MusclePharm Iron Test Review

Iron Test is a MusclePharm testosterone booster released under the Arnold Series brand. From an ingredients standpoint, it is similar to other testosterone boosters out there, but also includes some MusclePharm favorites like Arginine Nitrate…

MusclePharm Iron Test




Argine Nitrate is simply L-Arginine fused with Nitrate, the idea being that, since both compounds can stimulate increase Nitric Oxide that the combination may be synergistic. However, Arginine Nitrate has never been studied so all we have to go on is a theoretical mechanism of action. Furthermore, recent research has shown that Arginine is really not all it’s cracked up to be.

A 2012 study, published in “Nutrition and Metabolism”, found that acute (one-time) L-Arginine supplementation with 6 grams did not increase plasma (blood) levels of Nitric Oxide in people with normal Asymmetric Dimethylarginine levels. Asymmetric Dimethylarginine is a compound that is chemically related to Arginine and directly interferes with the production of Nitric Oxide.

A 2011, placebo controlled study, found that subjects performed worse after receiving 3700mg of Arginine Alpha-Ketoglutarate prior to resistance training.

While most studies have failed to prove that L-Arginine supplementation increases strength, a 2012 double-blind placebo controlled study, found that supplementation with 6 grams of L-Arginine increased muscle blood volume post-workout (but did not increase strength).

Nitrate supplementation has been shown to reliably increase time to fatigue at a given work load but there is no evidence indicating that Arginine-Nitrate is more bioavailable than standard L-Arginine or other forms of Nitrate. Furthermore, the dose of Arginine Nitrate present in the Iron Test formula is likely pretty negligible and multi-serving doses would probably be necessary to convey any noticeable benefit.


D-Aspartic Acid acts as a precursor to N-Methyl-D-aspartic acid (NMDA), which takes on a similar role to the excitatory neurotransmitter Glutamic Acid. In rats, D-Aspartic acid supplementation has been shown to significantly increase Testosterone. Out of the three human studies done specifically to test the effect of D-Aspartic Acid on Testosterone, two have shown a significant increase in Testosterone levels and one has failed to do so.

A 2012 study from “Advances in Sexual Medicine”, the subjects of which were infertile men (low testosterone) found that 2.66g of D-Aspartic Acid was able to significantly increase Testosterone levels when measured after 90 days of supplementation. These results were in-line with those of an earlier (2009) study in which D-Aspartic Acid supplementation raised Testosterone by 42% after 12 days in healthy men. However, a 2013 study published in “Nutrition Research” found that athletes who supplemented with D-Aspartic Acid for 28 days showed no difference in testosterone levels.

The researchers in the failed study noted abnormally high levels of D-aspartate oxidase, the enzyme which degrades D-Aspartic Acid, indicating that prolonged supplementation in individuals with healthy Testosterone levels may cause “negative feedback” which reduces the effects.

While D-Aspartic Acid may be an effective short-term Test booster, the dose present in the Iron Test formula is undoubtedly much less than what has been used in the above mentioned studies.


Trigonella Foenum Greacum (also known as Fenugreek) has gained serious traction in the supplement industry as a libido enhancer and alleged Testosterone-booster. However, a 2009 study, published in the “International Journal of Exercise Science”, found that Fenugreek supplementation had no influence on Testosterone (or any other hormone). A similar failure was noted in a 2011 double-blind, placebo controlled study in which 6 weeks of supplementation with a Fenugreek derived extract (Testofen) led to scoring 25% higher on a libido test (sexual arousal and orgasm in particular) than the placebo group, but with no increase in Testosterone levels, meaning that the mechanism of action was not an increase in Testosterone.

While two studies have failed to show any Testosterone-boosting effect of Fenugreek supplementation, one 2010 study, published in “The International Journal of Sports Nutrition”, found that supplementation with 500 mg of Fenugreek extract (Testofen again) resulted in a significant increase in free-Testosterone levels.

Ultimately, the results are mixed, with two studies failing and one study showing increased Testosterone. More research is needed to clear up this discrepancy, but for now it appears Fenugreek is only reliable as a libido enhancer, not a Testosterone booster. MusclePharm does not disclose the amount of Testofen present in Iron Test, but even at 500mg (unlikely), an increase in Testosterone is far from guaranteed.


Indole-3-Carbinol (I3C) is found mostly in cruciferous vegetables (broccoli, brussel sprouts, kale, etc), but has become relatively popular as a dietary supplement for its potential to alter estrogen metabolism, as evidenced in a 1990 study published in the “Journal of the National Cancer Institute” in which 500mg Indole-3-Carbinol administered to humans significantly up-regulated the conversion of estradiol (major estrogen) into its less active counterparts, Estrone and Estriol. It’s important to understand that the term “Estrogen” is really an umbrella term that refers to a group of compounds including Estradiol, Estrone, and Estriol. The type of “bad estrogen” hated by bodybuilders and cancer patients alike is Estradiol. However, Estradiol can be converted into Estrone and Estriol which don’t cause the negative effects “Estrogen” has become known for. Indole-3-Carbinol may in fact help this conversion take place, leaving less “bad estrogen”.

It’s safe to assume that Iron Test contains much less Indole-3-Carbinol than the 500mg dose used in the above-mentioned study, so the degree of efficacy is unclear.


In the early days of bodybuilding, Boron was actually quite popular as a pro-anabolic nutrient, but that popularity faded as more and more “pro-anabolic nutrients” arrived on the scene, not to mention the discouraging findings of a 1993 study which found that daily supplementation with 2.5 mg of boron over a 7 week period failed to increase testosterone levels in men. However, Boron is making a bit of a comeback after recent research indicates that, at high enough doses, it may be able to raise Testosterone. A 2011 study, published in the “Journal of Trace Minerals in Medicine and Biology”, found that boron supplementation (11.6 mg daily) over a one week period was found to increase testosterone to a statistically significant degree (28%).

The most obvious reason for the discrepancy between these two studies is that the positive (2011) study used about 4-5 times more Boron than the failed (1993) study. While more research is certainly needed to truly establish the efficacy of higher doses of Boron for boosting Testosterone, it would appear that Boron is, after all, moderately effective (assuming a high enough dose). MusclePharm does not disclose the amount of Boron in the Iron Test formula.


Studies investigating the relationship of Vitamin D to Testosterone have found a strong correlation between adequate levels of Vitamin D and normal Testosterone levels, indicating that Vitamin D plays a role in normalizing Testosterone. However, when looking at the research as a whole, nowhere is there an indication that excess Vitamin D supplementation may result in above normal Testosterone levels. Individuals who receive the proper amount of Vitamin D, either from direct sunlight or through supplementation, will not experience increases in Testosterone as a result of excess Vitamin D consumption. Iron Test contains 400IU of Vitamin D, which may encourage optimal Test levels, but will not increase them beyond normal.


Zinc is required for the conversion of cholesterol (and other lipids) into sex hormones, as well as the existence of androgen receptors, as evidenced in a 1996 study, in which rats fed a zinc deficient diet experienced a decrease in androgen receptor sites and an increase in estrogen receptor sites. So while Zinc deficiency can certainly result in low testosterone, there is no evidence indicating that supplemental Zinc can increase Testosterone above normal. In fact, there is ample evidence to the contrary.

A 2009 study, published in the “European Journal of Clinical Nutrition”, concluded that zinc (ZMA) supplementation had no influence on serum testosterone levels in non-zinc deficient men. A similar failure to influence testosterone via zinc supplementation was seen in a 2011 study, the subjects of which were trained cyclists who consumed sufficient dietary zinc.

However, a 2005 study, the subjects of which were wrestlers, demonstrated that zinc supplementation was able to attenuate exercise-induced declines in testosterone levels. Unlike Magnesium, The relationship of Zinc and Testosterone is quite clear: Zinc supplementation will not increase testosterone above baseline in healthy, non-zinc deficient humans, but can be effective for maintaining consistent testosterone levels during exercise.

Iron Test contains 30mg of Zinc, about 200% of the Recommend Daily Intake (RDI), more than enough to help ensure adequate Test levels.


Iron Test contains the usual alleged Test-boosters, some of which are a questionable (Testofen), and some which are effective (D-Aspartic Acid). However, given an overall proprietary blend of 1350mg multiple servings must be consumed to achieve an effective dose.

Still not sure which Testosterone Booster is right for you? Check out our Best Testosterone Boosters List!

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