As the protective caps located at the tips of chromosomes that safeguard DNA as our cells divide, the shortening of telomeres is seen as a key biological marker of the aging process. A new study has examined the relationship between telomere length and milk with different fat concentrations, suggesting there to be a link between low-fat variants and longer telomeres that can equate to several years of aging, according to the team.
The research was carried out by exercise scientists at Brigham Young University (BYU), who enlisted 5,834 US adults that were separated into different categories of milk drinkers. The goal was to explore how milk consumption habits might impact telomeres, which get shorter each time a cell replicates as we grow older.
Almost half of study participants drank milk daily, while a quarter drank milk at least weekly. A third of the subjects drank full-fat milk, 30 percent drank milk with a two-percent fat content, 10 percent of subjects reported consuming one-percent-fat milk, 17 percent drank milk with no fat, while 13 percent drank no milk at all.
The researchers examined the telomere length of these different groups and were able to tease out some apparent links. Chief among them was an overall correlation between high-fat milk consumption and shorter telomeres.
Subjects who drank two-percent milk had telomeres that were 69 base pairs shorter than those who drank one-percent milk, a figure the researchers equate to four additional years of biological aging. Meanwhile, the telomeres in adults who consumed full-fat milk were 145 base pairs shorter than those who drank non-fat milk.
“It was surprising how strong the difference was,” says BYU exercise science professor Larry Tucker. “If you’re going to drink high-fat milk, you should be aware that doing so is predictive of or related to some significant consequences.”
However, correlation does not equal causation and the researchers do recognize some limitations of their study – for example, those who drink low-fat milk may have a healthier lifestyle than those consume high-fat milk. However, they claim to have taken this and other potential confounders into account at the outset of the research and after making statistical adjustments say that those variables would have had little impact on the links they found between milk fat and telomere length. But they also accept that other variables not accounted for may be behind the correlation.
Obviously, more research is required before an explanation for the link between milk-fat and telomere length can be reached, but the researchers suggest that intake of saturated fats like those found in high-fat milk, which are known to trigger inflammatory pathways, alter gut microbiota and increase levels of oxidative stress, is one likely candidate for blame.
Interestingly, those who drank no milk at all had shorter telomeres than the adults who consumed low-fat milk, suggesting the drink has some anti-aging benefits but there could be a sweet spot to be found. The researchers say their research adds weight to the current dietary guidelines for Americans that recommends drinking milk with lower fat content as part of a healthy diet.
“It’s not a bad thing to drink milk,” Tucker said. “You should just be more aware of what type of milk you are drinking.”
The research was published in the journal Oxidative Medicine and Cellular Longevity.
Source: Brigham Young University
I read the paper, dated October 28, 2019, to see if they addressed this. It turns out they used all the data available to the public from the National Health and Nutrition Examination Survey that included enough DNA information and dietary information to correlate milk fat content with telomere length. The only data with that information was for the four years 1999-2002, with 3,072 women and 2,762 men having agreed to let you and everyone else in the world scrutinize all their DNA (not everyone is comfortable doing so). The available DNA was studied for telomere length by a UCSF scientist on behalf of this particular study.
Regarding antibiotics, since 2007 it has been illegal to sell milk containing any trace of antibiotics. To quote from http://milkfacts.info/Milk%20Microbiology/Antibiotics%20in%20Milk.htm, "The legal standard, as defined by the FDA, requires that milk contain no detectable antibiotics when analyzed using approved test methods (Grade A Pasteurized Milk Ordinance, 2007)." Conceivably some of the participants had been exposed to antibiotics earlier than 2007, in particular during 1999-2002, but there is no way a questionnaire of the kind used for this data could have obtained such information. In any event that information has been irrelevant since 2007.
Regarding hormones, all milk contains hormones including growth hormones. What's at stake here is added hormones. In 1993 the FDA allowed US dairy farmers to treat their cows with Monsanto's recombinant bovine somatotropin, rbST, or Sometribove, GH (growth hormone) for short. Many websites claim that organic milk cannot come from cows so treated, but so far I've been unable to find any government standards to that effect; furthermore while it is very likely to be true anyway today for organic milk, (a) that requirement even if in force today was almost certainly not a requirement before 2002 back when regulation of the term "organic" was almost nonexistent, and (b) organic milk was not a "thing" back then, at least not enough to bother including in a questionnaire of the kind available for this study.
Whether added GH in cow's milk (added to their diet, never to the milk itself which would be pointless since you can't make milk "grow" faster) would accelerate aging of humans more or less than naturally occurring growth hormones in milk is an interesting question (though not to my family because we eat organic whenever available and sensible, especially milk).