The number of people with dementia globally is forecast to increase as the world population ages [1], which will have implications for families and their health care, social care, and care costs. In the 11th edition (2019) of the International Classification of Diseases (ICD) systems, released by the WHO, dementia is referred to as a subgroup of “neurocognitive disorders” [2]. A diagnosis of dementia requires impairment in at least two cognitive domains (such as memory, executive functioning, attention, language, social cognition and judgment, psychomotor speed, and visuoperceptual or visuospatial functioning),
In 2020, the Lancet Commission on dementia prevention, intervention, and care estimated that 40% of dementia cases were associated with 12 potentially modifiable risk factors: hypertension, hearing impairment, smoking, obesity, depression, physical inactivity, diabetes, low social contact, excessive alcohol consumption, traumatic brain injury, air pollution, and less education [3]. From the above list of risk factors, it is obvious that at least indirectly, diet may impact dementia risk through its influence on hypertension, diabetes, and obesity. But might diet also have a more direct role? According to a recent publication by Sala-Vila and colleagues [4], researchers from institutions and universities in the US and Spain, the answer is yes.
This conclusion is based on an analysis of plasma levels of polyunsaturated fatty acids from nearly 300,000 middle-aged participants (mean age, 56.8 ± 8.1) of the UK Biobank who were free of dementia at baseline. During the mean follow-up period of ~15 years, a total of 5,799 incident dementia cases were identified. Compared to participants in the lowest quintile of plasma linoleic acid concentrations, those in the highest quintile were 18% less likely to develop dementia. Linoleic acid is the predominant fatty acid in most seed oils, especially oils such as soybean oil and corn oil. The results of this analysis were statistically significant even after adjusting for approximately 20 potentially confounding variables.
In contrast to linoleic acid, participants in the highest plasma quintile of non-linoleic acid polyunsaturated fatty acids, were 21% more likely to develop dementia. One of the major non-linoleic acid polyunsaturated fatty acids is arachidonic acid. Concern has been raised that consuming linoleic acids will raise arachidonic acid levels, but in most people, the in vivo conversion of the former into the latter is negligible [5]. Arachidonic acid is found in animal foods, not plant foods [6]. Interestingly, carriers of genetic variants of enzymes that promote greater transformation of linoleic acid into arachidonic acid are at higher risk for Alzheimer’s disease, the most common cause of dementia [7].
Clearly, the results of a single analysis of one cohort, no matter how large, are insufficient for drawing conclusions about the impact of linoleic intake on dementia risk. However, this study is one among several others reporting similar findings. At a time when there is some confusion among the public about the health benefits of seed oils, findings that linoleic acid may exert an important non-cardiovascular disease benefit are particularly notable.
References:
1. E. L. Ferguson, Zimmerman S. C., Jiang C., Choi M., Swinnerton K., Choudhary V., et al. Low- and high-density lipoprotein cholesterol and dementia risk over 17 years of follow-up among members of a large health care plan, Neurology. 101 (21) (2023) e2172-e84.
2. World Health Organization: International Classification of Diseases, Eleventh Revision (ICD-11), Licensed under Creative Commons Attribution-NoDerivatives 3.0 IGO licence (CC BY-ND 3.0 IGO). 2019/2021.
3. G. Livingston, Huntley J., Sommerlad A., Ames D., Ballard C., Banerjee S., et al. Dementia prevention, intervention, and care: 2020 report of the Lancet Commission, Lancet. 396 (10248) (2020) 413-46.
4. A. Sala-Vila, Tintle N., Westra J., DeJong E., Clark T., Miller P., et al. Plasma n6 polyunsaturated fatty acid levels and risk for dementia: A prospective observational study from the UK Biobank, Am. J. Clin. Nutr. (2026) 101220.
5. B. S. Rett, Whelan J. Increasing dietary linoleic acid does not increase tissue arachidonic acid content in adults consuming Western-type diets: a systematic review, Nutr Metab (Lond). 8 (2011) 36.
6. B. J. Meyer, Mann N. J., Lewis J. L., Milligan G. C., Sinclair A. J., Howe P. R. Dietary intakes and food sources of omega-6 and omega-3 polyunsaturated fatty acids, Lipids. 38 (4) (2003) 391-8.
7. S. Hammouda, Ghzaiel I., Khamlaoui W., Hammami S., Mhenni S. Y., Samet S., et al. Genetic variants in FADS1 and ELOVL2 increase level of arachidonic acid and the risk of Alzheimer’s disease in the Tunisian population, Prostaglandins Leukot. Essent. Fatty Acids. 160 (2020) 102159.
This blog is supported by SNI Global and U.S. Soy.
