What are nitric oxide supplements?
Nitric oxide supplements do not contain nitric oxide gas directly, but rather, they contain precursor ingredients that the body converts into nitric oxide. The most common precursors are the amino acids L-arginine and L-citrulline, and nitrates from sources like beetroot extract. These supplements are popular among athletes and fitness enthusiasts who hope to boost nitric oxide production to increase blood flow, enhance exercise performance, and reduce muscle soreness. By promoting vasodilation—the widening of blood vessels—nitric oxide is thought to improve the delivery of oxygen and nutrients to muscles during a workout. Beyond athletic performance, these supplements are also marketed for heart health and erectile dysfunction, though research on their effectiveness for these claims is often mixed and preliminary.
Common side effects to watch for
For most healthy individuals, taking nitric oxide precursors in appropriate dosages is considered relatively safe, with side effects typically being mild to moderate. However, exceeding recommended doses, particularly with L-arginine, can increase the likelihood of experiencing adverse effects.
Gastrointestinal issues
One of the most frequently reported side effects is gastrointestinal distress, which can include:
- Nausea and vomiting
- Bloating and stomach pain
- Diarrhea
These symptoms are more likely with higher doses, and some people may have a lower tolerance than others. Taking smaller, divided doses throughout the day can sometimes help manage these effects.
Effects on blood pressure
Nitric oxide's primary function is to relax and widen blood vessels to increase blood flow, which naturally lowers blood pressure. While beneficial for those with high blood pressure, this effect can be dangerous for individuals with hypotension (already low blood pressure). A sudden drop in blood pressure can cause dizziness, lightheadedness, and fainting.
Other potential side effects
Other potential side effects can include:
- Headaches
- Heart palpitations
- Dizziness
- Allergic reactions, such as itching or difficulty breathing
Comparison of nitric oxide supplement precursors
| Feature | L-Arginine | L-Citrulline | Nitrate (e.g., Beetroot) |
|---|---|---|---|
| Mechanism | Direct precursor to NO, but is largely metabolized before reaching systemic circulation. | Bypasses liver metabolism, more effectively increasing plasma L-arginine and thus NO levels. | Reduced by oral bacteria to nitrite, which is then converted to NO. |
| Effectiveness for Performance | Mixed results in studies; less reliable due to high metabolism. | Shows more consistent benefits for endurance and reducing muscle soreness. | Has been shown to improve exercise performance, particularly in untrained individuals. |
| GI Side Effects | High doses (>9g) are commonly associated with gastrointestinal discomfort. | Doses >9g/day may cause digestive discomfort. Often better tolerated than L-arginine. | Generally well-tolerated, but can cause benign red or pink urine and stool. |
| Overall Safety Profile | Considered safe short-term for most, but with a higher potential for GI side effects. | Considered generally safe, with a better GI tolerance profile. | Safe and effective when sourced naturally or from reputable supplements. |
Who should avoid nitric oxide supplements?
Certain populations should exercise extreme caution or avoid these supplements entirely due to significant health risks.
- Individuals with heart conditions: People with existing heart conditions, especially those who have recently had a heart attack, face serious risks. One study found that individuals taking L-arginine after a heart attack had an increased risk of death.
- Individuals with low blood pressure (hypotension): As vasodilators, these supplements can further lower blood pressure, which is dangerous for those already experiencing hypotension.
- Individuals with liver or kidney disease: These supplements can worsen existing conditions like liver cirrhosis or cause elevated potassium levels in those with kidney disease.
- People with the genetic condition GAMT: This deficiency affects the body's ability to convert arginine into creatine, so supplements containing arginine should be avoided.
- Those taking certain medications: The supplements can interact with blood pressure, diabetes, and erectile dysfunction medications, potentially causing dangerously low blood pressure or blood sugar.
- Pregnant or breastfeeding women: Insufficient research exists to confirm the safety of nitric oxide supplements for these groups.
- People with active herpes simplex virus: L-arginine may trigger viral outbreaks.
Are natural alternatives safer?
Many health professionals advocate for boosting nitric oxide production through diet rather than supplements. Foods rich in nitrates, L-arginine, and L-citrulline offer a safer and more reliable way to naturally support nitric oxide levels. Examples include leafy greens (arugula, spinach), beetroot, watermelon, and garlic. These natural sources provide nitrates in a more balanced way, accompanied by other beneficial nutrients, minimizing the risk of adverse side effects associated with high doses from concentrated supplements.
The supplement industry and safety
It is important to remember that dietary supplements are not regulated by the FDA with the same stringency as prescription medications. This means product contents and purity can vary widely. To mitigate this risk, consumers should seek out products that have been independently tested and certified by third-party organizations such as NSF International, USP, or ConsumerLab.com.
Conclusion: Navigating the risks and benefits
Deciding whether it's bad to take nitric oxide supplements involves weighing the potential, often modest benefits against well-documented risks, particularly for vulnerable populations. While some may experience improved exercise performance with minimal side effects, the evidence supporting these benefits is not always robust, especially for highly trained athletes. For those with underlying health conditions, a history of heart issues, or those taking certain medications, the risks, including a dangerous drop in blood pressure or exacerbation of existing illnesses, clearly outweigh the unproven benefits. A food-first approach, incorporating nitrate-rich foods and regular exercise, remains the safest and most recommended method for naturally enhancing nitric oxide levels in the body. Before starting any new supplement regimen, a consultation with a healthcare provider is essential to ensure safety and avoid potential complications. For further information on supplements and their safety, authoritative resources like the Office of Dietary Supplements at the National Institutes of Health are highly recommended. [https://ods.od.nih.gov/]
