In just two months, twins placed on an experimental vegan diet had lower insulin, decreased weight, and reduced levels of a protein associated with heart disease and stroke, new research shows.

The findings provide yet more evidence to show that vegan diets aren't just the best option for the environment – they can be great for people too.

"Based on these results and thinking about longevity, most of us would benefit from going to a more plant-based diet," explains Stanford University nutritional scientist Christopher Gardner.

For their study, researchers recruited 22 pairs of healthy identical twins – to control for genetic, upbringing and lifestyle differences – and divided the twins into two groups.

Both groups were provided with healthy diets containing vegetables, legumes, fruits, whole grains, nuts, and seeds. The only difference was one of each set of twins also consumed what's considered a healthy amount of meat, while the other's diet was strictly plant-based.

"Not only did this study provide a groundbreaking way to assert that a vegan diet is healthier than the conventional omnivore diet, but the twins were also a riot to work with," says Gardner.

"They dressed the same, they talked the same and they had a banter between them that you could have only if you spent an inordinate amount of time together."

For the first four weeks of the trial, both groups had specially prepared meals delivered to them for breakfast, lunch, and dinner, and were provided with strict instructions around what snacks they could have. These included avoiding processed foods and maintaining a balanced variety of food groups.

For the second part of the experiment, the participants had to continue the diet by shopping and cooking for themselves, for another four weeks.

"Although weight loss was not discouraged, our diet design did not include a prescribed energy restriction and was not intended to be a weight loss study," Stanford food scientist Matthew Landry and colleagues write in their paper.

"Participants were told to eat until they were satiated throughout the study."

While both groups improved their cardiovascular health, the twins on the plant-based diet experienced the greatest improvements. Not only did they lower their fasting insulin by 20 percent, but dropped their levels of low-density lipoprotein cholesterol (LDL-C) too.

This protein transports fat molecules around the body, specifically cholesterol, which increases the risk of cardiovascular disease. The optimum level of LDL-C is less than 100 mg/DL.

The average level before the experiment was 118.5 mg/dL for the omnivores, which dropped to 116.1. In the vegan group, it went from 110.7 to 95.5 mg/dL.

The authors explain that the study wasn't set up to control calorie intake, so the drop in LDL-C could be attributed to those on a vegan diet experiencing weight loss.

"We designed this study as a 'free-living' study; thus, the behavior of following a vegan diet may induce the physiological changes we observed," they write.

"However, the biological mechanisms cannot be determined to be causally from solely the vegan diet alone because of confounding variables (weight loss, decrease in caloric intake, and increase in vegetable intake)."

The study noted an expected drop in vitamin B12 too, but as it was such a short time period, it had not yet become significant, the researchers think.

Going strictly plant-based can be risky when done incorrectly, as it does become harder to obtain certain critical nutrients such as B12. People who go full vegan are often encouraged to take supplements to counteract this effect.

Unfortunately, we've been experiencing a strong push back against this dietary option, so much so that veganism has become a dirty word, despite most people agreeing with the principles behind it.

It's also extremely difficult for those of us with dietary health conditions to achieve.

But we also can't deny the increasing body of evidence pointing to the clear health benefits of a plant-based diet. These include weight loss, reducing blood pressure, and lowered risks of diabetes and heart problems across different ethnic groups.

As increases in health markers were also seen in the control group too, just shifting towards more plant-based foods can clearly also be beneficial.

So if we avoid the sticky, polarizing traps of black and white thinking and instead encourage each other to make healthier choices rather than demanding an absolute shift to veganism, there's more chance of shifting mindsets and maintaining changes.

The researchers acknowledge this.

"A vegan diet can confer additional benefits such as increased gut bacteria and the reduction of telomere loss, which slows aging in the body," explains Gardner. But "what's more important than going strictly vegan is including more plant-based foods into your diet."

This research was published in JAMA Network Open.