Cooking Spinach/Cabbage and tomato together causes Kidney stones, Is that true?

There is a rumor in South Asia especially in India that cooking spinach and tomato together causes kidney stones.

Is this rumor true?, the answer to this question is partially YES. My mother suffered from kidney stones few years back. After the operation I asked the doctor about the diet that my mother should follow. The doctor advised to avoid food that is rich in calcium for example milk, eggs, leafy vegetables etc.,
but he did not advised to cut them off completely from a regular diet, he told to reduce the intake.


When I also asked about this rumor, the doctor replied, of-course that is not completely false because Both Spinach and Tomatoes have Oxalates. These substances when the balance of minerals in body is disturbed, tend to mix with calcium( spinach, mint and other greens are rich sources) and form kidney stones. This happens only in people whose body metabolism predisposes them to form stones. The best way to avoid stone formation is to stay well hydrated. Drink atleast 1.5 litres of water in a day. 

Also when using tomatoes, it is good to de seed them and use. Other sources for oxalates are Coffee, tea, nuts like peanuts, chocolate etc...

About cabbage and kidney stones, it is not true. But it is true that goitrogens ( things that interfere with the goitre in the absorption of Iodine) in cabbage interferes with the production of thyroid hormone and hence people withHypothyroidism should take less amount of cabbage.