Milk is such a divisive nutrition topic.
While some believe that milk is a nutrient-dense complete source of nutrition, others claim it is harmful.
Does milk strengthen our bones or does it weaken them?
Are the benefits of drinking milk worthwhile or are there harms from doing so?
Unfortunately, there is a lot of conflicting information about this dairy food.
For this reason, this article will provide a strictly evidence-based guide to what the studies show.
There will always be pros and cons with any food, but does the totality of the evidence show that drinking milk is good or bad for you?
Here are the facts about milk.
1. Milk Has a Good Nutrition Profile and Contains Important Nutrients
First of all, we have to consider the nutritional value of milk.
Whole milk offers a complete source of nutrition; carbohydrate, fat and protein, alongside a range of vitamins and minerals.
Low-fat milk offers a similar nutrition profile except that it contains minimal fat and it is a less reliable source of fat-soluble vitamins.
The nutrition profile of a 240 ml glass of whole milk is as follows (1);
Calories and Macronutrients
|Nutrient||Amount (Grams / % RDA)|
|Saturated Fat||4.6 g|
|Omega-3 Fatty Acids||183 mg|
|Omega-6 Fatty Acids||293 mg|
As the table shows, milk provides all three macronutrients.
The carbohydrate comes from a milk sugar named lactose, and saturated fat is the most predominant type of fat.
|Nutrient||Amount (Grams / % RDA)|
|Niacin (vitamin B3)||1%|
Milk is a significant source of B vitamins and the fat-soluble vitamins A and E.
|Nutrient||Amount (Grams / % RDA)|
Milk supplies large amounts of the minerals calcium and phosphorus, both of which are important for skeletal health (2).
2. Some People Are Lactose Intolerant
While milk may be nutritious, some people are intolerant to the milk sugar lactose.
In fact, the prevalence of lactose intolerance around the world is extremely high, and in some parts of Asia, it affects more than 90% of the population.
Furthermore, 65% of the world’s population loses the ability to digest lactose after infancy properly (3).
The reason for this is that some people can no longer produce a digestive enzyme called lactase after early childhood. Lactase is necessary for the digestion of lactose in milk.
For people who cannot adequately digest milk, there can be a range of distressing symptoms. The side effects of drinking milk for these people include abdominal pain, bloating and gas (4).
Any lactose intolerant (or sensitive) individuals should avoid (or seriously limit) milk.
However, since milk plays such a prominent role in popular culture, some people do not want to give it up.
For these people, there is an over-the-counter option called Lactaid, which contains lactase enzymes.
3. Milk Contains the Highest Quality Protein
Aside from isolated fats (like oil) and sugars, almost every food in the world contains protein.
However, the total amount of protein is far from the whole story.
It is not just protein quantity, but also the protein quality of the source that is important.
Furthermore, milk contains two specific proteins;
- Casein: accounts for approximately 80% of the protein in milk.
- Whey: around 20% of milk’s protein is in the form of whey.
Notably, research shows that casein and (especially) whey are extremely efficient and bio-available protein sources (7).
These traits of casein and whey translate to milk being one of the very best foods for dietary protein.
4. Growth Hormones in Milk: a Big Concern?
Increasing vegan activism over the past few years has seen ethical concerns about the treatment of animals being confused with public health.
One of the most common negative claims that people make regards the dangers of hormones that are supposedly present in milk.
Is this something that should concern milk-drinkers?
Well, it is never nice to hear about medications and synthetic hormones in our food.
However, looking at the actual evidence, the claims of harm seem to be exaggerated at the very least.
What the Science Says
The big question here is whether hormones in milk affect humans.
Here is a summary;
- A food safety review demonstrated that recombinant bovine growth hormone (rbGH) is not biologically active in humans. Furthermore, the concentration of the hormone insulin-like growth factor (IGF-1) found in hormone-treated cow’s milk is no more than that of breast milk (10).
- Levels of IGF-1 in the human digestive tract are many hundreds of times larger than the concentrations found in hormone-treated milk. Additionally, oral consumption of IGF-1 appears to have no biological activity (11).
In other words, even if people do get traces of hormones through consuming milk, it will likely have no effect.
Yes, it isn’t nice that some cows are pumped full of hormones.
Personally, I don’t like the idea of consuming hormones either, but the evidence for harm just isn’t there.
For those who wish to avoid exposure completely, look for the ‘hormone-free’ label.
5. Does Milk Cause Weight Gain?
In a word; no.
It is not difficult to hear claims that milk is “fattening.”
However, no single food has unique properties that enable it to cause weight gain, and that goes for the worst foods out there too.
Can specific ingredients cause us to over-consume foods? Certainly.
Can ultra-processed foods cause cravings and damage our satiation signals when eating? Of course, and that can often lead to a negative cycle.
But can a food magically cause weight gain, irrespective of the amount consumed? No.
If someone drinks unlimited amounts of milk, then clearly, weight gain will follow, but just including milk in an overall healthy diet will have no such effect.
Ironically, several studies show the exact opposite of the “weight gain” claim;
- A systematic review suggests that consuming more dairy (including milk and cheese) may be protective against weight gain (12).
- Higher dairy fat and whole milk consumption have an inverse association with obesity in children and adults (13, 14).
6. Does Milk Weaken Our Bones?
Is milk good for our bones or will it weaken them?
“Milk is acidic, and high milk consumption can lead to a higher risk of fractures…” or so the claim goes.
Firstly, there is no credible science whatsoever to suggest that acidic foods can affect our body’s blood PH levels (15).
As for milk causing fractures, there was one study in particular that received media attention on this matter a few years ago.
The study in question was a cohort study featuring more than 100,000 people, administered by food frequency questionnaires.
Analysis of the results demonstrated that there was a higher risk of fracture and mortality in some of the population groups drinking higher amounts of milk.
However, observations from memory-based food questionnaires are very different to clinical trials, and the researchers noted this in their conclusion (15);
“Given the observational study designs, a cautious interpretation of the results is recommended.”
Unfortunately, the caution in media stories and certain websites was nowhere to be seen.
What Do More Rigorous Studies Show?
Here are the findings from several more extensive studies;
- A systematic review found that 200 g/day of milk may benefit bone health, but there was insufficient evidence to state this with confidence (16).
- A meta-analysis of existing studies demonstrated that there is no association between milk intake and fracture risk (17).
- Dairy sources of calcium are important for slowing bone loss, increasing bone growth and preventing osteoporosis (18, 19).
7. Milk Has a Neutral/Beneficial Effect on Disease and Mortality
Is milk good for you concerning long-term health?
According to recent randomized trials and systematic reviews, it certainly isn’t bad for you.
To demonstrate; here is a summary of recent, high-quality studies on milk that relate to specific health conditions.
Studies on Milk, Disease and Mortality
- A systematic review of 29 prospective cohort studies suggests that milk consumption has no negative effects on cardiovascular risk (20).
- A further systematic review of existing meta-analyses shows milk as having a neutral effect on cardiovascular risk and a possibly beneficial impact on stroke risk (21).
- Recently, a dose-response meta-analysis and systematic review of existing prospective studies investigated the link between milk and mortality. This research could find no association between higher milk consumption and all-cause (or specific) mortality (22).
While these studies are not conclusive (correlation does not equal causation), they suggest that milk is either neutral or possibly good for you.
8. Milk Is One of the Best Sources of Bio-available Calcium
Calcium in milk has a much greater bio-availability than plant sources.
Put simply; this is because plant sources of calcium contain various anti-nutrients like phytic acid that can reduce the absorption rate.
One such plant-based product is soy milk; it provides a source of calcium, but it also contains the very nutrients that hinder its absorption.
Calcium in milk, on the other hand, is very easy to digest, and just one glass of milk contains a substantial 28% of the RDA (1).
Ensuring sufficient intake of calcium is vital for a whole host of reasons (23);
- Calcium plays a key role in skeletal health and helps to grow and maintain healthy bones and teeth.
- The mineral is involved in nerve signaling and muscular contraction.
- Some studies also suggest that calcium may lower the risk of breast and colorectal cancers. However, there is no definite causal evidence for this, so take it with a pinch of salt (24).
Sufficient vitamin D is necessary to optimally utilize calcium, and milk contains the appropriate amounts of this vitamin.
9. Cow Milk Allergies Are a Genuine (But Rare) Concern
Just as everything was sounding so positive, it’s time for another negative point.
Some individuals have cow milk allergy (CMA), typically due to the milk protein casein, and this can potentially cause severe reactions.
Fortunately, CMA is relatively rare and only affects between 0.25 and 4.9% of the world’s population (25).
CMA usually develops in early childhood, and interestingly, it is much rarer in infants who were exclusively breastfed (26).
Allergies to milk may present as abdominal cramps, itching, vomiting, wheezing and trouble breathing.
Similar to all allergies, in case of a severe adverse reaction, anaphylactic shock is also a worst-case possibility (27).
Is Milk Good or Bad For You?
Just like any other food, the relative health merits of milk are not black or white.
Milk is a nutrient-dense source of vitamins and minerals, and it can play a role in a healthy diet.
However, it is not a necessary part of our diet by any means. Some people may also need to avoid it due to allergies, intolerance or other milk sensitivities.
Additionally, as milk sugars can quickly add up, milk may not be the best choice for someone trying to follow a very low-carb diet.
Other than that, milk is a convenient, healthy food that is an excellent source of several essential nutrients.
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