Berries

Raspberries and blackberries are among the lowest, with about 4–5 grams of sugar per 100 grams and roughly the same amount of fiber. Strawberries follow at around 5 grams of sugar, while blueberries sit higher at about 10 grams. Cranberries are very low in sugar in their raw form but are usually sweetened heavily when sold dried or as juice.

Most fresh berries fit into a keto plan in modest portions because their fiber lowers net carbs. A half-cup of raspberries or blackberries contains roughly 3 grams of net carbs, and the same amount of strawberries about 4 grams. Blueberries are denser in carbohydrates, so they are usually limited to a few tablespoons on stricter keto macros.

Berries are best known for vitamin C, with strawberries and blackcurrants particularly rich (blackcurrants can exceed 180 mg per 100 grams). They also supply vitamin K, manganese, and fiber, plus anthocyanin pigments that give blue, red, and purple berries their color. Compared with most other fruits, berries tend to be lower in total sugar per gram and higher in polyphenol content.

Yes, frozen berries are nutritionally very close to fresh because they are typically picked ripe and frozen quickly, which preserves vitamin C and anthocyanins. Some water-soluble vitamins decline slightly over months of storage, but fiber, minerals, and most polyphenols remain stable. They are often a more practical year-round source than out-of-season fresh berries.