Tomatoes are easily one of the most popular vegetables (fruits) across cultures and cuisines. Whether you’re popping them into curries, whipping up salads, boiling up broths or hearty stews, these recipes just wouldn’t be the same without tomatoes. A rich source of antioxidants, vitamins, minerals, and fiber, tomatoes bring a lovely fresh, tangy, and savory note to food. However, as amazing as they are, tomatoes and their seeds, specifically, are believed to cause kidney stones. But are these refreshing fruits really to be blamed?
Kidney Stones Are Mineral And Acid Salt Deposits
Kidney stones are hard deposits of minerals, oxalates, calcium, and uric acid in the kidneys, formed through a process called precipitation. These stones do not develop overnight. Accumulating over months and sometimes years, tiny crystals build up to become bigger, more detectable stones. They sometimes lodge themselves in your urinary tract, obstructing the flow of urine and causing pain. This pain can be excruciating and is often compared to that of childbirth! People who are prone to stones tend to quickly go “off balance” and form stones repeatedly.1
Specific Foods Aren’t Linked To Kidney Stones
While many of us are told to avoid tomato seeds because they bring on kidney stones, the scientific community doesn’t necessarily agree. According to the National Institute of Diabetes and Digestive and Kidney Diseases, consuming specific foods is not linked to stone formation in otherwise healthy individuals who are not susceptible or considered “at risk” of kidney stone formation.2
But what of those who are considered high risk – say, those who are obese, have diabetes, or high blood pressure?3 Does oxalate intake impact stone formation at all?
According to one view, consuming foods high in oxalates can contribute to kidney stone formation in those prone to problems of the kidney. In fact, recent research points out that half the cases of kidney stones have major dietary associations. Excess oxalates in the urine harden and precipitate to actively form kidney stones that cause extreme pain and discomfort. Researchers say that a subpopulation of “hyperabsorbers” whose bodies absorb more oxalate from food than others are especially prone to stone formation due to high consumption of oxalates.4
Tomatoes Can Lower Kidney Stone Risk
The University of Pittsburgh claims that a diet that keeps oxalate intake at under 40–50 mg each day is safe enough to help you avoid kidney stone formation.5 Although tomato seeds do contain oxalates, the levels are not high enough to contribute to kidney stones, with just 5.3 mg of oxalates per 100 g of tomatoes. What’s more, oxalate absorption rates from tomato seeds are lower than from other foods. Interestingly, some studies even suggest that consuming tomatoes could actually lower your risk of developing kidney stones. In short, if you don’t have a history of kidney problems, eating tomatoes raw or cooked should not cause you any kind of urinary problems or kidney stones.6
But Avoid Tomatoes If You Have A History Of Kidney Stones
However, if you’ve had a history of developing kidney stones, things shift a bit as your threshold for developing stones is lower than for other people. This is because your body is unable to strike the balance needed to maintain oxalates in a liquid state. This increases the risk of stone formation. You may therefore want to lay off eating too many tomatoes as the oxalate intake from tomatoes and their seeds, along with other foods rich in oxalate, may increase your risk.7
Tomatoes may have got more than their fair share of bad press, but for those with a history of kidney problems and kidney stones in particular, there is a longer list of foods to avoid or limit. This includes things like spinach, nuts, beetroot, chocolate, tea, soy, and parsley.8 It is also vital you keep your fluid intake to over 2 liters if you’re prone to developing stones, regardless of what you’re eating.9
The Potassium In Tomatoes Can Worsen Your Kidney Problem
Most people with a disorder of the kidneys have a problem regulating mineral levels, especially of potassium, in the blood. An abnormally high amount of blood potassium creates complications like an irregular heart beat and might even result in a heart attack. Since tomatoes are high in potassium content, they are usually avoided by those with kidney disease to keep potassium levels to the minimum.10 For everyone else, tomatoes are a great source of nutrition and eating them as part of a complete balanced diet is as good an idea as any.
|↑1||Longo DL, Fauci AS, Kasper DL, Hauser SL, Jameson J, Loscalzo J. eds. Renal calculi. Harrison’s Principles of Internal Medicine, 18e. New York, NY: McGraw-Hill; 2012.|
|↑2||Kidney Stones in Adults. National Institute of Diabetes and Digestive and Kidney Diseases.|
|↑3||Kidney Stones. National Kidney Foundation.|
|↑4||Massey, L. K. Dietary influences on urinary oxalate and risk of kidney stones. Frontiers in Bioscience. 2003.8(6), s584-594.|
|↑5, ↑7||Low Oxalate Diet. University of Pittsburgh.|
|↑6||Paswan, S. (2012). Tomato: A Natural Medicine and it’s Health Benefits. Journal of Pharmacognosy and Phytochemistry, 1(1), 9.|
|↑8||Ingelfinger, J. R.. Diet and Kidney Stones. New England Journal of Medicine, 2002.346(2), 74-76.|
|↑9||Diet for Kidney Stone Prevention. National Institute for Diabetes, Digestive and Kidney Diseases.|
|↑10||Frasetto L, Kohlstadt I. Treatment and prevention of kidneys tones: an update. Am Fam Physician. 2011 Dec 1;84(11):1234-1242.|