What is fatigue?
Whilst fatigue is commonly defined as ‘extreme tiredness resulting from mental or physical exertion or illness,’  in practice, diagnosing fatigue can be categorised in many varying ways. The most common type of fatigue recognised by the NHS as an ‘illness’ is Chronic Fatigue Syndrome (CFS).
Chronic Fatigue Syndrome
The NHS defines CFS as a long-term illness with a wide range of symptoms. The most common symptom is extreme tiredness. CFS is also known as ME, which stands for Myalgic Encephalomyelitis. Many people refer to the condition as CFS/ME. CFS/ME can affect anyone, including children. It’s more common in women, and tends to develop between your mid-20s and mid-40s. The main symptom of CFS/ME is feeling extremely tired and generally unwell. In addition, people with CFS/ME may have other symptoms, including:
- sleep problems
- muscle or joint pain
- a sore throat or sore glands that are not swollen
- problems thinking, remembering or concentrating
- flu-like symptoms
- feeling dizzy or sick
- fast or irregular heartbeats (heart palpitations)
Most people also find that over exercising makes their symptoms worse but the severity of symptoms can vary from day to day, or even within a day. The causes of CFS/ME are unknown but a variety of theories have been suggested such as a hormone imbalance, mental health problems, genetics, problems with immune system, etc.
Possible treatments for reducing fatigue are specified on their website as:
- cognitive behavioral therapy (CBT)
- a structured exercise programme called graded exercise therapy (GET)
- medicine to control pain, nausea and sleeping problems 
Whilst therapy and medication are a possible solution, therapy may be time consuming, especially as most wish to reduce fatigue at work and through their existing schedule as opposed to scheduling new things in such as therapist appointments. There seems to be an easier, more natural and accessible remedy that can alleviate fatigue without much routine change, and that is through your diet and looking at foods to reduce fatigue.
Foods to reduce fatigue
A study conducted in March 2015 regarding fatigue in children, raised the issue of a micro deficiency of minerals and vitamins as a possible cause for their fatigue. 
When put on a modified diet consisting of green vegetables, beef, whole milk and full-fat butter, results showed an improvement in sleep. The children slept better through the night and took fewer naps, and a significant larger decrease in cognitive fatigue symptoms was seen when eating green vegetables according to the diet guidelines. Although this study applies to children, the same foods that reduce fatigue could perhaps be beneficial for adults also.
A 2011 study analysing the impact of diet on swimming fatigue found that a diet supplemented with 1% 60 brix garlic extract and vitamin B group twice mixture had beneficial effects on fatigue recovery in swimming load tests. 
Furthermore, vitamins gained from fish oils have also been flagged as a potential reliever of fatigue; particularly that of mackerel, proven to prolong exhaustion swimming time in mice in a 2014 study.  Although not tested on humans, there seems to be a correlation between increased vitamin intake and decreased fatigue as indicated by the two previous studies. As well as vitamins being offered as a solution, minerals such as zinc, selenium, magnesium, and calcium have frequently been recommended also .
Therefore, as well as foods to reduce fatigue, consuming more vitamin and minerals may be a more natural solution to fatigue than medicine; however, it is advisable to speak to your doctor or GP surgeon first as although vitamins such as vitamin B are often regarded as safe due to their high solubility in water, toxicity symptoms such as impairment of vision and vibration sense below the knee have been associated with large intakes of vitamin B6. 
Diet isn’t the only way to reduce fatigue
Whilst these observations point to a diet of foods to reduce fatigue as being a remedial solution for fatigue, NHS guidelines cannot be ignored. With therapy being 2 out of the 3 remedial options, there seems to be a greater emphasis on psychological factors and how physical and mental wellbeing contribute to fatigue. The question may therefore not be what foods can I eat to reduce fatigue, but more what can I do to improve my cognitive and physical development. Diet will inevitably contribute to this, but eating one fish oil supplement per day will definitely not be an impactful solution.
In fact, a study conducted at 54 hospitals in China revealed that women tended to be more susceptible to fatigue then men, with the suggestion that physiological and psychological characteristics such as pregnancy and menopause.  In the study, fatigue was also associated with age, marital status, occupation, health related factors (exercise, regular diet, and health status) and work-related factors (hospital rank and turnover intention).
It therefore seems that the remedy for fatigue will vary depending on the individual, it is perhaps best to assess oneself and select the remedy that would be most applicable to their age, gender, etc. At the end of the day all bodies are different and you must tailor your solution to your unique self.
 Kang Min Jung, Shin Jung Hye, Sung Nak Ju, ‘Recovery Effect of Garlic Extract and Vitamin B Group Enhanced Diet on Swimming Fatigue’, Journal of Life Science, 21.6, (2011), 875-883 (p. 875), in https://pdfs.semanticscholar.org/6a5a/210da2211e131026750cc508b0b1eda1a31f.pdf [accessed 26 June 2020]. Chronic fatigue syndrome (CFS) (2017) https://www.nhs.uk/conditions/chronic-fatigue-syndrome-cfs [accessed 26 June 2020].
 Steenbruggen, T. G., Hoekstra, S. J. & van der Gaag, E. J., ‘Could a Change in Diet Revitalize Children Who Suffer from Unresolved Fatigue?’, Nutrients , 7.3, (2015), 1965-1977, in https://www.rug.nl/research/portal/en/publications/could-a-change-in-diet-revitalize-children-who-suffer-from-unresolved-fatigue(2b9a06af-4af7-4afa-b502-835a806ac731).html [accessed 26 June 2020].
 Kang Min Jung, Shin Jung Hye, Sung Nak Ju, ‘Recovery Effect of Garlic Extract and Vitamin B Group Enhanced Diet on Swimming Fatigue’, Journal of Life Science, 21.6, (2011), 875-883 (p. 875), in https://pdfs.semanticscholar.org/6a5a/210da2211e131026750cc508b0b1eda1a31f.pdf [accessed 26 June 2020].
 Xueqin Wang,ab Ronge Xing, Zuoyuan Chen, Huahua Yu, Rongfeng Li and Pengcheng Li, ‘Effect and mechanism of mackerel (Pneumatophorus japonicus) peptides for anti-fatigue’, Food & Function, 5.9, (2014), 2113-2119, in https://ezproxy-prd.bodleian.ox.ac.uk:4238/en/content/articlelanding/2014/FO/C4FO00121D#!divAbstract [accessed 26 June 2020].
 Stoff JA, Pellegrino CR. Chronic Fatigue Syndrome: The Hidden Epidemic. New York, NY: Harper & Row Publishers Inc; 1988.
 Schaumburg H, Kaplan J, Windebank A, et al. Sensory neuropathy from pyridoxine abuse. N Engl J Med. 1983;309:445-448.
 Shu Cai, Hong Lin, Xuan Hu, Yue-Xiu Cai, Ken Chen & Wen-Zhi Cai (2018) High fatigue and its associations with health and work related factors among female medical personnel at 54 hospitals in Zhuhai, China, Psychology, Health & Medicine