vitamin B12 levels drop. Studies have shown that patients with OCD have high levels of homocysteine and low levels of Vitamin B12 in comparison to healthy individuals14. It is also possible that OCD is an early manifestation of Vitamin B12 deficiency13.

Individuals following a vegan diet are most at the risk of Vitamin B12 deficiency as the richest sources of Vitamin B12 are of animal origin15. However, foods fortified with Vitamin B12 should meet requirements where there have been no previous deficiencies. 

Key Actions

  • Liver is the richest source of Vitamin B12, although it should be noted that liver is not appropriate for consumption by pregnant women due to the high levels of Vitamin A . Lean meat and fish, are also good source, including chicken, turkey, cod and salmon.
  • Eggs, milk, cheeses, and yogurt also provide Vitamin B12.
  • Include fortified foods, e.g., low and no added sugar breakfast cereals, plant-based milk if on a vegan or vegetarian diet. You should read the labels carefully to ensure that Vitamin B12 has been added to these products.   
  • Individuals on a vegan or vegetarian may consider supplementation. However, you should discuss with your GP before starting any supplements.

Introduce prebiotics and probiotics to normal diet

Prebiotics and probiotics have been found to be beneficial to gut health by increasing the “good” bacteria in the gut16. These bacteria are also involved in the production of Vitamin B12. Healthy gut flora will increase the production and absorption of Vitamin B12. The disruption in the gut microbiome is shown to have an impact of the mental health due to the gut-brain axis. This refers to the connection between the gut and the brain through a network of nerves and neuron pathways17. Studies undertaken record an improvement in OCD symptoms with the introduction of prebiotics and probiotics17

Key Actions:

  • Include fruits and vegetables in the diet as these are natural sources of prebiotics. You should try to have five portions of a variety of fruits and vegetables in a day. A portion of fruit is a piece of a medium-sized apple while a portion of vegetables is 4 heaped tablespoons of cooked kale/spinach. Tomatoes, berries, bananas, asparagus, onions, carrots, green vegetables, and salad are good sources. 
  • Increase the consumption of high fibre foods e.g., low sugar breakfast cereals, oats, beans, lentils, can promote gut health. 
  • It is important to increase water or fluid intake to prevent adverse gastric symptoms i.e., bloating and constipation, due to increased fibre intake.
  • Include fermented foods such as yogurt, kefir, sauerkraut, kombucha, and kimchi, in diet. These are rich sources of probiotics. 

Increase intake of Omega-3 Fatty Acids 

Omega-3 fatty acids are a type of essential fatty acids which can only be obtained from the diet because our bodies cannot produce it18. There are three types of omega-3 fatty acids namely, Alpha-linolenic acid (ALA), Eicosapentaenoic acid (EPA) and Docosahexaenoic acid (DHA). EPA and DHA especially, have been seen to be beneficial to mental health19

Fatty acids are present in the brain and are useful to regulate communication between the brain and neurons especially with brain processes that control mood20. Studies have shown that the combination of polyphenols and omega-3 fatty acids increase the availability of omega-3 due to anti-oxidative properties of polyphenols21. Polyphenols are found in red wine, tea, dark chocolate, fruits and vegetables.

Though there is insufficient evidence to support the recommendation of omega-3 fatty acid supplementation20, some research has shown an association between omega-3 intake with the alleviation of symptoms22.

Key Actions

  • Aim to eat oily fish at least once a week. The Eatwell Guide recommends that you should eat two portions of fish every week, one of which should be oily fish. Oily fish e.g., salmon, mackerel, sardines, are very high in omega-3 fatty acids. 
  • Omega- 3 fortified foods e.g., eggs are also good sources. 
  • Vegans and vegetarians may consider other sources such as nuts, seeds, and their plant oils (e.g., walnuts, chia seeds, flax seeds), seaweed, and algae.
  • Supplementation may be considered, especially vegan DHA supplements. However, consult with your GP before commencing supplements.

Researched by: Enitan Femi-Obasan, BSc Dietetics London Metropolitan University


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