Given the current trend towards more sustainable eating models, plant-based diets will undoubtedly be especially promoted and promoted. Therefore, it is important that the evidence of its relationship with health be analyzed and accumulated; and if it comes from the Cochrane initiative, even better, since its name is usually a guarantee of a high level of rigor and reliability in systematic reviews.
The diet that most strictly follows an exclusively plant-based pattern is the vegan one, as part of a philosophy that is becoming quite popular. It should be noted that Cochrane has already carried out a review on vegan diets Two years ago, analyzing the effect of this type of diet on cardiovascular health. But they just updated it today, publishing the work «Vegan dietary pattern for primary and secondary prevention of cardiovascular diseases» (2021), so it’s time to catch up
Without further ado, this would be the translation of the main conclusions of the review, in the «friendly» language to which Cochrane has accustomed us:
«(…) 13 randomized controlled trials (RCTs) were found (in 38 articles) that met our criteria. We grouped the studies into the following three categories for the interpretation of the results:
1. Vegan dietary intervention compared with no intervention or minimal intervention to prevent the development of cardiovascular diseases;
2. Vegan dietary intervention compared with another dietary intervention to prevent the occurrence of cardiovascular diseases;
3. Vegan dietary intervention compared to another dietary intervention in people with existing cardiovascular disease, to prevent recurrence.
None of the trials reported on the occurrence of cardiovascular disease in people with or without disease. Risk factors for cardiovascular disease were reported. There was moderate-certainty evidence for some small reductions in lipid levels with the vegan diet compared with no intervention or minimal intervention in people without disease, but also some very small changes in the opposite direction. In people who already had cardiovascular disease, information was very limited, as only one trial met our criteria. Four informative trials on the side effects of the diet, which were none or mild.
Most studies had limitations in design, so the evidence should be interpreted with caution. In particular, the total number of people participating in the studies was too small to rule out the possibility of chance findings and to detect differences in the effect of our measures.
Conclusions:
The review concludes that there is currently no information on the effects of a vegan diet on the occurrence of cardiovascular diseases. There is limited information on the effects of diet in those who already have cardiovascular disease and mixed results on risk factors for those who do not have cardiovascular disease. We found that there are eight other studies in progress and, when we have the results of these, we will incorporate them into the review to help reduce uncertainty.
The studies were generally small with few participants in each group. None of the included studies reported on cardiovascular disease clinical events. Currently, there is insufficient information to draw conclusions about the effects of vegan dietary interventions on cardiovascular disease risk factors. (…) There is a paucity of evidence regarding secondary prevention.»
For those who want to know the results in more detail, this will be the summary of them, translated from the text of the original summary:
«Thirteen randomized controlled trials-RCTs (38 articles, seven trial registries) and eight ongoing trials were found that met the inclusion criteria. Most of the trials studied primary prevention (four category 1 trials, eight category 2 trials and a category 3 trial). None of the trials reported on clinical endpoints; primary outcomes on lipid levels and blood pressure are included.
In category 1 there was moderate-certainty evidence from four trials with 449 participants that a vegan diet probably led to a small reduction in total cholesterol (-0.24 mmol/L) and LDL cholesterol (0.22 mmol/L), a very small reduction in HDL cholesterol levels (-0.08 mmol/L) and a very small increase in triglyceride levels (0.11 mmol/L). The very small changes in HDL and triglyceride levels are in the opposite direction than expected. There was no evidence of an effect of the vegan dietary intervention on systolic blood pressure and diastolic blood pressure (low-certainty evidence).
For category 2, evidence of the effect of the vegan dietary intervention on total cholesterol levels was lacking (-0.04 mmol/L; four trials, 163 participants; low-certainty evidence). There was probably little or no effect of the vegan dietary intervention on LDL (-0.05 mmol/L, 4 trials, 244 participants) or HDL cholesterol levels (-0.01 mmol/L, 5 trials, 256 participants) or triglycerides (0.21 mmol/L; 5 trials, 256 participants) compared with other dietary interventions (moderate-certainty evidence). We are uncertain about any effect of the vegan dietary intervention on systolic blood pressure (0.02 mmHg) or diastolic blood pressure (0.63 mmHg, five trials, 247 participants (very low-certainty evidence).
Only one trial (63 participants) contributed to category 3, where evidence of an effect of the vegan dietary intervention on lipid levels or blood pressure compared to other dietary interventions was lacking (low or very low certainty evidence) . Four trials reported adverse events, which were either non-existent or mild.
Authors’ conclusions: The studies were generally small and with few participants in each comparison group. None of the included studies report clinical events of cardiovascular disease. Currently, there is insufficient information to draw conclusions about the effects of vegan dietary interventions on cardiovascular disease risk factors. The eight ongoing studies identified will add to the evidence and report on primary prevention. «There is a paucity of evidence for secondary prevention.»
In short, it seems that as of today the evidence is very scarce. The trials that are underway seem like they will provide a lot of added evidence, so we will have to stay tuned for future updates.
For those who want to know the review in its entirety, which is quite extensive, you can do so at this link.
Update:
A few days after the publication of this review a similar one was published, «A systematic review of the association between vegan diets and the risk of cardiovascular disease» (2021). Its conclusions are similar to the previous one and its authors did not find solid evidence of a relationship either.
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