What Is Ornithine? Potential Benefits & Drawbacks

Ornithine was popular among weightlifters and bodybuilders back in the ’80s. Athletes used it along with arginine to get bigger pumps and flush out ammonia, a byproduct of protein metabolism. 

Today, this non-essential amino acid is found in a wide range of supplements, especially pre-workout formulas. Manufacturers say that it wards off fatigue, increases energy, and boosts sports performance. 

As our OSL Ambassador, the late Ric Drasin, notes, supplements will only work if your diet is in check. This applies to ornithine, too. 

This nutrient has also been studied for its beneficial effects on liver health. In clinical trials, it improved mood, reduced anxiety, and accelerated wound healing. L-ornithine also appears to be effective against stress and fatigue. 

Below we’ll discuss its potential benefits and see what the research says. Our team will also show you how this amino acid works and what you need to know about l-ornithine supplements. 

What Is L-Ornithine?

We’re all familiar with creatine, arginine, BCAAs, and other amino acids that support muscle growth and repair. But little is known about ornithine, a non-essential amino acid that reduces fatigue. 

This nutrient is responsible for 80% of the nitrogen excretion in the body, reports the U.S. National Library of Medicine. Along with arginine, it plays a key role in the urea cycle and supports liver function. 

Unlike most amino acids, l-ornithine is non-proteinogenic. Simply put, the human cannot use it to make protein. Citrulline, theanine, cystine, and beta-alanine fall into this category, too. 

Athletes take ornithine supplements to get more energy and bigger pumps. Some say that ornithine also makes it easier to build mass. 

Unfortunately, there is little evidence to support these claims. 

The primary benefit of ornithine lies in its ability to remove excess ammonia from the body. 

This amino acid works together with arginine to balance out urea and ammonia levels. If you can’t get of urea, ammonia can accumulate in the bloodstream and take a toll on your health. 

Interested to find out more? Let’s see how l-ornithine works. 

How Does Ornithine Work? 

The role of ornithine in human health is related to the urea cycle. No worries, though — we’ll try to keep it simple. 

Your body’s cells and gut bacteria produce ammonia (NH3) during protein digestion. In healthy people, this waste product is converted to urea by the liver. Urea is eliminated in the urine. 

Individuals with impaired liver or kidney function have difficulty eliminating urea, explains the University of Rochester. As a result, they can’t get rid of ammonia fast enough. 

Over time, this substance builds up in the bloodstream and may cause tiredness, seizures, brain disorders, coma, or even death. 

Even slightly elevated blood ammonia levels can be toxic to the central nervous system. Under normal conditions, they should not exceed 80 micrograms per deciliter. 

Ammonia levels also increase during exercise, reports an earlier study published in Clinical Physiology. A more recent study conducted on mice suggests that elevated ammonia concentrations may affect endurance and reduce fat burning. 

L-ornithine and arginine help break down ammonia into urea so that it can leave your system faster. Your body also needs ornithine to produce arginine and citrulline. That’s why this amino acid crucial to your health. 

The U.S. National Library of Medicine states that fish, eggs, meat, and other animal foods are a good source of ornithine. Vegans and vegetarians can get this nutrient from peanuts, soy, wheat, and oats. 

Additionally, the human body can synthesize this nutrient from other amino acids, so deficiencies are rare. 

Potential Benefits of Ornithine Supplementation

Ornithine is said to increase growth hormone levels, ward off anxiety, and boost immune function. Some say that it makes it easier to build muscle and get shredded. 

But how true are these claims? 

It depends on who you ask. Like with most supplements, the research is mixed. 

For example, a small study published in the journal Nutrition Research has found that ornithine improved lipid metabolism and reduced fatigue during exercise. 

As the scientists note, this amino acid helps your body use energy more efficiently, which in turn may lead to higher energy. Since most foods are low in ornithine, you may take it in supplement form. 

The above study sounds promising, but it only had 17 participants. Further investigation is needed to confirm its findings. 

Clinical evidence also suggests that ornithine may lower the stress hormone cortisol levels and reduce fatigue after a night of drinking. 

In a clinical trial, subjects who took 400 milligrams of this amino before and after drinking reported less fatigue and better sleep. Their cortisol levels were lower the next morning. 

Excessive ammonia may lead to oxidative damage and impair muscle function. It also affects energy metabolism and may cause fatigue during exercise. 

In most studies, ornithine decreased fatigue and ammonia concentrations. Therefore, its positive effects may be due to the reduction in ammonia levels. 

Now let’s take a closer look at other potential benefits of ornithine supplementation! 

L-Ornithine and Growth Hormone Release

Most athletes take ornithine in supplement form to boost growth hormone (GH) levels, notes the Canadian Academy of Sports Nutrition. GH promotes lean muscle growth and post-workout recovery, as well as fat loss. 

However, clinical research doesn’t fully support this claim. 

L-ornithine has been shown to increase GH levels in animal studies, but these results don’t necessarily translate to humans. One study suggests that combining ornithine and arginine may indeed elevate GH and insulin-like growth factor-1 in human subjects. 

The U.S. National Library of Medicine states that ornithine may indirectly boost GH levels. After ingestion, this nutrient is converted to arginine, an amino acid that stimulates the release of growth hormone. 

In a clinical trial, bodybuilders who took different doses of l-ornithine hydrochloride experienced an increase in GH levels. Growth hormone concentrations peaked at 90 minutes following ornithine administration — but only at the highest dosage (170 milligrams per kilogram of body weight). 

The problem is that excess ornithine may affect your health in the long run. 

Large doses of this supplement can be toxic to the retina, warns a 2011 review published in the British Journal of Nutrition. The risk is even higher for people with retinal lesions and HHH syndrome, a rare disorder that affects amino acid metabolism. 

Ornithine and Insulin Levels 

Insulin stimulates protein synthesis, inhibits muscle protein breakdown, and helps your body store glycogen in muscle cells. At the same time, it transports BCAAs into muscle tissue. Due to its anabolic action, it makes it easier to pack on mass. 

The Canadian Academy of Sports Nutrition states that ornithine boosts insulin levels. The evidence is mixed, though. 

In an earlier study, researchers asked 12 bodybuilders to take 40, 100, or 170 milligrams of ornithine on an empty stomach. All three dosage levels caused an increase in ornithine concentrations but didn’t affect insulin release. 

Based on these findings, we can conclude that ornithine isn’t a potent anabolic agent. Even so, it has other benefits you should be aware of. 

Ornithine May Decrease Anxiety and Fatigue

Fatigue, irritability, lethargy, and loss of appetite are all common signs of ammonia buildup in the body. Ornithine reduces ammonia levels and hence may attenuate these symptoms. 

As we already discussed, this amino acid lower cortisol levels and decreases fatigue. Additionally, it may help you get a better night’s sleep. 

What you may not know is that it also has anti-anxiety effects, as shown in a randomized controlled trial published in the Nutrition Journal. 

Another study, which was conducted on mice, has found that ornithine supplements reduced anxiety levels during a maze test. Although more research is needed, these findings suggest that has beneficial effects on the brain. 

It appears to be even more effective when combined with caffeine, according to a 2014 study in Preventive Nutrition and Food Science. Office workers who took 200 milligrams of ornithine and 200 milligrams of caffeine in the morning had a better mood than those who used caffeine alone. 

As the researchers note, caffeine and ornithine have a synergistic effect and may decrease hypothalamic-pituitary-adrenal (HPA) axis activity. This could lead to reduced stress and increased feelings of well-being. 

Does L-Ornithine Improve Liver Health?

This non-essential amino acid may improve liver function by keeping ammonia levels low. It’s particularly beneficial for people with liver disorders.  

A study published in the Journal of Hepatology investigated the effects of l-ornithine and l-aspartate on patients with cirrhosis and chronic hepatic encephalopathy, a liver condition that affects the brain. 

Subjects who took this supplement experienced a greater improvement in mental health compared to the placebo group. The study participants didn’t report any side effects. 

However, other studies indicate that there’s enough evidence to confirm the efficacy of l-ornithine for preventing or treating hepatic encephalopathy.

Ornithine Side Effects and Health Risks 

Ornithine supplements are generally safe when administered in appropriate doses. In some cases, it may cause diarrhea, stomach pain, and other gastrointestinal symptoms. 

Dosages above 10 milligrams per day are more likely to cause digestive distress, restlessness, and sleep problems. There is also a risk of retina toxicity due to long-term, high-dose ornithine, according to the British Journal of Nutrition. 

Like with most supplements, it’s best to stick to the daily recommended dosage and stop using the product if you notice any side effects. 

Dosage Recommendations 

Most studies used dosages of 2 to 6 grams of ornithine per day. As discussed above, dosages higher than 10 milligrams may cause digestive discomfort and other minor adverse effects. 

The daily recommended dosage depends on your age and overall health. If you have liver disease, you may benefit from slightly higher doses. In this case, stay on the safe side and talk with your doctor. 

WebMD recommends athletes to take 1 gram of ornithine twice a day for one week and then switch to 3 grams per day before exercise or competitions. Another option is to take 1 gram of this amino acid and 1 gram of l-arginine daily. 

Should You Take Ornithine Supplements?

Clinical evidence confirms that ornithine reduces stress and fatigue due to its role in the urea cycle. But your body produces this amino acid on its own — and you don’t need high doses to reap the benefits. 

All in all, this isn’t the most potent supplement on the market. If you’re feeling tired or stressed out, there are better options available. 

Vintage Blast™, for instance, might be exactly what you need to crush your workout. 

Our two-stage pre-workout formula combines B vitamins, caffeine, electrolytes, carnitine, and other amino acids for explosive energy with no crashes. Plus, it’s GMO-free and contains zero sugar. 

Also, remember that what you eat matters most. After all, you’re getting your energy from food. 

If you’ve been on a diet for a while, consider adding more protein or healthy fats to the mix. Both nutrients serve as a source of fuel and support your training goals. 

Have you ever used ornithine supplements? Did you notice any difference? Share your experience below!