The researchers at the Griffith University in Australia said the findings of the meta-analysis could have "pivotal" clinical and public health implications.
The link between cholesterol and cardiovascular disease (CVD) is well documented, but elevated TAG levels have recently been reported as a single important risk factor for CVD.
Many patients are treated with medication such as statins to control their lipid levels, but sometimes this treatment is ineffective and can also have side effects. There is therefore a great deal of interest in nutritional and lifestyle approaches to complement pharmaceutical treatments.
The authors systematically reviewed evidence using a meta-analysis of controlled trials on the effects of sesame consumption on blood lipid profile. A total of ten controlled trials were included based on eligibility criteria and were assessed for risk bias.
“It was concluded that sesame consumption can significantly reduce blood TAG levels but there is insufficient evidence to support its hypocholesterolaemic effects,” wrote the authors in the British Journal of Nutrition.
Sesame reduced TAG levels when consumed in its oil form, but not as whole or ground seeds.
Sesame as a potential dietary intervention contains lignans, which are plant compounds with anti-inflammatory and antioxidant activity. Lignans are metabolised in the liver where they can affect production of lipids and cholesterol.
The TAG-lowering properties of sesame could also be partly due to its high (40%) monounsaturated fatty acid (MUFA) content, which can decrease blood TAG levels.
Evidence from the current research shows a short-term intervention with a MUFA-rich diet can reduce TAG levels. Fibre, vitamin E and polyunsaturated fatty acid (PUFA) in sesame seeds, plus antioxidant activity of its lignans, could also affect TAG generation and metabolism.
Sesame was more effective on lipid reduction when taken with vitamin E precursor α-tocopherol and lignans such as those found in sesame may enhance tissue levels of vitamin E precursors.
Dietary lignans may also affect the gene expression of proteins and enzymes involved in fat metabolism, the researchers said.
Sesame was effective at reducing TAG levels in the form of oil, but not as whole or ground seeds.
The authors also found it had a greater impact on people with lower body mass index (BMI), but they said this could be due to analysis methods. Further investigation was needed with participants with higher BMI, they wrote.
The authors pointed to a number of limitations in their study, including a small number of controlled trials and limited subgroup analysis.
Results may also have been influenced by dietary changes not controlled for.
These limitations must be considered, but as the first meta-analysis of sesame's impacts on lipid profiles, these results showed for further investigation into sesame as an effective dietary intervention to reduce risk of CVD was warranted.
Source: British Journal of Nutrition
Published online ahead of print, doi: 10.1017/S0007114515005012
“Sesame fractions and lipid profiles: a systematic review and meta-analysis of controlled trials”
Authors: S. Khalesi, E. Paukste, E. Nikbakht and H. Khosravi-Boroujeni