Written by: Sandeep Ravindran, Ph.D. | Issue # 38 | 2015
- Oxidative stress has been implicated in aging and several neurodegenerative diseases, including Alzheimer’s disease and Parkinson’s disease.
- A new study finds that higher dairy consumption is associated with higher brain concentration of glutathione, a potent antioxidant that can help protect the brain from oxidative stress.
- A follow-up intervention trial could confirm whether increasing dairy intake could enhance the brain’s antioxidant defenses and protect against aging and various neurodegenerative diseases.
It’s well known that milk and calcium are good for your bones, but it turns out that they might also be good for your brain. A new study suggests that dairy consumption could potentially play a role in protecting the brain from oxidative stress, a process that has been implicated both in normal aging and in many neurodegenerative conditions such as Alzheimer’s disease or Parkinson’s disease [1,2].
The study, led by Debra Sullivan and In-Young Choi from the University of Kansas Medical Center, found that higher dairy consumption was associated with higher brain concentrations of glutathione, a potent antioxidant . Glutathione is part of the brain’s antioxidant defenses, which help stave off oxidative stress. “When we have higher antioxidant defenses, that helps the brain to be protected against neurodegeneration and also preserve our cognitive function,” says Choi, an associate professor of neurology.
Leading a healthy lifestyle with healthy food choices can boost our antioxidant defense system, says Choi. “Drinking milk could be one of the healthy choices people can make,” she says. The study’s results were consistent with a recent study in which individuals who consumed the Dietary Approaches to Stop Hypertension (DASH) diet, which is rich in diary foods, had higher plasma glutathione concentration .
The new study relied on a technique developed by Choi to detect glutathione in the brain using magnetic resonance imaging [5,6,7]. When Sullivan, a professor of dietetics and nutrition, first found out about this technique, she realized its potential in examining the effects of diet and lifestyle on brain glutathione concentration. “We did an exploratory study, and based on that, what was significantly related with brain glutathione was dairy food, and calcium,” she says.
The researchers were initially surprised at this association. Choi expected glutathione concentrations to be associated with “antioxidant-enriched vegetables like blueberry, pomegranate, and broccoli,” but the only statistically significant association was with dairy. Choi and Sullivan decided to do a larger study focused on dairy to see if they could confirm the results of their unpublished pilot study.
In the new study, the researchers recruited 60 healthy older individuals covering a broad range of daily dairy consumption. “The biggest challenge that we had was actually finding older individuals that were consuming the recommended three servings of dairy a day,” says Sullivan. The researchers assessed study participants’ diets in the week before their brains were scanned, and then examined the link between dairy intake and brain glutathione concentration.
Choi and Sullivan found that higher brain glutathione concentration was associated with higher daily dairy intake, confirming the results of their exploratory study. In particular, there was a significant correlation between glutathione concentration and milk consumption. Sullivan cautions that further studies will be needed to find out whether the effect is specific to milk or applies to other forms of dairy.
It is still unclear how exactly dairy consumption leads to increased glutathione in the brain, and one of the next steps is to figure out “what exactly is it within dairy that’s causing the effect,” says Sullivan. “There are various different components of dairy that could theoretically be responsible, and make sense based on what we know of the biochemistry and physiology,” she says.
One component of dairy that could play a role is the amino acid cysteine. “We know that dairy is high in cysteine, and cysteine would be the rate-limiting substrate that’s needed to make glutathione,” she says . In addition, dairy is a significant source of calcium and riboflavin, both of which have been implicated in maintaining glutathione concentration [9, 10, 11, 12].
While the current study can tell us about the association between dairy consumption and brain glutathione concentration, it is not designed to uncover cause-and-effect relationships. Sullivan and Choi hope to do a follow-up intervention study that would look at whether increasing the dairy consumption of low-dairy consumers would also increase their brain glutathione concentration. “In order to prove this concept, we would have to have a randomized control trial, and intervention,” says Sullivan.
If dairy consumption is found to have a causal effect on brain glutathione and brain health, then this could be yet another reason to promote increased dairy consumption in aging populations. According to national surveys, only 23% of older adults in the United States appear to meet dietary recommendations for dairy . “Sadly, the US population, whether they’re elderly or young adults or adolescents, don’t consume the recommended three servings of dairy a day,” says Sullivan. This study “is just the initial step, but it is very intriguing,” she says. “I think it sets the stage for a lot of future research and hopefully great health benefits if it holds true.”
1. Sies H. Oxidative stress: from basic research to clinical application. Am J Med 1991;91(Suppl 3):31S–8S.
2. Benzi G, Moretti A. Are reactive oxygen species involved in Alzheimer’s disease? Neurobiol Aging 1995;16:661–74.
3. Choi I et al. Dairy intake is associated with brain glutathione concentration in older adults. Am J Clin Nutr 2015;101:287-93.
4. Asemi Z, Tabassi Z, Samimi M, Fahiminejad T, Esmaillzadeh A. Favourable effects of the Dietary Approaches to Stop Hypertension diet on glucose tolerance and lipid profiles in gestational diabetes: a randomised clinical trial. Br J Nutr 2013;109:2024–30.
5. Choi I-Y. Regional distribution of glutathione in the human brain in vivo. J Neurochem 2003;87(Suppl 1):161.
6. Choi I-Y, Lee S-P, Denney DR, Lynch SG. Lower levels of glutathione (GSH) in the brains of secondary progressive multiple sclerosis patients measured by 1H magnetic resonance chemical shift imaging at 3 T. Mult Scler 2011;17:289–96.
7. Choi IY, Lee P. Doubly selective multiple quantum chemical shift imaging and T(1) relaxation time measurement of glutathione (GSH) in the human brain in vivo. NMR Biomed 2013;26:28–34.
8. Lu SC. Regulation of hepatic glutathione synthesis: current concepts and controversies. FASEB J 1999;13:1169–83.
9. Pascoe GA, Reed DJ. Cell calcium, vitamin E, and the thiol redox system in cytotoxicity. Free Radic Biol Med 1989;6:209–24.
10. Reed DJ, Pascoe GA, Thomas CE. Extracellular calcium effects on cell viability and thiol homeostasis. Environ Health Perspect 1990;84: 113–20.
11. Taniguchi M, Hara T. Effects of riboflavin and selenium deficiencies on glutathione and its relating enzyme activities with respect to lipid peroxide content of rat livers. J Nutr Sci Vitaminol (Tokyo) 1983;29: 283–92.
12. Dutta P, Rivlin RS, Pinto J. Enhanced depletion of lens reduced glutathione Adriamycin in riboflavin-deficient rats. Biochem Pharmacol 1990;40:1111–5.
13. Ervin RB. Healthy Eating Index scores among adults, 60 years of age and over, by sociodemographic and health characteristics: United States, 1999-2002. Adv Data 2008;395:1–16.