Soybean Meal

In a 2004 study, cats fed a soy-containing food showed measurable but mild increases in T4. Since an overactive thyroid is the most common hormone disease in older cats, this finding deserves attention.

Soybean meal is what is left after the oil is extracted from soybeans, and it is the most widely used protein in farm animal feed. Cats digest processed soy protein fairly well, but some soy sugars can cause gas and bloating. The Merck Veterinary Manual notes that plant protein sources contain no taurine, so cats need animal protein or added taurine. For a cat with a medical condition, ask your veterinarian.

Source: merckvetmanual.com

Soybean meal is one of the cheapest protein sources available, so it lowers the cost of raising a food's protein percentage. It also adds some carbohydrate and fiber. The crude protein number on the bag counts soy protein the same way as meat protein, so a food with soybean meal high on the list can show a strong protein figure while relying on a plant.

It can. Soybeans contain sugars called oligosaccharides, mainly raffinose and stachyose, that cats cannot digest. Bacteria in the large intestine ferment them and produce gas, which can show up as flatulence or bloating. More refined soy ingredients, such as soy protein concentrate, have much of this sugar removed. Soybean meal keeps more of it.

In feed terms, yes. Soybean meal is the solid material left after soybean oil is extracted, usually with a solvent, and then toasted and ground. The oil is the main product and the meal is the co-product that goes into animal feed. On a cat food label it appears as soybean meal or dehulled soybean meal.

Pettings gives soybean meal 1 out of 5 and lists it under soy. It appears on 38 of the 149 dry cat foods we list. It is a low-cost plant protein that does not replace meat, and its isoflavones act like weak estrogen in the body. Each food's page shows how it scores overall.