Tuesday, April 20, 2010

Chia Seeds Follow-up

Dear Readers,

This Q & A is in response to Dr. Cordain's special report on Chia Seeds, which appeared in a recent issue of our newsletter, The Paleo Diet Update. The full report is available in The Paleo Diet Update, Volume 6 Issue 7.

Q: Loren,

Hope all is well with you and your work!

After reading your article on chia seeds, I forwarded the article to Dr. Vlad Vuksan in Canada, one of the leading researchers/promoters of Salba Seeds. After he got your article, he seemed to object that your conclusions apply uniquely to chia seeds generically, but not to Salba Seeds (single variety).

Is such a distinction valid? Wouldn't your conclusions regarding chia seeds apply as well to Salba, a variety of chia?

Thanks for your insights,

A: Hi Frank,

I stand by my conclusions in the newsletter. Until further human trials are completed employing a sample size with sufficient statistical power to resolve these immune system issues, then the potential adverse effects of long term, chronic chia seed consumption may outweigh the potential benefits. I respect Dr. Vukan’s long time collaborative work with David Jenkins at the University of Toronto, particularly in regard to their pioneering work on the glycemic index. I have read both of Dr. Vukan’s recent chia seed papers1, 2, and in neither one do the authors make any distinction between generic Salvia hispanica L. and the trade name (Salba) version of the seed they employed in their two studies. Hence, unless Dr. Vukan and colleagues can show otherwise, the literature results I have uncovered remain unchanged and apply to both Salba and Salvia hispanica L. It should be noted that at least two of the subjects in Dr. Vukan’s first study2 refused to continue because of gastrointestinal side effects.

In regard to Dr. Vukan’s first chia study, Table 1 shows a non-significant decrease (7.0 %) in the treatment group’s CRP and a 32.9 % increase in the control group value. The authors interpret this bi-directional group change in the abstract and elsewhere as a significant reduction (40 + 1.6% p less than 0.04) in CRP. This kind of data reporting is misleading when the treatment group mean change was actually non-significant. Despite ANCOVA adjustment for age, gender and sequence in their repeated measures model, their interpretation of the CRP data is at best misleading but likely incorrect. An additional shortcoming in this study involves the reporting of ALA and EPA data (results p. 2806). Why weren’t the actual plasma concentrations (mean + SD) of both of these fatty acids reported in both the experimental and control group? Given that 2% or less of ALA is chain elongated and desaturated into DHA, the EPA data need further scrutiny. Did the reported % differences for ALA and EPA represent within group differences or factorial differences? These shortcomings potentially invalidate the conclusions of the paper that CRP was reduced. In contrast, Nieman and colleagues3 were unable to replicate Dr. Vukan and colleague’s results in a similar study with a much larger sample size and hence greater statistical power.

Loren Cordain, Ph.D., Professor

  1. Vuksan V, Jenkins AL, Dias AG, Lee AS, Jovanovski E, Rogovik AL, Hanna A. Reduction in postprandial glucose excursion and prolongation of satiety: possible explanation of the long-term effects of whole grain Salba (Salvia Hispanica L.). Eur J Clin Nutr. 2010 Apr;64(4):436-8.

  2. Vuksan V, Whitham D, Sievenpiper JL, Jenkins AL, Rogovik AL, Bazinet RP, Vidgen E, Hanna A. Supplementation of conventional therapy with the novel grain Salba (Salvia hispanica L.) improves major and emerging cardiovascular risk factors in type 2 diabetes: results of a randomized controlled trial. Diabetes Care. 2007 Nov;30(11):2804-10

  3. Nieman, D., C., E. J. Cayea, M. D. Austin, D. A. Henson, S. R. McAnulty, F. Jin. 2009. Chia seed does not promote weight loss or alter disease risk factors in overweight adults. Nutrition Research, 29(2009):414-418.

No comments:

Post a Comment