When one of my favorite researchers wrote on April 20 that "the potential adverse effects of long term, chronic chia seed consumption may outweigh the potential benefits," I took notice. Loren Cordain, Ph.D., is a professor in Colorado State University's department of health and exercise science. Dr. Cordain wrote one of the most intriguing books on nutrition, The Paleo Diet, which recommends that we avoid grains and dairy since our paleolithic ancestors weren't able to eat those foods.
Dr. Cordain's report in his April 10 newsletter is more detailed in his criticism of chia seeds. An excerpt is available online, but the guts of the chia seed report sells for $6.95 plus shipping and taxes.
My 2007 post here on chia seeds got lots of attention, including more comments -- 112 to date -- than any other. So I was concerned enough to contact the world's leading researcher on chia seeds.
Wayne Coates, Ph.D., is professor emeritus in the office of arid lands studies at the University of Arizona, Tucson. Dr. Coates has researched chia seeds for three decades and wrote the definitive book on the subject, Chia: Rediscovering a Forgotten Crop of the Aztecs (The University of Arizona Press, 2005).
Dr. Coates purchased a copy of the chia seed report. He shared it and his comments with me.
"I do not want to get into a long discussion about this," Dr. Coates writes, "but would like to make a few comments. In his article, Table 1 gives the nutrient profile for chia seeds. Interestingly he does not give the source of the data, and furthermore, he says it gives the 'entire' nutrient profile of chia seeds. In no way it is complete, and since the source is not identified, one can easily question its value as a reputable source.
"He talks about anti-nutrients in chia, yet he promotes flaxseed. The anti-nutrients in flaxseed are well-documented for both humans and animals. He criticizes the gel (which is soluble fiber) as possibly impairing fat absorption and the high fiber content as protein to be poorly absorbed. In some cases, there may be some negative effects, but the positive effects of consuming fiber in the diet in terms of bowel function and prevention of coronary heart disease are well-documented.
"He also does not like the fact that chia contains phytic acid. Phytic acid has been shown to have antioxidant, anticancer, hypocholesterolemic and other beneficial effects. So again, it is unclear why he states this is a negative aspect of chia.
"He also discusses the study by Nieman et al. and cites the author's statement that inflammatory markers increased. That is well and good, but even he notes that 'other confounding factors may have influenced the results.' In another study, which the authors listed as a preliminary study, he cites the results and states that IgE levels increased dramatically. The issue here is that the results were not statistically significant, and if you look at the standard deviation of the chia seed treatment, it was almost as large as the mean. In other words, the study should not be cited as being relevant.
"In a follow up to his first article, he talks about a study in which people 'refused to continue because of gastrointestinal side effects,' yet he never discusses the reason for such an effect. I have always advised people of two issues they should be aware of when consuming chia. First, if you start eating this and have been on a low fiber diet, diarrhea is possible since fiber is frequently used to promote increased bowel movement, simply back off on the amount and let your body adjust. The second issue is if people consume a lot of chia, but do not drink sufficient fluids. Chia is very hydrophilic, meaning it will adsorb a lot of water -- 7 to 9 times its weight. It only stands to reason that if you put a lot of chia in your stomach it will absorb the liquid in there and cramping could result.
"It is disappointing when someone cites articles that are not conclusive or utilizes part of studies to promote their own beliefs and biases. Until there are definitive studies that prove chia is unhealthy to consume, which I do not believe will ever be the case, I feel confident in saying there are no known negative or anti-nutritional issues when consuming chia."
After digesting Dr. Coates's rebuttal of Dr. Cordain's attack on chia seeds, I agree with Dr. Coates that the proven benefits of chia seeds outweigh the possible negatives that Dr. Cordain talks about. I recommend chia seeds to all of us who have diabetes for several reasons, not of the least of which is its high anti-inflammatory omega-3 content. I am happy to continue heaping chia seeds on most everything that I eat, including eggs, salad, and meat.
Dr. Coates tells me that he is still doing research of chia seeds and now sells chia seeds at the azchia.com website. That's where I will be buying my chia now.
Update July 11, 2010:
Here is Dr. Cordain's rebuttal:
Good to hear from you and many thanks for your kind words about my work.
I stand by my statement that phytic acid impairs absorption of divalent ions in a dose dependent manner. This data is unassailable and has been recognized in the nutritional community for more than 50 years. Hence, much of the calcium, iron, zinc and magnesium which on paper appear to be present in chia seeds are not available for absorption in vivo. Consequently, chia seeds are not good sources of these nutrients in living humans. In a typical western diet in which nutrients come from a variety of foods, particularly animal foods, these nutritional shortcomings in chia seeds likely are of little consequence. However, if chia seeds are consumed as staple foods comprising a substantial percentage of the caloric intake, overall nutrition would suffer similar to other human populations in which seeds (cereal grains, legumes) comprise more than half of the daily energy (1).
I also stand by my previous statement:
A recent review of all human chia supplementation studies concluded: "There is limited evidence supporting the efficacy of Salvia hispanica for any indication; thus far, only two clinical studies have examined the effects of Salvia hispanica on cardiovascular disease (CVD) risk factors (including body weight). One study showed some effects on some CVD risk factors, while the other did not. Neither study showed any effects of Salvia hispanica on weight loss."
Despite animal data showing certain positive health effects of chia seed consumption (which I listed in my paper), randomized controlled human trials have been unable to replicate these results. Consequently, until further clinical trials are conducted in humans, no good experimental data can support the notion that chia seed consumption has therapeutic value.
The preliminary data in both humans and animals suggesting pro-inflammatory and, pro-allergic effects with chronic high level chia seed consumption are problematic and should not be ignored. The study showing dramatic increases in IgE in animals was not statistically significant because the sample size was so small that it lacked statistical power to demonstrate a treatment effect. This is an experiment that could easily be replicated with an "n" of 10 to 20 animals. If Dr. Coates is so confident, "Until there are definitive studies that prove chia is unhealthy to consume, which I do not believe will ever be the case, . . ." perhaps he should replicate this experiment with a larger sample size.
I remember a similar circumstance a few years back when a number of well known acne researchers confidently stated that "diet had virtually nothing to do with acne."
Research from our laboratory first proposed that diet was the primary environmental trigger of acne; further we outlined the mechanisms involved (3, 4). Our work was later confirmed in a number of recent randomized controlled trials (5, 6).
Finally, in humans ALA by itself has little or no anti-inflammatory effects. It is the hepatic conversion of ALA to the long chain omega 3 fatty acids (20:5n3 and 22:6n3) which are anti-inflammatory. Because less than 5 % of ALA is converted to 20:5n3 and less than 0.5 % is converted to 22:6n3 (7), a better strategy than "to continue heaping chia seeds on most everything that I eat, including eggs, salad, and meat", would be to eat 100 grams of salmon every other day.
1. Cordain L. Cereal grains: humanity's double edged sword. World Rev Nutr Diet 1999; 84:19-73
2. Ulbricht C, Chao W, Nummy K, Rusie E, Tanguay-Colucci S, Iannuzzi CM, Plammoottil JB, Varghese M, Weissner W. Chia (Salvia hispanica): a systematic review by the natural standard research collaboration. Rev Recent Clin Trials. 2009 Sep;4(3):168-74.
3. Cordain, L. Implications for the role of diet in acne. Semin Cutan Med Surg 2005;24:84-91.
4. Cordain L, Lindeberg S, Hurtado M, Hill K, Eaton SB, Brand-Miller J. Acne vulgaris: A disease of western civilization. Arch Dermatol 2002; 138:1584-90
5. Smith RN, Mann NJ, Braue A, Mäkeläinen H, Varigos GA. A low-glycemic-load diet improves symptoms in acne vulgaris patients: a randomized controlled trial. Am J Clin Nutr. 2007 Jul;86(1):107-15.
6. Smith RN, Mann NJ, Braue A, Mäkeläinen H, Varigos GA. The effect of a high-protein, low glycemic-load diet versus a conventional, high glycemic-load diet on biochemical parameters associated with acne vulgaris: a randomized, investigator-masked, controlled trial. J Am Acad Dermatol. 2007 Aug;57(2):247-56
7. Plourde M, Cunnane SC. Extremely limited synthesis of long chain polyunsaturates in adults: implications for their dietary essentiality and use as supplements. Appl Physiol Nutr Metab. 2007 Aug;32(4):619-34.
Second Update from Dr. Cordain, July 10:
Thanks! I noticed as I read through my rebuttal that I forgot to put reference (2) in the text. It should follow directly after the long quote starting with " A recent review..."
I have also attached the abstract by Dr. Coates and colleagues showing the large increase in IgE in rats fed a high chia seed diet. I realize that you are not a research scientist, but I can tell you that the design and subsequent interpretation of this experiment is just bad science. For starters, the researchers did not report alpha,so it is unclear what value of "p" (i.e. .05, .01, .001) was used to reject the hypothesis that T3 IgE values were not different from either T2 or T1. Additionally, the terminology they used for the statistical comparisons either reflect an error in the analysis or statistical naivete. Although an ANOVA may have been employed, the small sample sizes (n=6) for each of the three groups, more correctly required a non-parametric test (say the Krusal Wallis Test), because the distribution of their sample is non-normal. Further, there is no such thing as a "ANOVA t test". There is an ANOVA and there are two types of t-tests (paired and unpaired). If indeed unpaired t tests were employed forpost-hoc analyses, it would have been an incorrect use of the statistic, as t - tests artificially inflate alpha.
But the bigger issue is the small sample size (n=6). In science, before we conduct an experiment, we typically do a statistical test called a "Power Analysis" to determine the sample size (n) needed to achieve significance at the given alpha. This test can easily be calculated if the mean and standard deviations are reported, as they are in this abstract. Based on these numbers, it is patently apparent that the sample size (n=6) used in this study would have been incapable of detecting a treatment effect. Hence, the conclusions reached in this study are invalid and the data trends actually point completely in the opposite direction -- that consumption of large amounts of chia seeds are strongly associated with a gut mediated allergenic response. I challenge Dr. Coats to replicate this experiment, using an n=20. I also suspect that the thymus data would also become statistically significant.
Update July 12, 2010:
Dr. Coates has now responded to the rebuttal by Dr. Cordain:
His statement is so general. He never talks about the amount of phytic acid that does this. Does he even know how much of this there is in chia? What other factors mitigate such a response, increase, it etc. and again phytic acid has been proven to have positive effects.
He says "Consequently, chia seeds are not good sources of these nutrients in living humans" Does that mean they are for "dead" humans ;-)
He talks about cerial grains and legumes. Chia is neither so what point is he trying to make?
To me it is clear he has a one track mind and no specific data to back up his statements, at least he does not quote any.