> Women are also more likely to regularly perform cardio/aerobic exercises, which can reduce bone density when done in excess and without adequate nutrition.
What is the biological mechanism behind this statement?
Elevated cortisol (in response to the stress of running or whatever) increases bone resorption and inhibits bone growth. This isn't necessarily an issue for anyone doing lots of cardio, but it's an increase in risk. It also reduces protein synthesis, which is important for both muscle and bone (it isn't just calcium).
> Elevated cortisol (in response to the stress of running or whatever) increases bone resorption and inhibits bone growth
Cortisol is also released during strength training, though.
Seems like a real issue is low impact cardio, which isn't negative for bone density (as far as I can tell) but does have a theoretical opportunity cost when you could be doing weight-bearing cardio, which does improve bone density.
Agreed with littlestymaar's comment higher up, though, that exercise rates being what they are, the theoretical opportunity cost may be quite theoretical.
The previous post was referring to the overall bone density change. The skeletal loading from strength training is a stronger signal for bone density increase vs the negative impact on bone density from increased cortisol production.
> Elevated cortisol … increases bone resorption and inhibits bone growth
Would that also be true for caffeine consumption? IIRC it increases cortisol levels, but I don't really know much about what else it does, I've only read the Wikipedia page and gone "Wow, I'm really glad I've already cut back".
What you said about caffeine worried me somewhat, so I looked it up on Wiki and what I found about it was mostly innocuous and some properties are even beneficial, it's even on WHO's list of essential medicines.
Many vegetables have much more dangerous compounds and toxins: oxalic acid (a rust remover and bleach that can rot your kidneys) in rhubarb and Popeye's spinach and many other green-leaf vegies, solanine in potatoes, and very dangerous cancer-causing aflatoxins in peanut butter, and that's just the beginning, there are many dozens more! Now you know, are you going to starve?
And to boot, caffeine is a nice looking heterocyclic purine-like molecule with a six and a five-member ring both heavily laden with nitrogen, so what's the worry about? What's not to like about it?
It’s really not indicative of much at all. They also spout off about artificial sweeteners despite a complete lack of scientific evidence. It’s a political organization, not a scientific one.
"""Consumption of 1–1.5 grams […] per day is associated with a condition known as caffeinism.[141] Caffeinism usually combines caffeine dependency with a wide range of unpleasant symptoms including nervousness, irritability, restlessness, insomnia, headaches, and palpitations after caffeine use."""
"""cases of very high caffeine intake (e.g. > 5 g) may result in caffeine intoxication with symptoms including mania, depression, lapses in judgment, disorientation, disinhibition, delusions, hallucinations or psychosis, and rhabdomyolysis."""
1-1.5g. Who do you know consumes 10 to 15 cups of coffee per day consistently? I'd suggest very few.
>5g. Now, who do you know consumes more than 50 cups of coffee per day consistently? I'd suggest none.
If you scaled up oxalic acid daily doses in the same ratio as for the caffeine example then in the first instance the person would almost undoubtedly have kidney stones. In the second example the person would be dead. Right, at that dose Popeye's spinach meal would almost certainly have killed him.
At least the 'caffeinated' person, whilst off his head, would likely be still alive.
Even water has a LD50 rating. As millions attest, caffeine is one of the safer less harmful chemicals that plants use to defend themselves with. Almost every other organic molecule that plants use to ward off insects is more toxic.
Here's a few we actually eat:
www.mashed.com/1299947/most-dangerous-vegetables/ There are tens of thousands of others that you'd want to keep well away from, Nux vomica, Manchineel, Death caps, Atropa belladonna, etc. By comparison, in the danger stakes, caffeine doesn't even get off the starting block.
> Who do you know consumes 10 to 15 cups of coffee per day consistently? I'd suggest very few.
Me in 2009, by dose, as a result of constantly increasing my consumption and ending up at multiple tablespoons (not teaspoons) of instant per cup and nothing else but coffee as daily fluid intake.
Hence being glad I'd already cut back by the time I'd read about the impact of too much.
They warned us in school about the dangers of tobacco and alcohol (and all the illegal drugs*), but nobody ever said "there is such a thing as too much caffeine".
There is, and the unlimited free coffee in most workplaces turns out to be a problem for me.
* regarding your point about LD50 water, school also lied about the dangers of Ecstasy. Leah Betts' actual cause of death was water overdose, but she was the literal poster-child for the anti-drugs campaign in my time.
No doubt! 10 to 20 caffeine pills could be taken at once, my example was cups of coffee per day (rough estimate ≈100mg/cup). Taken over a day it would be better tolerated (but I'd still not consume that amount).