Ways Nutrients Are Destroyed
- Heat: high cooking temperatures degrade sensitive nutrients — water-soluble vitamins like Vitamin C and B vitamins are especially vulnerable, and overcooking increases the loss.
- Light: some nutrients, such as Vitamin A and Vitamin D, break down when exposed to light.
- Oxygen: unsaturated fats can oxidize into rancidity, and vitamins like C and some B vitamins degrade through oxidation, especially in poorly sealed storage.
- Water (leaching): water-soluble vitamins can dissolve into cooking water and be lost if the water isn’t used — boiling vegetables, for example, causes significant vitamin loss into the water.
- Processing: refining grains into white flour removes the bran and germ (and their fibre, vitamins and minerals), and canning can cause some vitamin loss from high heat.
- Chemical reactions: pH changes can affect nutrient stability — Vitamin C degrades faster in acidic conditions — and enzymes like polyphenol oxidase cause browning that can reduce nutrient quality.
- Mechanical damage: cutting or grinding increases surface area exposed to air and light, accelerating nutrient loss.
- Storage conditions: high or fluctuating temperature and humidity can degrade nutrients and promote microbial growth.
Mitigating Nutrient Loss
- Steam instead of boil: steaming preserves more nutrients than boiling.
- Use minimal water when cooking, to reduce nutrient loss from leaching.
- Cook at lower temperatures for shorter times where possible.
- Use the cooking liquid from boiled vegetables in soups or sauces to recover leached nutrients.
- Store food properly in airtight containers, in cool, dark places.
- Use fresh ingredients promptly to maximize their nutrient content.
