The Secret to Longer Life? Scientists Uncover Unexpected Health Benefits of Eating Small Fish

Eating small fish whole can prolong life expectancy, a Japanese study finds. Credit: Chinatsu Kasahara

In Japan, people habitually eat small fish, such as whitebait, Atlantic capelin, Japanese smelt, and small dried sardines. Notably, it is common practice to consume small fish whole, including the head, bones, and organs, which are rich in micronutrients, such as calcium and vitamin A.

A new study from Nagoya University Graduate School of Medicine in Japan reveals that consuming small fish whole is associated with a reduced risk of death from cancer and all other causes in Japanese women. This finding, recently published in the journal Public Health Nutrition, suggests that incorporating small fish into diets may be a simple, but effective way to prolong life expectancy.

“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 the lead researcher, Dr. Chinatsu Kasahara. “I was interested in this topic because I have had the habit of eating small fish since childhood. I now feed my children these.”

Research Methodology

The research team investigated the association between the intake of small fish and mortality risk among Japanese people. The study included 80,802 participants (34,555 men and 46,247 women) aged 35 to 69 years nationwide in Japan. The participants’ frequency of the intake of small fish was assessed using a food frequency questionnaire at baseline. The researchers followed them for an average of nine years. During the follow-up period, 2,482 deaths from people included in the study were recorded, with approximately 60% (1,495 deaths) of them being cancer-related.

Significant Findings for Women

There was a significant reduction in all-cause and cancer mortality among women who habitually eat small fish. Women who eat 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, and 0.72, 0.71, and 0.64 times the risk of cancer mortality, compared to those who rarely eat small fish.

After controlling for factors that can affect mortality risk, such as participants’ age, smoking and alcohol consumption habits, BMI, and intake of various nutrients and foods, the researchers found that women in the study who eat small fish frequently were less likely to die from any cause. These findings suggest that incorporating small fish into their daily diet could be a simple but effective strategy to reduce the risk of mortality among women.

Men’s Health and Study Limitations

The risk of mortality from cancer and all causes in men showed a similar trend to that in women, although it was not statistically significant. The reasons for the lack of significance in men remain unclear, but the researchers posit that the limited number of male subjects or other factors not measured in the study, such as the portion size of small fish, may also matter. According to the researchers, the difference in the cancer type causing cancer mortality among the sexes may be related to a sex-specific association.

Implications and Future Research

Although acknowledging the need for additional research in other populations and a deeper understanding of the mechanisms involved, Kasahara is enthusiastic about the results. “While our findings were only among Japanese people, they should also be important for other nationalities,” she said.

In fact, previous studies have highlighted affordable small fish as a potentially important source of nutrients, especially in developing countries that suffer from severe nutrient deficiency. This study adds to the growing body of evidence supporting the health benefits of dietary practices that include eating small fish. As Kasahara explained, “Small fish are easy for everyone to eat, and they can be consumed whole, including the head, bones, and organs. 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.”

“The habit of eating small fish is usually limited to several coastal or maritime countries, such as Japan,” said co-author Associate Professor Takashi Tamura. “However, we suspect that the intake of small fish anywhere may be revealed as a way to prolong life expectancy. Further evidence is necessary to elucidate the potential role of the intake of small fish in mortality risk.”

Reference: “Association between consumption of small fish and all-cause mortality among Japanese: the Japan Multi-Institutional Collaborative Cohort Study” by Chinatsu Kasahara, Takashi Tamura, Kenji Wakai, Yudai Tamada, Yasufumi Kato, Yoko Kubo, Rieko Okada, Mako Nagayoshi, Asahi Hishida, Nahomi Imaeda, Chiho Goto, Jun Otonari, Hiroaki Ikezaki, Yuichiro Nishida, Chisato Shimanoe, Isao Oze, Yuriko N Koyanagi, Yohko Nakamura, Miho Kusakabe, Daisaku Nishimoto, Ippei Shimoshikiryo, Sadao Suzuki, Miki Watanabe, Etsuko Ozaki, Chie Omichi, Kiyonori Kuriki, Naoyuki Takashima, Naoko Miyagawa, Kokichi Arisawa, Sakurako Katsuura-Kamano, Kenji Takeuchi, Keitaro Matsuo and for the J-MICC Study Group, 3 May 2024, Public Health Nutrition.
DOI: 10.1017/S1368980024000831