Cow's milk provides a small amount of naturally occurring growth hormone typically in the form of bovine somatotropin (bST) ranging from 1-10 ng/ml of milk. [1] The chemical form of somatotropin varies drastically between species with bST and human growth hormone (hGH) differing in roughly 35% of their amino acids. [2]
It was shown in studies that non primate growth hormone as wholly ineffective at binding to primate growth hormone receptors. [2] bST is a relatively large protein and thus is broken down like other large proteins by digestive enzymes into much smaller amino acid chains, these digested fragments have no biological activity. [3]
Assuming you're drinking 2L the upper limit on the quantity of bST you could be consuming would be roughly 20µg, assuming all of it survives digestion intact (despite the evidence to the contrary) this quantity is minuscule in comparison to the 600µg that is naturally produced per day in the average adult. [4] [5]
Considering the ineffectiveness of bST in binding to human growth hormone receptors as well as the high likely hood that it is broken down well before entering the digestive lining as well as the small quantity present in a large amount of milk, we can safely conclude that the bST present in milk has no effect on muscle growth in adult humans.
Insulin-like growth factor 1 (IGF-1) is present in small quantities ranging from 1 to 1850 ng/ml in cows milk, however it is almost always found in levels below 100 ng/ml. [6] It is likely that like other large proteins IGF-1 is also broken down very quickly in the dietary tract. Additionally again like the growth hormone the quantity of IGF-1 consumed in 2L of milk is incredibly small compared to the almost 10 mg that is naturally produced in a person per day. [6]
Again like the growth factor taking these two facts low digestibility as well as relatively low quantities of the hormone suggest that we can safely conclude that there is no effect of the IGF-1 in dairy on muscle growth in adult humans.
| Nutrient | Quantity | % Daily |
|---|---|---|
| Measure | 250mL | |
| Calories | 155 kcal | |
| Protein | 8g | |
| Carbohydrates | 12g | |
| Total Fat | 8g | |
| Calcium | 291mg | 22% |
| Iron | 0.1mg | 1% |
| Sodium | 103mg | 4% |
| Potassium | 369mg | 11% |
| Magnesium | 26mg | 6% |
| Phosphorus | 235mg | 19% |
| Vitamin A | 72mcg | 8% |
| Vitamin D | 2.7mcg | 14% |
| Folate | 1.13mcg | 0.3% |
| Riboflavin | 0.47mcg | 0.036% |
Quantities of micro and macro nutrients in whole cows milk [7]
As can be seen from the % daily column of the above chart we can see that milk only contains a few key minerals in useful quantities (calcium, potassium, phosphorus, and vitamin D). Comparing the protein to the calorie content we can see that only roughly 20% of milk is actually protein.
Based on the nutrients we can conclude that milk introduces an undue quantity of calories relative to protein for muscle building and doesn't include large amounts of any important nutrients in special levels which could aide in muscle building. Consuming fortified skimmed milk would provide a much better nutritional composition and protein intake for muscle growth per calorie.
1: Hormones and Milk, Page 3 2: Bovine Growth Hormone: Human Food Safety Evaluation, Page 3 3: Bovine Somatotropin (bST) - FDA 4: Human Growth Hormone (HGH) 5: Growth Hormone - Wikipedia 6: Statement on possible carcinogenic hazard to consumers from insulin-like growth factor-1 (IGF-1) in the diet, page 4 7: Nutrient Value of Some Common Foods