Absence of A1 protein in milk may promote higher absorption rate of GSH antioxidant, study finds

By Mary Ellen Shoup contact

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Scientists found that milk naturally containing only the A2 type of beta-casein protein - rather than both the A1 and A2 found in most ordinary milk - doubled the concentration of glutathione (GSH) in healthy adults. ©iStock/Okea
Scientists found that milk naturally containing only the A2 type of beta-casein protein - rather than both the A1 and A2 found in most ordinary milk - doubled the concentration of glutathione (GSH) in healthy adults. ©iStock/Okea

Related tags: Nutrition

Dairy foods have been shown to play a role in the absorption of the antioxidant glutathione (GSH) in healthy adults, but new research has discovered that cow’s milk containing only A2 protein has been shown to double the concentration of the antioxidant compared to both A1 and A2 found in most conventional milk.

GSH acts as an aid to the human body’s internal defense system, and has been linked to warding off neurodegenerative diseases that can lead to pancreatitis and cancer. Prior to this clinical trial, only animal tests had been done examining the effects of A1 protein on the antioxidant’s concentration.

"It was quite remarkable to find that consumption of milk containing only the A2 type of beta-casein protein produced measurably higher blood levels of the antioxidant glutathione as compared to conventional milk (which has a combination of A1 and A2 proteins). While we have previously shown that opiate peptide from the A1 protein in conventional milk can affect glutathione levels in cultured cells and lab animals, it is satisfying to see these effects in people,"​ said Richard Deth, PhD, lead researcher and professor of pharmacology in the department of pharmaceutical sciences at Nova Southeastern University.

Segregation of A2 protein in cow’s milk

Depending on the cow’s genetic makeup, which can be identified through a genetic test, it can either be classified an A1/A1 producer, A1/A2 producer, A2/A2 producer, or A2/A2 producer, the study stated.

Once identified as A2-only producers, the cows can be separated from the dairy herd where their milk is collected and processed separately to result in milk that only contains the A2 type of beta-casein protein (free-from A1 protein).

Recent studies show that these two proteins digest differently from each other and, for some people, the presence of the A1 protein can cause gastrointestinal discomfort. Thus, milk containing only the A2 protein may provide a natural way to reduce the symptoms associated with post-dairy digestive issues.

A2 protein may ramp us GSH production

To explore the impact of the absence of A1 protein on the antioxidant's concentration, the team of nutrition researchers enlisted 21 healthy men and 24 healthy women in a two-phase crossover study.


During the randomized, double-blind, controlled trial, subjects consumed eight ounces of milk with either A1 + A2 protein or A2 only, twice a day. Researchers assessed differences in plasma GSH concentrations and beta-casomorphin-7 (BCM-7), a peptide produced by the breakdown of A1 protein and thought to reduce GSH concentrations.

Results showed that when consuming A2-only milk, levels of GSH were significantly higher compared to when participants consumed milk with both A1 and A2 proteins. No significant difference between groups in BCM-7 was detected.

The results of the trial were interpreted as an indication that consuming milk with A2 protein only may actually ramp up GSH production in the body.

It was noted in the report that funding of the clinical trial came from The a2 Milk Company, but their involvement was only in the concept and development, not in the data analysis or interpretation. 

Source: Nutrition Journal

Published online ahead of print, doi: 10.1186/s12937-016-0201-x

“Clinical evaluation of glutathione concentrations after consumption of milk containing different subtypes of β-casein: results from a randomized, cross-over clinical trial”

Authors: Richard Deth; Andrew Clarke; Jiayi Ni; and Malav Trivedi

Related topics: R&D, Fresh Milk, Dairy Health Check

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