Nocturia linked to high salt intake

Patients with nocturia may benefit from cutting some salt out of their diet, a Japanese study finds

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Most people over 60 get up during the night to urinate at least once. There are many causes for nocturia but doctors may be ignoring a simple contributing factor: salt intake.

Urologists generally do not recommend reducing salt intake as a treatment for nocturia. “It’s one of those things where I guess most people haven’t really thought about it,” Associate Professor Peter Chin, an urologist at Wollongong Hospital, said.

But salt could be playing a significant role in night-time urination, a preliminary study presented at the European Association of Urology showed.

Japanese researchers recruited around 300 individuals in their 60s who had a high salt intake and problems sleeping. They gave study participants guidance and support to help them reduce their salt consumption over 12 weeks.

Roughly 200 patients successfully cut back on the salt in their diet, dropping their estimated daily salt intake from 11g to 8g. At the start of the study, these patients were waking up on average 2.3 times a night to urinate.

After reducing their salt intake, they only urinated 1.4 times on average. By comparison, the participants who raised their salt intake over the study period (from 10g to 11g per day), experienced a slight increase in night-time urination.

“A simple dietary modification might significantly improve the quality of life for many people,”lead researcher Dr Matsuo Tomohiro, from Nagasaki University, said.

Professor Chin said the relationship between nocturia and salt made sense. Salt also contributed to hypertension, which increased blood flow through the kidneys.

“The more that the blood is filtered and the more urine you produce,” Professor Chin said.

“So there certainly a good physiological explanation as to why a high intake of salt can make you go to the toilet more.”

role of salt in nocturia could be important, particularly given the prevalence of fast foods and processed foods, Professor Chin said.

Most Australians consume more than the recommended salt intake of 1.15g to 2.3g, set by the National Health and Medical Research Council.

However, noturia had many causes and salt was only one, Professor Chin said.

Other causes included psychological factors, sleep apnoea, irritation of the bladder during menopause, and enlarged prostate glands obstructing the bladder.

The most common causes of nocturia were consumption of caffeine and alcohol.

“Caffeine does two things. It’s a diuretic so it makes you produce more urine and it also irritates your bladder,” Professor Chin said.

“Not only are you making more urine at night, you can’t hold it, so you have to go more often.”