Page 917 - Small Animal Clinical Nutrition 5th Edition

Feline Lower Urinary Tract Diseases 949

cium availability.
Table 46-15. Calcium-rich foods that should be avoided in cats
Excessive dietary calcium should be avoided to prevent
VetBooks.ir recurrence of calcium oxalate uroliths. The most important Food item Serving size Calcium (mg)
at risk for calcium oxalate urolithiasis.*
sources of excess calcium are commercial foods and mineral
Yogurt 1 cup (8 oz.) 415
supplements containing high calcium levels. High intake of Whole milk 1 cup (8 oz.) 291
dietary calcium may lead to hypercalciuria and urolith forma- Cheese 1 oz. 200-270
Ice cream or ice milk 1 cup (8 oz.) 176
tion in patients with intestinal hyperabsorption of calcium.
Cottage cheese, creamed 1 cup (8 oz.) 136
Calcium-rich human foods (Table 46-15) should be avoided in Broccoli, cooked 1 large stalk 88
patients at risk for calcium oxalate uroliths. In addition to foods *Mineral supplements and some commercial cat foods contain
much more calcium than these foods; therefore, a thorough and
naturally high in calcium, a number of different human foods
complete nutritional history is important for managing these
(e.g., breads and breakfast cereals) and beverages are fortified patients.
with calcium.The amount of calcium added to these foods can
be found on the product label.
Another potential unrecognized source of excess dietary cal-
cium is vitamin-mineral supplements,especially calcium supple- generally is considered to increase with ingestion of foods that
ments. A wide variety of calcium supplements are available over are high in protein. During the last century, the predominant
the counter.These supplements differ in the amount of elemen- urolith type in people in the U.S.has shifted from struvite to cal-
tal calcium provided. Calcium carbonate, for example, contains cium oxalate (Goldfarb, 1994). Cross-cultural studies have
40% calcium (by weight), whereas calcium lactate and calcium shown a shift from struvite to calcium oxalate uroliths with
gluconate contain 13 and 9% calcium, respectively. Little is increasing industrialization (Samuel and Kasidas, 1995). The
known about the relative availability of calcium from different reason for the increased incidence of calcium oxalate in these
supplements. Calcium supplements differ not only in their cal- human populations is unknown. However, dietary habits are
cium content, but also in their solubility. Increasing dietary cal- thought to play a major role. Nutritional epidemiologic studies
cium intake prevents dietary hyperoxaluria in human patients have emphasized the role of increased dietary intake of animal
eating oxalate-rich foods (Pak, 1990). This finding presumably protein.This link seems plausible because the amount of animal
is due to decreased intestinal absorption of oxalate. However, protein in the diet correlates with industrialization. Dietary pro-
women taking calcium supplements had a 79% increased risk of tein increases calcium, uric acid and possibly oxalate excretion
calcium oxalate uroliths (Curhan et al, 1995).The increased risk and decreases urinary pH. Animal proteins are rich in sulfur-
associated with calcium supplements may be due to timing of containing amino acids, which are metabolized to sulfate and
ingestion. If not taken with meals, calcium supplements may thus may reduce urinary pH and increase urinary calcium and
lead to increased urinary calcium excretion, without decreasing uric acid concentrations. High dietary protein intake reportedly
oxalate absorption in the gastrointestinal tract. increases urinary calcium excretion in dogs.The 24-hour urinary
Excessive restriction of calcium should also be avoided; it calcium excretion almost doubled when dogs were fed a food
may cause negative calcium balance and contribute to hyperox- containing 31% DM protein compared with calcium excretion
aluria, which increases risk for calcium oxalate uroliths. Cats fed for dogs fed a food containing 10% DM protein (Bartges et al,
foods containing moderate amounts of calcium had decreased 1995).The type of protein, duration of protein intake and phos-
risk of developing calcium oxalate uroliths compared with cats phorus intake influence the effect of protein on calcium.
fed either low or high amounts of calcium (Lekcharoensuk et At present, available evidence does not support that excessive
al, 2001a). The recommended range of dietary calcium for dietary protein is associated with calcium oxalate uroliths in
decreasing risk of calcium oxalate uroliths is 0.6 to 1.0% DM. cats. Healthy cats eating a high-protein food (13.7 g/100 kcal;
This is also the recommended range for the calcium content of 55% DM protein for a food with 4 kcal metabolizable energy
foods intended for prevention of both struvite and calcium [ME]/g DM) had increased water intake, urine volume and
oxalate urolithiasis. urinary pH; however, they did not have increased urinary calci-
um excretion (Funaba et al, 1996). In a case-controlled study of
Protein nutritional factors associated with urolithiasis, cats fed foods
Excessive dietary protein intake should be avoided in patients at containing more than 7.98 g of protein/100 kcal (32% DM
risk for struvite uroliths. Protein provides additional urea and protein for a food with 4 kcal ME/g DM) were less likely to
glutamine, which are metabolized to ammonia and ammonium, form calcium oxalate uroliths than cats fed low-protein foods
respectively. Urinary excretion of ammonia and ammonium (5.15 to 7.98 g/100 kcal; 21 to 32% DM protein for a food with
increases their availability to combine with magnesium and 4 kcal ME/g DM) (Lekcharoensuk et al, 2001a). It is possible
phosphate to form struvite crystals and uroliths. In addition, that increased urine volume associated with increased protein
foods that have increased amounts of protein also tend to have intake plays a role in decreasing risk of urolith formation. On
increased phosphorus, which is a component of struvite uroliths. the basis of current information, cats at risk for calcium oxalate
The recommended amount of dietary protein for struvite disso- uroliths should be fed foods with at least 32% DM protein.The
lution and prevention ranges from 30 to 45% DM protein. protein content of foods intended for prevention of both stru-
The risk of calcium oxalate urolithiasis in people and dogs vite and calcium oxalate should be between 32 and 45% DM.