Also known as urolithiasis, kidney stones are a common pathology since it affects 5 to 10% of the population. Often recurrent, it can nevertheless be prevented by food choices and a better lifestyle. What are the different types of kidney stones? What are they due to? What are the foods to avoid when you are prone to it? The answers of Marie Gruelle, liberal dietitian nutritionist in Montrouge, to take care of her kidneys.
What causes kidney stones (or urolithiasis)? Can the risk of these “little pebbles” appearing be reduced by diet? If so, what foods and in what quantity should we eat for the good health of our kidneys (vegetables, dairy products, etc.)? All the answers on this natural prevention with Marie Gruelle, dietitian nutritionist.
What is a kidney stone?
The kidney stone corresponds to the aggregation of crystals of mineral salts in the kidneys. The resulting small stone forms an obstacle, obstructing the urinary tract and hindering the proper functioning of the kidneys. The main symptom of kidney stones is the attack of renal colic which is manifested by a very painful crisis.
If these kidney stones often end up being naturally evacuated by the urine, sometimes they remain stuck in the urinary tract and then require surgical treatment.
This pathology, very common in industrialized countries, mainly affects adults between 30 and 50 years old and twice as often men as women. Very often recidivist, it is considered that one out of two people victim of a first calculation, is likely to make a new one in the 10 years which follow. Hence the importance of betting everything on prevention.
What are the causes ?
According to the French Association of Urology1, the urinary lithiasis curve evolves in parallel with the level of a country’s GDP – a marker of a country’s economic activity. This means that the more a country is industrialized, the more kidney stones are frequent there.
The prevalence of these calculations has also evolved considerably over the past century, with changes in eating habits linked to industrialization: we tend to consume less vegetables, more proteins, more industrial sugar and prepared meals rich in salt. Food is therefore the main cause of the appearance of kidney stones.
Less frequently, certain types of calculations can be favored by:
- Urinary tract infections;
- heredity;
- Drug treatment;
- Certain metabolic diseases such as obesity, gout or diabetes;
- Or by anatomical factors such as certain renal malformations.
What are the different types of kidney stones?
In the vast majority of cases (90%), kidney stones are calcium oxalate stones. The remaining 10% are essentially uric acid stones, the cause of the famous gout attacks.
What Foods to Avoid When You Have Kidney Stones
As you will have understood, when you have been affected for the first time by kidney stones, the risks of recurrence are great, and can be largely prevented by good food hygiene. “No food should be removed, but a number of intakes can be reduced to prevent the formation of new crystals” emphasizes the dietitian.
Rule number 1: reduce your consumption of animal protein
Meat, fish, eggs, seafood, cold cuts, organ meats… the consumption of these foods rich in animal protein increases the urinary excretion of calcium and tends to acidify the urine. “It is recommended to limit yourself to 150 g of meat / fish or eggs per day, which corresponds to one serving only. You can therefore choose to consume it at only one of the two main meals, or to have a half-portion at each meal. summarizes Marie Gruelle.
Rule number 2: limit oxalate-rich foods
Oxalate from food combines with calcium to form calcium oxalate crystals. Oxalate is found in large quantities in cocoa, and therefore in chocolate. The darker the chocolate, the higher the oxalate content. Other sources are:
- Certain fruits and vegetables: spinach, chard, sorrel, broccoli, beets, rhubarb, sweet potato, certain red berries, etc.
- Oilseeds: almonds, walnuts, hazelnuts, cashew nuts…
- Tea.
Be careful however, if certain fruits and vegetables rich in oxalates must be limited, a diet rich in plants is one of the first rules to follow to limit the appearance of stones!
Rule number 3: reduce your salt intake
Sodium promotes the excretion of calcium in the urine, so it should be strongly limited! In practice, it is recommended to limit yourself to 5 g of sodium per day. “To do this, you should reduce your consumption of foods that are naturally very salty, such as cheese, cold cuts and cured meats, as well as ready-made commercial meals. It is also recommended to limit table salt as much as possible.” insists the dietician. On the other hand, it is not useful to buy special foods “without salt” or “with reduced salt content”.
Rule number 4: soft pedal on sugary drinks, alcohol and fast sugars
Sugar and alcohol both promote insulin resistance, itself involved in the tubular absorption of calcium and therefore in the formation of kidney stones.
Calcium: a false enemy!
We have long heard that you should reduce your calcium intake when you are prone to lithiasis: that is not the case! By restricting dairy products and other foods that are sources of calcium, the risk is conversely to promote the formation of oxalate crystals.
If it is not advisable to make orgies of cheese (also for their salt content) and dairy products, it is recommended to respect the recommended intakes, namely between 800 and 1000 mg of calcium per day, which corresponds to two to three daily dairy products.
Absolute rule: drink plenty of water!
Before even talking about foods to avoid, the absolute rule to avoid the formation of kidney stones, is sufficient hydration. “It is essential to drink at least 2 liters of water per day, spread throughout the day, to dilute the urine and limit the risk of crystal formation“Insists Marie Ruelle. Water is the drink of choice, it can be from the tap, mineral or spring. On the other hand, we limit strong tea rich in oxalate and sugary drinks.
If the stones are made up of uric acid, alkaline waters, rich in bicarbonate, such as Vichy St Yorre and Vichy Célestin, are recommended.