Flavanols are plant compounds found in uneven amounts across fruits, vegetables, tea, and beans. The COSMOS trial, the largest flavanol study to date, linked a daily intake of about 500 mg to lower cardiovascular mortality. The new study measured actual flavanol intake with biomarkers in the US COSMOS cohort and the UK EPIC-Norfolk cohort, and found most people fall well short of 500 mg — fewer than one in five overall, and still short among people who follow standard produce guidance. The study's practical message was that the specific choices matter more than the total: a handful of blackberries, a whole apple, a cup of green tea make a measurable difference.
The flavanol-rich foods list and the oxalate table intersect at several points, and the intersection is where stone patients need the measured answer. Plums, blackberries, strawberries, and blueberries are flavanol-rich and carry real oxalate values. Green tea and black tea are flavanol sources and tea carries oxalate too. Apples and cherries are the easier overlap — flavanol-rich and low-oxalate. Beans — fava, pinto — carry moderate values. The table below shows the measured oxalate column for the flavanol list.
| Food | Oxalate (mg) | Serving | Rating |
|---|---|---|---|
| Apple with skin | 2 | 1 medium | Safe |
| Cherries | 3 | 1 cup | Safe |
| Peach | 3 | 1/2 cup | Safe |
| Plum | 4 | 1 medium | Safe |
| Strawberries | 6 | 1 cup | Safe |
| Blueberries | 27 | 1 cup | Caution |
| Blackberries | 45 | 1 cup | Caution |
| Green tea | 14 | 8 oz | Safe |
The reconciliation is the same one the stone diet uses everywhere: eat the heart-healthy foods, portion the ones with oxalate, and pair them with calcium at the same meal. The dairy pairing does the real work — the calcium in milk or yogurt at the meal binds oxalate in the gut before it reaches the kidneys, which lets the berries stay on the plate. A handful of blackberries with yogurt, a plum after a cheese serving, green tea alongside a meal that includes dairy — each pairing keeps the flavanol benefit and manages the oxalate column in one step. Apples, cherries, and peaches give the flavanol benefit with little oxalate at all, which makes them the daily defaults.
The flavanol study and the stone database agree on structure: variety within the produce groups, specific choices over generic advice, and the pairing that makes the choice work. A stone patient who eats the flavanol-rich fruits with dairy at meals, chooses apples and cherries as the daily fruit, and treats the berries as measured additions has solved both lists at once. The heart list and the stone list are not in conflict; they are the same plate read by two specialists.
No — the overlap is manageable with portioning and pairing. Apples, cherries, peaches, and plums are flavanol-rich and low-oxalate. The berries carry more oxalate, so they are measured additions paired with dairy, which binds oxalate at the same meal.
Green tea measures about 14 mg of oxalate per 8-ounce cup — low, and fine for most patients in normal amounts. The pairing habit (tea with a meal that includes dairy) and generous water intake keep the tea on the safe list alongside its flavanol benefit.
Choose the low-oxalate flavanol sources as the daily default — apples, cherries, peaches, plums — and add a cup of green tea. Then include the berries as measured portions with yogurt or milk at the same meal. The pairing is what lets the list stay complete.
Tea is the flavanol list's most efficient entry point — a cup of green tea delivers roughly 200 mg toward the 500 mg target — and it is also the item stone patients ask about most. The measured answer: green tea measures about 14 mg of oxalate per 8-ounce cup, which is low, and normal consumption is fine for most stone patients, especially with the pairing habit and generous water. The extreme versions — large amounts of brewed iced tea as a daily substitute for water — are the ones that concentrate the oxalate load, and the fix is the same as everywhere: tea as a counted beverage, water as the base. The patient who drinks tea with meals and water between keeps the flavanol benefit without turning the tea into the hydration default.
The flavanol study's deeper point applies to the stone diet directly: specific choices beat generic advice. Just as five servings of produce can miss the flavanol target, the stone diet's strength is its measured specificity — the value per serving, the portion, the pairing. The patient who applies that specificity to the flavanol list gets the heart benefit and the stone safety from the same plate, which is the reconciliation the study's own authors called for in dietary guidance.
See how oxalate values are measured and verified on our data methodology page.