kidney stone and proper diet
Kidney Stone Diet: What should you eat and what should you avoid to prevent kidney stones?
Current therapy for kidney stones depends more on basic nutrition and health support for medical treatment than on major food and nutrient restrictions.
Keywords: kidney stone، nutrition، High Oxalate Foods and Drinks،proper diet
In the United States, approximately 7.1% of women and 10.6% of men suffer form kidney stones at some point
during their lives. The etiology of nephrolithiasis is unknown, but many factors that relate to the nature of the urine itself (e.g., pH, concentration) or to conditions of the urinary tract environment contribute to supersaturation and stone formation. Co-morbidities such as obesity, diabetes, gout, and hyperparathyroidism increase the risk of stone formation. The most common types of kidney stones are calcium, struvite, and uric acid.
Calcium oxalate and calcium phosphate stones are the most common types, and they account for approximately 80% of all kidney stones. The supersaturation of kidney stone materials in the urine may from the following:
- Excess calcium in the blood (hypercalcemia) or urine (hypercalciuria)
- Excess oxalate (hyperoxaluria) or uric acid in the urine (hyperuricosuria)
- Low levels of citrate in the urine (hypocitraturia) result
High levels of urinary oxalate increase the risk of an individual forming a calcium oxalate stone. Oxalates are derived from endogenous synthesis (relative to lean body mass) and dietary sources (Box 1). A small percentage of the population are “hyperabsorbers” of dietary oxalate and thus are at higher risk of forming stones. Oxalic acid is a metabolite of ascorbic acid. Therefore, the long-term supplementation of vitamin C in excess of the tolerable upper intake (2000 mg/day) may pose a potential health risk for kidney stone formation.
Adequate dietary calcium intake from all sources (i.e., dairy foods, nondairy foods, and supplements) is
inversely associated with calcium oxalate stone formation. Essentially, individuals with a low dietary intake of calcium are at a higher risk for calcium oxalate stone formation than those who consume the Dietary Reference Intake (DRI) for calcium. Dietary calcium binds oxalates in the intestines, preventing absorption and thus the concentration of oxalates in the urine. Historically, it was a common misunderstanding to restrict the calcium intake of those patients who form calcium oxalate stones.
Struvite stones, which account for approximately 10% of all stones, are composed of magnesium ammonium phosphate and carbonate apatite. They often are called infection stones because they are primarily caused by urinary tract infections and because they are not associated with any specific nutrient. Thus, no particular diet therapy is involved. Struvite stones are usually large “staghorn” stones that are surgically removed.
Uric Acid Stones
Approximately 9% of kidney stones are uric acid stones. The primary risk factors for uric acid stone formation are overly acidic urine, excess urinary excretion of uric acid, and low urine volume. Hyperuricosuria may result from an impairment that involves the metabolism of purine, which is a nitrogen end product of protein metabolism from which uric acid is formed. This impairment occurs with diseases such as gout, and it can also occur with rapid tissue breakdown during wasting disease. Other conditions that are associated with persistently acidic urine and uric acid stone formation are diarrheal illness (e.g., short gut syndrome, inflammatory bowel disease), type 2 diabetes, obesity, and metabolic syndrome.
Other rare forms of kidney stones are often reflective of inherited disorders or complications of medications.
For example, cystine stones are caused by a genetic defect in the renal reabsorption of the amino acid cystine (as well as other dibasic amino acids), thereby causing accumulation in the urine (cystinuria).
Cystine is not soluble and thus a high concentration may result in stone formation.
medical nutrition therapy may include several aspects, and it will vary depending on the type of stone. General Dietary recommendations are as follows:
Energy: Overweight and obesity increase the risk for several chronic diseases as well as for kidney stone formation. Total energy intake should be customized to achieve an ideal body weight. Diets such as the DASH diet or Mediterranean diet are ideal. High-protein, low-carbohydrate diets are specifically discouraged for individuals at risk for stone formation.
Protein: Excessive protein intake from animal sources is a risk factor for stone formation. Thus, patients should normalize their intake to healthy population standard recommendations of 0.8 to 1.0 g/kg/day.
Calcium: Low dietary calcium intake is a risk for calcium oxalate stone formation. Thus, patients should be encouraged to normalize calcium intake to 800 mg/day for men and 1200 mg/day for women and balance intake throughout the day
Sodium and potassium
Sodium and potassium: High sodium intake increases the amount of calcium excretion in the urine, thereby precipitating hypercalciuria, and it is associated with an increased risk of stone formation. All stone formers should be counseled on a low-sodium diet (<2300 mg/day). Citrate and potassium are helpful in solubilizing calcium salts and preventing calcium oxalate stone formation. The diet should be rich in fruits (particularly citrus fruits) and vegetables to provide a potassium intake of >4.7 g/day.
Oxalates: Limiting dietary oxalates reduces urinary oxalate excretion and the risk of calcium oxalate
stone formation. Thus, avoiding foods that are high in oxalates is advised. Intake should be <200 mg/day (see Box 1).
Vitamins and minerals
Vitamins and minerals: Vitamin C should be limited to the Dietary Reference Intake, and all other vitamin and mineral intakes should meet the Dietary Reference Intake standards.
Fluid: A large fluid intake of ≥2 to 3 L/day helps to produce more dilute urine and thus to prevent the accumulation of materials that form stones. Exact fluid intake needs vary by patient, but enough
fluids—preferably water—should be ingested to produce at least 2 to 2.5 L of clear urine daily. For patients who consume soft drinks, reducing soft drink intake may lower the risk of recurrent stone formation.
Dietary recommendations relative to the specific type of stone formation:
Calcium stones. In some cases, dietary control of the stone constituents may help to reduce the recurrence of such stone formation. If a stone is made of calcium oxalate, then avoiding foods that are high in oxalate (see Box 1) may be beneficial. If a stone is made of calcium phosphate, additional sources of phosphorus (e.g., meats, legumes, nuts) should be controlled.
In addition to the recommendations listed previously, fiber intake should be considered in the case of calcium stones. Materials that bind potential stone elements in the intestine can prevent their absorption and remove them from the body. For example, phytate can bind calcium and thus help to prevent the crystallization of oxalate calcium salts. Phytates are found in high-fiber plant foods such as whole wheat, bran, and soybeans.
Cystine stones. Dietary modifications are geared toward reducing urinary cystine concentrations by decreasing intake of animal foods high in cysteine and methionine; reducing sodium intake; increasing the intake of vegetables high in organic anions, and diluting the urine. Diluting the urine requires the intake of copious amounts of water daily in order to void at least 4 L of urine per day.
Dietary recommendations relative to the specific type of stone formation:
Uric acid stones
Uric acid stones. Dietary attempts to alter urinary pH with alkaline diets (a diet that is low in animal protein and high in fruits and vegetables.) low in purines are helpful to prevent an increase of the concentration of uric acid and stone formation within the kidneys. Acidic urine favors the kidneys’ reuptake of uric acid whereas alkaline urine favors the excretion of uric acid. Potassium citrate treatments may also be used to raise the urinary pH, which decreases the supersaturation of uric acid. The primary goals of therapy are to establish and maintain a healthy weight and alkalization of the urine through a vegetarian-type diet with limited animal protein (including red meat, fish, and poultry).
Kidney stones may be formed from a variety of substances. For some patients, a change in the dietary intake of the identified substance (e.g., sodium, oxalate, purine) and an increase in fluid intake may decrease stone formation.
Chocolate drink mixes, soymilk, Ovaltine, instant iced tea, fruit juices of fruits listed in this table
Apricots (dried), red currants, figs, kiwi, rhubarb
Beans (wax, dried), beets and beet greens, chives, collard greens, eggplant, escarole, dark greens of all kinds, kale, leeks, okra, parsley, green peppers, potatoes, rutabagas, spinach, Swiss chard, tomato paste, watercress, zucchini
BREADS, CEREALS, AND GRAINS
Amaranth, barley, white corn flour, fried potatoes, fruit cake, grits, soybean products, sweet potatoes, wheat germ and bran, buckwheat flour, All-Bran cereal, graham crackers, pretzels, whole-wheat bread
MEAT, MEAT REPLACEMENTS, FISH, AND POULTRY
Dried beans, peanut butter, soy burgers, miso
DESSERTS AND SWEETS
Carob, chocolate, marmalades
FATS AND OILS
Nuts (peanuts, almonds, pecans, cashews, hazelnuts), nut
butters, sesame seeds, tahini (a paste made from sesame seeds)
Box 1- High-Oxalate Foods and Drinks