Eating Small Fish May Prolong Life in Women

Japanese women who regularly eat small fish whole have lower levels of mortality than women who don’t, according to a new study.

Given that small fish like juvenile anchovies and sardines are high in calcium, vitamin A and D, researchers from the Nagoya University School of Medicine posit that these nutrients may help reduce tumor development and cancer mortality.

These apparent benefits, however, were not seen as strongly in the male participants of the study.

The results were published in Public Health Nutrition.

Plenty more fish in the quay

“Previous studies have revealed the protective effect of fish intake on health outcomes, including mortality risks. However, few studies have focused on the effect of the intake of small fish specifically on health outcomes,” said lead researcher Dr. Chinatsu Kasahara of the Nagoya University School of Medicine. “I was interested in this topic because I have had the habit of eating small fish since childhood. I now feed my children these foods.”

To investigate further, Kasahara and their team accessed data from an ongoing Japanese health cohort. They identified 80,802 participants (42.77% males, 57.23% females, average age: 54.7) who had completed a dietary questionnaire.

The team then compared the health information and mortality levels of the participants between their first data entry and another entry after an average follow-up time of nine years.

Over that time, 2,482 of the participants died, 1,495 of whom from cancer, 340 from cardiovascular disease and 647 from other causes.

The female participants who reported consuming small fish every day, however, had significantly lower levels of all-cause and cancer mortality than other participants, even after considering the intake of larger fish.

Women who ate small fish 1-3 times a month, 1-2 times a week or 3 times or more a week had 0.68, 0.72 and 0.69 times the risk of all-cause mortality, respectively, and 0.72, 0.71 and 0.64 times the risk of cancer mortality, compared to those who rarely eat small fish.

Even after adjusting the data for lifestyle factors, body mass index scores and adherence to the general Japanese diet (a proxy score of healthy eating), the apparent benefits of small fish were still significant in the women who ate them.

This wasn’t quite the case for the men in the study, though. While a similar trend was observed between small fish consumption and lower mortality, the link was deemed less statistically significant.

The reasons for this apparent gender divide remain unclear, but the researchers suggest the relatively limited number of male subjects in the study may have hampered the group’s results.

In their paper, Kasahara and their colleagues also admit to another of the study’s flaws: a large proportion of participants (40.8%) only answered the questionnaire on seafood consumption once. As these participants could well have changed their dietary habits over the following nine years, the assertion that their health outcomes are tied to their initial penchant for small fish may be tenuous.

Nonetheless, the researchers argue that, at least in Japan, regularly eating small fish may well reduce the risk of all-cause and cancer mortality in women.

Those curious about taking a bite of these snack-size swimmers have been encouraged to do so.

“Small fish are easy for everyone to eat, and they can be consumed whole, including the head, bones, and organs,” Kasahara said. “Nutrients and physiologically active substances unique to small fish could contribute to maintaining good health. The inverse relationship between the intake of small fish and the mortality risk in women underscores the importance of these nutrient-dense foods in people's diets.” 

This article is a rework of a press release issued by the Nagoya University School of Medicine. Material has been edited for length and content.

Reference: Kasahara C, Tamura T, Wakai K, et al. Association between consumption of small fish and all-cause mortality among Japanese: the Japan Multi-Institutional Collaborative Cohort Study. Pub Heal Nutri 2024 Jan;27(1):e135. Doi: 10.1017/S1368980024000831