The phrase you've shared is a play on the well-known health adage "An apple a day keeps the doctor away." In this case, it suggests that consuming a small amount of fish daily could have beneficial effects on heart health.

This idea is supported by scientific research. Fish, particularly fatty fish like salmon, mackerel, and sardines, are rich in omega-3 fatty acids. Omega-3s are known to reduce inflammation, lower blood pressure, decrease triglyceride levels, and slow the buildup of plaque in arteries, all of which contribute to better heart health.

For optimal benefits, it's generally recommended to eat fish at least two times per week. However, it’s important to consider the method of preparation—opting for healthier cooking methods such as grilling, baking, or steaming can maximize the health benefits.

As always, it's advisable to consult with a healthcare provider or a dietitian to tailor dietary recommendations to individual health needs.