Diet Can Elevate Test Results, But How Much Is Unknown
According to Saudan, et al (2006), a diet rich in maize, sugar cane, millet or pineapple can elevate test results designed to show the presence of exogenous steroids.
Does that mean that if Floyd Landis ate a heaping helping of sugarcane after stage 16 he could have triggered a false positive for the IRMS?
Saudan, et al (2006) speculate that such a diet couldn't do such a thing. However they admit that there's much to be learned, and they also admit in their study that diet in experimental subjects was not monitored, logged, etc. So, in other words, the study assumes that there is some increase in dietary 13C but makes no strides to monitor the correlation between intake of certain foods and the degree to which 13C is elevated in tests. As the test was conducted, people who lived in Africa elevated their 13C by as much as 3%, certainly not enough to trigger a false positive.
But it is interesting to note that the % increase in 13C increased linearly the entirety of the time the test subjects were on this Kenyan diet. There's no decay in the increase, even over a 3 month period. Ostensibly, then, if one were on this diet for a year, then one might see a 12% increase in 13C, two years, 24% increase, and so on. The study lends itself to this interpretation.
If Floyd Landis ate somewhat like a Kenyan for three months, consuming some amount of sugarcane and millet, he could have elevated his 13C levels by 3%. That would have put his test results at 30% above test error, still leaving him 5% away from dubious test results. But if he's been eating loads of millet sweetened with sugarcane for a few years, it very well may have put him in false positive territory.
Several questions remain: how much does the intake of *any* amount of exogenous steroids elevate one's testable 13C levels? In other words, how uncommon is it for someone taking any amount of steroids to test as low as Landis did? Another question: how much sugarcane or millet or pineapple would it take to trigger a false positive? Some cyclists are fanatical about their diets, and many aspects of their diets are aspects that have witnesses. If the guy ate millet breakfast lunch and dinner there would be many individuals who could confirm it. Further, what effect does alcohol, a product of fermented sugar, have on the IRMS?
Whil;e the IRMS is a very good test, there are ways a false positive may be arrived at. The ways in which a false positive result is possible seem apparent yet they are poorly understood.
One thing is clear: if I ever get my knee healthy and try to compete at cycling, I'm going to eat lots and lots of millet and pineapple and give myself a natural means of supplementing with androsterone.
Seriously, though, the moral should be that if the UCI wants to test cyclists they should bear the burden of keeping record of each cyclist's diet.
(Short communication: Christophe Saudana, Matthias Kamberb, Giulia Barbatic, Neil Robinsona, Aurélien Desmarcheliera, Patrice Mangina and Martial Saugya. Longitudinal profiling of urinary steroids by gas chromatography/combustion/isotope ratio mass spectrometry: Diet change may result in carbon isotopic variations. Journal of Chromatography B, Volume 831, Issues 1-2 , 2 February 2006, Pages 324-327.)
Does that mean that if Floyd Landis ate a heaping helping of sugarcane after stage 16 he could have triggered a false positive for the IRMS?
Saudan, et al (2006) speculate that such a diet couldn't do such a thing. However they admit that there's much to be learned, and they also admit in their study that diet in experimental subjects was not monitored, logged, etc. So, in other words, the study assumes that there is some increase in dietary 13C but makes no strides to monitor the correlation between intake of certain foods and the degree to which 13C is elevated in tests. As the test was conducted, people who lived in Africa elevated their 13C by as much as 3%, certainly not enough to trigger a false positive.
But it is interesting to note that the % increase in 13C increased linearly the entirety of the time the test subjects were on this Kenyan diet. There's no decay in the increase, even over a 3 month period. Ostensibly, then, if one were on this diet for a year, then one might see a 12% increase in 13C, two years, 24% increase, and so on. The study lends itself to this interpretation.
If Floyd Landis ate somewhat like a Kenyan for three months, consuming some amount of sugarcane and millet, he could have elevated his 13C levels by 3%. That would have put his test results at 30% above test error, still leaving him 5% away from dubious test results. But if he's been eating loads of millet sweetened with sugarcane for a few years, it very well may have put him in false positive territory.
Several questions remain: how much does the intake of *any* amount of exogenous steroids elevate one's testable 13C levels? In other words, how uncommon is it for someone taking any amount of steroids to test as low as Landis did? Another question: how much sugarcane or millet or pineapple would it take to trigger a false positive? Some cyclists are fanatical about their diets, and many aspects of their diets are aspects that have witnesses. If the guy ate millet breakfast lunch and dinner there would be many individuals who could confirm it. Further, what effect does alcohol, a product of fermented sugar, have on the IRMS?
Whil;e the IRMS is a very good test, there are ways a false positive may be arrived at. The ways in which a false positive result is possible seem apparent yet they are poorly understood.
One thing is clear: if I ever get my knee healthy and try to compete at cycling, I'm going to eat lots and lots of millet and pineapple and give myself a natural means of supplementing with androsterone.
Seriously, though, the moral should be that if the UCI wants to test cyclists they should bear the burden of keeping record of each cyclist's diet.
(Short communication: Christophe Saudana, Matthias Kamberb, Giulia Barbatic, Neil Robinsona, Aurélien Desmarcheliera, Patrice Mangina and Martial Saugya. Longitudinal profiling of urinary steroids by gas chromatography/combustion/isotope ratio mass spectrometry: Diet change may result in carbon isotopic variations. Journal of Chromatography B, Volume 831, Issues 1-2 , 2 February 2006, Pages 324-327.)
posted by Patrick Herron at 11:02 AM
15 Comments:
The title of my blog at this point is misleading but it was always a little facetious to begin with.
In all sincerity I am not attached to his winning. In other words, if he's busted, then let him be busted. I can easily believe he doped, just as easily as I can doubt it.
But what's substantive here is that I'm trying to elevate the level of serious discussion. I'm trying to make the science accessible to those who don't like to do their homework or who are just curious and suspect the media isn't telling the whole story.
The bottom line is that while it is likely that based on what little we know of Landis that he's busted. But we should also realize that there are things that are verifiable that just might have caused a false positive.
Ultimately what I'm seeking is not an easy answer. What I'm seeking is justice, not justice American style, not justice media style, but justice premised on the truth.
Hi free floyd,
Interesting post. I think you are doing a great job elevating the level of serious discussion, and the media do a terrible job of covering these stories. Please keep going — and I think that your perspective would be useful in other doping cases, too.
However … according to the NYT article you linked to last week, the isotope ratio test doesn't just measure the ratio of C-13 to C-12 in the urinary testosterone; it measures that ratio in the testosterone and in another hormone:
"The test determines whether the testosterone in the athlete's urine has less carbon-13 than another naturally occuring hormone in the urine, like cholestorol. The test is considered positive when the carbon isotope ratio — the amount of carbon-13 compared to carbon-12 — is three or more units higher in the athlete's testosterone than it is in the comparison hormone. It is evidence that the testosterone in the urine was not made by the athlete's body."
This sounds like a very well-designed experiment, controlling for the influence of diet through the use of a reference hormone in the urine. The reference hormone and the athlete's natural testosterone presumably have the same source of carbon (i.e. food) unless some of the testosterone was made in a lab.
If Floyd is innocent there is some out-there physiology going on here. I think his goose is cooked.
simply put, no one knows how diet as a factor, in combination with time as a factor, affect the results of a IRMS. The only study, which wasn't really a study but rather a "short communication," supports my claim. the study indeed does not show that diet is sufficient for false positives, but that's simply because that study evaluates such a narrow profile: poorly defined diet measure, 1-3 month time span.
Great discussion. However, if Floyd's diet caused the elevated levels, wouldn't he have tested positive in the previous stage(s) where he wore the yellow jersey? It sounds like the dietary changes take months, not days, to maifest.
Pete, the T/E test examines the ratio of T to E, not how much T you have. So no the T/E is not set up to test T levels per se and it would not have been detected previously. Whatever the source of the elevation of T or the depletion of E in his body, it went undetected until he drank a bounch of alcohol, which is well-understood to help just about anyone fail the T/E test. That got him in the headlights.
The dietary changes are linear, about 1% a month. That doesn't mean that the changes take a month to manifest, it just means that the unit of measure was a month. Perhaps it manifests itself as an increase of 1/30th of a percent every day.
Hey Free,
There's a one line comment here pointing to another site that appears to me to be an attempt to commercially exloit the controversy. There's no substance, only ads for T shirts. You might want to moderate it away.
- TBV
Floyd is coming out strong, it seems. Check his website for all of his scheduled media appearances and links to more statements.
From what I've read so far, he seems to be doing a better job. I do think his explanation for his list of "excuses" makes some sense, but that doesn't mean he's innocent. It will be interesting to see what he can do.
I wish there was a way for informed folks to see his results, bat around ideas and narrow down the possible causes for his positive. Some kind of wiki or forum for science and research experts to collaborate and discuss his numbers and his case. It sounds like some bright minds are reading this blog, but we have so little concrete information.
Floyd, if you read this and you really are innocent, maybe you'll consider some 21st century tech wizardry to tap into the collective wisdom rooting for you. Sure would be cheaper than three big shot lawyers. Just a thought.
Cerberus what an awesome idea. There must be some way to communicate that to him.
MLS, apparently a lowered E level is concomitant with exogenous testosterone supplementation. so if is ratio is high because his E level is low, that doesn't indicate against taking T. I need to double-check that so don't hold me to it!
Erling, like I've said, I'm not attached to his winning. I am however attached, well into the fourth decade of my life, to the notions of truth and justice.
casualtourfan, there's no way to know for sure.l to know for sure, we'd need to recreate the conditions of that day and change factors. we don't have multiple copies of floyd landis or multiple copies of that day, so we have no avenue for knowing. but we caqn't get hung up on purifying the tribe. if he didn't ear that banana on his fourth birthday, would he have ever even ridden a bike? the way T is used, it's very difficult to demonstrate it as the proximal cause, the very difference maker between him and the other leaders. i'm still attached to my own theorry that his nearest competitors were suffering from greater muscular fatigue after 16 than Landis; Landis' metabolic crash on 16 left him, oddly enough, in better shape for 17, as metabolic fatigue is easier to recover from in 12 hours than muscular fatigue.
look, my cynic says that landis has millions of reasons (dinero + points of pride) to defend himself. those reasons are present regardless of his guilt or innocence.
it is unlikely from what I understand that IRMS was performed on earlier samples. again, another thing I need to double-check before I believe what I'm saying!
Yes, capitalize and exploit. There's nothing on the site to suggest support, only merchandising. The BBS has no entries but one asking "how do you feel?" which tries to have it both ways. The phrase itself is ambiguous and can be read either way, as an accusation or a defense.
I have nothing against T shirts or merchandising, but this is pretty shameless. Defending it here and still having the site contents be as vacuous as they are is telling.
This site is not a place to debate the relative merits of merchandising. Thanks.
If Floyd was doping, it wasn't short term. That's a straw man, easily knocked down. It would make more sense for there to have been a long term steroid program to build up sprinter twitch muscles for matching attacks up hills. This would increase the T, masked by synthetic E. What would make more sense is that stages 16/17 disrupted the masking, leading to lower E, a blown ratio, and synthetic showing up in IRMS. However, IRMS of samples before and after 17 should also show exogenous because of the half-lives involved.
Until we see IRMS results of samples on either side of stage 17, its hard to get a sensible picture. If there is no exogenous in the adjacent samples, that suggests that there is an anomaly with the stage 17 result. If the adjacent tests show exogenous, then that would indicate a long term doping program.
The problem is that there may not be any IRMS on the adjacent samples, and the samples may have been destroyed after being negative on the T/E screen.
I hope that Floyd and his lawyers have seen this article:
http://alcoholism.about.com/cs/abuse/l/blacer030117.htm
It seems that there is some evidence that his drinking binge the night before the 17th stage could have caused a spike in his testosterone levels, according to a study done at the Scripps Research Institute.
The CIA has no incentive whatsoever to make Landis' results positive. I can see how various spooky shadowy elements of our government participated in a conspiracy to shock and awe Americans into WWIII by blowing up the WTC in order to shake them down for trillions of war-appropriated dollars. I can and do believe that, but the evidence and the historical prcedents and familial linkages are there to support such a supposedly wacko idea. But sabotaging Floyd Landis' success? Maybe the French intelligence service would have many an incentive for messing with Landis, but certainly not the CIA. Jeez louise let's maintain some degree of credibility in our critiques of secrecy in government.
We've thoroughly covered the relationship between alcohol and the T/E ratio test. Alcohol is indeed a significant false positive source for the T/E ration test. Alcohol ingestion would not have made Landis positive for the IRMS test, however, and he did test positive on that test. So alcohol is at best a remote influence on why he's positive.
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