The risk of recurrence of urinary stones is 67% within 9 years and 75% within 25 years. The causes of stones can be attributed to both environmental and internal factors, and diet remains a promising treatment for urinary stones.
Diet can influence the composition and pH of the urine, thus affecting stone nucleation and growth. The principles of stone recurrence prevention are water instruction (maintaining a daily urine output of at least 2,000 ml) and a balanced dietary lifestyle.
I. Water intake guidance
①The intake of more water is essential to increase the urine volume to prevent recurrence. In order to ensure a daily urine output of more than 2 liters, it is recommended to consume more than 2,000 ml of water in addition to diet. Usually, we recommend drinking 250ml of water every 4 hours, plus 250ml with each meal.
It is important to drink a certain amount of water in the evening and 250ml of milk-free fluid during nighttime urination.
③ Regarding what kind of liquid to drink, it is agreed that milk-free liquid with less oxalic acid is appropriate, and tap water, mineral water and wheat tea with less oxalic acid are preferred. It is recommended that half of the fluid intake be water and the other half be of the patient’s choice. Drinking citric acidified beverages (lemon juice, orange juice) can reduce the incidence of urinary stones. Cool beverages (sodium bicarbonate beverages) and sweet beverages (such as apple juice and grape juice) are not recommended because they contain sugar and phosphoric acid, which can cause a decrease in urinary citrate and an increase in urinary calcium. Patients with calcium oxalate stones should minimize the consumption of soft drinks such as Coca-Cola. In addition, coffee has the potential to increase uric acid in the urine, but it should be fine as long as it is not consumed excessively. As for drinking soft and hard water, it is not necessary to force it, but the amount is the key, and it should be balanced day and night. Advice on tea consumption: As long as you do not drink strong tea, it does not increase the risk of stone effects.
II. Dietary guidance
People with a dinner-centered diet are prone to stone formation because of the excessive excretion of substances that are conducive to stone formation in the urine at bedtime, so it is important to maintain a balance between breakfast, lunch and dinner. It is also important to maintain a balance of breakfast, lunch and dinner. In addition, the time between dinner and bedtime is also very important because the amount of substances in the urine conducive to stone formation increases within 2 to 4 hours after a meal.
The components of urinary stones include calcium oxalate, calcium phosphate, uric acid, magnesium ammonium phosphate, cystine, etc. (About 80% of them are containing calcium oxalate, calcium phosphate, uric acid, cystine, etc.). (About 80% of them are calcium stones, and calcium oxalate is the main component.) The composition of stones is different, and the dietary attention is also different.
Dietary guidance for patients with calcium-containing stones (calcium oxalate, calcium phosphate)
1. Limit excessive consumption of animal protein
Moderation of protein in food, especially animal protein, is beneficial for all stone patients. The protein intake should be <1.0g/kg/day, and the ratio of plant to animal protein should be guided by a 1:1 standard.
2. Recommended intake of calcium (600-800mg/day)
It has been confirmed that the generally recommended practice of limiting calcium content in the diet will not reduce but increase the occurrence of kidney stones. Therefore, the active intake of calcium has now become the mainstream guidance, but for some special stone patients such as type II absorptive hypercalciuria patients, it is still necessary to adhere to the principle of dietary calcium restriction.
Tips.
① Dietary calcium should not be restricted, and more dairy products (milk, cheese, yogurt, etc.), tofu, small fish and other foods are recommended.
② Calcium should not be supplemented on an empty stomach, preferably at the same time as the diet, especially when the food is rich in oxalic acid.
③ Drug overdose calcium supplementation (>2500mg/d) can cause hypercalciuria and stones.
④ A low-calcium diet should be used for type 2 absorptive hypercalcemia and must be accompanied by a low-oxalate diet to avoid secondary hyperoxaluria.
⑤ Calcium supplementation in postmenopausal women does not increase the risk of stone formation, and if there is a risk, it occurs only during the first few months of calcium supplementation, so it is prudent to increase water intake during this period. Postmenopausal women with type 2 absorptive hypercalcemia should be treated with a low-calcium, low-oxalate diet, just like other patients with type 2.
3.Limit the excessive intake of oxalic acid
High oxaluria is known to be a risk factor for the formation of calcium oxalate stones in the urinary tract. Half of the oxalic acid in the urine is absorbed from the diet. Therefore, reducing oxalic acid intake from food and reducing its absorption is the only way to reduce the amount of oxalic acid in urine. However, because most foods are low in oxalate and have low absorption rates, the role of dietary oxalate restriction in patients with non-intestinal stones is unpredictable.
Suggestions.
① The effect of dietary oxalate restriction in patients with non-intestinal origin stones is unpredictable.
② In patients with chronic gastrointestinal diseases represented by Crohn’s disease, after bypass surgery, and after small bowel resection, reducing the dietary oxalate content or taking oral calcium to reduce the absorption of unconjugated oxalate may have a therapeutic effect.
The amount of oxalic acid and the amount of oxalic acid precursors in many other foods are not yet clear,
④ Oxalic acid itself is soluble and can be removed from the juice by boiling, so it is recommended that foods with high oxalic acid content be boiled and consumed.
⑤ Increased intake of calcium along with oxalate-rich foods can suppress dietary hyperoxaluria and reduce CaOx crystallization. Therefore, patients with primary calcium stones may have a lower risk of calcium oxalate stones if they consume a diet high in oxalate along with adequate calcium supplementation.
4. Moderate intake of citrate is recommended
Although long-term prospective studies are needed to further confirm the effects of citrate, it is now generally accepted that it is beneficial in preventing recurrence of oxalate stones.
Tips.
① When acidosis, renal tubular acidosis, chronic diarrhea, strenuous activity, low blood potassium, high blood sodium, high protein diet, etc., can reduce the excretion of urinary citrate, and on the contrary can increase its excretion in alkalosis. Therefore, it is important to control the excessive intake of animal protein and correct the subclinical acidosis.
(2) In calcium oxalate stone formation, urine concentration is highest between late night and dawn, and increases urinary calcium oxalate saturation and lowers pH, so a single dose of 3.5-5.0g sodium potassium citrate at night is more effective.
(3) Citrate is abundant in fruits and vegetables and can be consumed in large amounts in the diet, but the benefits of increased dietary citrate may be offset by the high intake of oxalic acid, which can lead to hyperoxaluria.
The following fruits are rich in citric acid: citrus, grapefruit, bilberry, pineapple. Citrus is more commonly used as an adjunct to the treatment of low-citrate calcium-containing kidney stones.
5, plant fiber
Although epidemiological studies on the role of fiber intake on the risk of urinary stones are contradictory, controlled studies have shown that dietary fiber supplementation in patients with high urinary calcium can reduce urinary calcium, thus significantly reducing the formation of new stones.
Suggestions.
① In patients with absorptive hypercalciuria, the use of rice bran and wheat bran is effective.
② The protective effect of dietary fiber on the prevention of urolithiasis in the normal population is not known.
③ fiber-rich plants are often rich in oxalic acid, should be noted, do not eat high oxalic acid plants such as spinach
6.Sugar
A large number of experimental studies have confirmed that refined sugar increases the risk of urinary stone formation mainly by increasing the excretion of calcium, oxalic acid and uric acid in the urine and lowering the pH of the urine. Therefore, the intake of sugar should be controlled.
7.Fat
Greg et al. determined the relationship between total fat intake and risk factors for urinary stone formation (urine volume, urine pH, magnesium, citric acid, oxalic acid, calcium, uric acid) and found no significant effect of dietary fat on risk factors for calcium stone formation.
8.Wine
Alcohol can change the formation factors of some urinary stones, moderate alcohol consumption does not increase the risk of stone formation. The Harvard School of Public Health conducted a 6-year follow-up study and learned that drinking 380 mL of beer per day reduced the risk of kidney stones by 21%, and drinking 180 mL of wine per day reduced the risk of kidney stones by 39%. It is believed that alcohol in wine can inhibit “antidiuretic hormone”, therefore, moderate consumption of beer, wine and other alcoholic beverages can play a diuretic role, resulting in increased urine output and lower urine specific gravity, which can prevent the occurrence of urinary stones. However, it is also believed that the wort used in brewing beer contains calcium, oxalic acid, uronic acid and other substances that contribute to the formation of kidney stones, therefore, patients with kidney stones should drink as little or even no beer as possible. As most seafood is rich in nucleic acid, nucleic acid consists of purines and pyrimidines, purines are metabolized to form uric acid, when the blood uric acid content increases, it will be gathered in the form of sodium salts in the joints and soft tissues around the kidneys, and beer is rich in vitamin B1, which is an important catalyst for the breakdown of uric acid purine metabolism. Therefore, if you consume too much seafood while drinking beer, the uric acid level in the blood will increase rapidly, causing uric acid stones.
Suggestions.
① Normal people who drink alcohol in moderation will not increase the risk of stone formation
② The wort of beer contains calcium, oxalic acid and uronic acid, which contribute to the formation of kidney stones, so patients with kidney stones should drink as little or as little beer as possible.
Do not consume too much seafood while drinking beer to prevent uric acid stones.
④ Gout patients should strictly abstain from alcohol
9.Limit the excessive intake of salt
Recommendation.
①Low sodium diet is recommended for all stone patients, especially for those with high urinary calcium
②The amount of salt in the diet should be <10g/d.
10.Purine
The intake of large amount of purine food not only increases the excretion of uric acid in urine, which is easy to form uric acid stones, but also increases the formation of endogenous oxalic acid and promotes the formation and growth of calcium oxalate crystals. So should limit fish, poultry, meat, offal and other high purine food.
11.Magnesium
It is now believed that the magnesium in the urine is one of the factors that prevent the formation of stones. Magnesium can be used as treatment secondary to intestinal inflammatory disease and short bowel syndrome caused by calcium oxalate stones. But it is not clear whether the dietary supply of magnesium can provide an appropriate level of urinary magnesium, to achieve the expected protective effect.
12, potassium
Most of the dietary potassium from citrus foods, due to the alkaline load, and the urinary citrate and PH increase. The effect of potassium on patients with stones is unclear, and the Parivar study confirmed that potassium supply reduces the risk of stones. Based on the limited data available, it appears that potassium supplementation does not increase the risk of stones. In the case of potassium deficiency, the risk of stones may be increased due to the complication of calciuria.
13. Phosphate diet
The effect of phosphate in food on urinary stones varies according to the composition of the stone (phosphate-containing or non-phosphate-containing). Reduce phosphate intake on magnesium ammonium phosphate stones (guano stones) patients have a beneficial effect. Calcium oxalate stones increase phosphate intake; calcium phosphate stones reduce phosphate intake; guano stones (magnesium ammonium phosphate) reduce phosphate intake.
14, vitamin C
It is one of the precursor substances of oxalic acid, and high dose application of vitamin C can increase the excretion of oxalic acid and uric acid in the urine. However, vitamin C can combine with calcium in the urine, thus reducing the concentration of free calcium and reducing the formation of calcium oxalate stones. Recently, it has been found that a daily intake of 4g of vitamin C does not lead to the development of hyperoxaluria, nor does it increase the supersaturation level of urinary calcium oxalate or the risk of urinary stone formation. Of course, mega-doses of vitamin C (6 g/d or more) can be harmful to some individuals. Therefore, taking large amounts of vitamin C is not advocated.
15.Vitamin B6 (pyridoxine)
Vitamin B6 is an essential coenzyme in the metabolism of oxalic acid and plays an extremely important role in the process of oxalic acid metabolism. In humans, if the diet is deficient in vitamin B6, the excretion of oxalic acid in the urine will increase. Patients with calcium oxalate stones can reduce the amount of oxalic acid excreted in the urine when they take 10 to 500 mg of vitamin B6 daily. In recent years, it has been found that taking high doses of vitamin B6 can significantly reduce the risk of urinary stone formation.
16.Vitamin D
Although plasma vitamin D and calcium excretion has a direct relationship, but has not found excessive consumption of vitamin D or prolonged sun exposure and the higher incidence of urinary stones related to the evidence
Four, ammonium magnesium phosphate – carbonate apatite stones (infected stones, guano stones)
① The most important thing is to choose antibiotics to control the infection;
② Acidification of urine
③ Appropriate low calcium and low phosphorus diet. As for the strict low phosphorus and low calcium diet, it is not recommended because most patients have difficulty in adhering to it, and too strict restriction of phosphorus intake may lead to myopathy or osteoporosis.
V. Uric acid stones.
The intake of large amounts of purine food not only increases the excretion of uric acid in the urine, which can easily form uric acid stones, but also increases the formation of endogenous oxalic acid and promotes the formation and growth of calcium oxalate crystals. Therefore, high purine foods such as fish, poultry, meat and offal should be restricted
① Alkalinize urine (but keep pH <7, otherwise it will easily lead to calcium phosphate stones) (potassium citrate?)
② Prevent overweight, protein should be <1.0g/kg/day
③ Strictly abstain from alcohol
④ Drink plenty of water
VI. Cystine stones
① Drink a lot of water, >4L/day;
②Alkalinize urine to make urine pH at 7-7.5 (eat more citrus, fruit juice) or make urine >4L/d
The causes of stone formation may be multiple metabolic disorders at the same time, and dietary modification to correct one risk factor may create another risk factor at the same time. The choice of a therapeutic diet for a specific patient should be considered in a comprehensive manner, taking into account the patient’s entire dietary history. The recommended diet is currently considered to be large amounts of water, limited sodium intake, limited oxalic acid, limited sugar and animal protein, avoided purine-rich foods, increased consumption of citric acid-rich fruits, and no blind restriction of calcium intake.