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The question

Is there a difference in terms of nutritional value (sugar content especially) between sour dough bread and 'normal' yeast based bread?

The answer

Nutritionally speaking, sourdough bread and one made from store bought yeast are the same. One small slice (29 grams) of each has 1 gram of sugar and 93 calories. The difference is in how they are made.

Regular bread is made using store bought yeast that reacts with gluten making the dough rise. Sourdough bread, on the other hand, is made with a "starter". This starter is made from a combination of yeast and bacteria growing inside a paste made of flour and water. These bacteria produce lactic acid which ferments the dough. They also give sourdough bread its characteristic sour taste.

The lactic acid in sourdough bread results in a lower glycemic bread than one made from regular yeast. (The glycemic index is a measure of how quickly a food causes your blood glucose to rise after eating it.) Compared to regular bread, sourdough bread is converted to blood glucose (sugar) more slowly - so it's a good choice for anyone managing their blood glucose levels.

For the most nutrition, I recommend choosing a whole grain sourdough bread instead of one made from refined (white) flour.

Look for a rye bread made with whole grain rye flour, rye kernels, rye flakes or rye meal. Because rye flour doesn't have enough gluten to react with yeast, a sourdough starter is used to make the bread. If you're not sure look for "sourdough" on the ingredient list.

Send dietitian Leslie Beck your questions at dietitian@globeandmail.com. She will answer select questions, which could appear in The Globe and Mail and/or on The Globe and Mail web site. Your name will not be published if your question is chosen.

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