Study under review: Effects of milk containing only A2 beta casein versus milk containing both A1 and A2 beta casein proteins on gastrointestinal physiology, symptoms of discomfort, and cognitive behavior of people with selfreported intolerance to traditional cows’ milk
Milk is an important food for young infants and a common source of nutrition among adults. However, many humans stop producing the lactase enzyme responsible for digesting the milk sugar lactose after weaning, a condition called lactose intolerance. When individuals with lactose intolerance consume lactose through milk or other forms of dairy, they may experience varying forms of gastrointestinal (GI) distress, including abdominal pain, bloating, gas, nausea, and diarrhea. These symptoms are caused by the fermentation of lactose in the colon, since it was not absorbed in the small intestine.
Roughly 65% of the human population is considered to have a reduced ability to digest lactose after infancy. However, the prevalence of true lactose intolerance is difficult to discern because studies have varied in their interpretation of what constitutes this condition. Many surveys rely on self-reported lactose intolerance, but many individuals who self-report lactose intolerance show no evidence of lactose malabsorption.
An alternative explanation for the high levels of self-reported lactose intolerance may be the type of protein in milk. The two major protein groups in milk are whey and casein, with the latter accounting for about 80% of total protein. The most common genetic variants of casein protein in milk are A1 beta-casein and A2 beta-casein.
A2 beta-casein is recognized as the original form of beta-casein and is the only beta-casein found in the milk of purebred Asian and African cattle. The A1 beta-casein variant is found among cattle of European origin and is believed to have arisen more than 5,000 years ago. Accordingly, most milk sold commercially is a combination of A1 and A2 beta-caseins, as it is sourced from European cattle or other cattle that have been crossbred with European cattle. Examples include Guernsey cows, Holsteins, and Ayrshires. Human milk and milk from goats and sheep contains only A2 beta-casein. The beta-casein proteins are degraded into beta-casomorphins (BCMs) during the digestive process. The main difference between A1 and A2 beta-casein is that A1 beta-casein produces BCM-7 upon digestion while A2 beta-casein does not. There is a growing body of evidence suggesting that BCM-7 is bioactive and is associated with inflammation and several disease states, such as diabetes and coronary heart disease. However, these associations are not without criticism.
Up until now, nearly all the evidence investigating health effects of BCM-7 and the beta-casein variants has been observational or conducted in test tubes and animals. The current study was designed to compare the human health effects of consuming milk containing only A2 beta-casein with milk containing A1 beta-casein type in terms of GI function, symptoms, and inflammation.
The two common forms of casein present in milk are A1 beta-casein and A2 beta-casein, which differ as a result of a genetic mutation in cattle over 5,000 years ago. There is observational, test tube, and animal evidence to suggest that A1 beta-casein may promote inflammation and be linked to inflammatory disease states. The study under review put this to the test in humans.
Other Articles in Issue #19 (May 2016)
Training hot for performance gains
Athletes know all too well that sudden exposure to heat or altitude can severely impact performance, so acclimation is a good idea. And it turns out that exposure to one of these stressors may actually help the other one.
The art & science of evidence-based practice and elite performance By Craig Pickering
As one of the rare athletes to participate in both the Summer and Winter Olympic Games, Craig has a unique perspective on the intersection of optimal performance and evidence-based practice.
Relaxing arteries with magnesium
To stave off cardiovascular disease, we want our arteries to be more pliable than stiff. This trial tested six months of magnesium supplementation for the purpose of reducing arterial stiffness.
Beating “the burn” with baking soda
Can you believe that something as simple as baking soda may boost performance? While this fact has been known for a while, researchers didn’t know that people’s responses to different doses can vary quite a bit
A compound from beer may help fat loss
Bitter, hop-derived compounds found in beer may actually reduce body fat levels. Previously only shown in mice, this study tested the theory in humans
Sugar is the ultimate antioxidant and insulin will make you younger: Appreciating a few poorly recognized but critical contributions of carbohydrate
By Chris Masterjohn, PhD: Sugar is widely demonized in the media and medical establishment. Professor Masterjohn provides an eye-opening and detailed view on some potential protective roles of glucose.
Arsenic in rice: big trouble for little infants?
Depending on where it’s grown, rice can have rather high levels of arsenic. Especially brown rice. This may be important for developing infants
How much protein does grandpa really need?
One of the many downsides to aging is altered protein mechanics. Based on the theory that protein requirements for seniors may be pegged too low, this study quantified protein needs in older males.
Is resistance exercise the next frontier for nitrates?
Nitrate use for athletics has exploded in the past few years, but research typically focuses on aerobic activities like longer-distance cycling or swimming. Could nitrates also show benefit for weightlifting?