McDonald's vs Burger King.

Two of the three biggest hamburger chains in the world have famous, iconic french fries. They have virtually nothing else in common.

The oil story.

McDonald's cooks its fries in a proprietary blend of canola, corn, and soybean oils, with "natural beef flavor" added — the flavoring is derived from beef tallow and is the thirty-five-year compromise behind the 1990 switch away from actual beef tallow. The fries aren't cooked in animal fat, but they are, in a meaningful sense, flavored with it. Vegetarians who think McDonald's fries are vegetarian are wrong — this is well-known in the vegetarian community, but less-known to casual diners.

Burger King cooks in a cleaner blend: soybean oil and corn oil, no added beef flavor, no hidden animal products. By ingredient alone, BK's fries are genuinely vegetarian. Vegan is another question (shared fryer), but vegetarian is a clean yes.

The coating story.

This is where McDonald's gets into trouble. The fry coating that gives McDonald's fries their signature texture contains wheat dextrin — a small amount of actual wheat, added for crispness. A McDonald's fry contains gluten before it even hits the fryer. For celiacs, McDonald's fries are never, ever safe. Not even at a theoretical "dedicated fryer" location.

Burger King's coating is rice flour and potato starch. Gluten-free at the ingredient level. The problem is the shared fryer — BK's fry oil cooks breaded chicken, onion rings, and Chicken Fries, all of which contain wheat. So BK's fries become unsafe for celiacs at the cooking step, not at the ingredient step. It's a better starting position than McDonald's, but the end result is the same: not celiac-safe.

The nutrition gap.

A medium order of McDonald's fries: 320 calories, 240 mg sodium. The same size at Burger King: 380 calories, 330 mg sodium. McDonald's wins handily on both metrics, largely because the BK portion is slightly bigger and the coating absorbs more oil.

If you're counting sodium specifically (and you probably should be — fast food is where most Americans exceed their daily sodium allowance), McDonald's is the cleaner choice. It's also tied for the lowest-sodium fry on Frypedia, matching Chick-fil-A at 240 mg.

The verdict.

Neither is an all-green chain. Neither is celiac-safe. Both have shared fryers. Both have major disqualifiers for at least one significant dietary restriction.

If you're vegetarian, Burger King wins. McDonald's natural beef flavor is disqualifying.

If you're watching sodium or calories, McDonald's wins by a clear margin.

If you're celiac, neither is safe, but BK is closer — the ingredient itself is clean; only the fryer is the problem. At McDonald's, even a theoretical fix to the fryer wouldn't help, because the coating contains wheat.

If you're picking a fry based on taste alone, we can't help you — Frypedia doesn't rank on deliciousness, only on facts. The McDonald's fry is iconic for a reason, and the Burger King fry has loyalists who will die on its hill. Get both, do your own taste test, and use Frypedia to decide which one to eat when a diet restriction is on the table.

See the full writeups: McDonald's · Burger King