Beta-Alanine has gone through some major updates, with special regard to its ability to enhance physical performance (demonstrated) and body composition (also demonstrated) with a fair bit of information on its health effects and pro-longevity aspects (theoretical at this point in time).
Beta-Alanine works via its product Carnosine, which is stored in muscle tissues almost exclusively and as such is available in the diet via meat products (a reason it has been added to our vegetarian stack). This product buffers acidity, and can prolong the ability of muscles to function under stressful conditions which leads to an apparent increase in endurance. This performance enhancement aspect has been studied in numerous intervetions and subject to meta-analysis, and appears to benefit the timeframe of 60-240s most with benefit to longer periods, and nonsignificant benefit to time frames below that.
It has thrice been implicated in increasing lean mass gain more than control, and in one of these studies also noted fat loss. The mechanisms for these observations are currently unknown, but they may underlie the increases in strength seen with beta-alanine chronically when taken part of a routine despite beta-alanine's apparent inefficacy in increasing acute strength output.
The health aspects of carnosine, which are theoretical, are due to the molecule acting as a mixed anti-oxidant and health protective agent that also has the capacity to sequester reactive species such as minerals, nitrogen, protein aldehydes and carbonyls, etc. A wide range of protective activity, and through these actions (mostly the carbonyls and aldehydes) carnosine has been linked to longevity and has twice been shown in rats to increase the median lifespan. It is too soon to suggest that Carnosine may increase human lifespan, as rats have much greater exposure to Carnosine than do humans and studies conducted in these rats may not apply to us humans.
Specifically, the enzyme that degrades Carnosine into its constituents is expressed only in the rat kidney (so it can float around quite a bit before going there) yet actually circulates in humans. For these effects to occur in humans, Humans would need to be treated with Carnosine and a combination therapy of a selective Carnosinase inhibitor (similar to the theory behind Levodopa/Carbidopa therapy for Parkinsons, to a degree)
Grapefruit was also finished, but is essentially a slight fat burner that interacts with most pharmaceutical drugs. Very little exciting science on this page.