Nicotine is the major update this week, and the Examine page is in-depth enough that a short summary will be featured in this blog post:
It does appear to have fat burning effects, but the amount of interventions with the basic double blind setup (two groups blinded, one give nicotine for X weeks, difference then measured) are lacking. Many studies note weight reduction associated with smoking, but these cannot be used as sufficient evidence for how effective nicotine is (especially due to social habits associated with smoking and appetite suppression). It is pretty much proven that nicotine has the mechanisms to burn fat, but it is unknown how effective of a fat burner nicotine is when consumed via Nicotine replacement therapy.
The mechanisms of fat loss are partly mediated by releasing catecholamines (adrenaline, noradrenaline), similar to how yohimbine partly acts, and nicotine can work in some other mechanisms to increase serum increases in glycerol (lipolysis). The degree of catecholamine release from nicotine appears to be slightly attenuated with time, with the degree of lipolysis from nicotine being fairly constant.
Addiction is inherently an issue with Nicotine (technically, with any stimulant that induces catecholamine release). A sort of mathematical relationship between how much Nicotine is consumed and the vessel it is consumed in; the faster it gets to your brain the more likely you are to be addicted to it (this also correlates highly with nootropic effects, so any attempt to use nicotine to enhance cognition is going to have to be approached cautiously). Due to this, patches and gums have less addiction potential than do cigarettes due to requiring more time to reach the brain, but one can still be addicted to gums or patches if enough gum or patches are used
Technically, nicotine is an anti-estrogen. It is able to inhibit aromatase that, while not too potent on an IC50 value, levels of nicotine in the blood associated with a cigarette do appear to be biologically relevant. Nicotine can also inhibit estrogen signaling via one of the subsets of the estrogen receptor (an anti-estrogenic effect independent of circulating estrogen), but this may underlie some side-effects of nicotine as well.
Nicotine, surprisingly, does not have too much long-term safety data on the isolated compound in non-smokers. It appears to be the lesser of two evils when used in nicotine replacement therapy (smokers are already tolerant to the effects of nicotine) and when consumed via cigarettes are clearly harmful, but nicotine per se has less evidence than desired. It appears to be similar to many other stimulant compounds, and its safety data probably correlates best to ephedrine (in which it can be used safely, but does carry inherent harms associated with stimulants)
Other updates this week include:
Sesamin, a lignan derived from Sesame seeds. It appears to possibly modulate the estrogen receptor (prevent periods of high activation, while activating the receptor during periods of low circulating estrogen; a sort of 'evening the hills and valleys' sort of thing) and although some studies suggest an enhancement of blood flow, they were confounded with the inclusion of Schisandra chinensis. Sesamin has mechanisms of fat burning, but these mechanisms are similar to those exerted by Conjugated Linoleic Acid and, despite being more potent, are not assured to work well in humans. PPARα activation as a means of fat burning does not have a good track record when rodent studies (especially mice) are extrapolated to humans. Sesamin appears to be healthy and protective of circulation, but is not seemingly remarkable in any way.
Boerhaavia Diffusa is an herb from Ayurveda that has, as the most practical implications, immunosuppressant actions. This is clearly a bad thing from a sickness perspective (less immune system activation means more sickness), but has potential benefit in treatment of metabolic syndrome or other hyperactive immune disorders (fish oil exerts some benefits merely secondary to immunosuppression), and a series of rat studies in type I diabetes noted benefits to glucose metabolism (fasting blood glucose mostly) with potency similar to Metformin and Glibenclamide, anti-diabetic pharmaceuticals. One study suggests potent anti-estrogenic effects independent of the estrogen receptor, but this has not been replicated. Additionally, one molecule shows remarkable anti-oxidant activities at a low concentrations but practical significance of this is currently not known. A promising herb.