The One Thing I Never Buy From Costco (and You Shouldn’t, Either)

My husband and I fell hard for Kewpie mayo during our honeymoon in Japan, thanks to an impressive (some might say alarming) number of 7-Eleven egg salad sandwich dinners. The magic of that creamy, rich egg salad filling, nestled between two crustless slices of sweet, cloudlike milk bread, cannot be overstated.

For me, that sandwich was life-changing, all because of the subtly tangy, umami-packed Kewpie mayo. Back in the U.S., no American mayonnaise could compare; most were too sweet, flat, and light. We needed to find our fix—and fast. So, imagine our excitement when we discovered Kewpie at Costco—it’s my husband’s favorite store, so of course I didn’t hear the end of it for the whole car ride home.

Why I Won’t Buy Kewpie Mayo at Costco

Our mayo dreams came crashing down the moment we tasted it. This Kewpie doppelgänger was sweeter, thinner, tangier, and far less rich. Costco’s U.S.-made version looks the part, but it isn’t the real deal. The low price is tempting, but if you’re chasing that custardy, melt-in-your-mouth egg salad—or any Japanese-style mayo moment—this bottle won’t deliver. It’s one Costco buy I skip every time.

Costco’s version of Kewpie is less than half the price of the authentic Japanese product, but a glance at the ingredient list explains a lot:

• Water is the third ingredient, explaining the thinner consistency and muted richness; real Kewpie contains no water.
• No malt vinegar is used.
• Mustard powder is added, likely to mimic the deeper orange hue of Japanese egg yolks.
• Only soybean oil is used, not canola.
• It contains sugar, which tips the balance away from that signature savory depth.

To make matters more confusing, there’s a third Kewpie variant sneaking around the grocery aisles: a U.S.-made Kewpie that’s not Costco’s unique blend. Its ingredient list mirrors Costco’s, but it replaces MSG with yeast extract.

The Real Deal: Japanese Kewpie Mayo

True Japanese Kewpie mayonnaise is made with egg yolks only, making it creamier and thicker than many American mayonnaises that use whole eggs, such as Hellmann’s and Best Foods. It’s made with canola and soybean oils, and gets its subtle tang from a proprietary vinegar blend, widely understood to be rice, apple cider, distilled, and malt vinegars.

Unlike most American mayos, Japanese Kewpie contains no sugar, creating a deeper, more savory flavor. To enhance its umami punch, it also contains monosodium glutamate (MSG), which is naturally found in tomatoes, mushrooms, and cheese and is added to countless savory dishes worldwide.

Japanese-made Kewpie is sold at most Asian markets, through the brand’s website, and increasingly in grocery stores. Yes, it’s more expensive than the Costco version—but for the real deal, I’d gladly pay extra.