This is according to a meta-analysis which studied 50 randomised and non-randomised trials that studied the impact of over 20 phytonutrients in improving metabolic health.
Aloe vera, fenugreek and spirulina, were the next most beneficial phytonutrients as they could improve two metabolic health parameters, namely lipid profiles and glycaemic control.
This meta-analysis was conducted by researchers from the National Cancer Center Graduate School of Cancer Science and Policy in South Korea.
The researchers searched for the relevant clinical trials found on PubMed, Embase, and Cochrane Library as of July 4 last year.
Fifty systematic reviews and meta-analyses published between 2010 and last year were included in this analysis. They were chosen because they measured effects related to the cardiovascular health, including hypertension, blood pressure, cholesterol levels, diabetes etc.
Of the 50 studies, 71 per cent were published in the last three years.
Black cumin was found to benefit blood pressure by decreasing systolic blood pressure.
Its benefits for cholesterol control was seen by its ability in statistically increasing the amount of “good cholesterol” HDL-cholesterol, as well as decreasing total cholesterol, triglycerides, “bad cholesterol” LDL-cholesterol, and very low-density lipoprotein cholesterol (VLDL-C)
As for glycaemic control, it has shown to reduce fasting glucose and glycated haemoglobin levels.
Citing existing findings, the researchers said this could be due to the presence of several key compounds. For example, it contains thymoquinone that could regulate blood pressure by increasing the urinary excretion of sodium, potassium, chloride ions, and urea.
Its high content of polyunsaturated fatty acids, soluble fibers, sterols, flavonoids, thymoquinone, and nigellamin may also help to alter lipid profiles by inhibiting VLDL secretion, cholesterol absorption and synthesis, and also by increasing the uptake of LDL-C from blood.
Next best phytonutrients
Ranking behind black cumin, the intake of aloe vera, fenugreek and spirulina was found to improve lipid profiles and glycaemic control.
In terms of lipid profiles, the trio, when taken separately, were shown to increase HDL-C levels and reduce total cholesterol, and LDL-C levels.
As for glycaemic control, they were shown to statistically reduce fasting blood glucose levels.
“[This study is] the first to summarise existing evidence obtained from published systematic reviews and meta-analyses of clinical trials examining the effects of phytonutrients on various metabolomic biomarkers related to hypertension, dyslipidemia, and diabetes.
“All evidence was based on moderate to high quality studies of randomised or non-randomised clinical trials,” the researchers said.
However, they added that the results must be interpreted with caution, since the meta-analysis contain a degree of heterogeneity as the trials analysed differed in a number of factors, such as the duration of intervention, study design, and study population.
For blood pressure
On the other hand, seven phytonutrients, namely garlic, ginger, green coffee extract, green tea, phytosterol, pycnogenol, and sour tea (hibiscus sabdariffa) have shown to improve blood pressure by statistically reducing both systolic and diastolic blood pressure in nine and eight studies respectively.
However, based on clinical significance, only ginger and sour tea could significantly reduce SBP by at least 5mmHg. Also, none of the phytonutrient mentioned in the above list could reduce SBP or DBP by more than 10 mmgHg.
Source: Phytotherapy Research
Phytonutrient supplements and metabolic biomarkers of cardiovascular disease: An umbrella review of meta-analyses of clinical trials
Authors: Hoang T and Kim J