Foods To Prevent Fainting

  • 1st Revision: Emma Soopramanien
  • 2nd Revision: Keri Wilkie
  • 3rd Revision: Conor Hodges

Fainting, also known as syncope or “passing out”, is a loss of consciousness that occurs when the supply of blood, and therefore oxygen, to the brain is briefly interrupted. Fainting spells typically last from a few seconds to a few minutes. There are several types of syncope, which include:

  • Vasovagal syncope (also known as neurocardiogenic syncope or reflex syncope) involves the vagus nerve. It can be triggered by emotional trauma, stress, the sight of blood, or standing for a long period of time. This is the most common cause of fainting.
  • Carotid sinus syncope happens when the carotid artery in the neck is constricted, e.g., after turning your head to one side or wearing a collar that is too tight.
  • Situational syncope. This type occurs due to straining while coughing, urinating, moving your bowels, or having gastrointestinal problems.
  • Postural syncope (also called postural or orthostatic hypotension) is caused by a sudden drop in blood pressure due to a quick change in position, such as from lying down to standing. Certain medications and dehydration can lead to this condition. 
  • Cardiac syncope is caused by a heart or blood vessel condition that affects blood flow to the brain. These conditions include an abnormal heart rhythm (arrhythmia), blockage in the cardiac blood vessels (myocardial ischemia) or heart failure.
  • Neurologic syncope or neurally mediated syncope is caused by a neurological condition such as seizure, stroke or transient ischemic attack (TIA, or mini-stroke).
  • Postural orthostatic tachycardia syndrome (PoTS) is caused by a very fast heart rate (tachycardia) that happens when a person stands after sitting or lying down. The condition is most common in people assigned female at birth (AFAB), but it can also occur in people assigned male at birth (AMAB).
  • Unknown causes of syncope occur in about one-third of patients.

Symptoms of syncope can include:

  • Blacking out
  • Feeling sick
  • Feeling suddenly warm
  • Turning pale
  • Blurred vision
  • Getting sweaty palms
  • Feeling lightheaded
  • Falling for no reason
  • Feeling dizzy
  • Feeling drowsy or groggy
  • Fainting, especially after eating or exercising
  • Feeling unsteady or weak when standing
  • Changes in vision, such as seeing spots or having tunnel vision
  • Headaches

Sources: Cleveland Clinic, Cedars-Sinai

Potential Causes of Fainting

You are more likely to faint if you have any of these conditions:

  • Diabetes
  • Heart disease
  • Atherosclerosis
  • An irregular heartbeat, or arrhythmia
  • Anxiety or panic attacks
  • Chronic lung disease, such as emphysema
  • Anaemia

However, fainting sometimes occurs in otherwise relatively healthy individuals with no obvious underlying cause. It is a particular problem in the elderly, who may injure themselves when fainting.

There are a variety of triggers for fainting, according to Healthline:

  • Fear or other emotional trauma
  • Severe pain
  • A sudden drop in blood pressure
  • Very low blood sugar (hypoglycaemia)
  • Hyperventilation
  • Dehydration
  • Standing in one position for too long
  • Standing up too quickly
  • Physical exertion in hot temperatures
  • Coughing too hard
  • Straining during a bowel movement
  • Consuming drugs or alcohol
  • Seizures

Some medications can cause low blood pressure and thus increase your chance of fainting. These include certain medications used to treat high blood pressure, allergies, depression, and anxiety.

Foods to Prevent Fainting in the Long Run

An important piece of advice here is not to skip meals. It is necessary to maintain a steady supply of nutrients to the body to prevent hypoglycaemia and other conditions. A healthy, balanced diet is recommended. There are no specific foods to avoid if you suffer from syncope.

Drink plenty of fluids to prevent dehydration and maintain blood volume, especially before and after physical activity. This can include water or any sugar-free drinks like tea. However, food and drinks containing caffeine and alcohol should be minimised. These have a diuretic effect and act to reduce blood volume, aside from their neurological effects.  

Eating a diet slightly richer in salt (sodium) can also help protect blood volume and blood pressure: these are key factors in preventing several types of syncope, including vasovagal syncope (VVS) and PoTS. However, this should be in relative moderation because elevating blood pressure too much is potentially harmful to several body systems, including the kidneys.

Vitamin B12 or folate-deficiency anaemia occurs when a lack of vitamin B12 or folate causes the body to produce abnormally large red blood cells that can't function properly. The resultant anaemia affects the delivery of blood to the brain, which can cause low blood pressure and syncope. The most common cause of B12 deficiency is pernicious anaemia, but others include a lack of vitamin B12 and folate in the diet, and the effects of some medications, such as anticonvulsants. 

B12 and folate deficiency can be easily treated by injections or dietary supplements, but your diet can also help if it includes meat, fish, eggs, dairy products, yeast extract (such as Marmite) and specially fortified foods (for B12). The best sources of folate include green vegetables such as broccoli, brussels sprouts, and peas. Anaemia can also be alleviated by taking iron supplements or eating red meat, poultry, or dark green leafy vegetables.

Vitamin D deficiency has been linked to the incidence of VVS,1 so eating foods rich in this vitamin could help prevent fainting, such as fortified foods, oily fish, and liver.

Wright and Thakore2, writing dietary advice for VVS patients, recommend a number of foods, including those high in fibre or with a low glycaemic index (GI), as well as salts such as potassium. They also advise drinking plenty of water to avoid dehydration and a potential drop in arterial blood pressure. Foods with a low GI release sugar at a slower rate, making you feel fuller for longer. Examples include bran or oat breakfast cereal, nuts, yoghurt, beans, fruit and vegetables, brown rice, pasta, and wholegrain bread.  

A fibre-rich diet and increased fluid intake are also advised in patients with syncope to help to avoid constipation which can worsen the instances of syncope, in some cases. Examples of high fibre foods include bran cereal, fruits, vegetables (including beans and lentils), and wholemeal foods like bread, rice, and pasta. 

Lastly, patients with PoTS and syncope treated with fludrocortisone show a decline in potassium levels. Therefore, the intake of potassium-rich foods is recommended, including bananas, avocados, dates, beans and lentils, spinach, mushrooms, melon, and dried fruits.

Foods to Eat

Some foods can help rescue you from fainting in certain circumstances, but the best dietary measures are the long term ones mentioned above.  

If feeling faint due to dehydration, the answer is to drink plenty of water or an electrolyte drink. The human body needs at least 1.2-1.5 litres (about 6-8 glasses) of water per day.

If the fainting feeling is due to hypoglycemia (low blood sugar), then a hit of simple carbohydrates, such as fruit juice, honey, or sweets will help. Be sure to follow this  with more complex (low GI) carbs such as a granola or cereal bars, some fruit like a banana, peaches, apples or grapes, or wholegrain bread. The rapid release of sugar from the simple carbs will raise your blood sugar quickly, while the slower-release, complex carbs will prevent blood sugar from rebounding downwards, better stabilising the blood sugar (see Fustany for more information).

Summary

Fainting or syncope has several causes. You can prevent some of the more common causes by making a few changes to your diet, such as increasing the intake of iron, folate, vitamins B12 and D, having plenty of sodium and potassium salts, drinking plenty of fluids, and having certain slow and fast-release carbohydrate-rich foods to hand.

References:

  1. Usalp S, Kemal H, Yüksek Ü, Yaman B, Günsel A, Edebal O, et al. Is there any link between vitamin D deficiency and vasovagal syncope? Journal of Arrhythmia 2020;36:371–6. https://doi.org/10.1002/joa3.12309
  2. Wright C.I, and Thakore E. Syncope: dietary advice to help manage the symptoms of syncope.  Integr Food Nutr Metab. 2016;3(5):436-437 https://www.oatext.com/pdf/IFNM-3-165.pdf

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Dr. Richard Stephens

Doctor of Philosophy (PhD), Physiology/Child Health
St George's, University of London


Richard has an extensive background in bioscience and bioinformatics with a PhD in membrane transport physiology and 28 years of experience in scientific publishing, bioscience research and computational biology.
On moving to Cambridge, UK, in 2015, Richard took the opportunity to broaden the application of his scientific background as well as to explore new avenues of interest. Among other things he mentored students at the Disability Resource Centre at the University of Cambridge and is currently working as an educator, pro bono for the Illuminate charity whilst further developing his writing and presentation skills.

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