Sweet Lies and Dry Truths: Sugar in Wine

 Is wine really “full of sugar”? What about those “zero sugar” labels, or the idea that wine is keto-friendly? In this episode of The Wine Lab, Andreea breaks down what you need to know about sugar in wine — from grapes on the vine to yeast in the tank, from chaptalization in Burgundy to back-sweetening in Riesling, and from Champagne dosage to carbs and calories. Along the way, we’ll uncover what’s legal, what’s marketing, and what really ends up in your glass. 

Glossary

• Glucose & Fructose – The natural grape sugars fermented by yeast into alcohol and carbon dioxide.
• Residual Sugar (RS) – Natural grape sugar left in wine after fermentation is stopped or incomplete. The main source of carbohydrates in wine.
• Chaptalization – Adding sugar before fermentation to increase alcohol, not sweetness. Legal in many cooler regions (e.g., Burgundy, Germany), illegal in warmer regions (e.g., California, Italy, Spain).
• Back-sweetening – Adding grape juice, concentrate, or in some U.S. states, sugar after fermentation to increase sweetness. EU law restricts this to grape-derived products only.
• Süssreserve – A German method of back-sweetening where unfermented grape juice is reserved and blended into the wine after fermentation.
• Dosage – In sparkling wines, a small addition of sugar solution before corking that sets the final sweetness level (e.g., Brut Nature, Brut, Demi-Sec).
• Fortification – Adding a spirit such as brandy to stop fermentation, leaving natural grape sugar in the wine (e.g., Port, Madeira).
• Dry Wine – A wine where nearly all sugars have been fermented away, leaving little or no residual sugar.
• Sweet Wine – A wine with sugar remaining in the finished product, either naturally or through winemaking choices.
• Keto-friendly Wines – Typically dry wines with 1–3 g of carbs per 5 oz glass, low enough to fit into a ketogenic diet.