Milk and dairy products are considered nutrient-dense foods. That’s why some health authorities, such as the United States Department of Agriculture (USDA), advise consuming dairy products daily (1).

However, scientific evidence on whether dairy is healthy or harmful is mixed — and there are complexities behind these labels.

With over half of the world’s population reporting trouble digesting dairy, you may wonder whether you should keep consuming it (2).

This article gives an in-depth look at dairy and explores how it may affect your health.

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Dairy refers to foods made from or containing the milk of mammals, such as cows, sheep, goats, or buffaloes.

The group includes foods like regular and lactose-free milk, yogurt, cheese, and kefir, as well as milk-containing products, such as ice cream, butter, ghee, cream, sour cream, cream cheese, whey products, and casein (3).

As you can imagine, dairy products are produced via different techniques and processing methods, which help enhance their desired qualities.

For example, liquid milk may be processed into semi-skimmed, skimmed, evaporated, or powdered milk, in which fat or water is partially or entirely removed to create lower fat, condensed, or dried versions of milk (3).

Furthermore, vitamins and minerals may also be added instead of removed, as is the case with fortified milk (3).

Given milk’s short shelf life, it typically undergoes pasteurization, which is a heat treatment that reduces the number of harmful microorganisms that may spoil it or present health hazards for consumers.

Other products, such as cheese, are produced via the coagulation of casein — one of milk’s main proteins — and its separation from milk’s whey (3).

In contrast, fermented products like yogurt and kefir are produced by increasing the acidity of milk by adding beneficial bacteria (3).

Summary

Dairy refers to foods made from or containing the milk of mammals. Some popular dairy products include milk, yogurt, kefir, ghee, butter, cream, cheese, and whey.

As mentioned before, milk and dairy products are nutrient-rich foods that provide many nutritional advantages. In fact, milk contains 18 of 22 essential nutrients, including vitamins, minerals, probiotics, and antioxidants (4, 5, 6).

A 1-cup (244-mL) serving of whole milk packs (7):

  • Calories: 146
  • Protein: 8 grams
  • Fats: 8 grams
  • Carbs: 11 grams
  • Vitamin B12: 55% of the Daily Value (DV)
  • Calcium: 23% of the DV
  • Phosphorus: 20% of the DV
  • Vitamin D: 13% of the DV
  • Potassium: 8% of the DV

It also provides good amounts of vitamin A, selenium, zinc, and magnesium.

Based on its nutrient composition, whole milk is quite healthy. Just 1 cup (244 mL) offers all 3 macronutrients — carbs, proteins, and fats.

The fatty components of milk depend on the diet and treatment of the animal it comes from. Dairy fat is very complex, comprising hundreds of fatty acids. Many are bioactive, meaning that they have beneficial effects on your body (8).

For instance, research shows that milk from grass-fed cows raised on pasture may have up to 92% more omega-3 fatty acids and 94% more conjugated linoleic acid (CLA) than milk from conventionally raised cows (9, 10).

Keep in mind that high fat dairy products like some cheeses and ice cream and fortified soy products have a vastly different nutrient composition than milk. Also, low fat or skim dairy products lack most or all of milk’s healthy fats.

Another important nutrient in dairy is lactose, the main type of carb in all mammals’ milk. Milk from ruminants — animals like cows and sheep — comprises about 5% lactose (2, 5).

The primary role of lactose in milk is to provide energy. It also has a potential prebiotic effect, meaning it promotes the growth of your gut’s friendly bacteria, leaving you with a healthier community of bacteria (2, 5).

Summary

Milk is quite nutritious, and its composition may be influenced by the diet and treatment of the animal it comes from. However, it varies greatly by product. Whole milk offers many more healthy fats than skim milk, for example.

May support your bones

Calcium is the main mineral in your bones — and dairy is the best source of calcium in the human diet (11, 12).

Therefore, dairy has many benefits for bone health.

In fact, health organizations recommend that you consume 2–3 servings of dairy per day to get enough calcium for your bones (1, 13).

Evidence indicates that dairy improves bone density, reduces the risk of developing osteoporosis, and lowers older adults’ risk of fractures (12, 14, 15).

That said, dairy is not the only dietary source of calcium. Nondairy sources of calcium include kale, leafy greens, legumes, and calcium supplements (12).

However, research shows that calcium isn’t the only nutrient responsible for dairy’s effects on bone health. Dairy also provides protein and phosphorous, which you need to achieve optimal peak bone mass during skeletal growth and prevent bone loss as you age (12, 15).

May lower your risk of obesity and type 2 diabetes

Dairy products have been associated with varying effects on body weight.

Evidence suggests that dairy products may improve body composition by reducing fat mass, waist circumference, and increasing lean body mass, especially when combined with a reduced calorie diet (12, 16, 17).

A review of 25 studies found that various types of yogurt — including conventional, low fat, high fat, and Greek — were associated with the prevention of metabolic syndrome risk factors, such as obesity, high blood pressure, and high blood sugar and triglycerides levels (18).

Some evidence also suggests that some dairy products may reduce your diabetes risk. However, studies have shown mixed results (6, 19).

Research finds that while yogurt may lower your risk of developing type 2 diabetes, the association between other dairy products and diabetes risk is inconsistent (6, 19, 20, 21).

One potential explanation for yogurt’s effect on diabetes risk is associated with its nutrient composition.

For instance, calcium and magnesium are linked to a lower frequency of insulin resistance, while whey protein has blood-sugar-lowering properties due to its positive effect on insulin production (19).

In addition, the probiotics in yogurt play a key role in managing blood sugar levels via mechanisms that involve multiple organs and systems, from your brain to your immune system and gut (22).

Dairy and heart disease

Current dietary guidelines recommend choosing low fat dairy products to limit saturated fat intake and reduce the risk of heart disease (13).

However, recent evidence suggests that saturated fat from dairy may not have the same detrimental effects on heart health as saturated fat from meat. That’s because dairy and meat have different fatty acid profiles (12, 16, 23).

Unlike meat, which has long-chain fatty acids, dairy has a greater proportion of short- and medium-chain fatty acids. Short- and medium-chain fatty acids affect heart health differently and may even offer some benefits (16, 23, 24).

Fermented products like yogurt and kefir provide probiotics, which are beneficial microorganisms that offer health benefits. Research suggests that their intake is associated with lower LDL (bad) cholesterol levels and reduced risks of high blood pressure and heart disease (23).

Nevertheless, there’s no consistent evidence on whether dairy fat helps or hinders heart health, and the scientific community is divided in its opinion.

Summary

Dairy products may benefit your bones, reduce your risk of developing type 2 diabetes, and improve your body composition. They may also improve heart health, although the evidence is inconclusive.

Lactose intolerance

As mentioned before, the main carbohydrate in dairy is lactose, a milk sugar comprising the two simple sugars glucose and galactose.

To digest lactose, children produce a digestive enzyme called lactase, which breaks down lactose from breastmilk. However, many people lose the ability to break down lactose in adulthood (2, 25).

In fact, about 65% of the world’s adult population cannot break down lactose, leading to lactose intolerance (2).

What’s more, only a small proportion of people — notably, populations with Northern European heritage — are known to have lactase persistence, meaning that they can still produce lactase. That ability may be an evolutionary adaptation derived from dairy cattle domestication (2, 25).

People who are lactose intolerant have digestive symptoms when they consume dairy products. These symptoms may include gas, bloating, abdominal cramps, and diarrhea (2, 26).

Current treatment for lactose intolerance includes a lactose reduced diet and enzyme replacement therapy (25, 26).

However, some people with lactose intolerance may still be able to tolerate 9–12 grams of lactose per day — the equivalent of about 1 glass of milk (200 mL) — as well as fermented products in small amounts (2).

Dairy and cancer

Dairy stimulates the release of the protein insulin-like growth factor 1 (IGF-1), which is associated with an increased risk of certain cancers — particularly prostate, breast, and colorectal cancers (27, 28).

However, research on the link between dairy and cancer is still inconclusive, and evidence shows that the type of dairy consumed may play an important role in the outcome (29).

For instance, one study among 778,929 people suggested that while total dairy products didn’t increase cancer mortality risk, whole milk intake did elevate the risk of prostate cancer mortality (30).

On the contrary, yogurt and other fermented dairy products are associated with a reduced cancer risk (31).

Affects of the dairy industry on our environment

The dairy industry is one of the largest food-related contributors to climate change.

In fact, dairy comes in second — only after meat — in terms of producing dietary Greenhouse Gas Emissions (GHGE). Dairy is estimated to represent about 20% of the emissions from food production worldwide (32, 33).

Greenhouse gasses — including methane, nitrous oxides, and carbon dioxide — are some of the largest contributors to climate change due to their ability to cause global warming (32).

As such, research shows that replacing dairy products with plant-based alternatives can significantly reduce GHGE (33).

However, following a diet high in plant-based foods may make it difficult for you to meet your dietary mineral requirements, such as those for calcium and vitamin D (34).

A carefully planned diet and supplementation can help. If you’re interested in dramatically reducing your dairy intake or switching to a plant-based diet, it’s a good idea to first talk with a medical professional like a doctor or dietitian to ensure you get all the nutrients you need.

Summary

Over half of the world’s adult population may struggle to digest dairy. Also, while some dairy products seem to increase cancer risk, others may reduce it. Yet, the evidence is mixed. Lastly, the dairy industry is one of the largest contributors to climate change.

The healthiest and most eco-friendly dairy products come from cows that are grass-fed and/or pasture-raised.

As mentioned above, their milk has a much better nutrient profile, including a more beneficial fatty acid profile.

Fermented dairy products like yogurt and kefir might be even better given that they provide probiotics, and research consistently links them to a lower risk of type 2 diabetes, heart disease, and cancer (19, 22, 31).

It’s also worth noting that people who can’t tolerate dairy from cows may be able to easily digest dairy from goats (35).

Summary

The best types of dairy come from animals that were pasture-raised and/or grass-fed, as their milk has a much more robust nutrient profile. Fermented products are also consistently linked to numerous health benefits.

Dairy products comprise a wide range of nutrient-rich foods and beverages that are made from or contain milk.

For the most part, they’re associated with numerous health benefits. However, evidence remains inconclusive regarding both their benefits and potential downsides.

In addition, most people become lactose intolerant and become unable to tolerate dairy at some point.

If you can tolerate dairy products and enjoy them, you should feel comfortable consuming them.

If you either don’t tolerate them well, don’t enjoy them, or have ethical concerns about farming practices or dairy production’s effects on the planet, plenty of dairy alternatives exist and may be available to you instead.