Because most milk available to consumers is pasteurized, heating milk before you drink it isn't typically necessary for safety reasons. However, boiling milk can provide other benefits, like a more favorable fatty acid profile and increased tolerance for people who are allergic.
On the other hand, boiling milk can cause some negative effects, like the breakdown of proteins. When debating whether you want to boil your milk before drinking it, you have to weigh the pros and cons and determine your main nutritional goal to make your decision.
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If you want to get more short-chain and medium-chain fatty acids in your diet, the best time to drink milk may be after you boil it. Boiling milk also reduces pathogens and may make it more tolerable for people with allergies. However, heat can break down the proteins in the milk, making them less beneficial.
More Beneficial Fatty Acids
Milk contains three major categories of fatty acids: short-chain, medium-chain and long-chain. Short-chain fatty acids (or SCFAs) help keep your gut and immune system healthy, reduce chronic inflammation and may decrease your risk of developing cancer.
Medium-chain fatty acids (also called medium-chain triglycerides or MCTs), are unique types of fats because, instead of being stored by the body as fat, they're used immediately for energy. This can help you maintain a healthy weight and boost your athletic performance.
Long-chain fatty acids, which include the omega-3 fatty acids EPA and DHA, promote growth and development, boost brain health and keep your eyes healthy. Long-chain fatty acids have also been linked to reduced cancer rates, decreased inflammation and better cognitive function; however they're not found in milk in significant quantities.
According to a report published in Lipids in Health and Disease in August 2017, boiling milk increases the concentration of short-chain and medium-chain fatty acids, while simultaneously decreasing the amount of long-chain fatty acids in the milk. So, it may be that boiled milk has an increased ability to improve energy, help you maintain a healthy weight and reduce inflammation, but a decreased ability to boost your eye health, brain health and cognitive performance.
However, because milk doesn't have a high amount of long-chain fatty acids, like omega-3s anyway, this isn't really a problem in this case. Whether boiling is right for you depends on what you're looking to get from the milk.
Read more: The Fatty Acid Composition of Coconut Oil
Increased Allergy Tolerance
But it's not just the nutritional profile that changes when you boil milk. Milk is one of the most common allergens out there. According to an August 2019 report in the Journal of Allergy and Clinical Immunology, boiling milk may also change the way it's tolerated by people who are allergic to milk.
The report notes that heating milk changes it's protein structure, which may also change the way your immune system reacts to it. Researchers tested this theory with children allergic to milk and found that 69 percent were able to tolerate the cooked milk, even though they couldn't tolerate uncooked milk.
Another study published in the same journal, the Journal of Allergy and Clinical Immunology a year earlier, in April 2018, reported similar findings, although they went a step further. Researchers found that not only were children who were allergic to milk able to consume the cooked milk without a problem, almost half of the children who were able to tolerate cooked milk were eventually also able to tolerate noncooked milk after a period of six to 12 months of exposure.
Of course, these studies were done under extreme medical supervision. If you or your child is allergic to milk, do not attempt to drink boiled milk to see if it will cause a reaction. Allergies to milk can be serious and even fatal if they cause an anaphylactic response, so allergy exposure tests like these are appropriate only under proper medical guidance and should never be done at home.
Slightly Fewer Pathogens
Most milk available for commercial sale is already pasteurized, which is a process that involves using heat to kill any potential pathogens, like bacteria or viruses, but if the milk you get is raw, it may benefit from boiling.
According to the U.S. Food and Drug Administration, raw milk may contain salmonella, E. coli, listeria or Campylobacter bacteria, all of which have the potential to cause food poisoning. Although it's possible that pasteurized milk and boiled milk contain some levels of these bacteria too.
A study published in the Pakistan Journal of Pharmaceutical Sciences in November 2017 measured the levels of pathogens in raw, boiling and pasteurized milk and found that raw milk contained five different strains, boiled milk contained three strains and pasteurized milk contained two. Researchers from the study noted that, while pasteurization of milk reduces pathogens a little more than boiling, boiling milk can still be an effective way to minimize contamination and reduce your risk of contracting milk-borne diseases.
The Downsides of Boiling Milk
The exact temperature at which milk boils depends on the type and fat content, but because milk consists of mostly water, the boiling points are similar. According to the Department of Physics at the University of Illinois at Urbana-Champaign, that boiling point is around 212 F (or 100 C). That means, if you're letting milk come to a boil, you're surpassing the temperature at which the proteins in the milk break down and reducing the quality and taste of the milk.
The broken down proteins are still a source of amino acids, though. So, as long as the milk is palatable and it doesn't affect the taste of the recipe you're using it in, it's OK to incorporate it as it's still a good source of protein.
Boiling milk may negatively affect the vitamin content, though. The August 2017 report in Lipids in Health and Disease indicates that boiling milk reduces its vitamin C content by as much as 42 percent. The researchers also found that boiled milk that sits in the refrigerator for three days also loses some of its antioxidant power, although they weren't clear on whether this was a delayed effect of the boiling or due to the storage and colder temperatures.
- Lipids in Health and Disease: "Antioxidant Capacity and Fatty Acids Characterization of Heat Treated Cow and Buffalo Milk"
- Pakistan Journal of Pharmaceutical Sciences: "Effect of Medicinal Plants, Heavy Metals and Antibiotics Against Pathogenic Bacteria Isolated From Raw, Boiled and Pasteurized Milk"
- Journal of Allergy and Clinical Immunology: In Practice: "Utilizing Boiled Milk sIgE as a Predictor of Baked Milk Tolerance in Cow's Milk Allergic Children"
- Journal of Allergy and Clinical Immunology: In Practice: "Increased Tolerance to Less Extensively Heat-Denatured (Baked) Milk Products in Milk-Allergic Children"
- U.S. Food and Drug Administration: "The Dangers of Raw Milk: Unpasteurized Milk Can Pose a Serious Health Risk"
- Korean Journal For Food Science of Animal Resources: "Experimental and Modelling Study of the Denaturation of Milk Protein by Heat Treatment"
- Department of Physics at the University of Illinois at Urbana-Champaign: "Q & A: Boiling Point of Milk"
- LibreTexts Chemistry: "Proteins"
- Proceedings of the Nutrition Society: "Very Long-Chain N-3 Fatty Acids and Human Health: Fact, Fiction and the Future"
- Advances in Immunology: "Chapter Three - The Role of Short-Chain Fatty Acids in Health and Disease"
- Nutrition Review: "Medium Chain Triglycerides"