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Taste of Science: Spicy Science

April 2, 2018

As the leaning tower of Jenga pieces fell after a heated battle of, what my friends and I liked to call “Spicy Jenga”, I could only dread the immense pain and suffering about to come my way. What awaited me was the big daddy, the jefe of the chili world — the undisputed hottest chili pepper in the world (in 2013), the Carolina Reaper. As I bit into that pepper I tasted only regret. And for the next 8 hours that’s all I felt too.

Regardless of how awful of an experience that was, I still continue to eat spicy foods to this day, so it made me think:

What’s the science behind spicy things anyway?

Turns out the main agent for “spiciness” is the chemical compound capsaicin. Found in the placental tissue – tissue that surrounds the seeds of a chili pepper – capsaicin is the primary chemical compound that leads to the “burning” sensation of spicy foods.

Chemical formula for capsaicin
Chemical formula for capsaicin

Strangely enough, your brain – quite literally – believes that is on fire! Capsaicin activates a specific receptor on the tongue called TrpV1, which sends pain messages to your brain, causing your body to react accordingly. TrpV1 is also responsible for more than just spicy foods, however. It reacts to:

  • Extreme heat and
  • Caustic acid

That’s why when we eat spicy foods, we tear up, have our noses run, sweat in strange parts of our body, etc. in order to flush out the nonexistent heat. However, to our brain, that heat is 100% REAL, and it tries its best to get us away from potential danger. Ever wonder why spicy and hot foods always seem to taste spicier than normal? They both amplify the pain messages sent to the brain! Now, instead of having just spicy pain, your brain also adds in extra pain from the temperature of the foods you ate! Try eating something spicy at different temperatures (heat one batch and refrigerate the other) and see how much of a difference temperature plays in the overall spiciness of the dish.

This pain-relieving patch is one of the many kinds of capsaicin (or capsicum) medication available over-the-counter.

Aside from being an essential additive in cuisines all over the world, spicy foods play a larger role in our daily lives than we might think. Research has shown that regular chili intake lowered the risk of high blood pressure in a sample of 13,670 adults by almost 40%, even when controlled for diet and weight! Additionally, spices have shown to fight congestion, aid digestion, and relieve muscle and joint pain, as well as play some part in raising our overall metabolism. In fact, capsaicin is used often in the medical field as an analgesic, or pain reliever, due to its ability to prevent the production of Substance P – Substance P being the primary neurotransmitter responsible for pain from capsaicin.

The most fascinating aspect of capsaicin is that, the more capsaicin you introduce into your body, the less and less you will feel (you probably noticed how spicy foods are when you first eat them when compared to your last bite). Thus, research has shown that in high concentrations (~8%), a 60 minute application of a capsaicin patch effectively provides pain relief for months on end. Widespread use is slow-going; however, certain prescriptions are available for cancer patients and other people with chronic pain to provide some relief to them.

The benefits of capsaicin are still being researched, but even now people are hopeful in its potential in advancing our health and the field of medicine. Though, until more research is done, the most we can do is appreciate capsaicin for how much it spices our lives up!

References:

Burks TF, Buck SH, Miller MS. 1985 June. Mechanisms of depletion of substance P by capsaicin. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/2581820

Byrnes, N., Hayes, J. 2013 April. Personality factors predict spicy food liking and intake. Retrieved from https://www.sciencedirect.com/science/article/pii/S0950329312001917

Anand, P., Bley, K. 2011 August. Topical capsaicin for pain management: therapeutic potential and mechanisms of action of the new high-concentration capsaicin 8% patch. Retrieved from https://academic.oup.com/bja/article/107/4/490/228083

Sharma, S., Vij, A., Sharma, M. 2013 November. Mechanisms and clinical uses of capsaicin Retrieved from https://www.sciencedirect.com/science/article/pii/S0014299913008200

Tékus, V., Horváth A., Hajna, Z. 2016 June. Noxious heat threshold temperature and pronociceptive effects of allyl isothiocyanate (mustard oil) in TRPV1 or TRPA1 gene-deleted mice. Retrieved from https://www.sciencedirect.com/science/article/pii/S0024320516302508

Miroslav, M. 2010 August. High-concentration capsaicin for the treatment of post-herpetic neuralgia and other types of peripheral neuropathic pain. Retrieved from https://www.sciencedirect.com/science/article/pii/S1754320710705290

Shi, Z., Riley, M., Brown, A., Page, A. Chilli intake is inversely associated with hypertension among adults. Retrieved from https://www.sciencedirect.com/science/article/pii/S2405457717304965

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About Author

Noah is an undergraduate student at Georgia Tech looking to change the world one step at a time. He loves to hike, stargaze and build computers and spends his spare time dancing, working out and gaming.

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  Timothy Durham was convicted of rape when a test showed his DNA genotype matched the DNA recovered from the crime scene. Eye witnesses testified that Durham was in a different state at the time of the incident, but he wasn’t exonerated from his 3000 year sentence until follow up DNA analysis showed that the preliminary forensic analysis used in the trial was misinterpreted (Thomas et al.). DNA testing serves an invaluable part in our criminal justice system, but it comes with complications and bias that can lead to wrongful convictions and misinformed juries.  

Background:

Forensic genetics aims to identify the origin of a biological sample. It can be traced back to Karl Landsteiner who discovered human ABO blood groups. With blood groups, suspects could be eliminated based on their blood type. For example, if a suspect had type A blood and there was type B blood left at the scene by the perpetrator, the investigators could rule out the suspect. Unfortunately, the reverse didn’t work. If the suspect and perpetrator both had the same blood type, it can’t be concluded that the suspect was guilty. Blood identifiers evolved into 8 distinct categories which improved the ability to eliminate suspects, but could only conclude that (if the system matched) it might be the perpetrator or this person might be related to the perpetrator (Jobling and Gill). The field evolved in the 1980s with the discovery of Minisatellites, lines of repetitive DNA that don’t encode proteins. Minisatellite patterns in DNA create what we know today as the DNA fingerprint, and it has a much higher accuracy rate than previous methods (Augustyn et al.). Around the same time, a breakthrough for victims of sexual assault was discovered. In the case of assault, bodily fluids of both the victim and the assaulter can get mixed. A process called differential lysis was created which could selectively increase the concentration of sperm in a fluid sample thereby allowing for accurate DNA testing (Jobling and Gill). Forensics evolved to use single-locus probe testing after several years because of its ease of interpretation. It looked at specific minisatellites that had high variability between subjects. This was the first DNA-based method to be used in a criminal investigation. Two murder homicides from several years apart were connected using DNA evidence. The evidence was then used to exonerate an innocent man, and the guilty party was found when he tried to evade mandatory DNA testing for all men in the small town. His guilt was then reinforced when the DNA profiles matched, and he gave a confession (Jobling and Gill). Finding DNA at a crime scene doesn’t guarantee that you’ll find a murderer. There are issues with non-pure samples and limited samples that make DNA work difficult, and accreditation of facilities and new techniques and take time (Jobling and Gill).  

Subjectivity of DNA Interpretation:

In a 2009 publication, the National Academy of Science discusses the possibility for subjective influence in lab based forensics. The interpretation bias happens in complex cases where, for example, there could be a mixture of DNA. A study published in 2011 looked specifically at this issue. A gang rape happened in Georgia, and the mixture in DNA from the case was used to prosecute one suspect after another suspect took a plea bargain to testify against him. With DNA mixtures, there are three possible conclusions: suspect excluded, suspect cannot be excluded, and inconclusive. If the suspect is excluded, it means that there’s little to no possibility that his DNA is part of the sample. If the suspect cannot be excluded, it means that there’s a possibility that his DNA is part of the sample. In the trial, the DNA examiners who knew the context of the case concluded that the suspect being prosecuted could not be excluded. The 2011 study gave the DNA evidence from this case and the DNA profiles of the suspects to 17 forensic examiners. These examiners had no context of the case, and they all worked independently. Of the 17, only 1 came to the same conclusion (suspect cannot be excluded) as the examiners who knew the context of the case. Twelve of the 17 concluded that the suspect who was prosecuted and convicted had no relation to the DNA found in the sample. Not only does this show that subjectivity occurs due to the context of the case, but the 17 examiners came up with different findings based on their past experiences meaning that not all DNA analysis is objective. Some organizations like the Scientific Working Group on DNA Analysis Methods say that quantitative statistical evidence should be presented with every categorical conclusion, but the US doesn’t require this (Dror and Hampikian).

False Positives:

There are two categories that cause wrongful identification in a DNA report: coincidental matches and false positives. Coincidental matches are DNA matches between two unrelated people. The probability of these matches is about 1 to 500,000 for white individuals and about 1 to 350,000 for black individuals. This small probability of coincidental matches makes people feel confident in DNA evidence. False positives, on the other hand, are matches between DNA and test DNA that result from issues in the forensics lab. There have been multiple cases of forensics labs accidentally switching victim and suspected rapist DNA which lead to convictions that were later overturned when the lab realized the error. There are also cases of misreading or misunderstanding a sample. In a case from 1993, a man was convicted of rape because someone interpreted a mixed sample of victim and perpetrator DNA as an individual sample. The conviction was again overturned. To prevent false convictions, retesting DNA is allowed, but it’s not an efficient solution. Many people are pushing for statistical information on the probability of false positives, so that the jurors can make accurate judgements based on DNA evidence (Thomas et al.).  

Conclusion:

DNA analysis is a useful tool for the criminal justice system, but subjectivity can be an issue in forensic testing. To combat wrongful convictions, there are organizations like The Innocence Project who use DNA testing to free the innocent, but reformed forensic testing standards should be put in place to prevent subjectivity and to ensure juries are correctly informed during trials. https://www.innocenceproject.org/    

Citation:

Augustyn , Adam, et al. “DNA Finerprinting.” Encyclopedia Britannica , 26 Apr. 2018, www.britannica.com/science/DNA-fingerprinting#ref153186. Dror, Itiel E., and Greg Hampikian. “Subjectivity and Bias in Forensic DNA Mixture Interpretation.” Science & Justice, vol. 51, no. 4, 2011, pp. 204–208., doi:10.1016/j.scijus.2011.08.004. Jobling, Mark A., and Peter Gill. “Encoded Evidence: DNA in Forensic Analysis.” Nature Reviews: Genetics, vol. 5, no. 10, Oct. 2004, pp. 739–751., doi:10.1038/nrg1455. Thompson, William C, et al. “How the Probability of a False Positive Affects the Value of DNA Evidence.” Journal of Forensic Sciences, vol. 48, no. 1, Jan. 2003, pp. 1–8., doi:10.1520/jfs2001171.