A recent study examined how dietary choices affect the levels of beneficial biomarkers in the body. The team was particularly interested in the impact of a plant-based diet.

Over recent years, vegetarianism and veganism have experienced a boost in popularity. Although people might switch to a plant-based diet for a range of reasons, many choose this path for its health benefits. For instance, there is some evidence to suggest that a diet that includes fewer animal products reduces the risk of colorectal and prostate cancers. Also, vegetarianism appears to reduce the risk of diabetes and help control the condition for those who already have it. There is also evidence to suggest that adopting a vegetarian diet can boost weight loss.

Why the benefits?

Scientists are steadily unpicking how plant-based diets can improve health. It is clear that there are many factors involved. One obvious place to start is that vegetarians and vegans do not eat red meat or processed meat products, both of which experts consider to increase the risk of cancer.

As well as choosing not to eat meat, people who follow a plant-based diet also tend to consume more vegetables, fruits, and nuts. With this increase in plant matter comes a similar increase in nutrients, fiber, and other potentially beneficial compounds. Vegetarians and vegans also typically have higher levels of compounds with anti-inflammatory and antioxidant activity, such as carotenoids and flavonoids, in their bodies. According to the team behind the new study, these chemicals protect against cell damage and chronic diseases. Also, vegetarians are likely to have higher levels of lignans and isoflavones in their blood serum; experts believe that both of these can protect against cardiovascular disease and cancer.

Recently, a group of researchers at Loma Linda University School of Public Health in California took a detailed look at the metabolic changes that a vegetarian diet can bring. They published their findings in The Journal of Nutrition.

The scientists wanted to understand whether dietary choices made a significant difference in the levels of disease-fighting markers in blood, urine, and fat tissue. To explore, they recruited 840 participants from five dietary categories:

• Vegans, who consume no animal products
• Lacto-ovo vegetarians, who consume eggs and dairy more than once per month but consume no meat or fish
• Pesco-vegetarians, who consume fish once or more times each month but avoid meat
• Semi-vegetarians, who eat meat more than once per month but less than once each week
• Nonvegetarians, who eat meat at least once each week

The analysis

The scientists analyzed plasma, urine, and adipose (fatty) tissue from each of the participants. They tested for a range of markers, including carotenoids, isoflavonoids, saturated and unsaturated fats, and vitamins.

As expected, the vegan group had the highest levels of bioactive markers that prevent disease. For instance, the highest levels of carotenoids, isoflavones, and enterolactone were present in the vegans, followed closely by vegetarians. Vegans also had the highest levels of omega-3 and the lowest levels of fatty acids.

"An awareness that a healthier biomarker profile is obtained with a plant-based diet should motivate people to be proactive about dietary habits that promote good health and prevent disease."

—Lead study author Fayth Miles, PhD

Also, interestingly, Miles explains that the "results for semi-vegetarians look very similar to [those of] nonvegetarians."

The study involved a large number of participants, which gives the findings weight. However, it is worth noting that the scientists only took tissue samples once for each participant. Also, they do not know how these biomarkers might fluctuate depending on nondietary factors, such as an individual's metabolic rate and their microbiome.

The findings are good news for those who follow a plant-based diet, but the study will also be useful for researchers. Currently, scientists depend on participants to report their dietary intake using food diaries, which is not always reliable. As the study authors explain, "Under- or overreporting is common, attributable to subjects' perceptions of social desirability, poor recall, questionnaire design, and other issues."

However, if researchers can develop a reliable way of assessing diet using biomarkers, it may help validate findings and avoid some of the issues that come with self-reporting. Understanding how nutrition affects health is a complex area of study; no two people eat the exact same diet. Hopefully, by understanding the biomarker profiles associated with different foods, it might be easier to pick out links between variations in levels and increased risk of disease.