Digestion vs. Kidney Stones

P eople think of kidney stones as occurring in the kidneys. But, as Daily Health News contributing editor Andrew L. Rubman, ND, is clear to convey, diet and digestion are significant contributors to this seemingly unrelated problem. Whether it's binge drinking or high-protein diets, how you fuel your body impacts its function. "Garbage in, garbage out" as they say. Going overboard on what you eat and drink can make you more susceptible to these painful, hard masses. Conversely, making smart and consistent dietary choices can help prevent kidney stones.

To simplify, kidney stones are formed in large part as a result of incomplete or out-of-balance digestion where nutrients are not available to the body when and where it needs them. Kidney stones are primarily made of calcium oxalate, although sometimes they also contain uric acid, cystine or struvite.

Once you have one stone, you are likely to develop more. Fortunately, according to Dr. Rubman, there are a number of steps you can take to prevent stone formation...

DRINK UP

The single most important thing you can do: Drink plenty of water, advises Dr. Rubman. Fluids make stone components such as calcium oxalate more soluble in the urine, so they are less likely to form into crystals. The standard recommendation is eight eight-ounce glasses of water daily. For a more precise calculation of how much water you should drink each day, divide your weight in half. That number in ounces is your recommended daily water intake.

What you drink matters, too. In one study, hard tap water increased urinary calcium concentration (a risk factor for calcium stones) by 50% compared with soft bottled water. If hard water is what's available in your community, it makes sense to invest in bottled water.

Other healthful drinks include mineral water with a splash of fresh lemon or lime juice. Mineral water contains calcium and magnesium that may reduce the risk of stone formation, while a half-cup of lemon juice daily raises the level of stone-fighting citrate. Note: Other citrus fruits, such as orange or grapefruit, do not have the same effect. In fact, as mentioned below, grapefruit can increase stone risk. Other studies have suggested that coffee and tea, both natural diuretics, have a beneficial impact by increasing urine volume.

Best to avoid: Cola and grapefruit juice. Cola reduces the level of citrate in urine... and multiple studies have suggested that grapefruit juice raises stone risk.

The jury is still out on beer. While some research indicates that beer acts as a natural diuretic to dilute urine and increase frequency of urination, Dr. Rubman points out that beer is packed with stone-prompting oxalates. If you do drink beer or other alcoholic beverages, do so in moderation (generally considered to be one drink a day for women and two for men). Binge drinking increases uric acid production and thus the risk of uric acid stones.

To monitor whether you're taking in sufficient fluids, keep an eye on the color of urine. If it's dark yellow, you're not drinking enough. Urine should ideally be pale and light in color.

UP YOUR CALCIUM CONSUMPTION

Nearly three out of four kidney stones are composed of calcium oxalate, so it stands to reason that restricting calcium should prevent stones, right? Wrong! There is an inverse relationship between calcium consumption and stone formation, explains Dr. Rubman. He points out that many people with osteoporosis develop calcium stones not because of calcium in food or supplements, but because of the body's reabsorption of calcium. If the body is not supplied adequate amounts of calcium, it steals its own from the bone. This results in more calcium circulating in the blood and eventually passing into the urine.

To make sure you get enough calcium in your diet, eat foods such as broccoli, kale, collard greens, almonds, sesame seeds and canned salmon or sardines. (Although dairy is the most obvious source of calcium, as I've written here before, cow's milk is best left to the calves.) If you don't get enough calcium in your diet, consider taking a supplement. The generally recommended dosage is 1,200 mg daily in two or preferably three divided doses. According to Dr. Rubman, calcium citrate is the supplement form most readily utilized by the body, and for best absorption he recommends that you take calcium with magnesium. In particular, he recommends Butyrex, made by T.E. Neesby, which already combines calcium and magnesium for you.

Caution: Do not take larger-than-recommended dosages of calcium supplements, because it can backfire and lead to stone formation. There is also a subset of calcium stone sufferers who have supersaturated calcium in the urine and must restrict calcium consumption. Only your doctor can determine if you are in this group. Do not take magnesium without calcium to attempt to offset the excess calcium. Always take calcium and magnesium together unless specifically told otherwise by a properly trained physician.

WATCH PROTEIN AND SODIUM INTAKE

Diets high in protein (especially animal protein) have consistently been associated with kidney stones. Protein raises levels of stone-causing calcium, oxalates and uric acid in the urine, and reduces protective citrate. Does this mean that those on the protein-heavy Atkins diet are more prone to kidney stones? As a matter of fact, Dr. Rubman worked for Dr. Atkins early in his career and in his experience, yes, they are.

Your best bet: Keep meat portion sizes moderate (about the size of a deck of cards), and fill the rest of your plate with fresh vegetables and whole grains.

Bad news for vegetarians: One study found no difference in kidney stone risk between people who consumed equal amounts of beef and plant protein. Dr. Rubman theorizes that this may be because soybeans, a common source of protein eaten by vegetarians, contain high levels of oxalates.

Sodium increases the level of calcium in urine, so those with calcium stones are best off restricting their intake of salt (whether from sprinkling it on food or consuming sodium-packed processed or fast foods). How do you know the type of stone you have? Use a cup to catch it and give it to your doctor for analysis.

MORE STONE-FIGHTING FOODS: FISH OIL AND FIBER

As if their heart-healthy benefits were not enough, eating cold-water fish such as salmon, mackerel, herring and sardines may also help prevent kidney stones. Inflammation plays a role in kidney stone development, and fish oil is naturally anti-inflammatory.

Goal: Try to eat fish at least twice a week. If you're not a fish eater, consider a daily supplement of 2,000 mg fish oil.

Fiber-rich foods such as vegetables and whole grains are an integral part of any healthful diet, and a compound called phytate in foods such as rice bran and wheat, which may inhibit formation of calcium oxalate crystals, may help prevent kidney stones.

MULTIPLE FACTORS -- MULTIPLE CHOICES

Just as there are multiple causes of kidney stones, there is no one single thing you can do to prevent them, says Dr. Rubman. A multi-pronged approach is required, one that emphasizes more fluids, calcium, fiber and fish oil, and more moderate consumption of protein and (for those with calcium stones) sodium. Next month: Strategies to ease the passing of stones.