The benefits of a vegetarian diet are not one-size-fits-all, says research

When it comes to determining whether a vegetarian diet is right for you, genetics plays an important part of the equation, according to a new study from the University of Georgia.

For many, vegetarianism leads to health benefits such as lowered cholesterol levels and a reduced risk of heart disease and type 2 diabetes. But for some, this specialized diet may come at a cost, the researchers said.

The work is published in the news PLOS genetics.

The study looked at how differences in genes affect how a person responds to nutrients and possible diet-related diseases. It provides a strong knowledge base for improving overall health outcomes through nutrition, says lead author Michael Francis, Ph.D., a graduate of UGA’s Institute of Bioinformatics. Francis was a vegetarian for seven years during his teens and twenties, and although he now eats meat, he said this was one of the main reasons he chose to study nutrigenetics.

“We are building an evidence base for personalized nutrition, which optimizes human health at the level of the individual, rather than one-size-fits-all nutritional recommendations,” Francis said.

The researchers analyzed data from more than 150,000 participants and identified 2,300 participants who followed strict parameters for a vegetarian diet to determine how genetics influences health benefits.

They found that most vegetarians had lower cholesterol levels at all levels, including total cholesterol, LDL and HDL levels, which may be beneficial for heart health.

Vegetarians also had lower vitamin D levels and higher levels of triglycerides than non-vegetarians. Vitamin D is important for bone health and immune function, and a deficiency can lead to negative health effects. Higher levels of triglycerides, a type of fat in the blood, can also increase the risk of cardiovascular disease.

Including a genetic component in their analysis, the study found that when specific gene variants, known as minor alleles, were present, participants saw different health outcomes. This included a variant of the gene MMAA, which relates to calcium metabolism.

While most vegetarians see decreased calcium levels, which can have a notable negative effect, individuals with this minor allele saw increased calcium levels. This could lead to improvements in bone and dental health, but high calcium levels can also have negative health consequences, including the development of kidney stones or cardiovascular problems.

Others may see an impact on their hormone levels. While the majority of vegetarians see a decrease in testosterone, a smaller group with a different gene variant saw increased testosterone levels. The third significant interaction, according to the study, was a gene variant related to kidney function and kidney filtration rate. The presence of this minor allele modified the effect of vegetarianism, moving it from increasing eGFR, or estimated glomerular filtration rate, to decreasing that filtration rate.

Highlighting these differences can help individuals find the best diet for their individual needs, Francis said.

“People with specific and immediate nutritional needs related to these three traits should consider getting tested for the variants we describe in this manuscript and make changes accordingly,” he said.

Going forward, this study may inform future nutrigenetics studies and clinical trials, allowing researchers to better understand the impact of diet on different groups.

The study was co-authored by Dr. Kaixiong Ye, from the UGA Department of Genetics. Other co-authors include Drs. Kenneth Westerman and Alisa Manning, from Harvard University.