What is Animal Milk and How Does It Differ from Plant-Based Drinks?

Animal milk is the natural mammary secretion of mammals, intended to nourish their offspring. Legally, only the liquid obtained from the hygienic milking of these animals, without additives or extractions, can be called "milk"

ANIMAL PRODUCTION

6/25/20257 min read

Animal milk is the natural mammary secretion of mammals, intended to nourish their offspring (1). Legally, only the liquid obtained from the hygienic milking of these animals, without additives or extractions, can be called "milk" (1, 2). In contrast, plant-based drinks are emulsions of water with extracts from cereals, legumes, seeds, or nuts (2, 3). They do not contain lactose or dairy proteins; they typically incorporate low percentages (2–17%) of the plant raw material and therefore require fortification to provide nutrients like calcium or vitamins. For example, animal milk is a natural source of bioavailable calcium and complete proteins, while plant-based drinks only contain "extra" calcium if artificially added, and usually in insufficient quantities (3, 4). In summary, animal milk comes exclusively from mammals and provides its own nutrients (lactose, caseins, milk fats), while plant-based drinks are aqueous plant preparations and are not nutritionally equivalent (2, 3).

Main Types of Animal Milk: Cow, Goat, Sheep, and Buffalo

Cow's Milk: It is the most widely consumed globally (5). It has a creamy-white color and a mild (slightly sweet) taste, with a homogeneous texture. Nutritionally, it contains approximately 3–4% fat, ~3.3–3.5% protein, and ~5% lactose (6). It is rich in calcium, phosphorus, and water-soluble vitamins (riboflavin B2, vitamin B12, pantothenic acid) (7). Thanks to its nutritional balance and availability, it forms part of the dietary staple for all ages. Some people experience digestive discomfort from cow's milk (e.g., due to A1 casein or lactose), which has led to "A2" or lactose-free versions, but in general, it is well-tolerated by the general population.
Goat's Milk: It is distinguished by its more intense and slightly salty aroma and flavor (due to higher chloride content) (8). It is pure white (lacks carotene), so the fat appears completely white (9). Its composition is similar to cow's milk (10): it provides ~3.5% fat and 3.2–3.6% protein; lactose is around 4.5% (11) (slightly lower than in cow's milk). It contains more calcium bound to caseinates than cow's milk (8), and stands out in riboflavin (vitamin B2) and preformed vitamin A (as it does not need to convert carotene) (9). Goat fat forms smaller globules, and its casein has a lower proportion of αs1, which produces a softer milk clot in the stomach, improving its digestibility (12, 13). Therefore, it is sometimes considered an option for infants with mild intolerances (though under strict medical supervision).
Sheep's Milk: It is very concentrated in solids. It contains about 6–7% fat and 5–6% protein, almost double that of cow's milk (14). It also has more lactose (around 5–5.5%) and higher mineral content (calcium, phosphorus) than cow's or goat's milk (15). Its taste is sweet and very pleasant; its texture is thick and creamy. Due to its high protein (casein) and fat content, it is ideal for producing high-yield cheeses and yogurts (16, 17). In the human diet, it is mainly used in Mediterranean regions for traditional cheeses (feta, Manchego, Pecorino, etc.).
Buffalo Milk (Water Buffalo): It is the richest in fat among common types, approximately double that of cow's milk (18). It contains between 7–9% fat and 4–5% protein (fat/protein ratio ≈2:1) (18). Its milk is very thick and creamy, with a more intense and sweet taste; it is mainly used in specialty cheeses (like the famous buffalo mozzarella) (19). The high casein and calcium content favors firm coagulation in cheese making. Nutritionally, buffalo milk provides similar nutrients to cow's milk (calcium, vitamins B12/B2), but with much more energetic lipids and natural cholesterol (which is reduced in semi-skimmed versions).

Nutritional Comparison

In general terms, animal milks differ in their macronutrient and micronutrient profiles. As an approximate reference per 100 ml of raw milk:

Cow: ~87 g water, 3–4 g fat, 3.3–3.5 g protein, ~4.8–5 g lactose (6), with calcium ~120 mg.
Goat: Similar composition to cow's milk (10): ~3.5 g fat and 3.2–3.6 g protein; lactose ≈4.5 g (10% less than in cow's milk) (11). It provides more soluble calcium and B vitamins (like riboflavin B2) and ready-to-use vitamin A (9).
Sheep: Very concentrated: ~6–7 g fat and 5–6 g protein (almost double that of cow's milk) (14); lactose ~5.1 g (11). It also contains high calcium and phosphorus.
Buffalo: Very high in fat (~8–9 g) with protein ~4–5 g (18); lactose ~4.5–5 g. Its calcium content is very high due to the extra casein.

Regarding micronutrients, all these milks are excellent sources of calcium and minerals (magnesium, phosphorus), as well as high-biological-value proteins (including all essential amino acids) (7). They also supply key water-soluble vitamins: vitamin B12, riboflavin (B2), and pantothenic acid. Goat's milk notably provides available vitamin A (instead of provitamin A) (9). Overall, animal dairy products contribute significantly to the daily intake of calcium, B vitamins, and quality proteins (7).

Benefits and Potential Drawbacks

Benefits: The consumption of animal milk provides essential nutrients. It is especially valuable during growth stages: adequate intake during childhood and adolescence contributes to optimal bone mass and prevention of future osteoporosis (20). Its high-quality proteins and amino acids promote muscle repair (of interest to athletes) (7). It provides bioavailable calcium, B vitamins, and fats (in whole milks) that help absorb fat-soluble vitamins. Some recent studies even suggest that moderate consumption of whole dairy products might be associated with lower cardiovascular mortality and lower average body weight in regular consumers (though these findings are still debated) (20, 21).

Drawbacks: The main critical point is lactose. A large part of the world's population (especially adults) has lactase deficiency and experiences intestinal discomfort after drinking "regular" milk. In these cases, lactose-free milks or fermented products (yogurt, aged cheeses), where lactose is reduced (e.g., aged cheeses have <1 g of lactose per 100 g) (22), should be chosen. Another drawback is allergy to milk proteins (CMPA): cow's milk contains caseins (αs1-, β-casein) and whey proteins that cause allergic reactions in 3–5% of infants. Most of these allergic individuals cross-react with goat, sheep, and buffalo milk (23, 24), so they must exclude all mammalian milks under medical supervision. Finally, whole milk is high in saturated fats and cholesterol: this can raise blood LDL ("bad") cholesterol (21). Therefore, experts recommend skimmed or semi-skimmed versions for people at cardiovascular risk (21), although there is no clear evidence that moderate consumption of fatty dairy products in a balanced diet increases coronary heart disease.

Recommendations Based on Person Profiles

Infants: Breastfeeding is ideal. When formula is needed (only under medical indication), the base is usually modified cow's milk or soy. The direct introduction of goat's or sheep's milk is not recommended for infants due to compositional differences and allergic risk. In fact, infants allergic to cow's milk should not receive goat's milk or other mammalian milks due to high risk of cross-reactivity (23, 24). Adapted goat milk formulas exist, but should only be used cautiously and never in allergic individuals without prior testing. If there is severe allergy, extensively hydrolyzed or amino acid formulas are used.
Children (1–12 years): Whole cow's milk is usually introduced after one year, providing key nutrients like calcium and protein. In healthy children, whole milk is recommended until 2–3 years (for bone and nervous development), then transitioning to semi-skimmed versions depending on energy needs and nutritional status. If the child is overweight or has risk factors, skimmed milk is preferable. Children with lactose intolerance can consume aged cheese, yogurt, or lactose-free milk with good nutritional results (25).
Adults: Milk is not indispensable but can be part of a balanced diet. It is advisable to consume it preferably semi-skimmed or skimmed to reduce saturated fats. For young and middle-aged adults, 2–3 daily servings of dairy (equivalent to 500–750 ml of milk) are usually recommended for their calcium and protein content, always considering alternative plant-based sources (green vegetables, nuts, supplements) for those who cannot tolerate it.
Athletes: Milk is a good post-exercise recovery drink due to its combination of proteins (casein and whey) and carbohydrates (lactose). Dairy proteins provide essential amino acids key for muscle repair (7). Additionally, goat and sheep milk contain more medium-chain fatty acids than cow's milk (26), which are rapidly absorbed as an energy source. This has led to the use of dairy products (or casein shakes) in muscle gain diets and may promote a more active fat metabolism (26).
Elderly Individuals: Older adults need to ensure sufficient calcium and protein to combat osteoporosis and sarcopenia. Low-fat dairy products (milk, yogurt, fresh cheese) provide both nutrients efficiently. Attention should be paid to digestive tolerance (lactose intolerance increases with age), opting for semi-skimmed or fermented options if discomfort occurs. Vitamin D (low in many unfortified milks) should also be covered through sun exposure or supplements in older people.
Lactose Intolerant Individuals: It is recommended to consume lactose-free (hydrolyzed) milks or fermented dairy products (yogurt, kefir, aged cheeses), which contain very low residual lactose (25). Enriched plant-based preparations (soy, almond, oat, etc.) can also substitute milk, although they provide less protein. In many cases, adding commercial lactase to regular milk is useful for digesting lactose (27).
Milk Protein Allergic Individuals: They must eliminate all mammalian milk from their diet (cow, goat, sheep, buffalo) (23, 24). For children, special hypoallergenic formulas (hydrolysates or amino acids) are used. Adults can use enriched plant-based drinks or milk from other species (mare, donkey) only under medical prescription, as there is high cross-reactivity between milk proteins from different mammals (23, 24).

Production and Pasteurization Process

Milk is extracted on modern farms through hygienic mechanical milking, then stored in refrigerated tanks (<4°C) for preservation. It is then transported to the dairy industry, where it is filtered and its fat content is adjusted. Next, it is homogenized (breaking down fat globules to prevent cream separation) and pasteurized: it is briefly heated (e.g., 72°C for 15 seconds) to eliminate pathogenic microorganisms without destroying nutrients (28). Alternatively, some milks undergo ultra-pasteurization (UHT, ≈135°C for 1–2 seconds), which almost completely sterilizes the milk and allows it to be aseptically packaged for long shelf life without refrigeration (29). After heat treatment, the milk is cooled and packaged in cartons, bags, or bottles, indicating its category (whole, semi-skimmed, skimmed). The entire process includes strict quality controls (germ count, fat content, pH, etc.) to ensure the safety and nutritional quality of the final product (28).

Sources: Information based on updated studies and data from specialized organizations and publications (FAO, nutrition and health institutions, pediatric and dairy literature) (2, 7, 9, 11, 17), as well as recommendations from medical and regulatory associations (21, 23, 24). These resources offer a rigorous overview of the properties, benefits, and limitations of animal milks.

(1, 5, 8, 19, 20, 28, 29) Leche - Wikipedia, la enciclopedia libre

https://es.wikipedia.org/wiki/Leche

(2, 4) ¿En qué se diferencian la leche y las bebidas vegetales? Ojo, no son lo mismo

https://www.infosalus.com/actualidad/noticia-diferencian-leche-bebidas-vegetales-ojo-no-son-mismo-20190111132037.html

(3) ¿Qué es una bebida vegetal? | Blog Ametller Origen

https://www.ametllerorigen.com/es/blog/que-es-una-bebida-vegetal

(6, 7, 10, 16, 18) Composición de la leche

https://www.fao.org/dairy-production-products/products/milk-composition/es

(9, 12) fen.org.es

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(11, 22, 25, 27) Recomendaciones de evitación de la lactosa – SaniAlergia

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