How Nutrients Change During Cooking

Raw broccoli has more vitamin C than steamed broccoli. But steamed broccoli has more bioavailable sulforaphane than raw. Boiled carrots release more beta-carotene than raw carrots — unless you boil them too long, in which case the beta-carotene degrades.

Cooking isn't just preparation. It's chemistry. And the cooking method you choose determines not just how your food tastes but what nutrients you actually absorb.

Heat as a Double-Edged Sword

Heat makes some nutrients more available and destroys others. The trade-offs are specific to each nutrient and each cooking method:

Boiling leaches water-soluble vitamins (C, B vitamins, folate) into the cooking water. If you drink the water — soups, stews — you keep the nutrients. If you drain it, you lose up to 50% of vitamin C and 35% of B vitamins. This is why broccoli boiled for 10 minutes retains far less vitamin C than broccoli steamed for 5.

Steaming is gentler. Food doesn't sit in water, so water-soluble vitamins stay in the food. Steamed broccoli retains about 80% of its vitamin C compared to raw. It's the best method for preserving heat-sensitive nutrients in vegetables.

Sautéing and frying in fat increase absorption of fat-soluble vitamins (A, D, E, K) and carotenoids. This is why spinach sautéed in olive oil delivers more usable vitamin A than raw spinach. The fat acts as a carrier. The trade-off: you're adding calories from the cooking fat.

Roasting concentrates flavors through Maillard reactions and caramelization. Nutrient loss is moderate — less than boiling, more than steaming. Roasted tomatoes have increased lycopene bioavailability compared to raw, because heat breaks down cell walls and releases the compound.

Grilling at very high temperatures can create heterocyclic amines (HCAs) on charred meat — compounds linked to health risks in high amounts. Lower-temperature grilling and shorter cooking times reduce HCA formation.

Nutrient Pairing

Some nutrient combinations enhance absorption:

  • Iron + vitamin C. Plant-based iron (from spinach, lentils) is poorly absorbed on its own. Adding a vitamin C source — lemon juice, tomatoes, bell peppers — can increase iron absorption by 2-3x. A squeeze of lemon on your lentil soup isn't just flavor; it's nutrition engineering.

  • Fat + carotenoids. Beta-carotene (carrots, sweet potatoes), lycopene (tomatoes), and lutein (spinach, kale) are fat-soluble. Cook them with a small amount of fat and you absorb significantly more. This is why traditional Mediterranean cooking pairs tomatoes with olive oil — the combination is nutritionally synergistic.

  • Allicin activation. Garlic's beneficial compound, allicin, forms when you crush or chop garlic and let it sit for 10 minutes before cooking. Adding garlic directly to a hot pan deactivates the enzyme that produces allicin. Chop first, wait, then cook.

What This Means for Recipe Design

Most recipes optimize for flavor. Some optimize for speed. Almost none optimize for nutrition. But with structured recipe data, this becomes possible.

If a recipe knows that it contains spinach and the cooking method is boiling, it could suggest: "Steam instead to retain 40% more vitamin C." If it detects iron-rich ingredients without a vitamin C source, it could prompt: "Consider adding lemon juice to improve iron absorption."

This is where Cooklang's structured format becomes relevant. A .cook file with tagged ingredients (@spinach{200%g}), cooking methods, and timers (~{5%minutes}) contains enough structured data for a tool to analyze nutritional implications of the cooking process — not just the raw ingredient list.

We haven't built this into CookCLI yet. But the structured data is already there in every Cooklang recipe. The ingredient annotations, cookware tags, and timer values provide the foundation. What's needed is a nutrient database mapping and rules about how cooking methods affect specific nutrients.

Practical Takeaways

If you want to preserve more nutrients with minimal effort:

  • Steam vegetables instead of boiling them. If you do boil, use the cooking water in a sauce or soup.
  • Add fat to carotenoid-rich foods. A drizzle of olive oil on roasted carrots or sautéed spinach increases absorption of vitamins A and E.
  • Crush garlic and wait before cooking. Ten minutes of air exposure activates allicin. Then cook it however you want.
  • Don't overcook. Shorter cooking times at moderate temperatures preserve more nutrients across the board. This also usually produces better texture and flavor — nutrition and quality align more often than you'd expect.
  • Eat a mix of raw and cooked. Some nutrients are better raw (vitamin C), others cooked (lycopene, beta-carotene). A varied diet with both raw and cooked preparations covers more ground than committing to either extreme.

The science of cooking and nutrition is still evolving, but one thing is clear: how you cook matters as much as what you cook. The same ingredients, prepared differently, can deliver meaningfully different nutrition.

-Alexey