The scores
Iams ProActive Health: C (58/100)
Blue Buffalo Indoor Health: B (76/100)
A 14-point gap and a full grade difference. This isn't a close call. Iams sits in the upper half of C grade — functional but unremarkable. Blue Buffalo lands firmly in B territory alongside other premium formulas. The gap reflects fundamentally different ingredient philosophies: one formula is built around cost, the other around nutrition.
How the ingredients compare
Here are the first five ingredients side by side:
Iams: Chicken, Corn Grits, Chicken By-Product Meal, Corn Gluten Meal, Dried Beet Pulp
Blue Buffalo: Deboned Chicken, Chicken Meal, Brown Rice, Barley, Oatmeal
Both start with chicken, which is the right move for a cat food. But look at what follows. Iams goes straight to corn grits - a cheap, refined carbohydrate with minimal nutritional value. Then chicken by-product meal (organs, necks, feet), then corn gluten meal - meaning two of the top four ingredients are corn-derived. Blue Buffalo follows chicken with chicken meal (concentrated animal protein), then three quality whole grains. Two animal proteins before any carbohydrate is exactly what you want to see in a formula for obligate carnivores.
Where Blue Buffalo pulls ahead
No corn, wheat, or soy. Blue Buffalo is completely free of the three most common filler grains in cat food. Iams has corn grits at position two and corn gluten meal at position four - two corn-derived ingredients in the top four. Corn gluten meal is a plant protein that inflates the protein percentage on the label without providing the amino acid profile cats need. Blue Buffalo's brown rice, barley, and oatmeal deliver actual nutritional value.
Dual omega-3 sources. Blue Buffalo includes both flaxseed and fish oil, covering plant-based ALA and marine-sourced EPA/DHA omega-3 fatty acids. Cats are poor converters of ALA to EPA/DHA, so the fish oil is what makes this functional. Iams has no fish oil and no dedicated omega-3 source - a notable gap for skin, coat, and inflammation support.
No by-products. Blue Buffalo uses deboned chicken and chicken meal - both named, identifiable animal proteins. Iams relies on chicken by-product meal at position three, which is made from lower-quality parts like organs, necks, and feet. By-product meal provides concentrated protein, but it signals cost-conscious sourcing over quality.
Fruits and antioxidants. Blue Buffalo includes cranberries, blueberries, and other whole-food ingredients that provide natural antioxidants. Cranberries in particular are associated with urinary tract health - a genuine concern for indoor cats. Iams includes none of these. Shop on Amazon →
Where Iams holds its own
FOS prebiotics. Fructooligosaccharides are a prebiotic fiber that feeds beneficial gut bacteria. This is a genuinely useful functional ingredient that Blue Buffalo doesn't include in this form. For digestive health, Iams has a legitimate edge here.
L-Carnitine. Both formulas include L-Carnitine for fat metabolism support, which is relevant for indoor cats prone to weight gain. This is a tie, but it's worth noting that Iams was including this ingredient when many competitors at its price point weren't.
Price. Iams costs significantly less per pound than Blue Buffalo. For multi-cat households on a tight budget, that difference matters. Iams is the best cat food in its price bracket - chicken first, FOS prebiotics, L-Carnitine, and natural preservatives. If budget is the primary constraint, Iams is a reasonable choice.
Dried beet pulp. At position five, dried beet pulp is actually a solid prebiotic fiber source that supports healthy digestion. Despite its unglamorous name, it's a more nutritious fiber choice than some alternatives. Shop on Amazon →
The bottom line
Blue Buffalo Indoor Health is the clear winner, and the 18-point margin tells you why. Double chicken protein, quality whole grains, omega-3s from both flaxseed and fish oil, fruits and antioxidants, and zero corn, wheat, soy, or by-products. This is what a cat food ingredient list should look like. Iams isn't bad for what it costs - the FOS prebiotics and L-Carnitine are genuine positives, and chicken at number one puts it ahead of the D-grade competition. But the corn-heavy formula and missing omega-3s keep it firmly in average territory.
If you're currently feeding Iams and considering an upgrade, Blue Buffalo is one of the best moves you can make. The jump from C to B represents a fundamentally different approach to cat nutrition - one where animal protein actually dominates the formula instead of sharing space with corn fillers. Your cat's coat, energy, and long-term health will likely reflect the difference.