Key learning points:
– Migraine is the most common form of disabling headache
– A good way to establish whether diet is a genuine trigger is by encouraging patients
to keep a headache diary and recording possible dietary triggers in relation to the headaches
– Migraine patients should be encouraged to have a balanced diet with regular meals to maintain a healthy weight and good nutrition
Migraine is a type of recurrent headache. It is disabling and common and affects one-in-five women and one-in-10 men.1 There are eight million sufferers or more in the UK but it is often not recognised. One reason for missed diagnosis may be that a person doesn’t have all the classical features of a migraine and so it's not recognised either by the patient or the GP. Other patients may have self-treated with over-the-counter painkillers, which can change the features of the headache. However, studies have shown that if a person sees their GP about headaches, it most likely is migraine,2 not a tension type headache.
The hallmarks of migraine are a throbbing headache, moderate to severe in intensity (typically disrupting normal activities) and associated with queasiness or even vomiting as well as light and sound sensitivity. The International Headache Society have set out specific diagnostic criteria for all the different headache types3 including migraine (see Box 1). This criteria has been extremely useful in conducting research studies and helping clinicians diagnose patients. However, it is important to recognise that many patients may not present with a full house of features. If a person has felt their headaches are sufficiently impacting their lives, leading to them having medical attention – there is a very good chance this will be migraine.
Migraine is divided into: ‘migraine with aura’ and the more common ‘migraine without aura’. Aura are warning neurological symptoms, usually just before the start of the headache. Most commonly this will take the form of visual phenomenon such as flashing lights or blind spots. It can also be sensory symptoms or even weakness.
Most patients with migraine have infrequent attacks. However, a substantial group develop chronic migraine. This is presently defined as having a headache of any description on more than 15 days per month, of which at least eight should have migraine characteristics.3 This pattern of headache should have been present for at least three months. It is unknown why some patients will develop this more severe and debilitating form of migraine.
Excluding secondary causes of headache
When a person develops headaches, it is always important to exclude an underlying problem. Patients often worry about brain tumours but this is very unlikely unless they are in a vulnerable group. For most people with headaches, including migraine, a brain scan is not necessary.
The National Institute for Clinical Excellence (NICE) has produced guidelines on the features that might prompt further investigations (see Resources for more information).
Causes of Migraine
Migraine is primarily a disorder of the brain and nerve function.4 The lining and blood vessels of the brain have pain fibres carried by a nerve known as the trigeminal nerve. When a migraine is occurring, the trigeminal nerve is activated and pain information is transmitted to pain centres in the brain.
Nerves communicate by sending electrical signals called action potentials that travel rapidly down their long processes. Action potentials cause the release of neurochemicals from the nerve terminals that cross a very small gap to reach the next nerve in the relay. The connection between one nerve and another is called a synapse. Proteins called ion channels control the electrical properties, such as excitability of nerves. Ion channels do this by regulating the flow of potassium, sodium, calcium and other salts in the nerve.
There are a rare group of migraines that are passed down from generation to generation in families. In these cases, a mutation in ion channel genes seems to increase the excitability of the nerve and synapses. The identification of these types of genetic mutations supports the idea that migraine arises from altered excitability and responsiveness of nerves. However, most people who suffer from migraines will not be carrying one of the rare gene mutations. Instead migraine vulnerability is likely to be a combination of subtle cumulative genetic effects and the environment.5
Several factors have been identified as capable of inducing a migraine attack in susceptible individuals. These triggers include food and hormones – with stress being one of the most common factors. Despite numerous studies, it is difficult to firmly establish many triggers that cause a migraine attack. Instead the perceived trigger may be a coincidental association or even a very early symptom of a migraine attack rather than a cause.6 Coincidental association is particularly a problem when a possible trigger factor is frequently experienced in daily life.
Diet and migraine
Dietary factors have been investigated in many studies as a trigger for migraines. Candidate dietary triggers in a migraine include alcohol, caffeine, chocolate, citrus fruits and fats. However, it is important to bear in mind that the majority of studies are retrospective with problems of recall bias or population studies where it is difficult to distinguish whether the association with migraine is by chance. The dangers of relying upon retrospective data and anecdote is evident from recent work examining the role of light as a provocant. As with diet, light is often considered a common trigger by many patients with migraine. But when a group of such patients were exposed to light stimulation, none of the patients had a migraine induced.6 There are much fewer prospective studies or published experimental studies where a person is explicitly exposed to the candidate trigger. Caffeine withdrawal and going without food are two dietary factors where such studies support their role as genuine triggers for headaches.7,8
On this basis there seems to be little direct evidence that alcohol, chocolate, caffeine, citrus fruits, dairy products or additives such as monosodium glutamate are common migraine triggers. Therefore, it is not appropriate to advise everyone with migraines to stop eating such food as it is unlikely to have a significant impact. Removing these foods will impoverish the diet and likely reduce the patients quality of life. It is worth pursuing further in these cases because it may potentially lead to a significant improvement in migraines.
Migraine and obesity
Migraine has a specific association with obesity, and obese individuals are more likely to suffer from chronic migraine.9 It is unknown whether obesity has a direct influence on migraine mechanisms or whether the increased risk is due to a shared susceptibility factor. It has been suggested that inflammatory mediators released by adipose tissue may increase migraine vulnerability.10 If there is a causal relationship between obesity and migraine, losing weight should be beneficial. A number of studies seem to support this, in obese women having bariatric surgery patients had reduced migraine frequency and disability.11,12 Furthermore diets such as ketogenic diets or low-calorie diets that result in a significant decrease in body mass index (BMI) also reduce headache frequency.13 A study examining low-fat diet without caloric restriction found that a reduction in fat ingestion led to a significant improvement in migraines, along with a decrease in the use of medications.14 In this study the majority of patients had more than 40% improvement in their migraine, with median headache frequency at baseline of six per month and changing to just one per month after a 28-day low fat diet.
Explaining the effects
Patients will often seek possible causes of their headaches. Therefore, it is important to carefully consider the patient’s experiences. A common problem is migraine patients removing different foods from their diet without much evidence. The risk is that an impoverished diet may reduce quality of life or even lead to nutritional deficiencies. When discussing the effect of diet with a migraine patient, it is important to explain that a healthy balanced diet is important for general health, as well as the evidence that for most people dietary factors are probably not major triggers. But if they feel something in their diet is provoking a migraine, it may be worth keeping a headache diary while removing and then re-introducing the potential trigger.
Helping migraine patients with their diets
The most important advice is that the diet should be healthy and balanced. This will promote good general physical and mental health, which will benefit the quality of life in migraine patients.
Skipping meals can trigger migraines, so advise patients to keep regular mealtimes. If the patient is overweight, discussing ways to reduce and manage weight will also be beneficial. Evidence suggests this will reduce the migraine burden and may reduce the risk of migraines becoming the more severe chronic form.
Caffeine withdrawal appears to be a genuine trigger for headaches, so ask patients about their coffee and tea intake. Since caffeinated beverages are often taken frequently through the day, the patient may perceive caffeine to directly trigger attacks rather than attributing problems to withdrawal. Reducing or stopping caffeine could then exacerbate migraines in the short-term and patients should be warned about this. Over-the-counter analgesic medications may also contain caffeine, and overuse of these medications is a big problem leading to migraines becoming refractory to definitive migraine treatments.
Keeping a headache diary is an excellent way of helping both patients and health professionals to understand the headache patterns and burdens. This should ideally be used in all migraine patients with frequent headaches. There are a growing number of electronic headache diaries and smartphone apps for this purpose. ‘Old-fashioned’ paper diaries are however just as effective. The patient should note any suspect triggers in the diary and if a consistent pattern emerges a trial withdrawal should be attempted.
Migraines are common but under-recognised, which is a tragedy because there are effective treatments available. The Migraine Trust estimate there are 190,000 migraine attacks every day and this results in 25 million days lost from work or school. A good diet to maintain a healthy weight and nutrition is important for migraine patients. Not skipping meals and avoiding caffeine dependence is advisable. While the popular conception that many things within a diet can provoke a migraine is probably not true, for an individual, it is worth exploring by using headache diaries. If a convincing dietary trigger is found then a simple change could result in a significant reduction in the burden of migraine.
NICE guidelines for managing headaches:
1. Steiner T, Scher A, Stewart F et al. The prevalence and disability burden of adult migraine in England and their relationships to age, gender and ethnicity. Cephalalgia 2003;23(7):519–527.
2. Kernick D, Stapley S, Hamilton W. General practitioners' classification of headache. Is primary headache underdiagnosed. The British Journal of General Practice 2008; 58:102–4.
3. Headache Classification Committee of the International Headache Society (IHS). The International Classification of Headache Disorders, 3rd edition (beta version). Cephalalgia 2013;33(9):629-808.
4. Zameel Cader M. The molecular pathogenesis of migraine: new developments and opportunities. Human Molecular Genetics 2013;15:22(R1):R39-44.
5. Weir GA, Cader MZ. New directions in migraine. BMC Medicine 2011 25;9:116.
6. Hougaard A, Amin FM, Hauge AW, Ashina M, Olesen J. Provocation of migraine with aura using natural trigger factors. Neurology 2013;29:80(5):428-31.
7. Juliano LM, Griffiths RR. A critical review of caffeine withdrawal: empirical validation of symptoms and signs, incidence, severity, and associated features. Psychopharmacology 2004;176:1–29.
8. Martin PR, Seneviratne HM. Effects of food deprivation and a stressor on head pain. Health Psychology 1997;16:310–318.
9. Ornello R, Ripa P, Pistoia F, Degan D, Tiseo C, Carolei A, Sacco S. Migraine and body mass index categories: a systematic review and meta-analysis of observational studies. The Journal of Headache Pain 2015;28:16:27.
10. Chai N, Bond D, Moghekar A, et al. Obesity and headache: Part II—Potential mechanism and treatment considerations. Headache 2014;54: 459–471.
11. V, Fuchs L, Lantsberg L, et al. Changes in headache frequency in premenopausal obese women with migraine after bariatric surgery: A case series. Cephalalgia 2011;31:1336–1342.
12. Bond DS, Vithiananthan S, Nash JM, et al. Improvement of migraine headaches in severely obese patients after bariatric surgery. Neurology 2011;76:1135–1138.
13. Di Lorenzo C, Coppola G, Sirianni G, et al. Migraine improvement during short lasting ketogenesis: A proof-of-concept study. European Journal of Neurology 2015; 22: 170–177.
14. Bic Z, Blix GG, Hopp HP, et al. The influence of a low-fat diet on incidence and severity of migraine headache. Journal of Women’s Health & Gender Based Medicine 1999;8:623–629.
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