Does potassium lower blood pressure?

What is potassium?

Potassium is an essential nutrient that is naturally abundant in many foods and supplements. Moreover, potassium is found in all of our bodily tissues and is crucial for normal cell function. In fact, along with sodium, it plays an important role in maintaining and regulating extracellular fluid volume (i.e. the fluid outside of cells) and plasma volume. 

Our kidneys control potassium excretion in our bodies in response to dietary intake of this nutrient. In fact, in healthy people, potassium excretion occurs rapidly through urine after having consumed potassium. However, one exception is if body stores are depleted, in which case the body holds on to potassium to make use of it. 

In healthy individuals with normal kidney function, abnormally low or high levels of potassium are very rare. However, conditions such as diarrhoea, kidney disease and vomiting can alter the potassium balance in our body and lead to either hypokalemia (low potassium) or hyperkalemia (high potassium).

Sources of potassium

Potassium is abundant in many different foods and beverages. Fruits and vegetables are some of the best sources of potassium, and some legumes such as soybeans are also great sources. Dried apricots, lentils and prunes are some of the richest plant sources of potassium. Furthermore, whole wheat varieties of breads and cereals contain higher potassium levels compared to their refined counterparts. Amongst animal sources, meat, fish, dairy products and poultry also contain potassium. 

In most western eating patterns, the top contributors of potassium in the diet are potatoes, milk, tea and coffee. Unlike for some other nutrients, our body absorbs most of the potassium we ingest. In fact, our body absorbs up to 90% of the potassium we consume through foods and beverages. 

Nowadays, many multivitamins and supplements contain potassium. However, most supplements only provide small amounts of potassium (about 99mg) per serving. Considering that the recommended daily allowance (RDA) for adults is 3500mg, potassium supplements do not significantly  contribute much to the diet.  

How do I know if I’m getting enough potassium?

The WHO has recorded that the world’s population overall consumes too much sodium and not enough potassium. In fact, a study conducted cross-nationally observed the intakes of sodium and potassium of four populations and compared them to recommended intakes for both nutrients. The results were astounding and it was found that the percentage of the population meeting their target sodium-potassium goals was 0.3%, 0.15%, 0.5% and 0.1% respectively in the USA, Mexico, France and UK. In fact, this is a global public health concern because of the health consequences associated with insufficient potassium intake and high sodium, namely cardiovascular disease.(1)

Not only is an inadequate diet the cause for low potassium intake, some population subgroups are more likely than others to struggle with adequate potassium consumption. For example, people with inflammatory bowel disease such as Crohn's disease have impaired intestinal absorption and may not absorb potassium adequately. Moreover, certain medications such as laxatives or diuretics can dramatically alter our body’s potassium levels. In addition, heavy sweating, vomiting, diarrhoea and dialysis can all contribute to low potassium levels, ultimately leading to hypokalemia. Some symptoms of hypokalemia include constipation, fatigue, muscle weakness and general malaise. 

Overall, ensuring that you eat a varied diet full of fruit, vegetables and whole grains is one of the top ways to ensure that you are meeting your potassium requirements. There is no need for supplementation in healthy individuals unless you have been recommended to do so by your doctor for a specific medical condition. 

What about high blood pressure?

It is a well known fact that high blood pressure is a major risk factor for coronary heart disease and stroke. Sadly this is a growing concern amongst the population and it has become a common occurrence in many individuals. There are many factors that can lead to high blood pressure including a diet high in salt, excess alcohol consumption, stress, a lack of physical activity and being overweight or obese. 

However, a sometimes overlooked cause of high blood pressure is a low potassium intake in the diet. This is especially the case if low potassium is accompanied by excess salt consumption. In fact, as previously mentioned, potassium and salt are tightly regulated in the body and when one of the two is out of balance, it directly impacts the other. 

Potassium does lower blood pressure 

Western diets have caused a decreased potassium intake due to a reduced consumption of fruits and vegetables. In parallel, this goes hand in hand with a significant increase in sodium consumption due to the increasing prevalence of ultra- processed foods. Potatoes are a high source of dietary potassium, however these are often accompanied by high levels of salt. Moreover, low potassium-to-sodium intake ratios are more strongly linked to the risk of heart disease compared to either of the two nutrients alone. In other words, it seems that simultaneously increasing potassium intake and lowering sodium intake would benefit most people.(2)

Several experimental and clinical studies have found that potassium is a crucial regulator of blood pressure. Moreover, surveys conducted around the world demonstrate that populations consuming low potassium diets have a higher prevalence of hypertension. A study in people with normal blood pressure who consumed normal amounts of sodium found that a short term decrease in potassium intake significantly increased average blood pressure. 

Moreover, In potassium-depleted individuals, a significant increase in sodium intake increased blood pressure. However, higher sodium intake did not impact blood pressure in individuals consuming adequate amounts of potassium.Other studies have shown that short-term potassium insufficiency also increases blood pressure in people with hypertension.  

Overall it seems that potassium intake is essential in regulating blood pressure in both normotensive and hypertensive individuals.(3)

Interestingly, although high blood pressure is typically dealt with in adulthood and later life, identifying risk factors in early life may be beneficial in the prevention of cardiovascular disease. 

And prevention can start as early as childhood

A 10-year prospective cohort study in young girls aged 9 to 10 years looked at the effects of dietary sodium and potassium intake on adolescent blood pressure. Mean blood pressure was taken throughout adolescence and at the end of the study period, when participants were aged between 17 and 21 years. Overall, the researchers found that higher levels of sodium did not have any adverse effects on blood pressure. However, on the contrary higher potassium intakes were inversely associated with blood pressure. In fact, potassium intake had beneficial effects on blood pressure. 

Overall, consumption of potassium rich foods during childhood can help to counteract high blood pressure in adolescence.(4)

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