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Potassium

Key points about potassium

Potassium is a naturally occurring mineral that's found in a wide range of foods including vegetables, fruit, grains, dairy products, meat and legumes.
Your body needs potassium for almost everything it does, including making sure your nerves, muscles and heart work properly.

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Potassium is a mineral that's important for the working of your heart, kidneys, liver, muscles and nerves. Getting enough potassium helps to maintain normal blood pressure and can also help lower your risk of heart disease and stroke.

The amount of potassium you need depends on your age, sex and any medical conditions you may have. It can also be affected by the amount of physical activity you do, your use of certain medicines and your intake of sodium (salt). You should be able to get all the potassium you need by eating a varied and balanced diet.

Your kidneys help to control the level of potassium in your blood. Potassium that's not needed by your body is usually passed out in your urine. Low or high potassium is more common in older people and those with other conditions, eg, kidney problems or heart failure.

Too much potassium

People with kidney problems often have high potassium levels as their kidneys are unable to remove potassium from the body. Some medicines can cause your body to hold on to potassium, eg, ACE inhibitors, spironolactone or angiotensin receptor blockers. Too much potassium can cause stomach pain, feeling sick and diarrhoea (runny poo). A high level of potassium can be dangerous, as it can affect your muscles and heart.

Too little potassium

Some conditions may lower your potassium levels, eg, ongoing diarrhoea and vomiting, inflammatory bowel disease and medicines including diuretics (water pills), corticosteroids or excessive use of laxatives. Too little potassium can make you feel tired or nauseous (sick). If your potassium levels are low for a long time, this can cause high blood pressure, breathing problems or can cause your heart to beat irregularly.

	Foods and drinks containing higher levels of potassium (more than 200 mg per serve)	Foods and drinks containing lower levels of potassium
Fruit	1/2 avocado 1 banana, orange, peach, nectarine or kiwifruit 1/4 cup dried fruit (eg, raisins, sultanas, apricots, prunes)	1 apple, pear, lemon or mandarin 1/2 cup canned fruit (peach, pear, pineapple, fruit salad).
Vegetables	1/2 cup cooked kale, silverbeet, brussel sprouts, beetroot, pumpkin 1 cup spinach, taro leaves 1 medium cooked potato or similar sized kūmara, taro, cassava, yam, green banana 100 g potato fries or wedges	1/2 cup cooked cabbage, peas, cauliflower, carrot, broccoli, eggplant 1/2 cup canned beetroot 1/2 cup raw carrot, onion, green capsicum, cucumber 1 cup lettuce 1 tomato, 1 tablespoon tomato paste
Grain foods	Whole grains (eg, 2 slices of whole grain bread, 1 cup rolled oats, brown rice or quinoa) 1 cup almond flour, coconut flour, wholemeal flour 1 cup breakfast cereals or muesli containing dried fruits, bran or nuts 3/4 cup cooked porridge made with milk	1 cup rice, pasta, couscous, semolina, noodles, rice noodles 1 white pita bread, wrap or bread roll 2 slices white bread 1 cup puffed rice cereal or cornflakes 2 wheat biscuits 3/4 cup cooked porridge made with water
Legumes, nuts, seeds, fish, chicken and meat	1 cup cooked or canned legumes (eg, red kidney beans, chickpeas, lentils, black beans, baked beans) 1/2 cup cooked edamame (soy bean) 130 g cooked pork, chicken, red meat 1 handful (30 g) Brazil nuts, almonds, cashews	1/2 cup cooked tofu 2 eggs 50 g canned corn beef 1 tablespoon tahini, peanut butter 1 tablespoon sesame seeds, pumpkin seeds, sunflower seeds
Dairy and plant-based alternatives	1 cup cow's milk 150 g yoghurt 1 cup coconut milk, soy milk 150 g coconut yoghurt	1 slice of cheese 1 tablespoon sour cream, cottage cheese or milk powder 1 teaspoon butter 1 scoop ice cream 1 cup rice milk, oat milk, almond milk
Snacks	30 g potato chips 1 muesli bar with dried fruit or nuts	20 g popcorn, corn chips 6–10 rice crackers or plain crackers (20 g)
Fluids	1 cup fruit and vegetable juices	1 cup cordial, soft drinks 1 cup tea or coffee (no milk).
Other	1/4 teaspoon low sodium salt substitutes (see below) 2 teaspoons Marmite/Vegemite

Low sodium salt substitutes

Some salts contain less sodium and more potassium than table salt and are referred to as 'salt substitutes'. There are a handful of products currently available. These products contain large amounts of potassium and shouldn't be used by people with kidney disease or renal failure. Ask your healthcare provider about whether these products are suitable for you.

The adequate intake (AI) is the recommended average daily intake of a nutrient and is used when there isn't enough information to determine the recommended dietary intake (RDI). Here is the adequate intake of potassium for people of different age groups:

Babies (0–6 months): 400 mg
Babies (7–12 months): 700 mg
Children (1–3 years): 2,000 mg
Children (4–8 years): 2,300 mg
Boys (9–13 years): 3,000 mg
Girls (9–13 years): 2,500 mg
Boys (14–18 years): 3,600 mg
Girls (14–18 years): 2,600 mg
Adult men (19+ years of age): 3,500 mg
Adult women (19+ years of age): 2,800 mg

Image credit: Canva

Testing

Potassium levels can be tested with a blood test.

If the results of a blood test show that you have too much or too little potassium in your body, your healthcare provider might advise you to make changes to your diet.

A varied and balanced diet should provide you with the potassium you need, but you may be prescribed a potassium supplement if you can't get enough potassium from your diet. It’s important that you only take a potassium supplement if advised by your doctor or pharmacist.

Too much potassium in your blood is known as hyperkalaemia and can be life-threatening.

Some dietary supplements contain potassium as an ingredient and may increase the risk of hyperkalaemia. Herbal ingredients that contain potassium include stinging nettle, evening primrose, turmeric and dandelion. Always talk to your doctor or pharmacist before you start any kind of supplement that has potassium as an ingredient or herbal ingredients, especially if you're at increased risk of hyperkalaemia.

If you've been advised to make changes to your diet, it may be harder to eat a well-balanced and varied diet. If you have concerns about the quality of your diet, talk to your healthcare provider to see whether a referral to a dietitian is possible.

Potassium chloride
Sodium

The following links provide further information on potassium. Be aware that websites from other countries may contain information that differs from New Zealand recommendations.

Potassium(external link) Kidney Health NZ