Eating whole small fish helps reduce the risk of death from cancer and other causes

There are many factors that influence the risk of developing and dying from cancer. Research shows that one of these factors is our diet.

Previous studies have linked eating a healthy diet, such as the Mediterranean diet, to a reduced risk of dying from cancer. Conversely, eating an unhealthy diet high in sugar, salt, and ultra-processed foods may increase the risk of dying from cancer.

Researchers from the Nagoya University Graduate School of Medicine in Japan have found that eating small fish whole may reduce the risk of dying from cancer or any other cause in Japanese women.

The study was recently published in the journal Public Health Nutrition.

Significant reduction in cancer mortality with whole small fish consumption

For the study, the researchers analyzed food frequency questionnaire data from more than 80,000 participants — about 34,500 men and 46,000 women — aged 35 to 69 in Japan. Based on the questionnaires, the scientists noted how often the study participants ate small fish whole.

The researchers followed the participants for an average of nine years, during which time about 2,400 participants died, about 60% of which were from cancer.

At the end of the study, the researchers found a significant reduction in all-cause and cancer mortality among women who regularly ate whole small fish.

When the researchers accounted for lifestyle factors such as smoking, body mass index (BMI) and alcohol consumption, they found that women who frequently ate small fish had a lower risk of dying from any cause.

Why the focus on small fish?

According to the researchers, it is common practice in Japan to eat small fish, including small horse mackerel, white anchovy, Japanese smelt and sardines, whole, including organs, bones and heads.

"Previous studies have shown protective effects of fish consumption on health, including a reduced risk of mortality," explains Chinatsu Kasahara, PhD, a professor in the Department of Preventive Medicine at Nagoya University Graduate School of Medicine in Japan and lead researcher of the study. "However, few studies have focused on the health effects of small fish consumption. I was interested in this topic because I had a habit of eating small fish since I was a child. Now I feed them to my children."

Small fish have sustainability advantages because they are not typically overfished like larger fish and contain less mercury.

"I regularly recommend the consumption of small fish because of their impressive nutritional value and low levels of toxic mercury compared to larger fish," said Molly Raposo, a registered dietitian and senior nutrition and health specialist at the Pacific Neuroscience Institute in Santa Monica, California, who was not involved in the study.

"Small fish are a component of traditional Japanese and Mediterranean diets, both of which are known for their longevity," she added.

Health Benefits of Eating Small Fish

In addition to being a healthy source of protein, small fish also provide a variety of nutrients, including omega-3 fatty acids and micronutrients such as calcium, vitamin A, iron, zinc and vitamin B12.

"The health benefits associated with fish in general, such as being a rich source of essential and protective nutrients like protein and healthy fats like omega-3 fatty acids, as well as a source of calcium from bones and a host of other vitamins and minerals, are pretty consistently supported in research," explains Monique Richard, a registered dietitian and owner of Nutrition-In-Sight.

"Often when someone eats small cold-water fish, they also choose other foods that complement the health benefits of the fish, such as fruits, vegetables and whole grains," she continues.

"Small fish are not usually suited to being battered and served with chips, they are more delicate and naturally portion controlled. They tend to be richer and more intense in flavour, which encourages eating more slowly, enjoying each bite and perhaps consuming less to feel full," she adds.

"This study adds to the existing evidence linking fish consumption and cancer mortality. In previous studies, regular fish consumption has been associated with a reduced risk of gastrointestinal cancers and may also be beneficial for cancer survivors who eat a diet rich in fatty fish," says Molly Raposo.

"This type of research is important because our diet has a significant impact on chronic diseases. Lifestyle changes, such as food choices, are an opportunity to reduce the risk of early death and disability. Evidence-based dietary strategies offer a practical approach to reducing the burden of chronic diseases, including cancer, and improving longevity," adds Raposo.

How can I add small fish to my diet?

While eating small fish whole may be a common practice in Japan, the same cannot be said about other countries such as the United States or European countries.

When considering cold-water fish that are low in mercury, heavy metals and other contaminants, yet still quite versatile, tasty and affordable, Richard recommends remembering the acronym SMASH — sardines, mackerel, anchovies, salmon and herring.

It is recommended to add a serving of 85-115 grams of fish or four to five small fish to:

• a piece of whole grain toast or crackers, as a salad topping,
• in whole grains such as farro, buckwheat, long grain or brown rice, or quinoa,
• in vegetable soups, stews or pasta, as a pate or spread.

Most grocery stores now offer a variety of canned or packaged fish flavored with spices, oils, herbs, or combinations of these.