Most cow’s milk available on market shelves today contains both A1 and A2 beta-casein proteins, but a recent study published in Nutrition Journal suggests that milk containing only the A2 protein may increase glutathione concentrations in healthy adults. Researchers report that while previous animal studies have suggested consuming A1 proteins may reduce glutathione levels, this is one of the first studies to explore the effect of A2 proteins on glutathione in humans. Glutathione imbalance is linked with pancreatitis, neurodegenerative diseases, and diseases associated with abnormal cell differentiation, researchers note.
The double-blind, crossover study included 21 men and 24 women (mean age of 46.6 +/- 14) who were randomized to consume 250 ml of cow’s milk, twice per day, containing either a combination of A1 and A2 proteins or A2 protein only. Each study period lasted two weeks, with a two-week washout period separating the phases.
Researchers found that plasma glutathione concentrations were significantly higher in the participants consuming milk with A2 protein alone. While participants consuming milk with both protein types finished the study with an average glutathione concentration of 1.99 +/- 0.50 nmol/ml, participants consuming milk with only A2 protein had an average glutathione concentration of 4.01 +/- 0.61 nmol/ml.
“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,” says Richard Deth, PhD, lead researcher on the study, in a press announcement. “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.”
The A2 Milk Company (Australia), which promoted the study results, notes that even though most available cow’s milks on the market contain both A1 and A2 proteins after dairies combine milk at processing, it is possible to identify cows that produce only A2 proteins and separate them from the rest of the herd. Aside from the aforementioned implications of consuming A2-only milk on glutathione concentrations, avoiding A1 proteins may also reduce digestive discomfort among sensitive populations, the firm notes.
“From earlier research we could appreciate how important glutathione is for combating inflammation and how critical it is for normal brain development and function,” Deth says. “The fact that something as simple as milk helps fuel glutathione production could have great implications for recommended dietary patterns in the future.”
Nutritional Outlook Magazine
Deth R et al., “Clinical evaluation of glutathiones concentrations after consumption of milk containing different subtypes of β-casein: results from a randomized, cross-over clinical trial,” Nutrition Journal. Published online September 29, 2016.