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Whether you heat your milk for health or culinary reasons, you might wonder how boiling may affect it.

In fact, boiled milk’s nutritional profile and health benefits are different than those of milk straight from the carton.

This article looks at the nutrients and benefits of boiled milk, and why you might or might not wish to boil your milk before drinking it.

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Why boil milk?

The boiling point of cow’s milk is around 203°F (95°C) (1).

That means if you’re adding milk to a recipe that’ll be cooked or baked, such as one for pudding or cake, it will technically reach its boiling point during the cooking process.

Some people also boil milk to kill bacteria and prevent foodborne illnesses. However, that’s unnecessary.

In the United States, commercially produced dairy milk that’s sold across state lines must be pasteurized. That does not always mean it’s boiled, but it’s heated to a high enough temperature — usually 161°F (71.7°C) for 15 seconds — to kill any harmful pathogens (2).

Thus, you don’t have to boil milk for safety reasons unless it’s raw, unpasteurized milk. In that case, bringing it to a boil or near a boil will significantly reduce most bacteria levels sufficiently (1).

People often boil milk when they use it in cooking. You can boil raw milk to kill any harmful bacteria. However, boiling milk is usually unnecessary, as most milk in the grocery store is already pasteurized.

Changes in nutrients with boiled milk

Milk is a very nutritious food. It contains a balanced mix of high quality protein, carbs, and fat.

It also supplies many important vitamins and minerals. A 1-cup (237-mL) serving of whole milk provides (3):

• Calories: 146
• Protein: 8 grams
• Carbs: 11.4 grams
• Fat: 8 grams
• Calcium: 300 mg (23% of the Daily Value (DV))
• Riboflavin: 0.337 mg (26% of the DV)
• Vitamin D: 2.68 mcg (13% of the DV)
• Phosphorus: 246 mg (20% of the DV)
• Vitamin B12: 1.32 mcg (55% of the DV)

Research examining changes in vitamin and mineral contents in raw versus heated milk found that regular pasteurization temperatures did not change nutrient content much (4, 5, 6).

On the other hand, ultra-high-temperature (UHT) pasteurization affects the content of many vitamins. This process heats milk past its boiling point to 275–302°F (135–150°C) (4, 5, 6).

Boiling also alters milk proteins. The two primary proteins in milk are casein and whey.

Casein comprises about 80% of the protein in milk, while whey accounts for about 20% (4).

The casein in milk is fairly stable, even when heated to the boiling point. However, heating whey protein will change its structure, even before it hits the boiling point of milk (4).

The primary carbohydrate in milk is lactose, and it’s sensitive to heat. When you boil milk, some of the lactose changes into a nondigestible sugar called lactulose and other compounds (4).

Boiling changes the fats in milk somewhat, too. Milk contains a mix of short-, medium-, and long-chain fatty acids (7).

While the total fat content is stable with boiling, some of the long-chain fats may be converted into short- and medium-chain fats (7).

Milk is a very nutritious food with a wide range of nutrients. When you boil it, some of the vitamins break down. Some of the fat, protein, and carbs may also change.

Benefits and downsides of boiling milk

There are pros and cons to boiling milk. Whether you should boil it depends on what you wish to gain from drinking milk.

More beneficial fats

The additional short- and medium-chain fatty acids in boiled milk might provide some health benefits.

Short-chain fats are an important fuel for the cells in your gut. They’re associated with better gut health and a lower risk of colon cancer. Some studies also suggest short-chain fats play a role in promoting a healthier body weight and blood sugar and blood pressure levels (8).

The body metabolizes medium-chain fats differently than other fats. Instead of storing them, the body absorbs them quickly and uses them as energy (9).

Some evidence suggests replacing long-chain fats in your diet with medium-chain fats may modestly increase the number of calories you burn, thus contributing to weight loss (9).

Better tolerance

Because of the changes in protein and lactose that occur when you boil milk, people who have milk protein allergies or lactose intolerance might find it easier to digest.

A study on heat treatments and milk protein identified 364 proteins in milk. After boiling, 23 of the proteins were substantially diminished (10).

That may be why some research has shown that children with milk allergies can sometimes tolerate cooked or baked foods made with milk.

A study in 134 children allergic to milk showed that 69% were able to tolerate some forms of cooked milk (11, 12).

Some of the lactose content of milk is also reduced in boiled milk. Boiling converts it into different types of acids and lactulose, a type of sugar that humans don’t absorb (4).

Still, if you have a milk protein allergy or lactose intolerance, it’s important to know that boiling may not cause enough of a change for you to safely consume milk.

Reduced nutrients

The B vitamins (thiamine, riboflavin, niacin, folic acid, B6, and B12) are sensitive to factors like light and heat.

One study looked at how boiling milk changed its vitamin content. The study found that boiling milk decreased levels of all of the B vitamins by at least 24%. Folic acid decreased by 36% (5).

While that’s significant, milk is not an important source of B vitamins in most people’s diets, with the exception of the B vitamin riboflavin (5, 6).

Riboflavin works with other B vitamins to convert the food you eat into energy. It’s rare to be deficient in riboflavin, as you can get it from many foods.

Still, milk is a major source of riboflavin, especially in children’s diets. Boiling milk reduces the riboflavin content by 27% (5, 13).

Additionally, the structural changes of some milk proteins cause the body to digest and retain less protein from milk. One study in 25 people found that when people drank UHT pasteurized milk, they retained 12% less protein than after drinking regular pasteurized milk (14).

If you rely on milk as a protein source, boiling it might cause you to get less protein than you’d like.

Taste and quality changes

Due to the Maillard reaction, boiled milk can have a slightly different flavor and darker color. This chemical reaction happens when foods are heated and proteins react with sugars (4, 15).

The changes in taste and color might not be noticeable if you flavor your milk or use it in cooking. However, if you drink it straight, your milk might taste and look a little different after it’s boiled.

Drinking boiled milk has pros and cons. You will get less riboflavin and digestible protein, but you might benefit from more short- and medium-chain fats. People with lactose intolerance and milk allergies may tolerate boiled milk better.

The best way to boil milk

Boiling milk might sound simple, but there’s an art — and some science — to boiling milk correctly, whether you plan to drink it or use it in a recipe.

Milk is made up of water, fats, carbs, and protein. When you heat it, the water starts to evaporate, and the other components begin to separate.

Bringing it to a boil too quickly can burn the sugars and curdle the whey protein. That causes scorching on the bottom of your pan and a skin to form on top. Boiling milk also forms a foam on top that can spill over quickly and make quite a burned mess on your stovetop.

It’s best to heat your milk slowly over medium heat, and stir it while it comes to a boil. Stirring and heating gently help hold the water, carbs, fat, and protein in milk together.

As soon as you see bubbles forming around the edges of the pot and just a few in the middle, turn off the heat.

The higher you heat your milk, the more likely it is that you’ll denature the proteins and cause curdling. When cooking at a higher heat, you’re also more likely to notice taste and color changes from the Maillard reaction.

Continue to stir your milk as it cools. That should prevent a skin from forming on top of the milk. If it does form, it’s perfectly safe to eat. However, if you don’t care for its chewy texture, you can skim it off and discard it.

To boil milk, heat it slowly, stir it while it heats, and make sure you do not overcook it. Turn the heat off as soon as you see bubbles that indicate it’s boiling. If you continue to stir it as it cools, it’ll be less likely to form a skin on top.

The bottom line

Boiling pasteurized milk will not necessarily make it any safer to consume. However, you might gain some nutritional benefits from boiling your milk.

These include more short- and medium-chain fats, which may help promote weight loss and better gut and metabolic health.

Since it has less lactose and some of the proteins are inactivated, there’s a chance that people with lactose intolerance and milk allergies might be able to tolerate it better than regular pasteurized milk straight from the carton. However, this is not guaranteed.

On the flip side, some negative effects can come with boiling milk. Namely, it provides less protein and fewer B vitamins.

Boiled milk can also have a different taste and texture. You can minimize this if you bring it to a boil slowly and stir it while it’s coming to boiling temperature and cooling.