Study Says Vegetarian Diets May Significantly Reduce Risk of Cancer, Heart Disease And Death

A diet rich in plants and plant-based foods significantly lowers the risks of developing cancer, heart disease, and dying early from cardiovascular disease, according to a large study that involved 23 years of data.

Dr. Angelo Capodici, of the University of Bologna in Italy who led the international team of researchers, said the “umbrella” analysis found a “protective effect” for specific cancers, including liver cancer, colon cancer, pancreatic cancer, lung cancer, prostate cancer, bladder cancer, melanoma, kidney cancer and non-Hodgkin lymphoma. The study also found that plants and plant-based foods helped in reducing blood pressure, cholesterol, and other cardiovascular risk factors.

When conducting umbrella reviews, researchers analyze data from previous reviews and meta-analyses of previous research.

The researchers analyzed 48 papers published between January 2000 and June 2023 that looked at the potential benefits of eating vegetarian, vegan, and lacto-ovo vegetarian diets. The investigators also looked at the links between plant-based diets, cancer, cardiovascular disease, and early death.

A vegetarian diet is mostly comprised of plant-based foods and excludes meat, poultry, fish, and seafood. A vegan diet, which is stricter than the vegetarian diet, consists of fruits, vegetables, beans, grains, and nuts and excludes foods that come from animals, including dairy products and eggs. A lacto-ovo vegetarian diet excludes meat, poultry, and fish but includes eggs and certain dairy products, such as yogurt, cheese, and milk.

The study, published in the journal PLOS ONE, found that eating plant-based diets was associated with a lower risk of ischemic heart disease (heart problems caused by narrowed heart arteries), type 2 diabetes, gastrointestinal and prostate cancer, and death from cardiovascular disease. This was primarily due to improvements in blood pressure, blood sugar management, and lower body mass index.

“This research shows, in general, that a plant-based diet can be beneficial, and taking small steps in that direction can make a difference,” Matthew Landry, one of the review’s authors and an assistant professor of population health and disease prevention at the University of California, Irvine, told NBC News. “You don’t have to go completely vegan to see some of these benefits. Even reducing a day or two per week of animal-based consumption can have benefits over time.”

The researchers noted that pregnant women, specifically those with vegetarian diets, had the same risk of gestational diabetes and hypertension as pregnant women who were not on plant-based diets.
This was an “intriguing finding” that needs further research, Dr. Federica Guaraldi, the study’s co-author, told CNN.

Since the hormones of pregnancy might affect findings, “we cannot rule out that participants have taken supplements during the study period that could have altered the impact of diet on the considered parameters,” said Dr. Guaraldi, who is also medical director of the pituitary unit at the IRCCS Institute of Neurological Sciences of Bologna in Italy.

One question the investigators wanted to answer is why plant-based diets are so healthy and lower the risk of disease. For one, previous studies show that people on plant-based diets eat less refined grains, added fats, sweets, snacks, foods, and high-calorie beverages.

In essence, plant-based foods help to prevent obesity, which is associated with heart disease and certain cancers. But, there is probably more to it than that, according to Landry.

“Some of it is independent of weight,” Landry told NBC News. “Even when weight is maintained or doesn’t change, we still see reductions in some of these other clinical health outcomes, especially when it relates to cardiovascular disease.”

The ingredients in plant-based foods might also contribute to the health factor. For instance, plant-based diets are known for their fiber content, which helps in lowering bad cholesterol levels, according to Brie Turner-McGrievy, a professor of health promotion, education, and behavior at the University of South Carolina.

“Soluble fiber that’s found in things like beans and oats is really a powerful tool to help lower LDL cholesterol levels,” Turner-McGrievy told NBC News. However, people can only reap the benefits of eating whole foods. “It’s not like you can take a fiber supplement and hope to have these same outcomes,” she said.

Turner-McGrievy was not involved in the umbrella review, but her research was included in the umbrella review. In 2014, Turner-McGrievy conducted a study showing that plant-based diets can lower risk factors for heart disease, stroke, and type 2 diabetes.

The research team cautioned that plant-based diets can be derailed by poor dietary choices, such as eating processed foods like sugary white bread, potato chips, and even candy.

“Diets that emphasize consumption of unhealthy plant foods, such as fruit juices, refined grains, potato chips, and even sodas” might cancel out the positives of a plant-based diet for health, Dr. Guaraldi told CNN.

For example, fruit juices, which are “full of sugars or sweeteners,” were shown “to have (a) detrimental impact on metabolism as much as or even more than white sugar,” Guaraldi said.

Experts Advise Taking Precautions With Plant-based Diets

While plant-based diets are beneficial to overall health, certain vitamins and minerals are found in meat, dairy, or fish, and health experts say that vegetarians and vegans must take extra precautions to add those into their diets.

The more foods taken out of a diet, the harder it is to get all of the nutrients that the body needs, according to the Mayo Clinic. A vegan diet, for example, eliminates natural food sources of vitamin B-12, as well as milk products, which are good sources of calcium. So, the Mayo Clinic recommends adding sources of B12, calcium, iron, zinc, iodine, and vitamin D to avoid a deficiency.

Lean meats, poultry, and fish are good sources of protein but are not part of a plant-based diet. However, experts say good sources of protein in plants include legumes such as lentils, chickpeas and beans, nuts, seeds, whole grains, and soy products such as edamame, tempeh, and tofu.
The umbrella review authors also noted in their study that plant-based diets might lead to vitamin B-12 deficiencies in the general population. Landry said that can be addressed by taking a B-12 supplement.  

“From my perspective as a dietitian, a healthy plant-based diet—either vegetarian or vegan—can really meet just about all your vitamin and mineral needs,” Landry told CNN. 

Source Links:

https://www.cnn.com/2024/05/15/health/vegetarian-vegan-cancer-heart-disease-wellness/index.html
https://www.nbcnews.com/health/health-news/vegetarian-vegan-diets-lower-risk-heart-disease-cancer-rcna151970
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0300711
https://www.mayoclinic.org/healthy-lifestyle/nutrition-and-healthy-eating/in-depth/vegetarian-diet/art-20046446