The Nitric Oxide Factor

Why this topic matters

Most people associate heart health with cholesterol, blood pressure and lifestyle. These are important factors, but they often miss the underlying signals that determine vascular health.

One of the most critical and least understood is nitric oxide.

At Functional Medicine Associates, we regularly see clients whose symptoms, lab results or cardiovascular risk profiles do not fully align with conventional explanations. In many of these cases, nitric oxide production and endothelial function are central to the clinical picture.

If you are reading this after seeing one of our social posts, or if you are searching for answers to persistent symptoms that have been labelled “normal”, you are not alone.

‍

You may relate if:

• Your blood pressure has crept up over the years, but your GP says it is still within range
  
  
• You are taking supplements or eating well, but your energy and recovery remain poor
  
  
• You feel lightheaded after standing, or experience cold hands and feet
  
  
• You have been told your bloods are fine, but you do not feel fine
  
  

These are often signs that nitric oxide  and the wider vascular signalling system  may not be functioning as it should.

‍

What is nitric oxide?

Nitric oxide (NO) is a gas produced naturally in the body. It plays a key role in maintaining the health of the endothelium, the thin layer of cells lining your blood vessels.

When nitric oxide is functioning optimally, it helps to:

• Regulate blood pressure and vascular tone
  
  
• Support healthy blood flow and oxygen delivery
  
  
• Prevent excessive clot formation
  
  
• Limit oxidative stress and vascular inflammation
  
  
• Improve metabolic and mitochondrial efficiency
  
  

Although small and short-lived, nitric oxide acts as a vital signalling molecule across multiple body systems. When production drops, the cardiovascular system loses its flexibility and responsiveness. This can lead to increased strain on the heart, impaired tissue oxygenation, and systemic inflammation  even if cholesterol levels appear within range.

‍

Are you concerned about your cardiovascular resilience?

Preventative Cardiology has been part of our offering for the last 20 years blending the best of functional medicine with leading cardiologists who use their expertise with advanced imaging. Thus allowing a precision and personalised approach to heart health.

‍

Why nitric oxide becomes depleted

We rarely see nitric oxide depletion caused by a single factor. In most cases, it reflects a broader pattern of physiological stress, lifestyle mismatch or biological ageing. Some of the most common contributing factors include:

1. Sedentary patterns
Regular movement stimulates nitric oxide production. Physical activity, particularly resistance training and aerobic intervals, triggers mechanical signals within the endothelium that lead to NO release. A sedentary lifestyle significantly reduces this stimulus.

2. Poor oral microbiome function
Few people realise that nitric oxide synthesis begins in the mouth. Dietary nitrates are first converted into nitrite by specific bacteria on the tongue. Antibacterial mouthwashes, poor oral hygiene, or disrupted microbiota can impair this process.

3. Low intake of nitrate-rich foods
Leafy green vegetables such as spinach, rocket and beetroot are naturally high in nitrates. If these are missing from the diet, or if digestive dysfunction affects absorption, nitric oxide pathways may be compromised.

4. Chronic stress and low vagal tone
Sustained sympathetic nervous system activation (the “fight or flight” state) suppresses nitric oxide production. This is often seen in individuals with low heart rate variability, poor sleep quality, and long-term psychological or metabolic stress.

5. Inflammation and glycaemic instability
Insulin resistance, high blood sugar and systemic inflammation damage the endothelium. This disrupts nitric oxide signalling and accelerates vascular ageing, even in the absence of diagnosed cardiovascular disease.

‍

What we see in clinic

Nitric oxide dysfunction often appears as part of a wider systems pattern. Some common client profiles include:

• A 52-year-old male with normal lipids and good fitness, but cold extremities and reduced performance during training. Testing revealed impaired NO production and subtle mitochondrial inefficiency.
  
  
• A 45-year-old perimenopausal woman with brain fog, blood pressure swings and poor stress tolerance. Symptoms linked to poor vagal tone, reduced endothelial signalling and early hormonal transition.
  
  
• A corporate executive in their late 30s with a strong family history of heart disease, high-output lifestyle and “fine” labs. Further investigation showed early endothelial dysfunction, low dietary nitrates and compromised recovery rhythm.
  
  

In all of these cases, nitric oxide was not the cause, but a key clue within the system, pointing us to the deeper interaction between stress, inflammation, genetics and environment.

‍

Understanding functional medicine

Functional medicine is a systems-based model of care that focuses on how and why illness occurs - not just what to name it.

It aims to restore optimal function by identifying and addressing the root causes of health disruption. Rather than focusing on symptoms in isolation, we investigate how different systems in the body interact, and what might be driving those systems out of balance.

In cardiovascular health, for example, this means asking:

• How resilient is the endothelium?
  
  
• What is the inflammatory and metabolic load?
  
  
• How is the autonomic nervous system regulating vascular tone?
  
  
• Are nitric oxide pathways supported or suppressed by diet, genetics and lifestyle?
  
  

At Functional Medicine Associates, this is how we approach nitric oxide. Not as a molecule to “boost”, but as part of a dynamic physiological conversation.

We support clients both from our London clinic and remotely across the UK. Whether you are dealing with unexplained symptoms, subclinical patterns or simply want a clearer picture of your health, this model is designed to offer answers that conventional frameworks often miss.

‍

Nitric oxide supplements: what we recommend  and when

Nitric oxide supplements have become more widely used in recent years, with growing interest in beetroot extracts, citrulline, arginine and polyphenol compounds. While they can be useful tools, we do not treat them as quick fixes.

Some clinical considerations include:

• Beetroot extract can be effective before exercise or as part of a broader vascular support strategy. It may not be well tolerated in individuals with oxalate sensitivity.
  
  
• Citrulline and arginine support NO synthesis, but only where cofactors are sufficient and endothelial function is intact.
  
  
• Polyphenols may help preserve nitric oxide once produced, particularly in those with oxidative stress or poor antioxidant capacity.
  
  

We only introduce nitric oxide supplements after assessing the system’s ability to respond. If oral microbiome function is impaired, or vagal tone is low, the impact of supplements is often minimal without foundational support.

‍

How we support nitric oxide in clinic

Our assessment process is highly individualised and typically includes:

• Dietary analysis to evaluate nitrate intake, micronutrients and flavonoid diversity
  
  
• Functional testing to measure inflammatory tone, insulin resistance, lipid quality and endothelial stress
  
  
• DNA analysis for key nitric oxide synthesis genes, including eNOS polymorphisms
  
  
• Oral and gut microbiome support, particularly where reflux, poor oral hygiene or dysbiosis is present
  
  
• Movement prescription based on resistance training and vascular conditioning
  
  
• Nervous system recalibration, using breathwork, HRV training.
  
  
• Supplementation, if clinically indicated, based on testing and physiological need
  
  

We do not follow protocols. We follow data. Each client is assessed within the full context of their biological, genetic and lifestyle profile.

‍

About Pete Williams and Functional Medicine Associates

Pete Williams is the founder and clinical director of Functional Medicine Associates. He holds postgraduate qualifications in sports science, endocrinology and molecular biology, and is one of the UK’s first fully certified functional medicine practitioners.

With over 20 years of clinical experience, Pete works at the intersection of complex systems medicine, performance physiology and human resilience. His work focuses on cardiovascular health, burnout, gut-brain interaction and metabolic repair.

Functional Medicine Associates supports clients both from our London-based clinic and online across the UK. We work with individuals who are ready to explore the next layer of their health  through investigation, education and systems-led intervention.

‍

What to do next

If you are looking for answers beyond “normal” test results If you want to understand your cardiovascular and metabolic health more deeply If you are ready to explore your nitric oxide function within a broader picture.

Make a clinic enquiry →

‍

You can also listen to the full podcast episode this article is based on:

Listen to the Functional Medicine Bite-Sized Podcast →

‍

Pete Williams
M.Med.Sci, CSCS, IFMCP
Founder, Functional Medicine Associates