|If you know the tricks you can increase and decrease your caffeine tolerance by varying environmental factors. Ramp up the amount of exercise, broccoli and smoked meats ➲ maximize the clearance and minimize the effects of caffeine.|
According to analysis Welfare et al. conducted and published in June 1999, there is actually no signifcant polymorphism in CYP1A2 in Caucasians which could explain the interindividual variation in caffeine activity, we all know exists (Welfare. 1999) - meanwhile, scientists have identified a handful of polymorphism - albeit with partly unknown acute or chronic implications (see Table 1).
One year before, Schrenk et al. had already reported that smokers have significantly increased CYP1A2 activities. Compared to a non-smoker, a nicotine-junkie is thus much more prone to become "caffeine resistant", solely because he is metabolizing and excreting the drug much faster (Schrenk. 1998). Genetics and sex, on the other hand, appeared to make only a minor difference.
|Table 1: Polymorphisms linked to acute and chronic response to caffeine (Yang. 2010)|
Did you know that the clearance of caffeine can vary to up to 40-fold within and between individuals (Kalow. 1991; Kashuba. 1998)? Or that Asian and African populations appear to metabolize caffeine at slower rate than Caucasians (Gunes. 2008)No wonder, the scientists were after all also able to confirm that CYP1A2 does not only vary according to sex (higher activity in men vs. women = faster clearance in men vs. women), but is also induced by smoking and inhibited by oral contraceptives.
"In the subsequent analysis of heritability, we included 49 monozygotic twin pairs and 34 same gender dizygotic twin pairs concordant for non-smoking and non-use of oral contraceptives.Now that's a statistically significant correlation, but it does also show that even with identical genes, environmental (or epigenetic) influences are responsible for more than 20% of the effects of caffeine.
The intraclass correlation coefficient was 0.798 (95% confidence interval, 0.696–0.900) and 0.394 (95% confidence interval, 0.109–0.680) in the monozygotic and dizygotic twins, respectively." (Rasmussen. 2002)
This does not change that the major determinant of CYP1A2 activity is still a genetic one, the fact that other studies, like Carmelli et al. (1990) report a heritability of only 36%, Kendler et al. (2007) who conducted one of the most recent investigations of the heritability of CYP1A2 activity say it's ~30-45% and rises from age 9–14 to remains stable, afterwards, I would not discard the possibility that your caffeine resistance or hyper-response is a result of certain dietary & lifestyle factors.
Now the question is: What are these environmental factors?
I don't pretend I could name them all, so I will just stick do those I can find within the hours I am willing to spend skimming study after study to abide by my promise:
- meat, when it's cooked at high temperatures increases the clearance of caffeine (Sinha. 1994) - the exact extend is unknown and probably varies depending on the cooking method and overall consumption
- broccoli and other brassica vegetable (similar effects have been reported for cumin and tumeric) increase the clearance of caffeine (Lampe. 2000) - in women the consumption of a high brassica diet (428g/day!) lead to 18% increase in CYP activity and thus caffeine clearance
- exercise increases, specifically chronic exercise, increases the expression of CYP1A2 and thus the clearance of caffeine significantly - in a 1992 study by Vistisin by a whopping 70%! (Vistisen. 1992)
- green tea extract increases the expression of CYP1A2 in the gut, already, consequently, your caffeine will be broken down before it even reaches the liver (Netsch. 2006) - interestingly enough, pure EGCG does not have this effect
- gingko biloba increases CYP1A2 activity and caffeine clearance in the liver (Hellum. 2007) - specific data on the effect size is not available
- insulin at least if you are diabetic insulin will reduce the half-life of caffeine by increasing - you guessed it - CYP1A2 activity (Flockhart. 2007)
- proton pump inhibitors such as omeprazol have also been shown to induce CYP1A2 activity and should thus likewise lower the half-life of caffeine (Flockhart. 2007)
- lutein has been shown to be associated with low CYP1A2 activity and could thus decrease caffeine clearance (Marchand. 1997)
- dill, celery, parsley, parsnips and carrot coins decreases the clearance of caffeine (Lampe. 2000) - in women the consumption of high amounts of apiaceous veggies led to a -13% reduction in CYP activity and a correspondingly reduced clearance of caffeine
- naringine from grapfruit reduces the clearance of caffeine (Fuhr. 1993) - the extend in single serving study was -23% oral clearance of caffeine and +31% half- life
- peppermint, chamomile, cannabis and dandelion teas are all relatively strong inhibitors of CYP1A2 activity and will thus increase the half-life and effects of caffeine
- Flockhart, D. A. "Drug interactions: cytochrome P450 drug interaction table." Indiana University School of Medicine (2007).
- Fuhr, Uwe, Klittich, K. and Staib, A.H. "Inhibitory effect of grapefruit juice and its bitter principal, naringenin, on CYP1A2 dependent metabolism of caffeine in man." British journal of clinical pharmacology 35.4 (1993): 431-436.
- Gunes, Arzu, and Marja-Liisa Dahl. "Variation in CYP1A2 activity and its clinical implications: influence of environmental factors and genetic polymorphisms." (2008): 625-637.
- Hellum, Bent H., Zhuohan Hu, and Odd Georg Nilsen. "The induction of CYP1A2, CYP2D6 and CYP3A4 by six trade herbal products in cultured primary human hepatocytes." Basic & clinical pharmacology & toxicology 100.1 (2007): 23-30.
- Izzo Jr, Joseph L., et al. "Age and prior caffeine use alter the cardiovascular and adrenomedullary responses to oral caffeine." The American journal of cardiology 52.7 (1983): 769-773.
- Kalow, Werner, and Bing-Kou Tang. "Use of caffeine metabolite ratios to explore CYP1A2 and xanthine oxidase activities." Clinical Pharmacology & Therapeutics 50.5 (1991): 508-519.
- Kashuba, Angela DM, et al. "Quantitation of three-month intraindividual variability and influence of sex and menstrual cycle phase on CYP1A2, N-acetyltransferase-2, and xanthine oxidase activity determined with caffeine phenotyping*." Clinical Pharmacology & Therapeutics 63.5 (1998): 540-551.
- Kendler, Kenneth S., John Myers, and Carol A. Prescott. "Specificity of genetic and environmental risk factors for symptoms of cannabis, cocaine, alcohol, caffeine, and nicotine dependence." Archives of General Psychiatry 64.11 (2007): 1313-1320.
- Lampe, Johanna W., et al. "Brassica vegetables increase and apiaceous vegetables decrease cytochrome P450 1A2 activity in humans: changes in caffeine metabolite ratios in response to controlled vegetable diets." Carcinogenesis 21.6 (2000): 1157-1162.
- Le Marchand, Loïc, et al. "Lifestyle and nutritional correlates of cytochrome CYP1A2 activity: inverse associations with plasma lutein and alpha-tocopherol." Pharmacogenetics and Genomics 7.1 (1997): 11-19.
- Netsch, M. I., et al. "Induction of CYP1A by green tea extract in human intestinal cell lines." Planta medica 72.06 (2006): 514-520.
- Paganini-Hill, Annlia, Claudia H. Kawas, and María M. Corrada. "Non-alcoholic beverage and caffeine consumption and mortality: the Leisure World Cohort Study." Preventive medicine 44.4 (2007): 305-310.
- Rasmussen, Birgitte B., et al. "The interindividual differences in the 3-demthylation of caffeine alias CYP1A2 is determined by both genetic and environmental factors." Pharmacogenetics and Genomics 12.6 (2002): 473-478.
- Schrenk, D., et al. "A distribution study of CYP1A2 phenotypes among smokers and non-smokers in a cohort of healthy Caucasian volunteers." European journal of clinical pharmacology 53.5 (1998): 361-367.
- Sinha, Rashmi, et al. "Pan-fried meat containing high levels of heterocyclic aromatic amines but low levels of polycyclic aromatic hydrocarbons induces cytochrome P4501A2 activity in humans." Cancer Research 54.23 (1994): 6154-6159.
- Tarnopolsky, Mark, and Cynthia Cupido. "Caffeine potentiates low frequency skeletal muscle force in habitual and nonhabitual caffeine consumers." Journal of applied physiology 89.5 (2000): 1719-1724.
- Vistisen, Kirsten, Henrik E. Poulsen, and Steffen Loft. "Foreign compound metabolism capacity in man measured from metabolites of dietary caffeine." Carcinogenesis 13.9 (1992): 1561-1568.
- Welfare, Mark R., et al. "Detailed modelling of caffeine metabolism and examination of the CYP1A2 gene: lack of a polymorphism in CYP1A2 in Caucasians." Pharmacogenetics and Genomics 9.3 (1999): 367-376.
- Yang, Amy, Abraham A. Palmer, and Harriet de Wit. "Genetics of caffeine consumption and responses to caffeine." Psychopharmacology 211.3 (2010): 245-257.