If you aren’t sure if eating eggs is good for you, you’re not alone. Let’s look at the historical journey of the egg and see how research has evolved over the years.

The earliest chicken-like fossils date back to 5400 BC in Southeast Asia, according to the Smithsonian. Confirmation with genetic material shows that today’s chickens descend from several prehistoric birds, one of them being red waterfowl. Male waterfowl have spurs on their lower legs that people have found useful for cockfighting. Today’s domesticated chicken has a gene that controls reproduction and allows it to lay hundreds of eggs throughout the year. With domestication, chickens were introduced to the world market via trade routes around 3,000 years ago.

Families used the hens and their eggs both as a source of income and for their own use. In the early 1920s, conditions such as seasonality and poor storage contributed to the deterioration of conditions for chickens. When animals were moved indoors in the 1930s, they were protected from environmental factors – weather, larger animals, disease – and their health improved.

As production increased and more hens survived, farmers noticed that their egg production increased. The chicken industry has become more affordable, as opposed to their previous role as a luxury feed.

The group’s first recommendations included no more than 300 milligrams of cholesterol per day and no more than three eggs per week. This was based on questionable animal and clinical studies. These animals are often herbivores, less suited to digesting dietary cholesterol than omnivores, such as humans. Additionally, clinical studies did not take into account other sources of cholesterol found in a typical diet. With more research, the guidelines have been changed.

As hens became more productive, food scientists and egg farmers realized the need for a new policy. Congress passed the Egg Products Inspection Act, which ensures eggs are safe for consumers.

Sylvester Stallone’s famous boxer Rocky drank raw eggs in the hit movie. But research has since shown that there is more protein available for digestion in cooked eggs (about 91 percent) than in raw eggs (about 51 percent). Consuming raw eggs also increases the risk of contracting salmonella bacteria and developing a deficiency of biotin, a vitamin important for the skin, hair and nails. Eggs contain avidin, a protein that is partially destroyed during cooking. In raw eggs, avidin binds more easily and reduces biotin. Rocky – and you – should consume plenty of raw egg whites to develop biotin deficiency, but it is possible.

Time magazine ran a cover featuring the face of cholesterol: a plate with two fried eggs for the eyes and a bacon frown. That same year, the Egg Nutrition Center was created with the aim of dispelling skepticism around cholesterol.

To create standard dietary recommendations in the United States, organizations like the American Heart Association, the National Centers for Environmental Prediction, and the FDA set a unified goal for Americans: less than 300 milligrams per day of dietary cholesterol. For reference, a large soft-boiled egg contains 186 milligrams of dietary cholesterol.

The organization waived its restriction on eating a certain number of eggs per week, but maintained the guideline of less than 300 milligrams of dietary cholesterol per day. As the United States continued its internal battle over what to do about eggs, other countries, like Australia, began to remove their national food restrictions on eggs.

A large meta-analysis concluded that consuming up to one egg per day is not associated with an increased risk of heart disease. In a literature search from 1966 to 2012, researchers looked at patients followed for coronary heart disease and a history of stroke. They found no significant association between egg consumption and heart disease.

The Italian Emma Morano was awarded the title of oldest person on the occasion of her 117th birthday; she has since died. Morano comes from a long line of women: a mother who reached the age of 91 and sisters who lived to be a century. While genes were most likely a factor, Morano partially attributed his longevity to a life of eating raw eggs. Her doctor said she had high cholesterol.

A study of more than 400,000 Chinese adults found an association between daily egg consumption and an 18% lower risk of death from cardiovascular disease. The authors said the country has its own dietary and lifestyle characteristics, so caution should be exercised in generalizing. Heart disease is one of the leading causes of death in China and around the world, according to the World Health Organization.

The evolution, domestication and research of chickens and eggs has led to our tables. The most recent research indicates that excessive egg consumption is associated with an increased risk of cardiovascular disease, but remember that cholesterol types, genetics, and lifestyle factors also play a role. While you have that in mind, we’ll be here awaiting the next study or guideline change.