Thursday March 31 2011
“Drinking milk produced by cows in the 48 hours after they give birth could enhance athletic performance,” reported the BBC.
It said UK scientists were testing the theory that the milk, called bovine colostrum, protected athletes from the gut leakiness linked to intense activity. The research involved 12 male volunteers aged 19 to 38 years, who took the milk or a control milk drink for two weeks before running on a treadmill for 20 minutes. Tests showed that gut permeability and one gut hormone called GLP-1, were different in the men while they were taking the colostrum milk compared to those who were taking the control milk.
This research suggests that gut permeability can be influenced by dietary factors. However, this is preliminary research, and further study is needed to establish the effects of bovine colostrum. It is not clear from this research exactly what the active component of bovine colostrum might be.
Ideally, larger randomised trials of more prolonged exercise should be conducted using unselected populations. Further evidence should be collected before this drink is promoted or marketed for this purpose.
Where did the story come from?
The study was carried out by researchers from Barts and the London School of Medicine, the Department of Sport and Exercise Science at Aberystwyth University and Imperial College London. It was partially funded by Fonterra, a multinational dairy company, owned by New Zealand dairy farmers and the producers of bovine colostrum. The researchers comment that the research was conducted on a “no strings” basis and that Fonterra were not involved in the interpretation of the data.
The study was published in the peer-reviewed medical journal, The American Journal of Physiology, Gastrointestinal and Liver Physiology.
The BBC reports the research accurately, and highlights the potential use of the milk for prevention of heat stroke. Armed forces operating at the extremes of temperature and endurance in desert war scenarios are, at this stage, a theoretical target group only.
What kind of research was this?
This randomised crossover trial was aimed at testing the researchers’ theory that bovine colostrum, produced commercially in New Zealand and imported to the UK, could be useful in preventing and treating adult gut injury. They say that its role in this so far has not been studied.
The researchers’ explain that colostrum is the first milk produced by the mother after giving birth, in both humans and cows. The milk is important for nutrition and growth. It is also particularly rich in certain proteins that are thought to boost immunity and fight infection in the newborn. They say that some studies in human newborn babies have shown that similar colostrum products can reduce infection.
Extended periods of strenuous exercise are known to affect the permeability of the lining of the intestine – that is, how easily digested molecules pass from inside the intestine across the intestinal walls and into the bloodstream. The researchers report that increased permeability of the intestine can allow passage of toxins from gut bacteria into the blood, which can provoke an inflammatory response. In extreme cases, these changes are thought to contribute to the gut symptoms and other more severe problems associated with extreme exertion.
The researchers had previously shown that bovine colostrum could reduce intestinal injury caused by certain drugs in animals and humans. They wanted to test whether it might also be able to prevent the increases in gut permeability seen with heavy exercise. If it did reduce gut permeability, this might increase exercise endurance.
The randomised crossover design of this trial is an appropriate way of testing the effect of an intervention in healthy volunteers. However, the trial itself is very small (in only 12 people), and such a small number means that it may not have the power to detect small differences between the groups. This is slightly mitigated by the fact that each person acted as their own control. This means it avoids some of the other differences between the intervention and control groups that can arise by chance in small randomised trials.
What did the research involve?
In this study, the researchers used a colostrum high-protein powder imported from New Zealand. The powder is low in casein and high in whey protein, the two main proteins found in milk. Typical milk has a higher casein content than this early milk. The control milk used in this study was a skimmed milk with lactose sugar removed. It had a similar energy content and contained the same main nutrient groups to the colostrum milk, with 80% overall protein content. It was also rich in immunoglobulins, growth factors and contained 1.3% fat and 9.1% lactose.
This form of colostrum is already commercially available as a health food in the US, UK and the rest of Europe. It is marketed as a general “health-promoting” product, particularly suitable for athletes.
The researchers picked 12 healthy male volunteers who were runners, boxers or rugby players. Average age was about 26 years, weight 75kg and body mass index 24kg/m2. Six men were first given 20g per day of bovine colostrum, while the other six started with the control drink. The supplement was taken daily for 14 days before the main exercise trials began.
On day 14, the researchers took blood and urine tests from the volunteers, who were then asked to carry out exercise at an effort equivalent to 80% of their maximum. To do this, the men ran on a treadmill for 20 minutes. Body temperature, expired oxygen and carbon dioxide were measured at 5, 10, 15 and 20 minutes. These methods allowed the researchers to standardise the exercise levels between participants who had different levels of fitness.
After a break of 14 days to “wash out” the milks from their bodies, each volunteer began another 14 days of supplementation with the other milk. The overall procedures were then repeated.
The researchers tested a range of things like glucose, haemoglobin and specific hormones in the blood. The men were tested for intestinal permeability using urine tests that the researchers had developed themselves. A ratio of sugars, one of which leaks across the gut, was reported as the measure of gut permeability. Also reported were the levels of GLP-1 a hormone released by the gut and involved in regulating sugar metabolism.
The researchers also carried out some laboratory tests to test theories about how cultured cells in a test tube might react to temperature changes with or without the colostrum.
What were the basic results?
The tests showed that after drinking both milks, exercise produced similar increases in blood lactate, heart rate and body temperature (an average 1.4°C rise).
Gut hormone profiles were similar in both groups except for GLP-1 levels, which rose on exercise following the control milk but not following the colostrum milk.
Intestinal permeability in men after taking the control milk prior to exercise increased 2.5 times compared to the level recorded before exercise (a sugar ratio of 0.38 at baseline increased to 0.92 after) whereas the increase after taking colostrum prior to exercise was 80% (a sugar ratio 0.38 at baseline to 0.49 after). Both of these before-after changes were significant.
Their analysis showed that the difference between groups was also statistically significant.
How did the researchers interpret the results?
The researchers claim that their findings show that colostrum appears to be helpful in maintaining
gut stability in sports testing. They suggest that colostrum may have this effect by reducing cell death and affecting the permeability of membranes.
They call for further research with longer exercise protocols and in different circumstances (such as
extreme-heat-stress situations) to test the value of the product in athletes or members of armed forces who may be subjected to such stresses.
This research has illustrated one way of testing a milk “supplement”. It is worth noting some of the researchers’ cautions in interpreting this research. They say that although there is currently insufficient evidence to conclusively establish the value of bovine colostrum in enhancing performance, it is already being used by track and field athletes. They say that as bovine colostrum is viewed as a natural or “alternative therapy” with potent biological activity, athletes would find it particularly appealing because there are many potentially performance enhancing products they cannot take, to avoid any risk of accusations of “doping.
The specific component(s) which make colostrum have these effects on the intestine have not yet been identified. The colostrum preparation used in the present study contains several ingredients that could be contributing. The researchers list epidermal growth factor, transforming growth factors and interleukin-1. In addition, colostrum contains other bioactive molecules, such as amino acids, lipids and fatty acids. There is also the possibility that the casein/whey protein differences between colostrum and the control milk account for the effects seen.
This small study provides preliminary evidence of the effects of colostrum on the intestine. Ideally, larger randomised trials of more prolonged exercise using unselected populations would need to be conducted to confirm the effects on the gut, and assess whether there are any effects on exercise performance.
The authors themselves note that “there is currently insufficient evidence to conclusively establish the value of bovine colostrum to enhance performance”. Further evidence should be collected before this drink is promoted or marketed for this purpose.