Low dietary K levels have been associated with increasing renal Ca excretion in humans, indicating a higher risk of calcium oxalate (CaOx) urolith formation. Therefore, the present study aimed to investigate whether dietary K also affects the urine composition of cats. A total of eight adult cats were fed diets containing 0·31 % native K and 0·50, 0·75 and 1·00 % K from KCl or KHCO3 and were evaluated for the effects of dietary K. High dietary K levels were found to elevate urinary K concentrations (P< 0·001). Renal Ca excretion was higher in cats fed the KCl diets than in those fed the KHCO3 diets (P= 0·026), while urinary oxalate concentrations were generally lower in cats fed the KCl diets and only dependent on dietary K levels in cats fed the KHCO3 diets (P< 0·05). Fasting urine pH increased with higher dietary K levels (P= 0·022), reaching values of 6·38 (1·00 % KCl) and 7·65 (1·00 % KHCO3). K retention was markedly negative after feeding the cats with the basal diet ( − 197 mg/d) and the 0·50 % KCl diet ( − 131 mg/d), while the cats tended to maintain their balance on being fed the highest-KCl diet ( − 23·3 mg/d). In contrast, K from KHCO3 was more efficiently retained (P= 0·018), with K retention being between − 82·5 and 52·5 mg/d. In conclusion, the dietary inclusion of KHCO3 instead of KCl as K source could be beneficial for the prevention of CaOx urolith formation in cats, since there is an association between a lower renal Ca excretion and a generally higher urine pH. The utilisation of K is distinctly influenced by the K salt, which may be especially practically relevant when using diets with low K levels.

Evidence exists that a more acidic diet is detrimental to bone health. Although more precise methods exist for measurement of acid–base balance, urine pH reflects acid–base balance and is readily measurable but has not been related to habitual dietary intake in general populations. The present study investigated the relationship between urine pH and dietary acid–base load (potential renal acid load; PRAL) and its contributory food groups (fruit and vegetables, meats, cereal and dairy foods). There were 22 034 men and women aged 39–78 years living in Norfolk (UK) with casual urine samples and dietary intakes from the European Prospective Investigation into Cancer and Nutrition (EPIC)-Norfolk FFQ. A sub-study (n 363) compared pH in casual samples and 24 h urine and intakes from a 7 d diary and the FFQ. A more alkaline diet (low PRAL), high fruit and vegetable intake and lower consumption of meat was significantly associated with a more alkaline urine pH before and after adjustment for age, BMI, physical activity and smoking habit and also after excluding for urinary protein, glucose, ketones, diagnosed high blood pressure and diuretic medication. In the sub-study the strongest relationship was found between the 24 h urine and the 7 d diary. In conclusion, a more alkaline diet, higher fruit and vegetable and lower meat intake were related to more alkaline urine with a magnitude similar to intervention studies. As urine pH relates to dietary acid–base load its use to monitor change in consumption of fruit and vegetables, in individuals, warrants further investigation.