Duh! Way to state the obvious, but Dr Ann-Charlotte Elkan and colleagues from the Karolinska University Hospital in Sweden carried out research to study "the vegan diet." I find it funny when people refer to it as "the vegan diet" as if it's some sort of cult or something. The study was based on participants that had rheumatoid arthritis and measured how effective a vegan diet was at lower their chances for cardiovascular disease.
I'm not sure why they chose to test on rheumatoid arthritis patients, but it should be noted that they did not directly look at arthritis in any way, so I'm not really sure what the connection was there. What the study found, was that there were significant reductions in LDL "bad" cholesterol and weight. (No, really?) These are the two main factors in cardiovascular disease and a vegan diet seemed to improve them. Well I think it's obvious because vegan diets contain no cholesterol and tend to be lower in calories and higher in nutrients, so it seems pretty logical that you would lose weight and lower LDL cholesterol.
It should be noted that they did say, "it may be difficult for people used to a non-vegan diet to make such a big change in their eating habits" and, "all individuals who wish to reduce their chances of cardiovascular disease should aim to eat a healthy diet, maintain a healthy weight, stop smoking and do an appropriate level of exercise". Once again, "the vegan diet" seems to be deemed too radical, but at least we're getting some positive press! It should also be noted that this is merely a trial study, so more need to follow for it to be fully accepted by the scientific community. Although, I can almost guarantee they will get the same results.