Cognition

In depth

Cognition

⏱ 3 min read

Cognition is not a single capacity but a heterogeneous set of mental processes that includes memory (working, episodic, semantic), attention (sustained, divided, executive), processing speed, executive function (planning, cognitive flexibility, inhibitory control), language, and visuospatial skills; each of these domains depends on partially distinct brain circuits and is affected by nutritional and lifestyle interventions in a non-uniform way: an intervention may improve memory without touching processing speed, or improve sustained attention without affecting executive function, an important nuance for interpreting the evidence on "nootropics" and cognitive supplements.

The brain as a metabolically expensive organ

The brain consumes approximately 20 percent of the body's total energy despite accounting for only 2 percent of body mass; it depends almost exclusively on glucose (and secondarily on ketone bodies) as fuel, which makes it particularly sensitive to disturbances in glycemic metabolism and mitochondrial function; it has specific requirements for polyunsaturated fatty acids (especially omega-3 DHA, which makes up a significant proportion of neuronal membranes), choline (a precursor of acetylcholine and membrane phospholipids), iron, B vitamins (especially B12, folate, and B6 for homocysteine metabolism), and several micronutrients involved in monoaminergic metabolism.

These requirements explain why classic nutritional deficiencies (iron-deficiency anemia, B12 deficiency, severe vitamin D deficiency, thiamine deficiency in alcoholism) have relevant cognitive manifestations, and why correcting these subclinical deficiencies can significantly improve cognitive function in people with low levels.

Interventions with clinical support for healthy cognition

In healthy adults without cognitive impairment, several interventions have modest but consistent clinical support for improving specific cognitive domains:

Caffeine and L-theanine (combination): caffeine improves sustained attention and vigilance with clear, dose-dependent efficacy; the combination with L-theanine from green tea produces a "calm alertness" profile with better cognitive performance and fewer adverse effects (nervousness, palpitations) than caffeine alone.

Creatine: besides its use in strength sports, several trials have documented modest improvements in working memory and processing speed, especially in situations of cognitive stress (sleep deprivation, altitude, demanding tasks).

Omega-3 EPA/DHA: DHA is a major structural component of neuronal membranes; adequate intake (especially from oily fish) is associated with cognitive preservation in aging, although specific supplementation in healthy adults has modest effects.

Bacopa monnieri: with several consistent trials showing memory improvement with supplementation for 12 weeks or more.

Citicoline and alpha-GPC: choline/acetylcholine precursors with modest clinical data on improving attention and memory.

Interventions for mild cognitive impairment and brain aging

In older adults with subjective or mild cognitive impairment, several interventions have stronger support:

B vitamins (folate, B12, B6): in people with elevated plasma homocysteine, supplementation significantly reduces brain atrophy and improves some cognitive parameters according to the VITACOG trial and later replications.

Vitamin D: severe deficiency is associated with a higher risk of cognitive decline; correction has modest but consistent effects.

Spermidine (from wheat germ or enriched extracts): several trials in mild cognitive impairment have shown modest improvements after supplementation for months.

Lion's mane (Hericium erinaceus): the Japanese Mori 2009 trial showed significant improvements in mild cognitive impairment with 3 g/day for 16 weeks.

Citicoline, phosphatidylserine, ginkgo biloba: with moderate data, especially for impairment of cerebrovascular origin.

What probably matters more than supplements

The strongest evidence on long-term cognitive preservation points not to supplements but to a set of lifestyle factors with cumulative effects:

• Regular aerobic exercise: increases BDNF (brain-derived neurotrophic factor), improves hippocampal neurogenesis, and is associated with preservation of brain volume with age.
• Good-quality, adequate sleep: during deep sleep the brain clears toxic metabolites via the glymphatic system and consolidates memory.
• Continuous cognitive stimulation and lifelong learning: builds cognitive reserve that delays the clinical manifestation of underlying brain pathology.
• Active social life and meaningful ties: robust predictors of cognitive preservation.
• Control of cardiovascular risk factors (hypertension, diabetes, dyslipidemia, smoking): cerebral vascular health is one of the main determinants of long-term cognition.
• Mediterranean or MIND diet: supported by prospective studies and by trials such as PREDIMED for cognitive preservation.

When to see a doctor

Significant and progressive cognitive complaints, especially in people over 65, require medical evaluation (not self-supplementation) to rule out treatable causes (depression, B12 deficiency, hypothyroidism, sleep apnea, medication with cognitive effects, true mild cognitive impairment, incipient dementia). Effective intervention depends on the correct diagnosis.

References

1. Smith, A.D. et al. (2010). Homocysteine-lowering by B vitamins slows the rate of accelerated brain atrophy in mild cognitive impairment: a randomized controlled trial (VITACOG). PLoS One 5, 9. doi:10.1371/journal.pone.0012244
2. Mori, K. et al. (2009). Improving effects of the mushroom Yamabushitake (Hericium erinaceus) on mild cognitive impairment: a double-blind placebo-controlled clinical trial. Phytother Res 23, 3. doi:10.1002/ptr.2634
3. Stough, C. et al. (2008). Examining the nootropic effects of a special extract of Bacopa monniera on human cognitive functioning: 90 day double-blind placebo-controlled randomized trial. Phytother Res 22, 12. doi:10.1002/ptr.2537
4. Erickson, K.I. et al. (2011). Exercise training increases size of hippocampus and improves memory. Proc Natl Acad Sci USA 108, 7. doi:10.1073/pnas.1015950108
5. Livingston, G. et al. (2020). Dementia prevention, intervention, and care: 2020 report of the Lancet Commission. Lancet 396, 10248. doi:10.1016/S0140-6736(20)30367-6