Why fish can give you kidney stones

IN 1979, scientists reported a striking relationship between the prevalence of kidney stones since the Fifties and increasing consumption of animal protein.

To test it, they asked subjects to add extra animal protein to their daily diets, the equivalent of about an extra tin’s worth of tuna fish.

Within two days, their levels of stone-forming compounds — calcium, oxalate and uric acid — shot up, raising the subjects’ kidney stone risk by 250%.

In 2014, researchers at Oxford University found vegetarians had a lower risk of going into hospital for kidney stones — and the more meat people ate, the higher the risk was.

For years, doctors assumed that because the stones are made of calcium, they should advise patients to reduce their calcium intake.

This changed with a landmark study, which found that eating less meat and salt was about twice as effective as the conventional low-calcium diet, halving kidney stone risk.

Reducing animal protein intake also lowers uric acid build-up, which can form crystals that seed calcium stones or form stones all by itself.

Removing all meat from a standard Western diet appears to reduce the risk of uric acid crystallisation by more than 90% within days.

When urine is more alkaline, stones are less likely to form.

The standard Western diet yields acidic urine. When people are put on a plant-based diet, however, their urine can be alkalinised to a near neutral pH in less than a week.

The single most acid-producing food is fish, followed by pork, poultry, cheese, eggs and beef. Bread and rice can be a little acid-forming, but not pasta.

Beans are acid-reducing, but not as much as fruit is, and vegetables are the most alkaline-forming of foods.

Diet changes can even cure kidney stones without drugs or surgery.

Studies show that uric acid stones can apparently be dissolved away by eating more fruit and veg, restricting animal protein and salt intake, and drinking at least ten glasses of fluid a day.

Furthermore, an acid-forming diet can produce a chronic condition of excess acid in the bloodstream that is thought to contribute to muscle breakdown as you age.

So, how can you determine how acid-forming your diet is? Why not use what you (should) have in your refrigerator: purple cabbage.

Boil some purple cabbage until the water turns deep purple. Pee into your toilet, then take your purple-cabbage cocktail and pour it into the toilet bowl.

If the liquid there remains purple or, even worse, turns pink, your urine is too acidic. Blue liquid is the target you’re seeking — it means your urine is not acidic.