Animal Stak: A Scientific Review on Ingredients, Dosage, and Side Effects
Animal Stak Review

Animal Stak: A Scientific Review on Ingredients, Dosage, and Side Effects

Review of: Animal Stak by Universal Nutrition





  • Proven micronutrient support
  • Improved endurance
  • Libido enhancer


  • Proprietary blend (can't be sure of dosage)
  • exclamation-triangle
    8 pills per serving
  • exclamation-triangle
    Irritability and aggression

Summary: Animal Stak is a hormonal support supplement manufactured by Universal Nutrition. It contains a long list of ingredients comprised within a bunch of proprietary blends. Although we can't be sure of the dosages of each ingredient within this supplement, I've gone through each ingredient and dug out the applicable research on its interaction with testosterone. Based on my analysis of the research, some of the ingredients within Animal Stak may have a positive influence on testosterone. But I still don't recommend it. In my view, it's very important to know the dosage of each ingredient within a supplement before taking it. This is simply not possible with Animal Stak.

View my rankings of the top 10 test boosters on the market.


I haven't used this supplement so I cannot comment based on personal experience. But based on some customer reviews I've read online, Animal Stak seems to have a positive impact on muscle and strength. 

A​nimal Stak contains more ingredients than any supplement I've reviewed in the past. It's primary ingredient, however, Tribulus Terrestris, has been shown to have no impact on muscle growth, body composition, or testosterone levels. There are a bunch of other ingredients as well, some proven to boost T, some not, and some with mixed evidence, but the bottom line is that Animal Stak hides behind proprietary blends. We cannot be sure of how much of each ingredient is included within each serving, which is why I don't recommend it. 


By now you know my view of this supplement. But if you want to dive deep into the research that led me to my conclusion, then keep reading...

Animal Pak Ingredients: 2.5/5

What I liked most about Animal Stak is that it provides 100% or more of the daily requirement for zinc, magnesium, and vitamin D3. These three micronutrients have been proven to have a positive impact on testosterone levels. 

What I didn't like about Animal Stak was that all of its other ingredients were contained within proprietary blends. Therefore, even though some of the ingredients may have research backing up its positive interaction with testosterone, we can't be sure of the extent of this interaction, since the dosages are unknown. ​

Animal Stak Ingredients

Vitamin B6

​Vitamin B6 is involved in a number of bodily functions including metabolism, memory, and movement. Although B6 is required by our body to perform a number of biological functions, there are no unique benefits associated with supplementation. If you live in a developed country, you are more likely to have a B6 surplus than a B6 deficiency. 

The fact that Animal Stak provides 525% of your daily requirement for vitamin B6 doesn't hurt, but don't expect it to provide any noticeable benefits either.



​Magnesium is an essential mineral in the human body involved in a variety of functions; increased energy, better sleep quality, better digestion, a healthy heart, and strong bones are just some of the many benefits associated with maintaining magnesium balance. 

Turns out magnesium is also directly correlated with testosterone. Let's take a quick look at the research:  

  1. After analyzing the blood work of 399 men over the age of 65, researchers found magnesium levels to be strongly and directly correlated with testosterone levels (1). 
  2. 4 weeks of supplementing with 10mg of magnesium per kg of bodyweight, both athletic and sedentary subjects saw significant increases in T (2).

The fact that Animal Stak provides over 100% of your daily requirement for magnesium really is a plus point. I haven't seen this high a dosage in any other test booster that I've reviewed in the past.



​Zinc is another essential mineral that is involved in many of our body's functions: hormone balance, growth, development, and heart health are a few of the many benefits that come with maintaining zinc zinc balance. 

Zinc impacts testosterone levels much the same way as magnesium:

If you're deficient in it, then topping up your levels can significantly increase testosterone levels. If your levels are already normal, then supplementing with it will not increase your levels  further.

Here's a quick look at the research: ​

  1. Elite athletes supplementing with 3mg of zinc per kg of bodyweight were found to have significantly higher testosterone levels compared to placebo (3). 
  2. Subjects put on an exercise bike were found to experience a drop in testosterone levels. Supplementing with 3mg of zinc per kg of bodyweight prevented this decrease (4).

A lot of zinc is evaporated when we sweat. This is why supplementing with it is  especially important if you exercise or live in a hot environment. 

Animal Stak has your zinc needs covered and more. ​

Vitamin D3

We need vitamin D to survive. It is involved in over 1000 bodily functions and controls everything from bone mineralization to keeping our immune system strong and healthy. Maintaining optimal vitamin D levels means that your heart is healthy, bones are strong, and that you have a decreased chance of developing cancer. 

Vitamin D can be acquired through foods like fish, dairy, and some meats, but the best source of it is through sunlight. 

Vitamin D levels, as it turns out, are also directly correlated with testosterone. Here's what the research says:

  1. Men with sufficient vitamin D levels were found to have significantly higher testosterone levels compared to men with deficiencies (5). 
  2. Men supplementing with 3332IU of Vitamin D daily were found to have 25.2% higher testosterone levels 1 year later (6). 
  3. Older men supplementing with vitamin D were less likely to have low testosterone levels compared to men who didn't supplement with the vitamin (7). 

There are a bunch of other studies that prove this positive correlation as well, but the bottom line is this: 

If you have sub-optimal vitamin D levels then you'll most likely have sub-optimal testosterone levels as well.

According to recent estimates, almost half of American adults are deficient in vitamin D (​8). 

I love Animal Stak's micronutrient formula because it provides at least 100% of the daily requirement for the vitamins and minerals that have been proven to have a direct relationship with testosterone.

So far, so good. ​


Tribulus Terrestris

Tribulus is the first ingredient in Animal Stak's Pro Testosterone Complex. Ingredients are usually listed out in order of dosage, which means that tribulus is Animal Stak's primary ingredient. 

Tribulus is a herb that has traditionally been used as an aphrodisiac. Today, it is a common ingredient in some of the most popular testosterone supplements on the market. But does it work? Here's what the research says: 

  1. Elite rugby players supplementing with 450mg of Tribulus daily for 5 weeks experienced no change in testosterone levels compared to placebo (9).
  2. Two groups of subjects consumed either 10mg of Tribulus per kg of bodyweight or 20mg of Tribulus per kg of bodyweight. 10 days later, no differences in testosterone levels were noted (10). 
  3. Infertile men supplementing with 6g of Tribulus for 60 days were noted to experience an increase in T-levels by 16.3% (11). 

Based on the research, Tribulus Terrestris is more hype than substance. The effect on testosterone levels in healthy men is non-existent. Even in infertile men, the impact is not significant. 

The fact that Tribulus Terrestris is the primary ingredient in Animal Stak is really a let down.


Longjack Extract

​Eurycoma Longifolia Jack, aka Tongkat Ali or Longjack, is another aphrodisiac herb that has also found its way into the ingredient profile of many popular testosterone supplements. 

Let's take a look at some studies:

  1. Men with hypogonadism (low testosterone) supplementing with 200mg of Longjack Extract experienced a 46% increase in testosterone levels after just 1 month (12).
  2. Subjects with moderate stress supplementing with longjack extract experienced 37% higher testosterone levels and 16% lower cortisol levels after 4 weeks (13). 

On the surface, supplementing with Longjack seems to be a great way to increase testosterone levels. But when we look deeper, the two studies cited above had subjects who either had very low testosterone levels to begin with, or were moderately stressed. Whether these effects carry on to affect otherwise healthy men the same way still needs further research to back it up. 

That being said, I think that Longjack is definitely one of the bette ingredients, since there is more evidence than not to support its positive interaction with testosterone. 



Trigonella foenum-graecum, aka fenugreek, is a popular herb in India that has traditionally been used as an aphrodisiac. Today, it finds its way into the ingredient profile of many of the best-selling testosterone supplements. The studies, however, report mixed results as to its actual interaction with T:

  1. 30 resistance-trained men supplementing with 500mg of fenugreek experienced significantly higher testosterone levels compared to placebo after 8 weeks of use (14).  
  2. 60 healthy males supplementing with 600mg of fenugreek for 6 weeks experienced increased markers of arousal, but no actual increase in testosterone levels (15). 
  3. 45 resistance-trained men supplementing with 500mg of fenugreek experienced no increase in testosterone levels after 8 weeks of use (16). 

Although one study has shown fenugreek supplementation to increase testosterone levels, 2 others have shown no such impact. At this point, further research is needed to confirm the interaction between fenugreek and T-levels. 


Stinging Nettle Root

Stinging Nettle is a plant that has traditionally been used for its anti-inflammatory properties. Today, it included in many of the most popular testosterone supplements. Let's take a quick look at the research:

  1. 558 patients undergoing treatment for a prostate condition supplemented with 360mg of Stinging Nettle Root for 6 months. Although they had improved symptoms for their prostate condition, testosterone levels remained unaffected (17). 

There are a couple of test-tube and petri-dish studies that have shown Stinging Nettle Root to have an inhibitory affect on SHBG (18, 19), but based on the lone human study this effect does not carry on to affect us the same way. 


Maca Extract

Maca is a vegetable from the broccoli family that has traditionally been used as an aphrodisiac. Its libido enhancing abilities have been proven in many studies (20, 21), but let's see if it does so by influencing testosterone:

  1. 57 men supplemented with either 1.5g or 3g of Maca over 12 weeks. Although they experienced subjective increases in sexuality, no influence on testosterone was  found (22). 
  2. Another study with basically the same design as the one above (56 men, 1.5g Maca or 3g, 12 weeks) also arrived at the same conclusion: Supplementing with Maca has no impact on testosterone levels (23). 

Although higher testosterone levels can mean an increased sexual desire, the reverse is not necessarily true; an increased sex drive does not translate to higher testosterone levels. 

Maca is one of those ingredients that leads users to believe that they are experiencing higher testosterone levels because of their morning wood. But this is simply not the case. Maca's influences take place without having any impact on hormones. ​


Arginine Complex

Arginine is an amino acid important for blood flow and nitric oxide levels. Oral supplementation, however, is not a reliable means to improve blood flow in humans due to its poor absorption rate. Let's take a look at the one human study on its interaction with testosterone:

  1. 30 endurance-trained men supplementing with L-Arginine over a course of 4 weeks did not experience any change in testosterone levels (24). 

L-Arginine is an ingredient proven not to work. If you do want to increase your blood flow and boost nitric oxide levels, a much better alternative is L-Citrulline. It is a precursor to L-Arginine and has a much better absorption rate in the body. 


Mucuna Pruriens

Mucuna Pruriens, aka Velvet Bean, is a bean that grows from trees. It provides a hefty source of L-DOPA. 

L-DOPA is a precursor to Dopamine, i.e. the hormone that controls our feelings of pain and pleasure. ​Let's take a quick look at the research on its interaction with hormones: 

  1. 60 infertile men screened for high levels of stress supplemented with 5g of Mucuna Pruriens daily for 3 months, after which they had significantly lower cortisol levels (25). 
  2. 75 infertile men supplementing with 5g of Mucuna Pruriens over a period of 3 months experienced significantly higher testosterone levels (26). 
  3. 180 infertile men supplementing with 5g of Mucuna Pruriens daily for 3 months experienced, on average, 17-43% higher testosterone levels (27). 

Although the effects of Mucuna Pruriens have only been studied on infertile men, it is definitely one of the more promising testosterone supplement ingredients out there. 



I wasn't able to find much information on SuperSerum, but from what I did find it seems to be used as an ingredient for skincare (28). Not sure what its doing as an ingredient inside a testosterone booster supplement though. 


Sustamine is the trademarked name for L-Alanyl-L-Glutamine, a combination of alanine and glutamine (two amino acids). It is commonly used as a sports supplement to improve performance. As per its effects on testosterone, there has only been one human study: 

  1. Physically active men supplementing with Sustamine were found to experience no changes in hormonal parameters after exercise (30).


Alpha Glycerophosphocholine

Alpha-GPC is a compound used for its cognitive enhancing abilities and to enhance power output in athletes. It is included inside Animal Stak's Growth Hormone Support proprietary blend so let's take a look at the research behind that: 

  1. 8 healthy males supplementing with 1g of Alpha-GPC experienced increases in GH 60-120 minutes after ingestion (31).
  2. 7 resistance-trained men supplementing with 600mg of Alpha-GPC before exercise experienced a significant spike in GH levels post-workout (32).

Although the sample sizes were small, and not much research has been done in the area, Alpha-GPC does seem to have a positive interaction with growth hormone levels. 


Polygonum cuspidatum

Japanese Knotweed, or Polygonum Cuspidatum, is a herbal medicine that has traditionally been used for circulation and heart health. The active ingredient is resveratrol, and most of its benefits can actually be tied back to that. 

Although not studied directly for its impact on testosterone levels, this compound has been shown to have a significant anti-inflammatory effect (33) which could indirectly support better health and, in turn, increase testosterone levels. 


Calcium D-Glucarate

Calcium D-Glucarate is a natural substance that is largely associated with anti-oxidant benefits. It is added in Animal Stak for its apparent anti-aromatase properties.

No human studies have been performed in this area, but in one animal study, rats given 10mg of Calcium D-Glucarate experienced 23% lower estrogen levels relative to control (34). 



Diindolylmethane (DIM) is a compound found in cruciferous vegetables that shows promise for its anti-cancer and anti-aromatase benefits. It is also an ingredient in Animal Stak's anti-aromatase blend, so lets take a quick look at the research: 

  1. 6-7 mg/kg of DIM supplementation allowed both men and women to excrete more estrogen through urine (35).

That is the only human study I was able to find, but other studies show that DIM supplementation helps the liver metabolize estrogen more effectively (36) and that it has a part to play in converting more potent estrogens in the body to less potent forms (37). 


L-Carnitine Fumarate

L-Carnitine is an amino acid that in naturally produced in the body. It is largely involved in energy regulation and mitochondrial protection. 

L-Carnitine has largely been studied for its  fat-loss effects, with scientists theorizing that it will make your body more effective at using fat for fuel, but studies do not show promising results.

No impact on testosterone has been found with L-Carnitine supplementation, but the benefits exist to the extent that you're deficient in it. If you're not eating enough red meat and other animal products, low carnitine levels could go on to negatively affect other areas of your life. ​


Agmatine Sulfate

Agmatine is derived from L-Arginine. It has largely been used for alleviating neuropathic pain and drug addiction. As per its effect on hormones, it has been studied to impact Luteinizing Hormone (38) (precursor for testosterone), but other than that, no direct impact has been noted. 


Glycine Propionyl L-Carnitine (GPLC)

GPLC is another form of carnitine that is mostly used as a sports supplement to improve performance and endurance. More studies are needed to confirm these effects though. 


Quercetin is a bioflavonoid found in fruits and vegetables, and most abundantly in apples and onions. It is mostly known for its anti-oxidant effects. 

Studies performed in a test-tube have revealed pretty amazing results, but studies performed on animals and humans have not been quite so impressive. This is because upon consumption, a lot of Quercetin is not absorbed. 



Astaxanthin is a naturally occuring compound found in shrimp, lobster, crab, and salmon. It has been touted an an anti-inflammatory and anti-oxidant. Although no direct impact has found as per its interactions with hormones, it does seem to be beneficial for overall health. 



Bioperine is a patented formula largely comprised of black pepper extract. Although it doesn't provide any benefits on its own, it is added to many supplements to help increase the absorption rate of other ingredients. 


Milk Thistle Extract

Milk Thistle is a herb that has largely been used for liver health. No particular benefits with regards to hormones have been found. 



Astragalus membranaceus is a fundamental herb in traditional Chinese medicine. It is largely known for its anti-inflammatory properties as well its supposed ability to increase lifespan. 

As per its interaction with hormones, it may increase IGF-1 (39), but no interaction with testosterone or estrogen has been found. 


Ashwagandha Extract

Ashwagandha is an adaptogen, i.e. it treats the physical and chemical effects of stress. This is an ingredient that I really like to see as part of a testosterone supplement, but the fact that this is so far down on the list means that its likely one of the least dosed ingredients. Either way, here's what the research says about ashwagandha and its interaction with testosterone: 

  1. Men screened for chronic stress supplmented with 300mg of Ashwagandha for 60 days, after which they experienced almost 30% lower cortisol levels (40).
  2. Infertile men supplemented with 5g of ashwagandha for 3 months, after which they were found to have, on average, 10-22% higher testosterone levels, and 36-48% lower cortisol levels (41).
  3. Healthy men that supplemented with 600mg of Ashwagandha were found to have significantly higher testosterone levels (42).

So its pretty clear that Ashwagandha is one of the few herbal ingredients that have been clinically proven to have a positive influence on testosterone levels. However, I wouldn't rely too much on the dosage in Animal Stak, as it is way down on the list.


Na-R-Alpha Lipoic Acid

Na-R-Ala is alpha-lipoic acid bound to sodium. It is involved in energy regulation and controlling blood sugar. Supplementing with Na-R-Ala has anti-oxidant and inflammatory benefits. 


Coenzyme Q10

Coenzyme Q10 (COQ10) is a compound produced in the body to aid energy production. It is not necessary for optimal body function, and therefore not needed as a supplement.


Testimonials: 4/5

On Animal Stak has an average rating of 4/5 stars based on 214 customer reviews. 

On Animal Stak has an average rating of 8.3/10 based on 467 customer reviews.

​Mostly the reviews are positive, but here's an example of a negative review I came across on Amazon:

Animal Stak Results

Price: 3/5

Animal Stak retails for $34.99 for 21 servings. That comes out to about $1.67 per serving. This seems to be the mid-range price of a supplement in this category. 

Animal Pak Side-Effects

Keep in mind that the side-effects listed below are associated with taking beyond the recommended dose of the supplement. If you follow the instructions on the label, then you are not likely to experience the following side effects. 

Animal Pak is a supplement with the most ingredients out of any supplement that I've reviewed in the past. Therefore, I will not go over the side effects of every single ingredient on the list, only the most prominent ones. ​

Possible Side-Effects of Tribulus Terrestris

  • Difficulty sleeping


Possible Side-Effects of Longjack Extract

No information currently available about side-effects.


Possible Side-Effects of Fenugreek

  • Diarrhea
  • Stomach upset
  • BloatingGas
  • "Maple syrup" odor in urine
  • Nasal congestion
  • Coughing
  • Wheezing
  • Facial swelling
  • Lower blood sugar


Possible Side-Effects of Mucuna Pruriens 

  • Vomiting 
  • Headache
  • Sleeplessness
  • Hair loss
  • High blood pressure
  • Hallucination


Possible Side-Effects of Nettle Root

  • Mild stomach upset
  • Fluid retention
  • Sweating
  • Diarrhea
  • Hives or rash 


Possible Side-Effects of Maca

  • Over-load of iron
  • Impaired thyroid function
  • Hot flashes
  • Fatigue
  • Abdominal cramps
  • Headache



For this portion of the review, let's see how Animal Stak compares to some other popular testosterone supplements on the market. 

Even though I recommend Animal Stak above all the supplements listed below, at the end of the day, it is still not a supplement that I recommend. That should provide insight into the supplement industry as a whole: the market is flooded with products that are proven not to work. 

Animal Stak vs TestoFuel

​Unlike Animal Stak, Testofuel contains no proprietary blends. 

The primary ingredients in Testofuel are D-Aspartic Acid, Ginseng, Fenugreek, and Oyster Extract. None of these ingredients have been prove to have a positive impact on testosterone. 

Testofuel has a decent micronutrient profile, but Animal Stak's is even better. The only place where Testofuel takes it is in its vitamin D dose. 

Even though Animal Stak has a bunch of proprietary blends, I'd say that its the better supplement due to its proven micronutrient formula and a bunch of extra ingredients that may or may not work. 

Winner: Animal Stak

Animal Stak vs Test Freak

Test Freak is another supplement full of proprietary blends. The primary ingredients are Tribulus, Fenugreek, Saw Palmetto, and Stinging Nettle. None of these ingredients have been proven to impact testosterone positively. 

Test Freak's ingredient formula is comparative to Animal Stak, however Animal Stak has the addition of vitamin D and it also provides the daily requirement for zinc. 

I'd say that Animal Stak is the better supplement since it includes most of the ingredients that Test Freak has and more. 

Winner: Animal Stak

Animal Stak vs Testogen

Testogen has no proprietary blends, all of its ingredients are listed out as is. 

The primary ingredients are D-AA, Tribulus, Ginseng, and Fenugreek. Once again, none of these ingredients have been definitively proven to positively impact testosterone. 

We can't be sure of the dosages of each ingredient in Animal Stak, but given that it includes most of the ingredients as in Testogen, I'd say that it takes the cake due to its superior micronutrient formula. 

Winner: Animal Stak

Animal Stak vs Animal Pak

Animal Pak is Universal Nutrion's flagship product. It is a multivitamin that packs a bunch of required vitamins and minerals. 

A lot of the ingredients across these two supplements are similar, but given that Animal Stak is geared towards hormonal support, it has a bunch of extra ingredients as well. 

Since I'm reviewing supplements based on their ability to influence the androgens in our body, I'd say that Animal Stak takes the cake. 

Winner: Animal Stak

Animal Pak

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