The summer table is unusually kind to stone patients. Melons measure near zero oxalate and are high in water — a hydrating snack that pulls double duty. Corn, peaches, and tomatoes are all low. Grapes and apples are low. The exceptions are the berries — blueberries at 27 mg per cup and blackberries at 45 mg sit in the caution range — and any dried fruit, which concentrates oxalate by removing water.
| Food | Oxalate (mg) | Serving | Rating |
|---|---|---|---|
| Watermelon, fresh | 1 | 1 slice | Safe |
| Cantaloupe | 2 | 1 cup cubed | Safe |
| Corn on the cob | 2 | 1 ear | Safe |
| Peaches, raw or canned | 3 | 1/2 cup | Safe |
| Tomatoes, raw | 17 | 1 cup | Safe |
| Grapes, green or red | 3 | 1 cup | Safe |
| Blueberries, fresh | 27 | 1 cup | Caution |
| Blackberries, fresh | 45 | 1 cup | Caution |
Most summer produce can be eaten freely. Watermelon and cantaloupe are near-zero and hydrating. Corn measures 2 mg per ear. Peaches, tomatoes, and grapes are all low. The practical rule for the season: fill the plate with the low members freely, portion the berries, and keep the dried versions — dried apricots, raisins, banana chips — in measured amounts, because drying concentrates both oxalate and sugar. The season also solves part of the hydration problem: melons and tomatoes are water-rich foods that contribute fluid alongside the water glass.
Peak-season prices are the lowest of the year, which makes August the right time to build the winter pantry. The stone-aware version of preservation is blanching before freezing — a brief boil followed by an ice-water shock — which removes soluble oxalate where it matters and holds the low-oxalate profile through the winter. Corn kernels, peach slices, and green beans frozen at peak carry their values into the months when the same foods cost more and taste less. A freezer full of summer corn and peaches is a stone-safe hedge against the processed options of the off-season.
One caution on the drying trend: dehydrators are popular for summer produce, and dried fruit concentrates both oxalate and sugar. A few dried apricots or raisins are fine in portions, but dried fruit leather made from berries and high-oxalate fruits deserves the measured eye. The season's gift is the fresh form — while it lasts.
Portioning is the whole story for the season's berries. A cup of blueberries at 27 mg and blackberries at 45 mg are caution-range on their own, but a half-cup mixed with yogurt brings the serving into a reasonable range while the yogurt's calcium binds the oxalate in the same meal. The pairing rule — berries with dairy — turns the season's one caution item into a manageable part of the summer table.
In portions, yes. Strawberries and raspberries are low (6 mg and 21 mg per cup), while blueberries (27 mg) and blackberries (45 mg) sit in the caution range. A portioned cup with calcium-rich yogurt is a classic safe pairing.
Excellent. Watermelon measures about 1 mg of oxalate per slice and is mostly water — it hydrates and adds almost nothing to the oxalate load. It is one of the best summer foods for stone patients.
Dried fruit concentrates oxalate and sugar by removing water. Dried apricots measure about 12 mg per five pieces and raisins 6 mg per quarter-cup — moderate but easy to overeat. Portion the dried versions and prefer fresh while the season lasts.
A quick mental map of the farmers market turns the whole trip into a measured decision. The melon and corn tables are the safe zone — near-zero oxalate, eat freely. The tomato and peach stalls are low. The berry stand is the caution section, where a pint is a portion rather than a bottomless bowl, and the dried fruit and nut vendors are the measured section, where a small bag is the serving. The stone-safe choices are the ones in season, which is exactly what the market sells at its peak.
Pick-your-own farms add one more consideration: the tasting table. Most of what a pick-your-own farm offers in August — peaches, corn, melons, tomatoes — is low-oxalate, which makes the farm stand one of the few places a stone patient can sample freely. The rule is the same as the database: fill the basket with the low members, portion the berries, and freeze the surplus while it is cheap.
And a closing note on what not to freeze: the berries that need portions fresh also need portions frozen, and the same rule applies to any high-oxalate harvest. Freezing preserves the values, it does not change them. The label habit that marks the frozen bags with the oxalate rating turns the winter pantry into a readable version of the summer table — the low-oxalate rows used freely, the caution rows portioned, and no guesswork in January about what is in the bag. The freezer is only a stone-safe tool if the labels survive the season with the food.
See how oxalate values are measured and verified on our data methodology page.