Modern humans have long associated birth months with gem stones, astrological signs, and the creatures on a Chinese restaurant menu, but should we also use them to determine future health and well-being?

New research published in the journal Heliyon suggests that babies born in the summer have a health advantage over those born during other times of the year. An extensive study of nearly a half-million people in the United Kingdom found that those born in June, July and August were slightly heavier at birth, taller as adults, and entered puberty at a later date. Those born in winter had "directionally opposite differences in these outcomes."

"This is the first time puberty timing has been robustly linked to seasonality," Dr. John Perry, lead author of the study, said in a news release. "We were surprised, and pleased, to see how similar the patterns were on birth weight and puberty timing. Our results show that birth month has a measurable effect on development and health, but more work is needed to understand the mechanisms behind this effect."

birth weight monthMonth of birth associations with birth weight from the new study published in Heliyon. (Photo: Heliyon)

So why the advantage for summer babies? The researchers theorize it may have something to do with the levels of vitamin D mothers are exposed to during pregnancy. The team studied "each participant's sunshine exposure during each trimester of pregnancy using meteorological data on monthly total hours of sunshine in the U.K." In particularly, they found the greatest advantages for vitamin D exposure occurred during the second trimester.

The relationship between birth month and health may also factor into our susceptibility to certain diseases. A recent study of 1.75 million medical records found 55 diseases with seasonal birth links including ADHD, asthma, cardiovascular illnesses and reproductive issues. Those born in October and November had elevated risk, while those born in the months of February, March, April, May and July tended to be associated with decreased risk.

“Not only was it surprising that nobody had studied the relationship between heart disease and birth month yet, but we found not just one association but several with the same trend of increased lifetime risk of heart disease for those born in late winter and early spring,” Nicholas Tatonetti, a scientist at Columbia University Medical Center, told Time. “That’s suggestive of a mechanistic relationship, although we don’t yet know what that is.”

In both cases, researchers were quick to stress both the early nature of their research and the results as only factors in overall health. Diet and exercise are still the largest pieces of the puzzle in determining a healthy, long life.