No Link Between Citrus Flavonoids and Lower Cholesterol

Summary
Naringin and hesperidin are related chemicals called flavonoids found in fruits such as grapefruit, oranges, mandarins and lemons. There have been many studies conducted on this group of chemicals, showing their relation to reduction of blood cholesterol content.  According to the authors of this paper, “the evidence from previous studies in humans is not convincing”;  therefore, this study was done to evaluate the inconsistent results from previous studies. Results showed that there was no significant reduction in the cholesterol levels on intake of capsules containing naringin and hesperidin.

Introduction
Obesity is a major problem in most countries and hence is an area of active research. Citrus fruits are known sources of naringin and hesperidin. These compounds have been studied extensively in relation to reduction of blood cholesterol levels. The authors however, doubt this relationship, as either there were no placebos used in most previous studies or the studies lacked a good design. The examiners would know who had been given the tested compounds and hence the study suffered from severe bias and errors. This study intended to improve the method of the study and to evaluate the relationship between the flavonoids and cholesterol, especially LDL-C (low density lipoprotein cholesterol), in an unbiased manner.

Methodology
•    Around 216 men and women with moderately high cholesterol levels participated in this study. There was an initial period of four weeks, during which the subjects were restrained from consuming citrus fruits and fruit juices, supplements of the said flavonoids and any cholesterol-reducing drugs.
•     In the next stage, the participants were randomly given capsules of naringin, hesperidin or placebos. They were not told which medicine they were given.
•    The dosage was two capsules before breakfast and two before dinner for four weeks.
•    The cholesterol levels in their blood were determined before and after the study.

Results
•    There were a few dropouts from the study, owing to sickness and other medical conditions.
•    There was no significant drop in cholesterol levels after taking naringin and hesperidin supplements.
•    Total cholesterol, low density lipoprotein cholesterol (LDL-C), high density lipoprotein cholesterol (HDL-C) and triglyceride (TG) levels were all found to be almost similar to those prior to the study.

Shortcomings
The metabolic breakdown of these chemicals in the body occurs quickly. The researchers did not assess the level of these by-products in the blood of the subjects. They claim that there could have been quick elimination of the metabolic by-products, leaving a limited reaction time for these with the body.

Conclusion
While earlier studies, which were non-placebo controlled, indicated that intake of the hesperidin and naringin led to a reduction in various components of cholesterol in the blood of persons with moderately high levels of cholesterol, a convincing study design like the current one, with placebo controls, failed to prove a relationship between them. Most current treatments for obesity still remain elusive. The authors state the “…outcome suggests that the citrus flavonoids hesperidin and naringin exert no cholesterol-lowering effect in humans, at least not when consumed in capsule format.” Further studies are required to investigate the claims made by the earlier experiments.

For More Information:
Citrus Flavonoids Do Not Affect Serum Cholesterol
Publication Journal: The Journal of Nutrition, July 2010
By Isabelle Demonty; Yuguang Lin; Unilever R&D Vlaardingen, The Netherlands

*FYI Living Lab Reports Are Summaries of the Original Research.
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