Caffeine metabolism + individual variation
I'm curious to know what the literature says about the variation in how different individuals respond to caffeine. Is it true that there is a genetic predisposition to caffeine metabolism? Some seem to be able to consume it with little impact while others, such as myself, can only handle small amounts. For example, if I want to have coffee, I need to drink decaf. While I am able to have caffeinated teas (black, oolong, green, and white), I have to be very conscious about the quantity I drink, whether I have eaten food, time of day, etc. Finally, are there any recommended strategies for (1) discovering one's unique caffeine metabolism and (2) mitigating "over-caffeination"? Thank you, Danny and Alan, for all the work you do here. So grateful for the resource of Sigma. - Jessica Schroeder
Game Changers / James Wilks JRE
Years ago when these first came out I kind of stubbornly brushed them both off (that is, the Doc and also James' grilling of Chris Kresser with the help of Avi Bitterman MD) and kept my blinders on. Since then, I've came to the conclusion that actually the research behind veganism is actually pretty robust and some of the 'cons' that bodybuilding circles commonly mention such as 'nutrient deficiencies' are very weak and easily addressed (both directly but also within the argument itself) Which brings me to my question: have you watched either of the documentary and/or the JRE episode, and if so, what are/were your thoughts? As mentioned above, I did a complete 180. Thank you - big fan! Cameron
Vitamin C and Low-Carb diets
A former guest Mike Sweeney RD, had an interesting recent interview on a Keto podcast: https://m.youtube.com/watch?v=8fGQ8mU3TGo The claim is at timestamp 46:20. It was interesting to hear a registered dietitian with such *ahem* different views, but I wanted to focus on one particularly interesting claim which I have dug into myself because I previously heard the same claim within the last year. You can listen above for his exact words but the basic claim is this: "Those on low carb diets require less vitamin C than those on high carb diets. This is because Vitamin C and Glucose have a shared transporter (GLUT#). The more carbohydrate in the diet, the more glucose, the more glucose, the higher the vitamin C requirement as they compete for the same transporter. On low-carb, there is less glucose, thus less competition for the transporter, thus a lower Vitamin C requirement." I have heard that this means the RDA for Vitamin C is "irrelevant" and "doesn't apply" to low carb dieters ..... I see a couple of significant problems: (1) Competition for the transporter would only be relevant if either Vitamin C or Glucose were sufficiently high in those areas where the transporters do their job. I believe in the case of hyperglycaemia, there can be an issue with Vitamin C uptake. But where is the evidence that high carbohydrate diets, of themselves result in sufficiently high levels of glucose to make competition for these transporter an issue that would affect Vitamin C requirements? (2) Why would cell requirements for Vitamin C be lower? Rummaging in "Nutrient Metabolism: Structures, Functions and Genes" (Martin Kohlmeier), carbohydrate metabolism does not seem to require Vitamin C. Maybe he is saying that although cell Vitamin C requirements are the same, because of high glucose levels, more vitamin C is needed to outcompete the glucose and reach the cells? It all sounds pretty sketchy so would love to hear you guys take it apart.