Tuesday March 18 2008
The vegan gluten-free diet was followed for one year
People with rheumatoid arthritis could cut their risk of heart attacks and strokes by removing meat, dairy products and gluten from their diets, the Daily Mail reports. A Swedish study has found that a vegan diet reduced levels of ’bad’ cholesterol (LDL) and “boosted levels of natural antibodies to fight compounds in the body that are implicated in rheumatoid arthritis,” the newspaper says.
The story is based on a trial that looked at whether a vegan diet could lower cholesterol and other indicators of cardiovascular disease in people with rheumatoid arthritis. Unlike the suggestions in some of the newspaper headlines, this study did not look at the effect of a vegan diet on the participants’ arthritis directly. The study found that there were reductions in weight and ‘bad’ cholesterol for those on the vegan diet. However, it did not involve enough people or last long enough to look at the effects of the vegan diet on cardiovascular events, such as heart attacks or strokes. Furthermore, the long-term effects of the gluten-free vegan diet are uncertain. Many of the people assigned to the vegan diet did not keep it up for the entire year, and it may be difficult for people used to a non-vegan diet to make such a big change in their eating habits.
Most bad LDL-cholesterol is generated by eating saturated animal fat, so eating more vegetables and less meat is a well-known technique for reducing bad cholesterol and heart attacks. People who stuck to the vegan diet lost weight, but it is not clear whether the gluten-free vegan diet would offer any specific advantages over other healthy diets aimed at weight loss. 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.
Where did the story come from?
Dr Ann-Charlotte Elkan and colleagues from the Karolinska University Hospital in Sweden carried out this research. The study was funded by the King Gustaf V 80-Year Foundation, the Swedish Rheumatism Association, the Swedish Science Fund, the Swedish Heart-Lung Foundation, Stockholm county council, the Karolinska Institute, and the Sixth Framework Programme of the European Union. It was published in Arthritis Research & Therapy, a peer-reviewed medical journal.
What kind of scientific study was this?
This was a randomised controlled trial that looked at the effect of a vegan diet on people with rheumatoid arthritis (RA). The researchers were interested in people with RA because they can have altered fat levels in their blood and an increased risk of cardiovascular disease. The researchers wanted to see whether a vegan diet, which contains less saturated fat and more polyunsaturated fat than a non-vegan diet, would improve the fat levels in the blood of people with RA and the levels of certain antibodies associated with a decreased risk of cardiovascular events.
The researchers recruited 66 adults (20 to 69 years old) who had been diagnosed with RA between two and 10 years previously. To be included, participants had to have at least two of the following signs of active disease: early morning stiffness for at least an hour, at least six swollen and/or tender joints, or a specific biochemical marker (ESR, erythrocyte sedimentation rate). Participants had to be generally healthy other than their RA. They could not currently have cancer, diabetes or severe heart, lung or kidney disease.
The participants were assigned at random to either a vegan diet that was free of gluten (found in wheat products) or a well-balanced non-vegan diet. They were asked to eat their assigned diet for one year. The gluten-free vegan diet included vegetables, nuts, fruits, buckwheat, millet, rice, corn, sunflower and sesame seeds. Participants in both groups were trained about the diet in the first week of the trial, and had access to a dietician and physicians for advice after this. All the participants took vitamin B12 and selenium supplements and were allowed to continue or start using non-steroidal anti-inflammatory drugs, oral steroids (glucocorticoids) and other anti-RA treatments during the study.
Participants were assessed at three, six, nine and 12 months. They provided three-day food diaries at each of these meetings to see how well they were sticking to the study diet. Blood samples were taken when the study began, and at three and 12 months into the study. The levels of different fats and antibodies in the blood samples were measured. The researchers also measured participants’ height, weight, disease activity and physical function. The results of the vegan and non-vegan groups were then compared.
What were the results of the study?
Thirty of the 38 people (79%) in the vegan group completed three months of the study and 22 people (58%) completed all 12 months. All the participants in the non-vegan group completed the study. The vegan and non-vegan groups were similar at the start of the study, except that the vegan group had higher levels of ‘good’ cholesterol (HDL). Participants had had their disease for five to six years and were mainly female with an average weight of about 67 kg.
After one year, the vegan group had significantly lower weight, body mass index and levels of bad cholesterol than the non-vegan group. Levels of one of the two antibodies associated with a protective effect against cardiovascular disease was increased in the vegan group. Disease activity was greater in the non-vegan group, but there was no difference in physical function between the groups.
What interpretations did the researchers draw from these results?
The researchers concluded that a gluten-free vegan diet in people with RA causes changes that may protect against cardiovascular disease.
What does the NHS Knowledge Service make of this study?
This research used a good study design to investigate the effects of a vegan diet on levels of fats in the blood of people with RA. However, there are some limitations to this study:
- This trial was relatively small. Randomly assigning people to groups aims to make the groups as similar as possible, but randomising a small number of people is not as effective as randomising larger numbers.
- This trial only looked at biochemical risk factors for cardiovascular disease (blood fats and certain antibodies) over a relatively short time. We cannot be certain that the changes seen would be maintained in the longer term, or what effect this level of change would have on the risk of cardiovascular events, such as heart attacks or strokes.
- Almost half of the people assigned to the gluten-free vegan diet (42%) dropped out of the study before one year elapsed. A gluten-free vegan diet is very restrictive, and could be difficult to stick to if people are used to a non-vegan diet.
Despite having a relatively normal body mass index of around 24, people who stuck to the vegan diet managed to lose weight. They also significantly reduced their bad LDL-cholesterol from an average of 3.2mmol/L to 1.3mmol/L at three months and 2.4mmol/L at 12 months. Reducing LDL-cholesterol is known to reduce the chances of a cardiovascular event.
It is not clear from this study whether the gluten-free vegan diet offers any specific advantages over other healthy diets aimed at reducing bad cholesterol or weight loss. 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.
Sir Muir Gray adds...
The evidence is mounting; if you want to stay healthy and save the planet – eat less, eat more plants and eat only food that your great grandmother would recognise if she were alive today.