Guide

Quinoa has the strongest reputation of any grain in the shop. On glycemic load it finishes mid-table.

Pearl barley, which turns up mainly in soup and has no wellness marketing behind it whatsoever, wins this ranking comfortably. That gap between reputation and number is why it's worth going through them properly.

The ranking, per cooked cup

Glycemic load per one cup cooked, which is a realistic side-dish portion:

• Pearl barley: GI around 28, GL about 11
• Bulgur: GI around 48, GL about 12
• Buckwheat: GI around 50, GL about 15
• Freekeh: GI around 43, GL about 16
• Steel-cut oats: GI around 45, GL about 13 per cooked cup
• Quinoa: GI around 53, GL about 18
• Farro: GI around 45, GL about 19
• Wild rice: GI around 57, GL about 18
• Couscous: GI around 65, GL about 22
• Brown rice: GI around 68, GL about 28
• Millet: GI around 71, GL about 25

Two of those deserve a second look, because they're the ones most likely to be sitting in a kitchen bought specifically as the healthy option.

Brown rice has a health halo it hasn't earned

Brown rice is better than white rice. It has more fibre, more magnesium, and tests around 68 against white rice's 73. That's a real improvement and a small one.

The problem is that brown rice is dense, so a cup delivers around 45 g of carbohydrate, and a modest-sounding GI applied to a large carbohydrate load produces a glycemic load near 28. That's the highest number on this list, from the grain most often chosen as the responsible swap.

Barley in the same bowl, at the same volume, is roughly a third of that. So is a cup of barley mixed half-and-half with cauliflower rice.

Why barley wins

Beta-glucan. Barley contains a soluble fibre that forms a viscous gel in the gut, slowing both gastric emptying and glucose absorption. It's the same compound that gives oats their cholesterol-lowering claim, and barley has more of it.

The practical catch is that pearl barley has had the bran polished off, which reduces the fibre somewhat. Hulled or pot barley keeps more of it and takes longer to cook. Even pearled, it outperforms every other common grain here.

It also behaves well in food. Barley holds its texture in soup, works cold in salads, and takes about 30 minutes on the hob with no attention.

Couscous is not a grain

Worth clearing up: couscous is pasta. It's semolina — refined durum wheat — rolled into tiny pellets. It cooks in five minutes because it's essentially pre-cooked, and it carries the glycemic load of refined pasta rather than of a whole grain.

Wholewheat couscous exists and is a modest improvement. Pearl or giant couscous is the same material in a bigger shape.

Bulgur, which looks similar and is often shelved next to it, is a genuinely different food: cracked whole wheat, parboiled, with the bran intact. It's the better buy at the same convenience.

The three that are worth knowing better

Freekeh is durum wheat harvested green and roasted. High protein for a grain, high fibre, nutty flavour, and it cooks in about 20 minutes. It's the one I'd suggest to someone bored of quinoa.

Buckwheat isn't wheat at all — it's a seed, gluten-free, and it comes with rutin and a favourable amino acid profile. Toasted, it's kasha; ground, it's the flour in soba and galettes.

Farro is an ancient wheat with a chewy texture that holds up in salads better than almost anything else here. Its number isn't outstanding, but its texture means a smaller portion still eats like a full bowl.

Portion is doing more work than variety

Every grain on this list is carbohydrate-dense. The spread from best to worst is roughly two and a half times, and the spread between a half-cup and a one-and-a-half-cup serving is three times. The portion decision is bigger than the grain decision.

Which is why the most useful technique isn't picking the winner. It's cutting the grain with something that isn't one: half barley and half cauliflower rice, a bulgur salad that's two-thirds vegetables and herbs, a bowl where the grain is the base rather than the bulk.

Tabbouleh done traditionally is the model. It's a parsley salad with some bulgur in it, not a bulgur salad with parsley on top.

If you're avoiding gluten

Four on this list are safe: buckwheat, quinoa, wild rice, and millet — buckwheat and quinoa being seeds rather than grains despite how they're used. Barley, bulgur, farro, freekeh and couscous all contain gluten, and barley in particular catches people out because it hides in soups and stocks.

That's an unfortunate overlap, since barley is the best performer here. For coeliac disease or genuine gluten sensitivity, buckwheat is the closest substitute on both texture and number.

Cooking notes that affect the number

Cook grains al dente rather than soft. Overcooked starch is more gelatinised and digests faster; the difference is measurable.

Cook them ahead and chill them. Retrograded starch forms in cooled grains as it does in rice and potatoes, and grains reheat well.

And add fat and acid. A grain salad dressed with olive oil and lemon has a lower response than the same grain plain, which is fortunate, because that's also how it tastes best.

Batch cooking helps on both fronts. A pot of barley on Sunday covers four dinners, gets chilled in the process, and removes the moment mid-week where rice wins because it's faster.