Effect of chia seed (Salvia hispanica L.) consumption on cardiovascular risk factors in humans: a systematic review

Introduction: chia is a seed rich in such nutrients as proteins, n-3 fatty acids and especially alpha-linolenic acid (ALA), minerals, fibers and antioxidants. Efforts have been made to assess whether human consumption of chia can reduce cardiovascular risk factors; however, it has not been established as effective and the findings of the few studies to have looked into the matter are inconsistent. Aim: to systematize the findings of studies assessing the effect the consumption of chia seed, either milled or whole, has in the prevention/control of cardiovascular risk factors in humans. Methods: this is a systematic literature review (SLR) with no meta-analysis. The articles scrutinized were identified in the electronic databases Lilacs, Medline (Pub-Med version), Cochrane, Scielo, Scopus, and Web of Science under the keywords"dyslipidemia" or "dislipidemia", "hyperlipidemia" or "hiperlipidemia", "obesity" or "obesidade", "salvia"or"salviahispanica", "Lamiaceae" or "chia", "hypertension" or "hipertensao", "hypertrygliceridemia" or "hipertrigliceridemia", and "riscocardiovascular" or "cardiovascularrisk." We chose for our selection English-, Portuguese- or Spanish-language articles about clinical trials on humans and published within the last ten years. The biases of risk analysis were carried out considering 6 of the 8 criteria of the Cochrane Handbook for Systematic Reviews of Interventions Version 5.1. Findings: seven studies (n=200) fit our inclusion criteria. Of the chosen clinical trials, only one was not randomized. Five of the studies were blind experiments. Two of the studies were acute trials, both of them randomized. Of the chia seed interventions, one study showed a significant drop in systolic blood pressure (SBP) and inflammatory markers, yet there was no change in body mass, lipid profile or blood sugar. In four of the studies reviewed there was a significant spike in ALA and eicosapentaenoic acid (EPA), with no significant change to other parameters. In the acute trials, post-prandial blood sugar was significantly lower. Only one study showed a significant drop in triglycerides (TG), body mass and inflammatory markers; however, the chia seed in that case was mixed with other foods. Most of the studies showed unclear or low risk of bias. Two studies showed a high risk of bias because not all the pre-specified primary outcomes were reported in the findings. Conclusion: most of the studies did not demonstrate statistically significant results in relation to cardiovascular disease (CVD) risk factors. The evidence regarding the relationship between chin seed consumption and cardiovascular risk factors are insufficient, and the studies included in this review present numerous limitations. Further research is hence needed.