Page 501 - Small Animal Clinical Nutrition 5th Edition

Obesity 517

VetBooks.ir breaking antioxidant that prevents propagation of free radical mechanisms have been proposed for this effect, including
enhanced antioxidant activity via glutathione peroxidase (Neve,
damage of biologic membranes. Vitamin E inhibits lipid per-
oxidation by scavenging lipid peroxyl radicals much faster than 2002).Therefore, for increased antioxidant benefits, the recom-
these radicals can react with adjacent fatty acids or membrane mended range of selenium for weight-management dog and
proteins. Levels of vitamin E higher than recommended cat foods is 0.5 to 1.3 mg/kg (DM). There are no data to base
requirements confer specific biologic benefits. Based on antiox- a safe upper limit of selenium for dogs or cats, but for regulato-
idant biomarker studies in dogs and cats, for improved antiox- ry purposes, a maximum standard of 2.0 mg/kg (DM) has been
idant performance, weight-management foods for dogs and cat set for dog foods in the United States (AAFCO, 2007).
should contain at least 400 and 500 IU/kg (DM), respectively
(Jewell et al, 2000). SODIUM AND PHOSPHORUS
Dogs and cats that are overweight may be experiencing some
VITAMIN C degree of hypertension (See Health Risks of Obesity discus-
Besides regenerating vitamin E, vitamin C (ascorbic acid) sion, above and Table 27-1). Also, because they may be fed
also: 1) regenerates glutathione and flavonoids, 2) quenches free weight-management foods for extended periods of time, and
radicals intra- and extracellularly, 3) protects against free radi- subclinical renal disease is relatively common, sodium and
cal-mediated protein inactivation associated with oxidative phosphorus levels in weight-management foods are important.
bursts of neutrophils, 4) maintains transition metals in reduced Therefore, the recommendations for sodium in foods for
form and 5) may quench free radical intermediates of carcino- weight management in dogs and cats are 0.2 to 0.4% and 0.2 to
gen metabolism. 0.6% (DM), respectively. The recommended phosphorus levels
Dogs and cats can synthesize required amounts of vitamin C. for weight-management foods for dogs and cats are 0.4 to 0.8%
However, their ability to synthesize vitamin C may be much and 0.5 to 0.8% (DM), respectively.
less than for other mammalian species (Chatterjee et al, 1975).
Dogs can rapidly absorb supplemental vitamin C (Wang et al, Key Nutritional Factors: Metabolic-Control
2001). In people, high levels of oral vitamin C increased urine Foods for Weight Loss in Cats
oxalate excretion and risk of urolithiasis (Massey et al, 2005). The use of metabolic-control foods is an alternative to calorie-
Cats given vitamin C supplements (0, 200, 400 and 1,000 control foods for weight loss in overweight cats. This approach
mg/day) had a small progressive reduction of urinary pH from is similar to the “low carb” human weight-loss programs that
6.9 to 6.5 (Kienzle and Maiwald, 1998). Moderate supplemen- have resurged in popularity. The first low-carbohydrate diet
tation (193 mg vitamin C/kg of food, DM; approximately 10 that enjoyed popular success in people was used in the 1860s
mg/day) of foods for healthy adult cats with vitamin C did not (Bravata et al, 2003). Contemporary variations on the low-car-
seem to increase the risk of oxalate production (Yu and Gross, bohydrate theme for people include programs such as the
2005). Supplemental vitamin C (224 mg/kg DM), in combina- Atkins and South Beach diets. The metabolic approach to
tion with supplemental vitamin E and β-carotene improved weight loss in cats is probably more like the South Beach diet
antioxidant status in dogs (Wedekind et al, 2002). Until more in that it is less restrictive in carbohydrate and lower in fat than
studies are available, for improved antioxidant performance, the Atkins diet approach. Although the popular emphasis is on
and in conjunction with recommended levels of vitamin E, lowering carbohydrate intake, both the Atkins and South
weight-management foods for adult dogs and cats should con- Beach diets rely on a multifaceted approach. Dietary protein is
tain at least 100 mg vitamin C/kg DM and 100 to 200 mg vita- also important, as with traditional calorie-restricted foods dis-
min C/kg DM, respectively. cussed above.The South Beach diet recommends less fat, lower
glycemic index carbohydrate sources and, to a lesser extent,
SELENIUM increased dietary fiber. The basic premise of the metabolic
Glutathione-peroxidase is a selenium-containing antioxidant approach is to shift energy metabolism from energy storage to
enzyme that defends tissues against oxidative stress by catalyz- energy use.
ing the reduction of H O and organic hydroperoxides and by Clinical trials have shown the efficacy of metabolic-control
2 2
sparing vitamin E. In addition to the antioxidant function of foods to be equivalent to traditional low-calorie foods for safe
a
selenium-dependent glutathione-peroxidase, it affects regula- weight loss in cats. The key nutritional factors for metabolic-
tion of proinflammatory cytokines including leukotrienes, control cat foods for weight loss are discussed below and sum-
thromboxanes and prostaglandins, which might benefit the marized in Table 27-6.
adipokine component of the pathology associated with obesity
(Table 27-2) (Surai, 2002, 2003). The minimum requirements Carbohydrate
for selenium in foods for dogs and cats are 0.10 and 0.13 mg/kg Limiting dietary carbohydrate is an important component of
(DM), respectively (Wedekind et al, 2002a, 2003, 2003a). metabolic control for weight loss. There are three key advan-
Animal studies and clinical intervention trials in people have tages to limiting dietary carbohydrate to 20% (DM) or less: 1)
shown selenium to be anticarcinogenic at much higher levels lower glycemic index, 2) metabolic shift from energy storage to
(five to 10 times) than recommended human allowances or energy usage and 3) increased satiety.
minimal requirements (Combs, 2001; Neve, 2002). Several As discussed for the key nutritional factors for calorie-