The researchers responsible for both studies suggest their studies raise serious questions about the efficacy of the supplements, but an industry association spokesperson noted limitations with the study that may undermine such conclusions.
Policosanols are waxy, mostly linear C20 to C34 alcohols, and can be extracted from beeswax and a range of plant sources including sugar cane, rice bran, green vegetables, wheat bran and saw palmetto.
Clinical trials from Cuba in 2001 reported that policosanols extracted from sugar cane could reduce cholesterol levels by 10 to 30 percent, and further studies from the same research group and sponsored by the same enterprise (Dalmer) have continued to report LDL-cholesterol activity of similar magnitude. Further studies however have yielded mixed results.
"Because most positive findings derive from studies conducted by one research group, out study supports the need for systematic evaluation of available products containing policosanol to determine their clinical lipid-lowering efficacy under rigorous experimental conditions," wrote author Luigi Cubeddu from Mount Sinai Medical Center in Florida.
Cubeddu's study is published in the American Heart Journal and was a randomized, parallel, double-dummy, placebo-controlled trial involving 99 people with an average LDL-cholesterol level of 160 milligrams per deciliter of serum.
The participants were assigned to one of four intervention groups: 20 mg policosanol (Cholesstor, Pharmed), 10 mg atorvastatin (Lipitor, Pfizer), a combination of both, or placebo, for 12 weeks. The policosanol used was derived from sugar cane wax, but no formulation, dispersion or delivery details were provided by the researchers. The study was funded by a grant from Pharmed.
The doses selected were based on previous studies that reported an effect at these levels.
At the end of the study, Cubeddu and his co-workers report that supplementation with policosabol did not significantly change plasma lipid levels, including LDL-C, total cholesterol, HDL-C and triglycerides, compared to baseline values or placebo.
The pharmaceutical intervention using atorvastatin was associated with a reduction of LDL-C by 35 percent and total cholesterol by 27 percent. No additional effect was observed when policosanol was used in addition to atorvastatin.
The researchers do report that the sugar cane extract was safe and no effects on liver enzyme levels was documented.
Commenting on the studies, Daniel Fabricant, PhD, from the supplements industry association, the Natural Products Association (NPA), told NutraIngredients-USA.com: "For what is mostly a well-designed drug trial (Cubeddu, et al.,), the lack of a higher dose is concerning. A higher dose or some type Phase I trial to establish if there is a dose-response relationship, would offer some insight as to why the authors chose the dose they did, apart from the past studies, this really limits the usefulness of the science for the future.
"Higher doses also seem to be relevant in lowering triglycerides (not measured in this study), in previous studies," he said.
Dr. Fabricant pointed out that octacosanol, the major component of Cuban Sugar Cane Policosanol, can also be found in rice, wheat, apples among other foods and a diet high in these foods may limit the effectiveness of supplementation in a clinical study.
"While the authors do recommend the AHA type-I (cholesterol lowering) diet there is no mention of adherence to the diet nor any mention or record of food intake in the study.
"A food intake log which would shed light on if there was interference or overlap due to dietary factors and foods that could limit the effectiveness of supplementation in a clinical study."
Fabricant also reacted to Cudeddu's concluding statement: "We propose that policosanol should be added to the list of nutritional supplements that lack appropriate scientific validity to support their use," said Cubeddu. Fabricant said that this did not take into account the "benefits millions and millions of people worldwide currently derive from taking a dietary supplement s a part of their healthy lifestyle."
"There is no real scientific or public health benefit in making such statements in a research article," said Fabricant.
A second study, by researchers at McGill University in Canada, investigated the cholesterol-lowering effect of the Dalmer sugar cane policosanol in Golden Syrian hamsters. A comparison with an alternative policosanol mixture (Degussa Bioactives) was also performed.
The hamsters were randomly assigned to one of four intervention: non-cholesterol control; control diet plus 0.1 percent cholesterol; 0.1 percent cholesterol diet plus Dalmer policosanol (275 mg/kg diet); and 0.1 percent cholesterol diet plus Degussa policosanol (275 mg/kg diet).
Lead author Amira Kassis reported in the journal Atherosclerosis that neither policosanol formulation significantly affected plasma lipid levels, compared to cholesterol control.
"The outcome of the present study questions the clinical usefulness of policosanol mixtures as cholesterol-lowering nutraceuticals," concluded Kassis.
NPA's Daniel Fabricant also offered an opinion on this study. Fabricant told NutraIngredients-USA.com: "The authors (Kassis, et al.,) of the animal study perform a much more thorough job of documenting the diet, and indicate that the diet used in their study may be responsible for the divergence in results from previous animal studies as well as the use of a hamster model, which may differ in lipid metabolism from other animal species used in the earlier studies."
"This is an area where further research is needed, especially to determine if there are genetic differences in lipid metabolism or expression of enzymes responsible (for lipid metabolism), which may be further applicable to future human studies as well as offer some additional insight to past studies," said Fabricant.
Sources: American Heart Journal November 2006, Volume 152, Issue 5, Pages 982.e1-982.e5 doi:10.1016/j.ahj.2006.08.009 "Comparative lipid-lowering effects of policosanol and atorvastatin: A randomized, parallel, double-blind, placebo-controlled trial" Authors: L.X. Cubeddu, R.J. Cubeddu, T. Heimowitz, B. Restrepo, G.A. Lamas and G.B. Weinberg
Atherosclerosis Published on-line ahead of print: doi:10.1016/j.atherosclerosis.2006.10.008 "Lack of effect of sugar cane policosanol on plasma cholesterol in golden syrian hamsters" Authors: A.N. Kassis, C.P.F. Marinangeli, D. Jain, N. Ebine and P.J.H. Jones