Does “denaturing” nutrients in milk by boiling it make them less useful, or actually more useful, as they undergo “denaturation” anyway during digestion? I've read online that boiling milk "denatures" nutrients such as protein, calcium and others contained in milk, rendering the milk less nutritious. At the same time, I've also read that because the nutrients in milk (and other foods) undergo "denaturation" in our body during digestion anyway, boiling it will not make milk less nutritionally valuable, and will actually help the body to more readily absord the nutrients in it into the bloodstream right after ingestion. What is the truth in this matter? Thanks for any knowledgeable answers! I put the word "denature" in quotes because it's a technical term and I'm not really sure in which ways it can correctly be used.

  • Not an answer but one thing that comes immediately to mind is that boiling will destroy water-soluble vitamins such as C and B1. But I don't see how it would have much effect on minerals such as calcium. – Carey Gregory May 22 at 0:56
  • Hi Carey, thank you much for your response!! When you say that boiling will destroy water-soluble vitamins, do you mean that the the vitamins will evaporate due to boiling, or they will remain in the water but will be "destructured" (for lack of better term) and therefore unusable by the body when ingesting? Please clarify. Thank you once again!! – avdmr May 22 at 4:55
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    You imagine me to be much more of a chemist than I am. It's not by evaporation. – Carey Gregory May 22 at 5:19

In short: Cooking milk has probably only a minor effect on its nutritional value.

MICRONUTRIENTS:

According to USDA Table of Nutrient Retention Factors (p. 5), in milk heated for 10 minutes, the vitamin loses are: vitamin B1, B6 and choline: 10% ; vitamin C and folate: 15% ; vitamin B12: 20%. Other vitamins and minerals are not affected.

From the mentioned vitamins, milk is high only in vitamin B12, so it seems that destruction of 20% of vitamin B12 is the only meaningful negative effect of cooking milk on micronutrients.

Milk cooking appears to have no significant effect on the bioavailability (absorption and utilization) of calcium (ScienceDirect, 2013).

MACRONUTRIENTS:

Proteins are denaturated by cooking and stomach acid (Elmhurst.edu). Denaturation affects only "the shape" of the protein molecule but not its composition or nutritional value. Proteins are digested (broken down) into amino acids before absorption and cooking makes them more digestible (concluding from cooked/raw egg protein digestibility study).

Lactose, the major carbohydrate in milk, is not affected by cooking and decomposes to glucose and galactose only at 203.5 °C (PubChem, section 5.3).

Fats should also not be affected by milk cooking (concluding from the smoke point - the temperature at which fatty acids start to break down - of most oils, which are all well above 100 °C).

  • Can you explain that why boiling only affect watersoluble vitamins? Is it by evaporation? – user237650 2 days ago
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    Some vitamins, including fat-soluble ones, decompose at certain temperatures, they do not likely evaporate at milk boiling temperatures. NutritionData mentions that cooking can destoy 25% of vitamin A (fat-soluble), but this apparently did not happen in the experiments with milk used in the USDA table (the first link in my answer). – Jan 2 days ago

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