Saturday, January 11, 2014

Quackery or Solid Science: The Zinc Tally Test - Does it Work? How Does It Work? And How Reliable is It?

"Any idea if zinc tally test is reliable? Google spits somewhat mixed conclusions." That's what SuppVersity reader David Salda asked two days ago on the SuppVersity Facebook Page and this article is a somewhat lengthy answer to a short, but very valid question.
I know that only few of you are running a website, let alone one with daily updates, but if you do you the following incident may sound vaguely familiar: You are just trying to keep up with the comments on questions on the Facebook page of your website, when an innocent question like "Any idea if zinc tally test is reliable? Google spits somewhat mixed conclusions." someone (in this case David Salda) posted on your Facebook wall, reminds you of the written, yet never finalized and published articles that lie dormant in the depth of your website's draft folder... don't get me wrong, this is unquestionably a good thing - I mean I guess there will be more people than David, who would like to have the following two questions answered, correct?

How does the Zinc Tally Test work?

Actually the procedure is pretty straight forward. You hold a 10ml solution of zinc sulphate hydrate in a distilled water base (can be bought at the pharmacy) in your mouth for 10 seconds (don't swallow it!) and see how it tastes: (1) If you don't taste anything you are zinc deficient, (2) if there is no immediate taste, but a furry/dry mineral taste develops, your are low on zinc, (3) if a definite taste is detectable right away, you are supposedly in the lower normal range, and (4) if a strong unpleasant taste is immediately present, you got plenty of zinc already.

Is the Zinc tally test an adequate means to test whether you should Supplement W/ Zinc?

No. While it cannot be totally excluded that you can identify individuals with low zinc status on the basis of the Zinc Tally Test the scientific evidence for the accuracy of this method is clearly insufficient, highly conflicting and in large parts bugged with the usual methodological flaws you see in studies on topics most allopath would deem nuturapathic *bs*.
Take a short cut to the answer to your question: If we take into consideration the currently available literature (an ebook someone sells on his own website is no "literature"), there is little to add to the conclusion the researchers from the Southern Cross University in Lismore,  Australia fomulate in the abstract of their study: Despite being widely used, the Zinc Tally Test does is not sensitive and specific enough to assess marginal zinc status in humans. It's thus not really surprising that a 1999 study by Jenna Jameson shows that its results don't even correlate with with dietary zinc intake (Jamison. 1999)
In 2012 Gruner & Arthur conducted a systematic review of the available literature in which they included only studies which provide full reports of clinical trials comparing the tally test (ZTT) to at least one other zinc test within the same sample population. The mere number of studies which matched these more or less self-evident minimum requirements, is telling, already: "3", in words "three" studies matched the criteria of inclusion.
If your breakfast looks even close to this extraordinary beans, eggs and bacon breakfast, it's him time that you learn and apply(!) the "Three Simple Rules of Sensible Supplementation" | more
"Study I compared the ZTT with sweat zinc in patients with food intolerance, reporting moderate correlation. Study II recruited pregnant women using the ZTT and serum zinc to assess zinc status, with above 70% congruence between the two tests at the start of the trial and 100% congruence at the end. Study III also recruited pregnant women at three stages during gestation, assessing ZTT and leukocyte zinc initially, later adding dietary zinc intake and at delivery cord blood zinc. No significant correlation was found between the results of these different methods; however, statistically significant differences in the ZTT responders (tasters and nontasters) were found for pregnancy outcomes." (Gruner. 2012)
And guess what: Even these studies suffered from all sorts of methodological problems. The laboratory assays that were used in the studies lacked sensitivity to zinc status. They were poorly standardized and did often deviate from the original design of the zinc tally test as it is described on the Internet.

Zinc deficiency alters general taste acuity - but not in a linear / reliable fashion

Something else that's worth mentioning in this context is the influence of low zinc levels on taste acuity in general. While the number of respective studies is not exactly high, there is good evidence that subjects with a generally impaired ability to taste tend to have lower zinc concentration in the blood and exhibit a lower ratio of apo/holo-activities of angiotensin converting enzyme (ACE), a zinc dependent enzyme in the serum (ACE ratio), than controls (Ueda. 2006). A 2010 follow up study did yet reveal that a definitive correlation between serum zinc levels and the scores on a visual analogue scale for the severity of the symptoms of did not correlate in after supplementation - whether zinc is the the cause or as so often just a corollary factor is therefor still in the open (Takaoka. 2010)
Suggested: " Zinc: 15mg Are Plenty - After 120 Days Rodents on Diets Containing 2xRDA of Zinc Develop Metabolic Syndrome" | more
Bottom line: While it stands out of question that the zinc tally test should not be your method of choice, when it comes to testing your zinc status, the observation Ueda et al. and Takaoka et al. made with respect to the ratio of apo/holo-activities of angiotensin converting enzyme (ACE) could actually be used as a measure of your zinc status. It would provide an alternative and accurate tests to determine the adequacy of your dietary zinc intake.

That's at least what the results of a 2012 experiment by Sarakura et al. in the course of which mice were zinc depleted for 9 days would suggest (Sarakura. 2012). The ACE ratio would thus be #4 on the list of tests that are considered to reflect the zinc status human beings more or less adequately. The other three tests are plasma, urinary, and hair zinc analysis (Lowe. 2009).
References:
  • Jamison, JR. Mineral Deficiency: A Dietary Dilemma? Journal of Nutrition and Environmental Medicine.1999; 9(2):149-158.
  • Lowe NM, Fekete K, Decsi T. Methods of assessment of zinc status in humans: a systematic review. Am J Clin Nutr. 2009 Jun;89(6):2040S-2051S.
  • Sarukura N, Takai S, Ikemoto S, Korin T, Ueda Y, Kitamura Y, Kalubi B, Yamamoto S, Takeda N. Effects of dietary zinc deprivation on zinc concentration and ratio of apo/holo-activities of angiotensin converting enzyme in serum of mice. Auris Nasus Larynx. 2012 Jun;39(3):294-7.
  • Takaoka T, Sarukura N, Ueda C, Kitamura Y, Kalubi B, Toda N, Abe K, Yamamoto S, Takeda N. Effects of zinc supplementation on serum zinc concentration and ratio of apo/holo-activities of angiotensin converting enzyme in patients with taste impairment. Auris Nasus Larynx. 2010 Apr;37(2):190-4.
  • Ueda C, Takaoka T, Sarukura N, Matsuda K, Kitamura Y, Toda N, Tanaka T, Yamamoto S, Takeda N. Zinc nutrition in healthy subjects and patients with taste impairment from the view point of zinc ingestion, serum zinc concentration and angiotensin converting enzyme activity. Auris Nasus Larynx. 2006 Sep;33(3):283-8.

1 comment:

  1. Lol! A "1999 study by Jenna Jameson"? Was the study about whether you could gauge someone's zinc status by tasting his semen?

    ReplyDelete