The Truth About Senior Diets
Your cat’s individual lifestyle may be more important than his calendar age.
By David A. Dzanis, DVM, PHD, DACVN
Your cat is getting on in years, no longer the spry, playful kitten or active young adult he one was. You have been feeding a cat food product specifically formulated for adult maintenance, since he no longer needs the higher levels of calories, protein and other nutrients found in "kitten" or "all life stages" products. However, you’re wondering if you should switch to a "senior" diet, one of many products specifically geared toward the older cat. Before you decide, you should consider more than simply his chronological age.
Is your cat a "senior"?
A slowly progressive decline in metabolic rate, lean body (muscle) mass and physical activity characterize the senior years of a cat’s life. The body simply doesn’t function as well or effectively as it once did, and becomes less capable to respond to illnesses and life’s other stresses.
Various authors have tried to designate a certain range of years as when the senior life stage begins in cats. Labels for senior diets often suggest a specific age, and may bear phrases such as "for cats 8 years of age and older." However, there is a great deal of variation between individuals - while one 10-year-old cat may be indeed be "old," another 10-year-old may still be well away from reaching his senior years. So while your cat reaching a certain birthday may be a milestone worthy of a suitable celebration, it is a poor basis upon which to choose a food for the rest of his life.
Just as in people, some cats may tend to get fatter in their older years, while many others will become thinner. While some cats are plagued with chronic diseases associated with old age, others retain healthy functions. Obviously, the nutritional needs for these various scenarios are different, so one formulation cannot hope to meet the needs of the older cat under all circumstances. Thus, depending on how gracefully your cat ages, a given senior diet may or may not be the best choice.
Compared to the scientific information available for other life stages, there is little known regarding the nutritional requirements of older cats. Because of this fact, it is not surprising that there is a lack of consensus among nutritionists and veterinarians as to the true dietary needs of the senior cat. There are no AAFCO Cat Food Nutrient Profiles or National Research Council recommendations for seniors as there are for other stages, such as kittens and reproducing queens. For this reason, most senior diets are formulated or tested to be complete and balanced for "adult maintenance."
Theoretically, then most senior diets are suitable for adult cats of any age. What makes them different from other adult products is that the are usually restricted in calories and certain nutrients, which although still adequate for the healthy adult, are lower than the typical adult maintenance product. There can be many differences between various manufacturers’ versions of senior diets, but some common trends may be seen.
"Typical" senior food
Many senior foods are lower in calories than all life stage and adult maintenance foods, although not to the extreme as that for "lite" foods designed for weight reduction. This is done by formulating the diet to be lower in fat content and/or higher in fiber content, which also often lowers its palatability (taste appeal). It is know that there are usually decreases in physical activity and metabolic rate as a cat becomes older, hence the caloric needs are presumed to be proportionately lower as well.
However, what is not taken into account is the fact that the older cat also may have a decreased appetite or ability to consume and utilize the nutrients in the food. In reality, the problem of an older cat consuming too many calories is not as a great a concern as it is for a younger animal. Evidence of this is the fact that the incidence of obesity is much lower in the older cat population compared to middle-aged. Getting too few calories will precipitate the loss of lean body mass, cause a further decrease in physical activity, and make the cat "old" much faster.
Also, high fiber in the diet could further interfere with absorption of nutrients, just when the ability for the body to absorb nutrients is on the decline already. For many seniors, then, while they may need fewer calories per day, a change to a decreased-calorie, less palatable diet is not necessarily the answer. Rather, slightly less amounts of the food the cat is already eating may be a better solution.
Don’t cut back protein
With respect to the nutritional requirement for protein, the decreased ability for the body to digest and absorb nutrients probably means that the requirement actually goes up between adulthood and old age. Most senior foods, though, are lower in protein than their adult maintenance counterparts. This was based on the premise that protein restriction may be of some help in preventing or retaining the progression of kidney disease, a common ailment of older cats.
Recent studies have shown that lower protein does not have the preventative powers once assumed. In fact, too little protein in the diet will cause a loss of muscle mass and decrease the ability for the cat to fight illness and recover from injuries. Thus, unless directed by your veterinarian on the basis of clinical signs or blood test results suggesting moderate to marked kidney impairment, switching to a lower protein diet may not be the wisest choice.
Some minerals are often lowered in senior diets as well. Phosphorus levels are often decreased, for the same reason as protein. However, there is no clear demonstration that restricted phosphorus is helpful in cats that are not suffering from kidney disease. When phosphorus is restricted, calcium levels are often lowered to maintain the calcium-to-phosphorus balance, eve though the dietary requirement for calcium is probably higher.
Finally, some senior diets are also restricted in salt. While this restriction is not harmful, it may decrease the palatability of the food. Since the older cat may already have a decline in his taste and smell perceptions, this combination of factors may mean the cat would not voluntary et enough to meet his daily needs. No matter how well balanced, a diet is worthless if it’s not eaten.
In addition to restriction of calories and some nutrients, a few senior diets have nutrients added to them, on the premise that they are useful in combating the effects of old age.
Most common are the addition of antioxidants, such as vitamin C and beta-carotene. While some studies suggest that these substances may help in fighting age-related changes in humans and laboratory animals, there is little work to show the same is true for cats, or eve if it were true, what the proper levels would be. Neither of these two substances is recognized as dietary essential nutrients for the cat.
Cats synthesize the vitamin C the body needs in their livers, so a dietary source of vitamin C has never been shown to be necessary at any life stage. Too much vitamin C could also aggravate some medical conditions, such as if the cat had a predisposition towards formation of some types of bladder stones - calcium oxalate, for example.
With respect to beta-carotene, it is known to act as an antioxidant at some levels, but can actually be a pro-oxidant (encourage age-related damage) at higher levels. Without further study, it is unclear whether the levels in some senior cat foods are truly helpful or not.
Senior diets: yes or no?
Senior diets can be helpful in some older cats. For the cat that has a tendency to gain weight, these moderately calorie-restricted diets may be just the thing to prevent obesity and help keep him lean and active.
In fact, since senior diets are usually formulated for adult maintenance, they might also be useful for feeding to the slightly chubby but not quite senior adult. An obese older cat may even need a more restrictive diet, although any weight loss plan should be conducted under the direction of a veterinarian.
For cats with mild evidence of degenerative disease, such as kidney, liver or heart problems, senior diets can be helpful as an intermediate step or as an alternative to the more restrictive therapeutic diets. If your veterinarian diagnoses a problem of this nature in your cat, discuss with him or her what diet would be best in your particular case.
If your older cat is maintaining a good weight, keeping active, and gets a clean bill of health from your veterinarian, there may be no pressing need to switch to a senior diet just because he has reached a certain birthday.
For the older cat that has a propensity to lose weight, a senior diet more likely is not appropriate. Rather, a more rational switch may be from a maintenance food to one even higher in calories and nutrients, such as an all life stages product.
Dr. Dzanis is a board certified veterinary nutritionist. He served for eight years as the U.S. Food and Drug Administration’s expert on pet food. He now is a private consultant for the government and the pet food industry.
How to feed is as important as what to feed
Feed the right amount. The amount to feed depends on many factors, including what type of food you are feeding. If your cat has maintained his weight well through adulthood, anticipate that you would need to feed about 20 percent less in old age. Regardless, the amount should be adjusted up or down as needed to maintain normal weight and condition. If the cat continues to lose weight with increased amounts, a more calorie-dense food may be required.
Feed often enough. An older cat may not be able to consume the volume of food he once did as a young adult. If he is eating dry food, you may want to keep it freely available. However, if you’re feeding canned food or other food that spoils relatively quickly, frequent small meals are preferred.
Keep a routine. Keep to a consistent schedule. Skipped meals should be avoided.
Accommodate the cat’s needs. Dental problems or other conditions may compromise a cat’s ability to eat dry food. Moisten the foods with water or switch to a canned or semi-moist variety if necessary. Some dry senior foods are made to be a little easier to chew, so it may be helpful in this circumstance.