White bread, 1 small slice (30g)
3.7 teaspoons
GI 71 · GL 10
Brown bread, 1 small slice (30g)
3.3 teaspoons
GI 74 · GL 9
The figures
Dr David Unwin's bread chart, distributed by the Public Health Collaboration, lists seven breads. Each is a small 30g slice. The GI values are taken from the scientific literature, and the glycaemic load and teaspoon figures are calculated using the method in Unwin, Haslam and Livesey's 2016 paper. The table below reproduces all seven rows in the order the chart prints them.
| Bread, 30g slice | GI | GL | Teaspoons |
|---|---|---|---|
| White bread | 71 | 10 | 3.7 |
| Brown bread | 74 | 9 | 3.3 |
| Wholemeal bread, stoneground flour | 59 | 7 | 2.6 |
| Wholemeal pita | 56 | 8 | 2.9 |
| Oatmeal bread | 62 | 9 | 3.3 |
| Rye bread (69% whole-grain rye flour) | 78 | 11 | 4.0 |
| Wholegrain barley bread (50% barley) | 85 | 15 | 5.5 |
A second chart from the same series, titled "White, brown or green foods?", shows two slices together (60g). There, white bread has a glycaemic load of 22 and a teaspoon figure of 8. Wholemeal brown bread has a glycaemic load of 16.2 and a teaspoon figure of 6.
The two charts do not scale exactly: 8 is not quite twice 3.7, and 6 is not quite twice 3.3. They draw on different entries in the published GI tables, for different loaves. Both are recorded on the sources page, and the calculator uses the single-slice chart.
How the brown bread figure is worked out
The 2016 paper uses brown bread as its main worked example. Box 2 in the paper sets out the arithmetic in three steps.
1. Carbohydrate: 40g per 100g × 30g ÷ 100 = 12g
2. Glycaemic load: 12g × GI 74 ÷ 100 = 9g
3. Teaspoons: 9 ÷ 2.73 = 3.3
The figure 2.73 is the glycaemic load of one 4g teaspoon of table sugar: 4.2g of carbohydrate after digestion, multiplied by table sugar's GI of 65 and divided by 100. The page what is glycaemic load covers that step in full.
What the names on the loaf mean
Bread names are not standard from one country to the next. In the UK, wholemeal bread is made from flour that contains the whole grain: bran, germ and endosperm. "Brown" can describe a wholemeal loaf, or a loaf made partly from wholemeal flour. In the United States, "whole wheat" usually corresponds to the UK's wholemeal, while "wheat bread" can be made mostly from refined flour. Multigrain and seeded loaves may use either kind of flour as a base.
The chart rows are specific. "Wholemeal, stoneground flour" is a loaf made from coarsely milled whole grain. "Rye" is a bread containing 69% whole-grain rye flour. "Wholegrain barley" contains 50% barley. The GI of a loaf depends on its recipe, so a bread with a similar name in a different shop may test differently.
In both the UK and the United States, ingredients on a packaged loaf are listed in descending order of weight. The first flour named on the label is the one the bread contains most of, which is the quickest way to see what a loaf called brown, wheat or multigrain is mainly made from.
Why the GI values sit close together
White flour and wholemeal flour are both mostly wheat starch. When grain is milled into fine flour and then baked, the starch is swollen with water and heat and becomes easy for digestive enzymes to reach. The bran in wholemeal flour is present, but once the grain has been ground fine, it does little to slow how quickly the starch inside is digested. That is the usual explanation in the GI literature for why finely milled white and wholemeal breads test at similar values.
The particle size of the flour is a larger factor. Coarsely milled and stoneground flours, or breads containing intact grains, tend to test lower, because enzymes reach the starch more slowly. On the chart, the stoneground wholemeal loaf has a GI of 59 and a teaspoon figure of 2.6. The rye and barley loaves on the same chart test higher than white bread, at GI 78 and 85.
The amount of carbohydrate per slice is similar across ordinary loaves too, at around 40g per 100g in the paper's example. Glycaemic load multiplies the two, so two breads with similar GI and similar carbohydrate content produce similar loads.
What the chart does not measure
Glycaemic load is a measure of the blood glucose response. It does not describe fibre, vitamins, minerals, protein or how full a slice keeps someone. Wholemeal and white flour differ on several of those measures, and none of them appear in the teaspoon figure. The chart answers one question only: how a small slice is likely to affect blood glucose compared with a teaspoon of table sugar.
GI values are averages from small groups of volunteers, and individual responses vary. Butter, cheese, eggs or other foods eaten with the bread tend to change the response of a whole meal.
Try it in the calculator
Every bread in the table is in the calculator under Breads, along with wheat and almond-flour roti from the South Asian foods chart. Add two slices of any loaf to see the figure for a sandwich, or add them alongside the other foods from the same meal.