Are vegetarians at a higher risk of stroke? Could this apparent increased risk be due to reverse causation? And what about the comparison between vegetarians and vegans? Let’s delve into the research to uncover the truth.
In the EPIC-Oxford study titled “Risks of Ischaemic Heart Disease and Stroke in Meat Eaters, Fish Eaters, and Vegetarians Over 18 Years of Follow-Up,” it was found that vegetarian diets were associated with lower heart disease risk compared to meat eaters. However, vegetarian diets were linked to a slightly higher risk of stroke. This raises the question of why there is this extra stroke risk. Could it be due to reverse causation?
Reverse causation is a phenomenon seen in studies where an observed link between two factors may not indicate direct causation but rather an underlying condition influencing the results. For example, individuals who quit smoking may have higher mortality rates compared to smokers, not because quitting smoking leads to death, but because underlying health issues prompted them to quit. This phenomenon can also be seen in non-drinkers who appear to have higher rates of liver cirrhosis, which is likely due to existing liver issues prompting them to stop drinking.
Similarly, new vegetarians may initially show higher rates of heart disease as they could have adopted a vegetarian diet after being diagnosed with heart disease, leading to the appearance of elevated risk in the early stages. By excluding the initial years of data, researchers can better evaluate the true impact of the diet on health outcomes, revealing a significant reduction in heart disease risk over time.
Despite these considerations, the increased stroke risk among vegetarians persisted even after accounting for the initial data. Further analysis revealed that vegetarians had a higher incidence of hemorrhagic strokes, which are caused by blood vessel ruptures, compared to ischemic strokes. This raised concerns over the stroke risk in vegetarians and vegans.
While vegans did not show a significantly higher risk of stroke compared to meat eaters, the findings indicated a notable increase in hemorrhagic strokes among vegetarians. The prevalence of this type of stroke, which is less common than ischemic strokes in the general population, raised questions about the factors influencing stroke risk in plant-based diets.
Previous studies on stroke mortality have highlighted the lower heart disease risk among vegetarians but have not shown a statistically significant difference in stroke mortality rates. A recent study provided some relief by revealing that vegetarians do not face a higher risk of dying from stroke but still have the same stroke mortality rate as meat eaters.
One potential explanation for the increased stroke risk in plant-based eaters could be linked to vitamin D levels. Vegetarians and vegans often exhibit lower vitamin D levels compared to meat eaters, and low vitamin D status has been associated with an elevated risk of stroke. However, the role of vitamin D in stroke risk requires further investigation through randomized studies to establish a direct causal relationship.
Contrary to expectations, examining individuals with genetically lower vitamin D levels from birth did not conclusively point to an increased risk of stroke. This suggests that the relationship between vitamin D and stroke may be more complex and multidimensional.
Alternative factors contributing to the stroke risk in vegetarians and vegans warrant exploration to uncover the mechanisms underlying the observed trends. As we continue to unravel the intricate interplay between diet, health outcomes, and stroke risk, further research is essential to shed light on the nuanced relationship between plant-based diets and stroke incidence.
Stay tuned for more insights on stroke prevention strategies and dietary considerations in our ongoing series. Let’s unravel the complexities of stroke risk factors and delve deeper into the impact of plant-based diets on cardiovascular health.
