Key Topics Covered

As requested by a listener, today we are going to discuss how cooking changes the nutritional composition of foods. We will discuss how the absorption of micronutrients changes throughout various cooking methods, pre and post cooking and how weights and overall volume change. We won’t be covering everything in this podcast but hope you find this interesting.

Cooked vs Raw Weights

raw chicken breast calories versus cooked chicken breast calories

  • This is more applicable to people who are tracking/measuring their intake.
  • But obviously weights of most foods will change when cooked vs raw. 
  • How it changes can depend on the cooking method, duration and temperature.
  • Raw weight is considered more “accurate” because the calories and macros remain constant, regardless of how long it’s cooked.
  • Cooking alters the weight, but the total calories stay the same.
  • As a general guide though:

Cooked meat = 25-30% lighter than raw.

Cooked pasta/rice = 2-3x heavier than raw.

Potatoes typically lose 15-20% when cooked if baked/roasted.

Loss of Nutrients

  • The most common example is that soluble vitamins, so things like vitamin C and the B vitamins, are often reduced when exposed to heat.
  • The temperature and cooking method matters though.
  • Research looking at boiling has found that broccoli, spinach and lettuce lose 50% or more of their vitamin C. Some will be lost in the water, but a lot is also lost to heat. 
  • Microwaving reduced it by 20-30%.
  • Steaming by 7-10%.
  • Other research looking at the omega 3 content of seafood found baking led to minimal losses while frying led to a 70-85% loss.
  • So how you cook things and the temperature at which they are cooked will influence potential loss of nutrients.
broccoli boiling in a pot

Increased Nutrient Absorption

  • Eggs are well known for having higher protein digestibility when cooked. One study found a 180% increase in digestibility, but regardless of the actual number, it is a consistent increase.
  • The absorption of beta-carotene in carrots is higher after cooking. One study found a 6.5x increase.
  • Tomatoes sautéed in olive oil led to an 80% increase in lycopene. This is likely due to a combination of the cooking process breaking down cell walls to make the lycopene more bioavailable AND the fact that it is fat-soluble, which means that the olive oil would further help absorption.
  • There’s a pretty long list of interesting changes like these – including a lot of plant based foods where the bioavailability of many micronutrients is altered.

Summary

Too be honest, we don’t think it’s that deep. Keeping in mind the points we discussed, having a variety of food cooked and some raw, particularly in the case of fruit and vegetables is going to provide you with the best of both worlds, an array of micronutrients. Personally, we would not focus on how to cook certain vegetables to optimise the amount of micronutrients you will receive. Focusing on this will cause unnecessary stress. It is best to focus on variation.

Relevant Blogs/Research

Relevant studies: