Well, Mike Mahler did it again! First, he was one of the pioneers in vegan strength training and bodybuilding. He became a vegan in the mid 90's and, back then, many in the muscle industry doubted that one could build strength and mass on a vegan diet. Mike Mahler showed it could be done and is one of the leading kettleball teachers and instructors right now. Yes, plant protein can PACK on the muscle.
NOTE: I am not a vegan but rather plant-based (almost entirely for health reasons), i.e. I eat an almost entirely vegetarian diet but will occasionally eat meat if on the road or in social settings. See My Bio if you want a little more background information.
This time Mike Mahler probably did what the FDA was hoping no one could do: come up with a legitimate herbal testosterone booster that falls outside, as far as I know, of the FDA's scope and regulations. (Time will tell regarding that.) More on that in a minute, but let's go first to the ingredients in Mike's new formulation called Aggressive Strength: bulbine natalensis, mucuna pruriens and Stinging Nettle Root. Now mucuna pruriens and Stinging Nettle Root have been around for years and years, but, here in the U.S., bulbine is not as well-known. Of course, like almost every herb, it has been used for probably centuries in Africa, including the well-known Zulu tribe, as an herbal remedy. However, to those of us in the U.S., it definitely seems like a newcomer.
However, that unknown factor has allowed it to sneak in under the rader and now shine as a potential superstar. This all started from a 2009 study in the International Journal of Andrology that showed that bulbine actually increased mounting frequency in rats more than Viagra.  The researchers found something else that I doubt they anticipated: the heightened sexual interest likely came from a HUGE testosterone boost in the animals. Ergo-log has a Great Summary of the 2009 Bulbine Study if you are interested. It turns out the animals on the hightest dosage of this herb approximately tripled their testosterone levels. Of course, this got the attention of the bodybuilding world.
Well, apparently, Mike Mahler was all over it and contracted with a high quality manufacturer that has run their own studies. According to this manufacturer - ProLensis is the brand - their high quality bulbine "has been shown in studies to increase testosterone by a whopping 347% and crush estrogen by 35%." Based on the results in the above animal study, it is not hard to believe.
This has got to have the FDA agents sweating just a little! Even if most men who tried Aggressive Strength got half of those results, it would be profound to say the least. This just leaves the latest testosterone booster, D-Aspartic Acid, in the dust, since it ony produces an average boost in testosterone of around 35% and has a reputation for disproportionately increaseing estradiol.
Having a well-known and well-liked fitness figure like Mike Mahler behind the product only enhaces the presentation and lend credibility to the fact that this does, indeed, very likely raise testosterone although none of the Peak Testosterone Forum members have tried it yet to verify. So should you try it if you're low testosterone? Well, this is product is so new that I will have to leave that to you and your own personal research. However, I do want to point out several areas of concerns that I have and the answers and solutions that Mike Mahler has developed to hopefully overcome them:
1. Lipids. Bulbine natalensis works by pushing cholesterol into the testes. (It also greatly increases LH (leutinizing hormone) apparently, something you can read about in Mike Mahler's Fact Sheet.) However, there is an animal study out there that shows it does not just increase cholesterol in the testes but also in the plasma.  This study was published just six months prior to the testosterone study and it gave rats identical dosages (25, 50 and 100 mg/kg body weight).
What they found was that bulbine had a profound initial affect on total cholesterol, more than doubling it on day one for example. After 14 days, the values had decayed somewhat to a lower value, but still cholesterol remained about 50% higher than the starting point. This is obviously still a huge increase in cholesterol. Just as troubling was a big drop in HDL in the animals after 14 days. In fact, the motivation for the study itself may have been concern over this issue and the authors point out that "alterations in the serum lipids of animals administered with extract of medicinal plants appear to be a significant factor in the development of premature atherosclerosis."
Now does this mean that Aggressive Strength will hammer your arteries?
Well, I certainly am not saying that, but I would recommend (if you can afford
it) a lipid profile before and after taking bulbine if you decide to try it.
Furthermore, Mike Mahler seems to have developed a strategy that will hopefully overcome this issues.
I actually got the opportunity to ask Mike Mahler out about this via Twitter and he stated the following:
"@PeakT Personally I have not seen any negatives with lipids on 8 week cycles or less which is what I recommend."
"â€@PeakT Cholesterol is increased initially to convert into testosterone into testes but normalized after a few weeks is my experience."
So what he is saying is that in his experience, you can protect yourself by 1) 8 weeks on and 8 weeks off and 2) realizing that your lipids will normalize after a few weeks. Again, since no formal study has been done on humans, so I would recommend doing your own testing and verify that your own physiology does not react poorly. After all, it does little good to boost your testosterone if you've blown out your arteries!
2. Liver. Again, in that same year - you can tell bulbine was red hot! - researchers found in a study of rats some signs of liver damage.  In fact, they concluded that "histological examination revealed slight distortions in the architecture of the liver lobules as well as proximal and convoluted tubules of the kidney. The alterations produced in some of the functional indices as well as in the hepatorenal architecture may adversely affect the normal hepatic and renal functions. The parameter-specific effect of the extract suggests selective toxicity. This is an indication that the extract is not completely "safe" as an oral remedy."
ProLensis, the supplier of bulbine in Mike's formulation, followed up and actually a followup study on men in 2012.  They looks at a variety of kidney and liver function tests and found that "alkaline phosphatase (AP) increased marginally in the ProLensisâ„¢group." In other words, there was a slight effect on liver function (and possibly kidney) but they felt it was not enough to be a concern.
However, one thing that is interesting, and I don't know whether is deliberate or not, but Aggressive Strength contains Stinging Nettle Root, a known liver protector. It has in various studies been shown to protect the liver of lab animals from various toxins and poisons, such as aflatoxin and carbon tetracholoride. Since the bulbine already decreases estradiol, there really is no need from an E2 standpoint for the Stinging Nettle Root. Regardless, my point is that this formulation coupled with the cycling should protect your liver enzymes. Again, though, it would probably be prudent to be tested before and after as men have a wide range of liver reactivities and, again, it is always best if you can afford it to monitor your own personal physiology.
3. Distraction. Another concern I have is that hypogonadal men may become distracted from getting the testosterone therapy that they need, assuming they have very low testosterone, if there is an herbal solution. Low testosterone puts a man at increased risk for arteriosclerosis, erectile dysfunction, heart disease, diabetes, venous leakge, osteoporosis, Metabolic Syndrome and so on. The 8 weeks off during cycling may not provide the kind of relief that he needs to make a dent in some of these issues for him. Again HRT (or possibly Clomid or HCG monotherapy if fertility is an issue) seems like the more consistent therapeutic response imo so that the man is not left for several weeks in a hypogonadal state.
4. Lack of Long Term Studies. This herb is potent. Most of the properties seem good. For example, one study shows that bulbine speeds wound healing.  It also has strong anti-clotting abilities as well.  So who knows? Perhaps this herb will be shown to be part of a nice anti-againg strategy eventually. But, in the meantime, there are really very few studies on this herb: it's just not like a Ginseng that has a broad swath of research behind it.. It is simply not that well-studied of a plant yet. The good news is that it has been used by the Zulus and other South African tribes for a long time now.
Should you take it if you are low or lowish testosterone? Well, I will leave that up to you and your own personal research. Regardless, it is an interesting product and that there are athletes and bodybuilders world wide that will be using this to enhance their performance and hypertrophy.
And I can hardly wait to see what the FDA will do this supplement. You only have to back to 1994 to remember when they pulled androstenedione off the market - can you say Mark McGuire? - for being "adulterated". The FDA used this term, because they are allowed to pull products that are adulterated if they meet the following criterion:
"a significant or unreasonable risk of illness or injury under ... conditions of use recommended or suggested in labeling"
" or ... if no conditions of use are suggested or recommended in the labeling, under ordinary conditions of use" 
And the paper also points out that the FDA does not even have to provide evidence that any consumers have been injured! Clearly an herb like bulbine natalensis is in a different category than a direct prohormone such as androstendione. I think the public at large does NOT want the FDA telling them what herbs they can and cannot buy and I suspect the FDA will be very cautious in touching this one.
1) Int J Androl, 2009 Dec, 32(6):629-36, "Effect of aqueous extract of Bulbine natalensis (Baker) stem on the sexual behaviour of male rats"
2) Indian Journal of Experimental Biology, Apr 2009, 47:283-288, "Effect of aqueous extract of Bulbine natalensis Baker stem on haematological and serum lipid profile of male Wistar rats"
3) J Med Food, 2009 Aug, 12(4):814-20, "Effect of Bulbine natalensis Baker stem extract on the functional indices and histology of the liver and kidney of male Wistar rats"
4) Int Soc Sports Nutr, 2012, 9(Suppl 1):P33, "Short term safety of bulbine natalensis supplementation in healthy men"
5) Journal of Ethnopharmacology, 18 December 2012, 144(3): 523â€“532, "Bulbine Natalensis and Bulbine Frutescens promote cutaneous wound healing"
6) http://uzspace.uzulu.ac.za/handle/10530/613, "In vitro anti-platelet aggregation activity of the extracts of bulbine natalensis"
7) Journal of the International Society of Sports Nutrition, 2004, 1:52-60, "Adulterated Androstenedione: What FDA's Action against Andro Means for Industry"