What we eat cannot change the DNA sequence we were born with, but it may change how our cells use that DNA.
A new randomized study found that just four weeks on a vegan diet altered hundreds of thousands of chemical signals across the genome in patterns connected with immunity, metabolism and aging.
Researchers from the University of California San Diego and the University of Freiburg in Germany compared a vegan diet with a meat-rich diet. Their results offer a glimpse into how quickly the body can respond at the molecular level when everyday eating habits change.
Every cell contains essentially the same genetic instruction book, yet a liver cell behaves very differently from a brain cell or an immune cell. One reason is that cells use chemical controls to determine which parts of that instruction book should be read.
These controls are part of what scientists call the epigenome. Unlike a mutation, an epigenetic change does not alter the letters of DNA itself.
The researchers focused on DNA methylation, in which small chemical groups become attached to particular places on DNA. Depending on where these marks appear, they can influence whether certain genes become more or less active.
Previous research has connected diet with heart disease, type 2 diabetes and some cancers. But scientists want to understand the steps between eating a particular food and eventually developing better or worse health, and epigenetic changes may be one piece of that puzzle.
The trial included 48 healthy adults. Everyone first followed the same diet for a week, after which participants were randomly placed on either a completely vegan diet or a diet containing plenty of meat for one month.
The researchers deliberately designed the diets to contain similar amounts of calories. That allowed them to ask whether food composition itself could influence the epigenome rather than simply measuring what happens when people eat less and lose weight.
Blood samples taken before and after the experiment were used to examine DNA methylation. The scientists studied more than 800,000 locations across the genome, giving them a broad picture of how molecular regulation changed.
The vegan group showed changes connected with the immune system. Computer analysis of the DNA patterns predicted a decline in neutrophils, immune cells that are important for fighting infection but can also contribute to inflammation when their activity remains high.
The same analysis predicted an increase in CD4 T cells, which help organize and regulate immune responses. Importantly, actual blood cell measurements from the trial showed a similar pattern.
First author Lukas Karbacher said this agreement indicated that the researchers were seeing more than an abstract change in computer data. The methylation patterns lined up with measurable changes in the participants’ blood.
Other differences appeared in pathways related to how cells grow and divide. The vegan diet increased methylation in control regions of some genes involved in cancer-related and cell-growth pathways, which could reduce the activity of those genes.
That result may sound dramatic, but it should not be read as evidence that vegan eating prevents cancer. A change in gene regulation over four weeks cannot tell researchers whether a person will develop cancer years later.
The team also found molecular patterns suggesting reduced activity in pathways involved in fat metabolism. Other changes pointed toward insulin signaling, cellular stress responses and systems that repair damaged DNA.
The researchers then asked whether the diets affected measures of biological aging. To do this, they used epigenetic clocks, which are mathematical models that examine DNA methylation and calculate a score related to aging.
Biological age is different from the number of birthdays a person has had. It is an attempt to describe how old the body appears biologically, but there is no single perfect way to measure it.
Two epigenetic clocks designed to predict health-related outcomes suggested slower biological aging among participants on the vegan diet. However, another clock designed mainly to predict chronological age showed a different pattern.
Co-senior author Jerome Mertens said the contrast is a reminder that different aging clocks measure different biological features. The researchers believe the consistent results from the health-related clocks may indicate changes in pathways connected with disease risk and general health.
The study was published in the journal MedComm. It was carried out by researchers from UC San Diego and the University of Freiburg, including co-senior author Max Storz of the University of Freiburg Medical Center.
Storz emphasized that the observed differences were not simply caused by cutting calories. Because the diets were designed to provide similar energy intake, their composition appears to have played an important role in the changes.
Even so, several unanswered questions remain. The study included only 48 people, which is small for research intended to uncover subtle biological differences across a very complicated human genome.
Four weeks is also a short period. Scientists do not yet know whether the methylation patterns would become stronger, disappear or reverse if people continued or stopped the vegan diet.
The study also measured biological markers rather than actual long-term disease outcomes. It cannot show that the vegan participants will experience fewer heart attacks, develop less cancer or live longer because of the changes observed.
This makes the findings intriguing rather than definitive. The randomized trial provides evidence that changing diet can rapidly alter molecular signals in the body, but it does not prove that one month of vegan eating reverses aging or protects people from chronic disease.
Larger studies lasting months or years will be needed to determine whether the epigenetic changes persist and whether they translate into measurable improvements in health. Researchers will also need to learn which parts of the vegan diet—such as more fiber and plant foods or the absence of animal products—are responsible for the effects.
For now, the research offers a fascinating example of how responsive human biology can be. Our genes may provide the basic instructions, but factors such as diet can influence how those instructions are used, sometimes within a surprisingly short period.
Source: University of California San Diego and University of Freiburg.
