Potassium is needed in the body for the normal functioning of nerves and muscles. Low potassium levels can lead to muscle weakness and problems with the heart rhythm. High potassium levels can also lead to dangerous heart rhythms.
High and low potassium
Having low levels of potassium in the blood is known as hypokalaemia. It can occur:
- As a side-effect of medication, especially 'water' tablets (diuretics).
- If you lose a lot of fluid in diarrhoea and through being sick (vomiting).
- With excessive sweating - for example, in very hot countries.
- If you have anorexia nervosa (this is due to a combination of being sick and taking too many laxatives).
- If you eat too much licorice or take high doses of licorice-containing herbal medicines.
Low levels of potassium can make you tired and give you high blood pressure. Very low levels can give you muscle weakness, swelling (oedema) and dangerous heart rhythms.
High potassium in the blood is known as hyperkalaemia. It can be caused by:
- Sudden injury to the kidneys.
- Severe chronic kidney disease.
- Some medications - most commonly angiotensin-converting enzyme (ACE) inhibitors.
If you need to follow a low-potassium diet because of kidney problems, you should be referred to a specialist dietician who will be able to advise you.
But for most people, eating foods which are rich in potassium will be part of a healthy diet. High potassium intake helps to reduce blood pressure, which in turn reduces the risk of strokes and heart attacks.
The World Health Organization recommends that adults should eat at least 3510 mg of potassium daily. However, a recent study looking at potassium intake and stroke risk found that very few people met that target.
Which foods contain potassium?
Potassium is present in many different foods, particularly in fruit and vegetables. Therefore, making sure that you have at least five portions of fruit and vegetables daily is very important.
Processed foods tend to contain lower levels of potassium. For example, wholemeal bread and brown rice have higher levels or potassium than their white equivalents.
Low-sodium salt is made from potassium and using it instead of salt will increase your potassium intake. However, it is probably healthier to get used to things tasting less salty than to replace salt with this alternative.
Foods which are particularly rich in potassium
Some vegetables which contain high levels of potassium are:
- Medium baked potato (skin on) 925 mg.
- Medium baked sweet potato (skin on) 450 mg.
- Medium raw tomato 290 mg.
- Half an avocado 490 mg.
Dark green leafy vegetables are also rich in potassium.
Fruits which contain high levels of potassium include:
- Medium banana 425 mg.
- ¼ cup of raisins 270 mg.
- Small orange 240 mg.
- Medium pear 200 mg.
Many more unusual and tropical fruits are also rich in potassium, such as mango, papaya, kiwi and melon.
Protein foods which contain high levels of potassium include:
- Salmon (80 g portion) 534 mg.
- ½ cup of lentils 365 mg.
- Turkey (80 g portion) 250 mg.
- 2 tablespoons peanut butter 210 mg.
Other pulses and beans are also good sources of potassium.
Dairy foods rich in potassium:
- Small pot of yoghurt 350 mg.
- 1 cup of milk 360 mg.
These are just examples of potassium-rich foods but most fresh foods contain quite high levels of potassium. So a normal healthy diet containing a variety of fruit, vegetables and other fresh foods will provide a good quantity of potassium for most people.
Further reading and references
WHO guidance on dietary salt and potassium; World Health Organization
Vinceti M, Filippini T, Crippa A, et al; Meta-Analysis of Potassium Intake and the Risk of Stroke. J Am Heart Assoc. 2016 Oct 65(10). pii: JAHA.116.004210. doi: 10.1161/JAHA.116.004210.
Omar HR, Komarova I, El-Ghonemi M, et al; Licorice abuse: time to send a warning message. Ther Adv Endocrinol Metab. 2012 Aug3(4):125-38. doi: 10.1177/2042018812454322.
Strohm D, Ellinger S, Leschik-Bonnet E, et al; Revised Reference Values for Potassium Intake. Ann Nutr Metab. 201771(1-2):118-124. doi: 10.1159/000479705. Epub 2017 Aug 11.
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