Oxalic acid (oxalat) is a natural substance found in many vegetables, fruits and cereals. When oxalate is absorbed, it can combine with calcium to form calcium oxalate, the most common component of kidney stones.
Medical studies show that increased oxalate levels in urine are one of the factors that increase "hypersaturation" and promote the formation of calculus crystals. Therefore, reducing oxalate in the diet is sometimes recommended for people who have had kidney stones, especially calcium oxalate stones.
Tomatoes are a familiar food, rich in vitamin C, lycopene and minerals such as potassium, nutrients that are beneficial for overall health. However, for people with kidney stones, especially calcium oxalate stones, there are some scientific reasons why they need to limit eating tomatoes or eat them cautiously:
Oxalate in food, both from tomatoes and many other vegetables, when absorbed into the body can increase the amount of oxalate in urine, thereby promoting the crystallization of calcium oxalate, especially when hydration is not sufficient or if the amount of calcium in the intestines is low.
Therefore, in a diet that reduces the risk of stones, limiting oxalate-rich foods or eating them with optimal absorption is considered.
A nutritional principle supported by many experts is to combine oxalate-rich foods with calcium sources from foods (such as milk, yogurt) so that calcium binds to oxalate in the intestines instead of into the urine. This helps reduce oxalate absorption into the blood and kidneys.
Because oxalate in tomatoes can contribute to increasing oxalate levels in urine, the abuse of tomatoes, especially concentrated forms such as tomato sauce or juice, can increase the risk of gravel recurrence. This is often personalized based on urine tests.
Eating too many tomatoes every day can accumulate oxalate beyond the necessary level, especially for people with "super oxalate absorption" - a group of people who absorb oxalate more strongly than normal.
Concentrated tomato products (such as sauces, juices) may concentrate oxalate more than fresh tomatoes.
