In the news: Omega-3s Not Linked to Prostate Cancer & May Benefit Mental Function

Omega-3s not Linked to Prostate Cancer

In 2013, a widely publicized meta-analysis conducted by Brasky, et al reported an association between omega-3 fatty acid intake (EPA / DHA) and the risk of developing prostate cancer. However, a comprehensive new meta-analysis by Alexander, et al (1) does not support those earlier findings.

The results of the Brasky paper were met with some degree of skepticism by lipid researchers for several reasons. First, the omega-3s are known to have anti-inflammatory, pro-apoptotic and anti-proliferative effects on prostate cancer cells – effects suggesting that these long chain fats might inhibit prostate cancer development. In addition, no plausible mechanism by which omega-3s could contribute to prostate carcinogenesis has been identified.

The meta-analysis also found trans-fatty acids to be protective, contrary to the widely held position that consuming trans-fats increases the risk of heart disease and stroke.

Using a fixed-effects meta-analysis model to examine prospective nested case-control and case-cohort studies, Brasky, et al found significantly positive associations between EPA / DHA intake and prostate cancer incidence. At the time this meta-analysis was published, some experts suggested that using a random-effects statistical model might have delivered different results, as it accounts for variation both between studies and within individual studies.

The new paper by Alexander et al utilized a random-effects meta-analysis. It included prospective studies: 12 self-reported dietary intake studies (446,243 participants) and 9 biomarker studies (14,897 participants).

Employing the random-effects model – and even when using the same statistical model as Brasky, et al – no link between omega-3 fatty acids intake and prostate cancer risk was found. In fact, some trends observed by Alexander and colleagues suggest a potentially protective effect, though they did not achieve significance.

Omega-3s & Mental Flexibility in At-Risk Adults

Higher intake of the omega-3s might benefit cognitive function in healthy older adults at risk of Alzheimer’s, according to a cross-sectional study conducted by researchers at the University of Illinois (2).

The study examined the neural mechanisms that mediate the relationship between omega-3 fatty acids (EPA / DHA) and executive functions in 40 at-risk (APOE e4 carriers), cognitively healthy older adults aged 65-75. Carrying the e4 version of the APOE (apolipoprotein E) gene increases an individual's risk for developing late-onset Alzheimer disease.

The researchers hypothesized that higher blood levels of omega-3s are associated with better performance in a particular component of the executive functions, namely cognitive flexibility. Cognitive flexibility has been described as the mental ability to switch between thinking about two different concepts, and to think about multiple concepts simultaneously. It’s the ability to change what one is thinking about, how one thinks about it, and even what one thinks about it.

Participants with higher blood levels of the omega-3s fared better on tests assessing cognitive flexibility. Measured by MRI, these participants also had a greater volume of gray matter within regions of the prefrontal cortex called the anterior cingulate cortex – a region thought to be important for cognitive flexibility.

The findings suggest that consuming DHA and EPA might support mental flexibility by bolstering the size of the anterior cingulate cortex. According to the authors, the anterior cingulate cortex appears to mediate the relationship between the omega-3s and cognitive flexibility in cognitively intact adults at risk for cognitive decline.

References

1. Alexander DD, et al. Meta-analysis of long-chain omega-3 polyunsaturated fatty fcids (LCω-3PUFA) and prostate cancer. Nutr Cancer 31:1-12, 2015.
2. Zamroziewicz MK, et al. Anterior cingulate cortex mediates the relationship between O3PUFAs and executive functions in APOE e4 carriers. Front Aging Neurosci. Published online May 21, 2015.