Evidence that vitamin E reduces the risk of heart disease comes from several observational studies, which vary depending on the type of study. People who take vitamin E supplements are very different from those who do not: they tend to be better educated and better off. As a group, this group are more proactive about their health and have the motivation and means to seek preventive health care, including healthier diets and increased physical activity.
Not surprisingly, the group that takes better health care is less likely to suffer from heart attacks. Large and rigorous observational studies are expensive but easier to organize than randomized experiments (Athey & Imbens, 2017). In the experiment, everyone will receive either therapy with an increased intake of vitamin E or their substitute. The task is performed by tossing a coin so that every person is equally likely to receive any treatment. By 2019, several experiments had concluded that vitamin E did not reduce the risk of heart attacks (Sozen et al., 2019). The medical authorities changed their recommendations, faced with this better evidence.
Observational studies have shown that α-tocopherol supplementation may positively affect CVD. In an observational study among men, individuals who took at least 100 IU of additional α-tocopherol per day showed a decrease in the progression of atherosclerosis of the coronary arteries. It was measured by angiography compared with those taking less than 100 IU/day of α-tocopherol. A randomized trial in the UK found that 400-800 IU supplementation of synthetic α-tocopherol patients reduced the incidence of non-fatal heart attacks by 77% (Vilar‐Gomez et al., 2019). However, vitamin E supplementation did not significantly reduce overall cardiac mortality.
People who received vitamin E therapy were, on average, more educated and affluent, so it’s not surprising that they had fewer heart attacks. We cannot conclude that hormone replacement therapy reduces heart attack rates just because we see this relationship in the data. In this example, education and wealth are background factors that help explain the relationship between therapy and good health. For example, a person who swims, on average, has greater endurance and a healthier body than those who do not swim. However, this does not mean that swimming is a factor that lowers deaths from heart diseases. Careful statistical studies try to measure possible hidden variables external factors to correct their influence (Hanin, 2017). As experiments on the benefits of vitamin E show, ‘swimming’ is not always the key to a completely healthy life, in which the risk of a heart attack is reduced to a minimum.
In observational studies, the researcher usually does not perform any actions with the studied patients. Thus, it overlooks the hidden factors that underlie many experimental results. Such studies have less evidence than randomized controlled experimental clinical trials. It is due to the lack of the possibility of randomization and blinding (Galli et al., 2017). They cannot be implemented when conducting observational studies since the very essence of the study distributes patients into groups, and patients know in advance which group they are included in (Moore et al., 2017). The question, “What could underlie this relationship?” is part of the statistical thinking underlying randomized trials.
There is a belief that the effect of vitamin E supplementation in a person who leads a healthy lifestyle increases performance, reducing the risk of a heart attack. Considering that the doctor in observational studies does not have any effect on patients, only the development of the situation is recorded, which does not depend on the researcher. Healthy user bias has higher health indicators on average, so they have a greater effect in observational experiments (Lassale et al., 2018). If one asks the question of statistical analysis, a healthy lifestyle will not be the only factor that positively affects the results. Moreover, often after the experiments with a doctor’s intervention, the results of the studies change.
Thus, observational studies and randomized controlled trials show different results. Indeed, a high supply of vitamins to the body has a therapeutic and prophylactic effect on the development and course of some diseases. However, the appointment of synthetic vitamins to increase the vitamin status does not always lead to a positive preventive and/or therapeutic effect. It has been observed that observational studies provide a more positive response to vitamin E supplementation in reducing heart attack risk factors than rigorous experiments. Of course, observational studies are still very useful, but it can be said right away that some samples cannot be trusted.
There are many external factors that have a significant impact on research results. In observational experiments, a healthy user bias greatly influences the results, which does not occur in randomized trials. The factor of a healthy lifestyle is key since external signs positively affect observations. At the same time, given the intervention of the doctor and many hidden factors, then careful experiments show that vitamin E does not have such an effect. Different types of experiments give different results, so there is no consensus on the benefits of taking vitamins E to reduce the risk of developing heart disease.
References
Athey, S., & Imbens, G. W. (2017). The econometrics of randomized experiments.Handbook of Field Experiments, 73–140. Web.
Galli, F., Azzi, A., Birringer, M., Cook-Mills, J. M., Eggersdorfer, M., Frank, J., Cruciani, G., Lorkowski, S., & Özer, N. K. (2017). Vitamin E: Emerging aspects and new directions.Free Radical Biology and Medicine, 102, 16–36. Web.
Hanin, L. (2017). Why statistical inference from clinical trials is likely to generate false and irreproducible results.BMC Medical Research Methodology, 17(1). Web.
Lassale, C., Batty, G. D., Baghdadli, A., Jacka, F., Sánchez-Villegas, A., Kivimäki, M., & Akbaraly, T. (2018). Healthy Dietary Indices and risk of depressive outcomes: A systematic review and meta-analysis of observational studies. Molecular Psychiatry, 24(7), 965–986. Web.
Moore, D. S., Notz, W., & Fligner, M. (2017). The basic practice of statistics. Macmillan Learning.
Sozen, E., Demirel, T., & Ozer, N. K. (2019). Vitamin E: Regulatory role in the cardiovascular system. IUBMB Life, 71(4), 507–515. Web.
Vilar‐Gomez, E., Vuppalanchi, R., Gawrieh, S., Ghabril, M., Saxena, R., Cummings, O. W., & Chalasani, N. (2019). Vitamin E improves transplant‐free survival and hepatic decompensation among patients with nonalcoholic steatohepatitis and advanced fibrosis.Hepatology, 71(2), 495–509. Web.