A common concern is whether cooking "destroys" protein — the short answer is no, not meaningfully, but the longer answer involves some real, useful nuance about what cooking method does affect.
Protein content itself is largely heat-stable
Unlike vitamin C or certain B vitamins, which degrade meaningfully with heat and cooking time, the actual protein content of a food changes very little through normal cooking — the total grams of protein in a raw chicken breast and the same breast cooked are essentially the same, adjusted only for water loss (which slightly concentrates the protein per 100g in the cooked version, not destroys it).
What cooking does change: protein digestibility
Cooking generally improves protein digestibility rather than harming it, particularly for eggs and legumes — raw egg white, for instance, contains a compound called avidin that binds biotin and a trypsin-inhibiting effect that reduces protein digestibility; cooking denatures both. This is part of why raw egg white is a notably worse protein source than cooked, independent of any foodborne illness concern.
Where cooking method matters more: fat content and micronutrients
The real differences between cooking methods show up in added fat (a chicken breast pan-fried in oil carries meaningfully more calories than the same breast grilled or baked) and in water-soluble nutrient loss — boiling leaches more B vitamins and minerals into the cooking water than roasting, grilling, or steaming do, since those methods don't submerge the food in liquid that then gets discarded.
High-heat cooking and compound formation
Very high-heat methods (grilling, especially charring, and pan-searing at high temperatures) on meat specifically can form compounds called heterocyclic amines (HCAs) and polycyclic aromatic hydrocarbons (PAHs), which have been studied for a potential cancer-risk association in epidemiological research, though the evidence is observational rather than fully causal. Marinating meat before high-heat cooking and avoiding directly charred, blackened portions are the most commonly cited practical mitigations from the research.
Practical takeaway
Don't worry about cooking "destroying" your protein grams — that's not a real concern. Do favor baking, roasting, grilling, and steaming over deep-frying for calorie control, and moderate very high-heat charring on meat specifically as a general precaution rather than a protein-preservation issue.