Potassium in a vegetarian diet – how can you ensure an adequate intake?

In 1997, the results of the DASH study were published, showing that a diet rich in vegetables, fruit and low-fat dairy products can help lower blood pressure. This was a significant milestone in research into the importance of the overall dietary pattern, rather than any single food. The study did not allow the observed effect to be attributed to potassium alone, but it also drew attention to the minerals supplied in large quantities by plant-based foods. Potassium is particularly important in this respect.

1. Properties of potassium
2. Potassium in the diet
3. The interaction between potassium and sodium
4. FAQ – Potassium in a vegetarian diet. How can you ensure an adequate intake?

Properties of potassium

Potassium is a mineral and one of the most important electrolytes in the human body. The body does not use it as fuel, but as an ion it is necessary for maintaining the correct conditions inside and outside cells. Most potassium is found inside cells, which is necessary for maintaining the cells’ electrical properties.

Maintaining the correct balance of potassium and sodium is managed, amongst other things, by specialised proteins in cell membranes, including the sodium-potassium pump. This pump uses energy to transport ions in opposite directions and restore the conditions necessary for the cell to continue functioning. This is of particular importance in excitable tissues, such as muscles and the nervous system. Changes in the flow of ions across the membrane contribute to the generation and conduction of electrical signals, as well as to the initiation of muscle fibre contraction.

Potassium interacts with sodium in this process; therefore, both elements should be regarded as components of the same physiological system, rather than as complete opposites. According to authorised health claims, potassium contributes to the normal functioning of muscles and to the maintenance of normal blood pressure.

Potassium in the diet

On food and supplement labels in the European Union, a reference intake value (RWS) of 2,000 mg per day is used for potassium. However, this is not the same as a dietary guideline specifying an appropriate intake. The European Food Safety Authority (EFSA) has identified 3,500 mg of potassium per day as an adequate intake for adult men and women, as well as pregnant women.

In practice, a well-balanced vegetarian diet can provide plenty of potassium, as a significant proportion of its staple foods belong to groups that are naturally rich in this nutrient. Potatoes, beans, lentils, chickpeas and soya play an important role, as do tomatoes, leafy vegetables, pumpkin, avocados and fruit. Potassium is also provided by nuts, seeds and dried fruit, although the latter have a more concentrated composition and are usually consumed in smaller portions.

Vegetarians often do not need to focus particularly on increasing their potassium intake if their diet is genuinely based on a variety of minimally processed plant-based foods. Problems may arise, however, when a meat-free diet consists mainly of refined cereal products, sweets, cheese and highly processed meat substitutes.

The best plant-based sources of potassium

The interaction between potassium and sodium

Potassium and sodium are often portrayed as opposing elements, but the body needs both. The nutritional issue is not usually about eliminating salt entirely from the diet, but about maintaining a sensible intake of sodium whilst consuming adequate amounts of foods rich in potassium. The EFSA considers 2 g of sodium per day to be a safe and appropriate level for the general adult population in the European Union. This corresponds to approximately 5 g of table salt, as salt is not composed solely of sodium.

A large proportion of dietary sodium may come from bread, cheese, ready-made sauces, snacks, ready meals and other processed foods; therefore, simply limiting the salt added during cooking is not always sufficient to assess total intake. On the other hand, there is no need to regard every amount of salt as a dietary mistake.

Salt is a practical culinary ingredient, and in its iodised form it can also be a source of iodine. This is particularly important in a vegetarian diet, as the iodine content of non-animal products is not high. According to an authorised health claim, iodine contributes to the normal production of thyroid hormones and the normal functioning of the thyroid gland.

"A well-planned vegetarian diet usually provides sufficient amounts of potassium without the need for supplementation. A varied intake of plant-based foods is crucial, as vegetables, fruit, pulses and nuts are its most important natural sources. Potassium helps the muscles and the nervous system to function properly and helps maintain normal blood pressure; however, supplementation should not replace a balanced diet." Łukasz Domeracki – Dietitian

FAQ – Potassium in a vegetarian diet. How can you ensure an adequate intake?

Does a vegetarian diet provide enough potassium?

In most cases, yes. A well-balanced vegetarian diet, based on vegetables, fruit, pulses, potatoes, nuts and seeds, usually provides ample amounts of potassium. Problems may arise when the diet consists mainly of highly processed foods.

Are bananas the best source of potassium?

This is a common myth. Bananas do contain potassium, but dried apricots, pumpkin seeds, pistachios, beans, lentils, potatoes, tomatoes and spinach, amongst others, provide significantly more of this mineral.

Does cooking reduce the potassium content in vegetables?

Yes. Potassium is highly soluble in water, so some of it leaches into the cooking liquid during cooking. If the cooking liquid is discarded, the amount of potassium in the food will be lower. For this reason, soups and dishes prepared with the cooking liquid help to retain more of this nutrient.

Should vegetarians take potassium supplements?

In healthy people, there is usually no need to do so. The easiest way to ensure an adequate intake of potassium is through one’s daily diet. Supplementation should only be considered in justified cases and, ideally, after consulting a doctor or dietitian.

Does potassium lower blood pressure?

According to a health claim approved by the EFSA, potassium helps maintain normal blood pressure. However, this does not mean that potassium supplementation cures high blood pressure or replaces medication.

Why should potassium and sodium be discussed together?

Both elements work together to maintain water and electrolyte balance and the proper functioning of nerve and muscle cells. In practice, maintaining the right balance between sodium and potassium intake is more important than completely eliminating salt.

Sources:

• Filippini, T., Naska, A., Kasdagli, M. I., Torres, D., Lopes, C., Carvalho, C., Moreira, P., Malavolti, M., Orsini, N., Whelton, P. K., & Vinceti, M. (2020). Potassium Intake and Blood Pressure: A Dose-Response Meta-Analysis of Randomized Controlled Trials. Journal of the American Heart Association, 9(12), e015719. https://doi.org/10.1161/JAHA.119.015719
• Joshi, S., Hashmi, S., Shah, S., & Kalantar-Zadeh, K. (2020). Plant-based diets for prevention and management of chronic kidney disease. Current opinion in nephrology and hypertension, 29(1), 16–21. https://doi.org/10.1097/MNH.0000000000000574
• Perez, V., & Chang, E. T. (2014). Sodium-to-potassium ratio and blood pressure, hypertension, and related factors. Advances in nutrition (Bethesda, Md.), 5(6), 712–741. https://doi.org/10.3945/an.114.006783