Which nutrients are fragile
Not all nutrients survive cooking equally [1]:
- Most fragile: water-soluble vitamins, especially vitamin C, folate, and thiamin (B1), which are sensitive to heat, light, air, and leaching into water.
- More stable: minerals (they don't break down, though they can leach into cooking water) and the fat-soluble vitamins A, D, E, K, which tolerate heat better.
How cooking method matters
The biggest variable is water plus heat plus time [2]:
- Boiling leaches water-soluble vitamins into the cooking water — discarding that water discards nutrients.
- Steaming, microwaving, stir-frying, and roasting with little or no water tend to preserve more, partly because they're faster and use less water.
- Long cooking at high heat and keeping food hot for a long time increase losses.
Storage and prep also count
- Time and light slowly degrade vitamin C and folate, so very old or light-exposed produce has less.
- Cutting far in advance exposes more surface to air; cut closer to cooking when practical.
- Frozen produce is often comparable to fresh, since it's frozen soon after harvest.
Keep it in perspective
These losses are real but usually modest, and cooking also has benefits — it improves the absorption of some nutrients (like certain carotenoids) and makes food safe and digestible. A varied diet easily accommodates normal cooking losses; you don't need a supplement to 'replace' what cooking removes.
Practical guidance
- Favor steaming, microwaving, or roasting over long boiling for vegetables.
- Use the cooking liquid (e.g., in soups) to recover leached vitamins and minerals.
- Eat a variety of produce, some raw and some cooked, and don't overthink it — see [food-first guidance](/learn/do-you-need-supplements-food-first).