Olive oil - 7 grams a day can prevent dementia!

In a recent study published in JAMA Network Open, researchers used a large prospective cohort study to examine the long-term associations between olive oil consumption and the risk of dementia-related death. Their cohort of 92,383 American adults found that consuming seven or more grams of olive oil per day was associated with a 28% reduction in dementia-related deaths, compared with participants who did not consume olive oil. This study highlights the importance of diet in age-related cognitive decline and mortality. It suggests that olive oil consumption may be an effective strategy for reducing the risk of dementia-related death.

Food May Influence Age-Related Cognitive Decline

Dementia is an umbrella term for a range of conditions that affect a person’s ability to remember details and events, process data, or make rational decisions, and affects more than 55 million people and accounts for more than 33% of all adult deaths worldwide. Despite recent advances in medicine that have led to an overall decline in deaths from cardiovascular disease (stroke and heart disease), the prevalence of dementia and dementia-related deaths are alarmingly increasing, with more than 10 million new cases reported each year.

Extensive research, particularly during and immediately following the coronavirus disease 2019 (COVID-19) pandemic, has revealed complex but compelling links between good health habits (especially sleep, physical activity, and diet) and chronic disease outcomes, with dietary interventions increasingly being explored for their beneficial effects on age-related cardiovascular and cognitive outcomes. The Mediterranean dietary pattern and its derivatives (e.g., Dietary Approaches to Stop Hypertension – DASH), inspired by the traditional eating habits of people in southern Spain, southern Italy, and Crete, are gaining global popularity due to their observed anti-inflammatory and neuroprotective benefits.

Olive oil is a fundamental part of the Mediterranean diet and the main source of oils and fats in this diet. This oil is known for its rich content of monounsaturated fatty acids, vitamin E and polyphenols, antioxidant-rich compounds that have been shown to delay the onset of dementia and reduce the risk of Alzheimer's disease. Previous studies on olive oil consumption have shown that regular consumption of olive oil, combined with a healthy diet rich in fresh fruits and vegetables and low in processed fats and meat, can effectively improve cognitive outcomes compared to occasional or irregular consumption. Unfortunately, most studies examining the potential benefits of olive oil have been conducted in Mediterranean countries, with a lack of data from other countries.

In this study, the researchers examined the long-term effects of olive oil consumption in a large US cohort to investigate possible improvements in dementia-related mortality outcomes in this population. They also examined how these outcomes varied with diet quality (adherence to a healthy diet) in combination with regular olive oil consumption. Their prospective study included participants (N = 92,383) from two existing long-term studies - the Nurses' Health Study I (NHS; cohort of female participants) and the Health Professionals Follow-up Study (HPFS; cohort of male participants).

Data for the study were collected over a 33-year period from 1990 to 2023 and included biennial assessments of participants’ lifestyle habits and medical histories. NHS and HPFS participants with a clinical history of CVD, cancer, unrealistic daily energy intake or incomplete olive oil intake data were excluded from subsequent analyses. The questionnaire (the Food Frequency Questionnaire [FFQ]) was validated by experts in a smaller test cohort and included over 130 items. A modified version of the Alternative Mediterranean Diet (AMED) index was used to assess diet quality.

"Participants were asked how often they consumed certain foods, including types of fats and oils, used for cooking or added to meals over the past 12 months. Total olive oil consumption was determined by summing the responses to three questions related to olive oil consumption (i.e. olive oil used for salad dressing, added to food or bread, and olive oil used for baking and frying at home)."

Because the apolipoprotein E ε4 allele (APOE ε4) is almost always associated with an increased risk of dementia, particularly for homozygous carriers, blood (or mucosal scraping) samples from a subset of participants (N = 27,296) were collected for APOE genotyping. Deaths and covariates (smoking status, body weight, physical activity level, menopausal status, medication and dietary supplement use) were obtained from the National Death Index and biennial questionnaires, respectively. For statistical validation, age-stratified Cox proportional hazards models were used to calculate the association between olive oil consumption and dementia-related mortality.

Research results and conclusions

Of the 92,383 participants (65.6% women) included in the study, 4,751 dementia-related deaths were reported over a 33-year follow-up period. Mean olive oil intake across cohorts was 1.3 g/day, with adherence to the Mediterranean diet estimated at 4.5 and 4.2 points for the NHS and HPFS cohorts, respectively.

"Olive oil consumption was inversely associated with dementia-related mortality in age-stratified and multivariable-adjusted models. Compared with participants with the lowest olive oil consumption, the pooled HR for dementia-related death among participants with the highest olive oil consumption (>7 g/day) was 0.72 (95% CI, 0.64-0.81), after adjusting for sociodemographic and lifestyle factors."

This study highlights that consistent olive oil consumption, when consumed as part of a healthy balanced diet (here, the Mediterranean diet), can significantly reduce the risk of age-related dementia-related mortality, particularly among women. Surprisingly, consuming more than 7.0 g/day of olive oil was able to reduce the risk of dementia even in the absence of a Mediterranean diet, suggesting its independent ability to slow the progression of cognitive decline.