A U.S. government-led study found that zinc and folic acid supplements don’t boost men’s fertility. Previous studies on whether over-the-counter supplements might boost sperm health have had conflicting results. The study in the Journal of the American Medical Association showed they don’t help. Lead author Enrique Schisterman of the National Institute of Child Health and Human Development called the results disappointing. Supplements cost about $60 a month compared with tens of thousands of dollars couples spend on treatment for infertility.

What’s really normal for body temperature?

We seem to be getting cooler. Since 1851, when the standard was set at 98.6 degrees Fahrenheit, the average human body temperature has steadily declined.

Researchers studied three databases: 23,710 readings obtained between 1862 and 1930 in Civil War veterans; 15,301 records in a national survey from 1971 to 1975; and 150,280 entries in a Stanford University database from 2007 to 2017. The analysis is in eLife.

Overall, average body temperature decreased by 0.05 of a degree per birth decade. The decline was evident even within each database, year by year, and the drop between the two modern databases, when techniques were presumably the same, was identical.

Why this is happening is unclear, but the scientists suggest that improvements in sanitation and improved dental and medical care have reduced chronic inflammation, and the constant temperatures maintained by modern heating and air-conditioning have helped lower resting metabolic rates. Today, a temperature of 97.5 may be closer to “normal” than the traditional 98.6.

“We’ve looked at the U.S.,” said the senior author, Dr. Julie Parsonnet, a professor of medicine at Stanford, “and we have to see if this holds true elsewhere. We’re evolving physiologically.”

Drinking tea tied to better heart health

Chinese scientists analyzed data from a continuing health study conducted on 100,109 adults since 1998. Compared with people who had fewer than three cups of tea a week, those who drank more had a 20% reduced risk for a cardiovascular incident, a 22% reduced risk for cardiovascular death and a 15% reduced risk for all-cause premature death.

The study, in the European Journal of Preventive Cardiology, was observation and does not prove cause and effect. But tea, especially green tea, is a source of flavonoids that could reduce oxidative stress, relieve inflammation, increase the efficiency of heart muscle cells and improve blood vessel function, researchers said.

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