Study: urinary acidity can affect how many UTIs you get

A research project looked into how well bacteria are able to grow in the urinary tract in different pH environments – more acid or more alkaline – and in the presence of small molecules that are passed through our system from food.

This research was to see how we could adjust our treatments of urinary tract infections (UTIs), a common source of grief amongst women and some men.

Turns out the acidity of our urine and what we eat matters when it comes to how well bacteria grow in the urinary tract. Urinary tract infections are typically (80 per cent of the time) caused by Escherichia coli (E. coli), with antibiotics the first line of defence.

Antibiotic resistance is now a major cause for concern, with bacteria finding new and novel ways to evade antibiotics, rendering them useless.

The study

The researchers cultured E. coli in urine samples from people without urinary tract infections to look at immune proteins that limit bacterial growth. The samples could be divided into two by their ability to restrict or allow bacteria to grow

Findings of the study

Urine that prevents bacterial growth has more of a key protein, a protein the body naturally makes as a result of infection, compared with the urine that allows bacteria to grow.

The protein? Siderocalin. This protein is thought to operate by depriving the bacteria of iron – a necessary component of bacteria growth. The researchers then asked what was associated with the differences in the efficacy of siderocalin.

Age and sex – nope. pH? Yes. If the urine was acidic or alkaline mattered the most in whether this protein was effective at allowing or disallowing bacterial growth.

Except it wasn’t urine that was either acidic or basic that was the clincher – it was urine that was more neutral, nearer to the pH of pure water. This allowed the siderocalin to better restrict bacterial growth than more acidic samples did.

The researchers could encourage or discourage bacterial growth by changing its pH. This means you could adjust your urinary acidity to help kill off the bacteria using your own proteins.

But that’s not all

Diet turned out to be another contributor, since from the diet, tiny molecules called aromatics are passed through to the urine. These aromatics also affect how easily or not bacteria are able to proliferate.

Urine with more aromatic compounds had less bacterial growth, compared with urine with fewer aromatic molecules, which allowed more bacteria to proliferate.

Aromatics, interestingly, are not produced by us, but by our gut bacteria and possibly certain foods. (Many bacteria in our gut actually help us to digest food.)

Cranberries, for example, have long been used for urinary tract infections, but results of studies have been mixed. This could be because you need certain bacteria in the gut for cranberry to work.

Cranberry extract or juice might be more effective when combined with another pH increasing strategy (to make urine less acidic/more alkaline). The researchers postulate that some of the aromatics are actually good iron binders, which reduces the ability of the bacteria to survive.

No iron, no bacteria. E. coli, for example, makes a bacteriocin called enterobactin that binds very well with iron, robbing your digestive system (and you) of your iron supplies.

This is one of the reasons why some people with chronic gut dysbiosis or other infections may end up iron-deficiency anaemia, or ‘anaemic for no reason’.


Shields-Cutler RR, Crowley JR, Hung CS, Stapleton AE, Aldrich CC, Marschall J, Henderson JP. Human urinary composition controls siderocalin’s antibacterial activity. The Journal of Biological Chemistry. June 26, 2015

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Jessica Lloyd - Vulvovaginal Specialist Naturopathic Practitioner, BHSc(N)

Jessica is a degree-qualified naturopath (BHSc) specialising in vulvovaginal health and disease, based in Melbourne, Australia.

Jessica is the owner and lead naturopath of My Vagina, and is a member of the:

  • International Society for the Study of Vulvovaginal Disease (ISSVD)
  • International Society for the Study of Women's Sexual Health (ISSWSH)
  • National Vulvodynia Association (NVA) Australia
  • New Zealand Vulvovaginal Society (ANZVS)
  • Australian Traditional Medicine Society (ATMS)