The Cognitive Ageing Problem
Normal cognitive ageing involves gradual declines in processing speed, working memory, and executive function beginning in the fourth decade of life. These changes are driven by multiple mechanisms: reduced neuroplasticity (lower BDNF and NGF levels), increased neuroinflammation, mitochondrial dysfunction, and accumulation of amyloid and tau proteins.
The distinction between normal cognitive ageing and pathological decline (mild cognitive impairment and Alzheimer's disease) is one of degree, not kind — the same mechanisms are involved, but at different intensities. This means interventions that support the underlying mechanisms of healthy ageing may also reduce the risk of pathological decline.
Three functional mushrooms have the strongest evidence base for cognitive protection in older adults: lion's mane, reishi, and cordyceps — each working through different but complementary mechanisms.
Lion's Mane: NGF and Neuroplasticity
Lion's mane mushroom stimulates nerve growth factor (NGF) production — a protein that supports the survival and maintenance of neurons, particularly cholinergic neurons in the basal forebrain that are critical for memory and attention. These are the neurons that degenerate in Alzheimer's disease.
The landmark human trial (Mori et al., 2009) found that 16 weeks of lion's mane supplementation significantly improved cognitive scores in older adults with mild cognitive impairment. A 2020 study found that lion's mane extract reduced amyloid-beta accumulation in a mouse model of Alzheimer's disease. A 2023 randomised controlled trial in healthy older adults (65–85) found that 12 weeks of lion's mane supplementation improved scores on multiple cognitive domains compared to placebo, with the greatest effect on memory and processing speed.
Reishi: Neuroprotection and Immune Regulation
Reishi mushroom has two mechanisms relevant to cognitive ageing: direct neuroprotection (ganoderic acids reduce neuroinflammation and oxidative stress in neurons) and immune regulation (beta-glucans modulate the immune response, reducing the chronic low-grade inflammation that drives cognitive decline).
Neuroinflammation — chronic activation of microglia (the brain's immune cells) — is increasingly recognised as a central driver of both normal cognitive ageing and Alzheimer's disease. Reishi's anti-inflammatory effects in the brain are well-documented in animal models; human trials specifically in older adults are more limited but consistent with the animal data.
Cordyceps: Mitochondrial Function and Energy
Mitochondrial dysfunction — reduced efficiency of cellular energy production — is a key mechanism of both cognitive ageing and physical ageing. Cordyceps enhances ATP production and mitochondrial efficiency through cordycepin and adenosine mechanisms. The 2010 clinical trial found a 7% improvement in VO2max in elderly subjects after 12 weeks of cordyceps supplementation — a measure that reflects mitochondrial function throughout the body, including the brain.
The practical implication for older adults: cordyceps addresses the energy deficit that underlies both physical fatigue and cognitive fatigue in ageing. Many older adults report that cognitive difficulties are worst when they are physically tired — cordyceps may address both simultaneously.
Practical Guidance
For older adults seeking cognitive protection, the evidence supports a combination approach: lion's mane (3–5g/day) for NGF-mediated neuroprotection, reishi (1.5–3g/day) for neuroinflammation and sleep, and cordyceps (1–3g/day) for mitochondrial function and energy. Effects are cumulative and typically emerge at 4–12 weeks of consistent supplementation. All three are well-tolerated in older adults, with no significant drug interactions at standard doses.