The Role of Cholesterol

Why this misunderstood molecule is vital to your health

Cholesterol has been cast as the villain of modern cardiovascular medicine for decades. Yet this waxy, fat-like substance is not a toxin the body accidentally produces — it is a molecule the body deliberately manufactures, in almost every cell, because it is indispensable to life. The liver alone synthesises approximately 75–80% of the cholesterol in circulation. If cholesterol were simply dangerous, evolution would not have designed us to make so much of it.

"Cholesterol is so essential to human physiology that the body has multiple redundant systems to ensure it always has enough. The liver ramps up its own production whenever dietary intake falls short."

Why Was Cholesterol Demonised?

The concern, therefore, is not with cholesterol itself — which the body manages with precision — but with the conditions under which it becomes problematic: principally, chronic inflammation, oxidative stress, and the metabolic disruption caused by excess carbohydrate and insulin.

In the 1950s, American physiologist Ancel Keys proposed that dietary fat raised blood cholesterol and caused heart disease. His landmark Seven Countries Study appeared to prove it — but he had data from 22 countries and cherry-picked the 7 that supported his hypothesis. When he later received funding to test his theory properly, the results disproved it. Those findings were not widely published.

Then came a more deliberate intervention. Internal documents unearthed by researchers at UC San Francisco and published in JAMA Internal Medicine (2016) revealed that the sugar industry had quietly funded Harvard scientists in the 1960s to shift blame for heart disease onto fat and cholesterol — and away from sugar. The resulting article, published in the New England Journal of Medicine in 1967, declared there was "no doubt" that reducing fat was the only dietary intervention needed. The industry funding was not disclosed.

Once embedded in official guidelines, the hypothesis proved almost impossible to dislodge — especially after statin drugs arrived in the 1980s, building a pharmaceutical industry worth hundreds of billions on the premise that lower cholesterol means better health. The net result was decades of low-fat dietary advice, widespread cholesterol-phobia, and the replacement of fat in processed foods with sugar and refined carbohydrates — arguably the very thing driving the chronic disease epidemic the advice was meant to prevent.

Seven Essential Functions of Cholesterol

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Five Consequences of Long-Term Cholesterol Deficiency

While elevated oxidised cholesterol in the context of chronic inflammation is associated with cardiovascular risk, the opposite extreme — chronically low cholesterol — carries its own serious and underappreciated dangers. The following consequences have been documented in research literature.

• 1
  Hormonal Collapse and Reproductive Dysfunction

  Because all steroid hormones are synthesised from cholesterol, chronically low levels can result in deficiencies across the entire hormonal cascade — low testosterone in men, disrupted oestrogen and progesterone in women, impaired adrenal output of cortisol and DHEA. This can manifest as fatigue, low libido, infertility, irregular cycles, poor stress resilience and reduced vitality.

• 2
  Neurological and Cognitive Decline

  Low cholesterol has been linked in multiple studies to increased risk of depression, anxiety, memory impairment and, in some research, a higher incidence of dementia. Since cholesterol is critical for synapse formation and maintenance, a sustained shortfall can impair the brain's ability to maintain neural connections and produce neurotransmitters effectively. Some research has also found associations between very low cholesterol and increased risk of Parkinson's disease.

• 3
  Impaired Cell Membrane Integrity

  Every cell in the body depends on cholesterol to maintain its membrane structure. A chronic shortfall reduces membrane stability, impairing the cell's ability to regulate what passes in and out, to communicate with neighbouring cells, and to respond appropriately to hormonal signals. Over time, this affects every tissue and organ system in the body and can contribute to a generalised loss of cellular resilience.

• 4
  Compromised Immune Response

  Low cholesterol is associated with increased susceptibility to infection. Studies in hospitalised patients have found that low total cholesterol levels are a predictor of poorer outcomes in serious illness. The immune system's capacity to mount effective responses, including the neutralisation of bacterial toxins by LDL particles, is diminished when cholesterol availability is chronically low.

• 5
  Vitamin D Deficiency and Downstream Effects

  Since cholesterol is the substrate from which the body produces vitamin D under sunlight exposure, low cholesterol can impair this conversion pathway. Given that vitamin D deficiency is already widespread in northern latitudes, a low-cholesterol state compounds this risk — with downstream effects on immune function, bone density, mood regulation, insulin sensitivity and protection against certain cancers. This is a particularly relevant concern in the UK, where sun exposure is limited for much of the year.

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