The WHO report is based on clinical evidence from a systematic review of 26 randomised controlled trials (RCTs) (from 1986-2021.)(1) After examining all the evidence and weighing up the risks versus benefits, WHO concluded the following recommendations:(5)

• Salt manufacturers around the world should change to producing and marketing LSSS.

• Government policies are required to promote LSSS and discourage regular salt use.

• People should be encouraged to cook, season and preserve foods using LSSS over regular salt.

The WHO recommendations apply to ‘discretionary’ salt, which is the salt people add to their food or in cooking.(2) However, LSSS are increasingly being used in processed foods, providing a further source of dietary potassium in the form of potassium additives.(1) This raises the concern regarding potassium intake, which may have harmful effects for those with kidney impairment.(9,10)

CONCERNS RAISED ABOUT LSSS

People with kidney impairment are not able to excrete potassium normally, and high intakes of potassium can lead to hyperkalaemia, in turn causing cardiac arrhythmia and cardiac arrest if untreated.(9,10)

WHO acknowledges the hyperkaliaemic risks of LSSS: “…settings where a considerable proportion of the population may have undiagnosed kidney disease for which it would not be advisable to increase potassium intakes”.(1)

WHO points out, though, that few of the studies included actually reported on hyperkalaemia and the studies that did were variable in quality.(1) Some studies reported that using LSSS instead of regular salt led to a “mean increase of 0.12 mmol/L in the level of potassium in the blood (moderate certainty evidence.)” Although a small increase, this is potentially harmful for some people.(1)

WHO also agree that there is “uncertainty about the balance between the benefits and potential harms” and I agree with this.(1) Although LSSS are not being recommended to those with impaired kidney function, those with hypertension, CVD and diabetes may well have undiagnosed kidney impairment and high intake of potassium from LSSS and processed foods with added potassium is a more significant risk.(6,9,10)

Additional risk is present from some medications that increase potassium levels, including angiotensin-converting enzyme inhibitors (ACEs), angiotensin 2 receptor blockers (ARBs) and spironolactone.(9,10)

It is questionable whether the results of the larger studies apply to the UK, as diet and lifestyle in rural China are different to other countries.5 Also, the study participants included were those with a previous history of stroke or people 60 years or over with already poorly-controlled high blood pressure.(5)

As well as CKD, WHO’s guidance does not extend to children and pregnant women, as currently, there is not enough data to recommend LSSS for these groups.(1)

Another factor to consider is cost. LSSS are more expensive than regular salt, and this could affect the public’s willingness to switch over to them.(1)