D-Aspartic Acid 3000 mg - D Aspartic acid is a solid inclusion although as previously mentioned 3000mg is at the high end, and some people would probably benefit from taking a half dose to start with to get used to it. It's been shown to improve muscle gains in men who are training and those that aren't with it having a mild to moderate increase in free testosterone.
Fenugreek Extract (50% saponins) 700 mg - Fenugreek extract has been shown to be effective at delivering a moderate increase in testosterone levels in both healthy and unhealthy men. There's been a couple of double blind trials that would suggest that 700mg is within the effective range for fenugreek, although with it only being 50% saponins it's the bottom end of the effective range.
Epimedium Extract 625 mg - Horny goat weed has unfortunately not been well studied in humans, it's not necessarily a bad ingredient for a testosterone booster, but it may not actually be a good one either. It's main backing is that it contains compounds which can improve blood flow, which could improve certain functions, but again it's another potential flop for our nugenix reviews.
Stinging Nettle Extract 300 mg - Stinging nettles do have some positive effects for reducing the impacts of low testosterone levels, but the extracts don't really raise testosterone levels very much. You can also get all of the benefits from lower dosages which is why it's typically a filler ingredient in better boosters.
Maca Extract (root) 200 mg - Maca doesn't actually raise testosterone levels, it has been shown to be effective at improving libido in both men and women in double blind studies. It's pretty well backed at this point, but it's not going to do anything to help raise free testosterone levels or improve lean muscle mass etc.
Eurycoma longifolia Extract (root) 150 mg - Longjack or Tongkat ali is reasonably well backed for having an impact on raising testosterone levels. 150mg is right in the middle of the dosage range so this is a good inclusion, nothing wrong here at all making this one of the better inclusions in nugenix ultimate testosterone booster.
Mucuna pruriens Extract 125 mg - Velvet bean is an interesting choice for a testosterone booster, it seems to improve dopamine levels, energy levels and there is one human study that shows a mild knock on for testosterone, although this could be due to reducing stress hormone build up. The catch is that whilst we can say improving energy levels and mood are good for mitigating low t symptoms, the dosage needs to be closer to 500mg. Normally we don't mind a couple of symptom mitigation ingredients, but as can be seen in this nugenix ultimate review it's the bulk of the product and that isn't what the marketing promises.
Boron 10 mg - Boron is a great ingredient and 10mg is the correct dose, there's a host of applications for it beyond as a free testosterone booster, and the ingredient takes up relatively little in the way of capsule space. It's been shown to work in double blind trials even in people who seem to have enough in their diet. 10mg does seem to be the maximum dose with more not offering further returns, this is a decent inclusion for nugenix natural testosterone boosters.