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Late-Summer Berries: Blackberries and Raspberries at Their Peak

By the GlycemicWise Data Editorial Team · Published 2026-08-09 · Last reviewed 2026-08-09 · Seasonal · 6-8 min read · Dietary reference only

August brings the blackberry and raspberry season to a close. Two of the lowest-GL fruits you can buy — with the fiber to back it up.

The August Harvest

August is the tail of blackberry and raspberry season in the US — the moment the market flats are full and the prices are lowest. For anyone watching glucose, this is one of the best fruit windows of the year: both berries sit near the very bottom of the fruit GL scale.

Blackberries carry roughly 5–6g of fiber per cup — among the highest of any fruit — with a GL around 4 per cup. Raspberries are similar: high fiber, GL ~5 per cup, and both are naturally low in sugar relative to their volume.

Why Berries Punch Above Their Sweetness

Berries taste sweet but behave differently from other fruit because of fiber and water content. The fiber slows sugar absorption, and the volume fills the plate for few carbs — which is why the food pages rate them Low GL while a banana or mango sits higher. They are also the fruit most often shown in the ADA 2026 pregnancy-diet work we covered: the fiber-dense fruit that shows up in the better-glucose patterns.

Ways to Use the Season

The berry window rewards simple uses: berries over plain yogurt (a GL 2 + GL 3 breakfast), berries in overnight oats, or a berry-and-melon bowl at the Labor Day picnic (melon season is running in parallel). Frozen berries at season's end are just as good — nutrition holds, and the price drop makes stocking the freezer worthwhile. A frozen-berry habit is effectively a year-round low-GL dessert that does not need a 'treat' exception.

Dietary reference — not medical advice. Information provided for educational purposes.