Too much sugar isn’t good for anyone. But how much is too much? The Institute of Medicine suggests no more than 25 percent of our daily calories should come from added sugars, but new research suggests that even when concerns about weight are not a problem, too much sugar can shorten lives and reduce fertility.

Americans consume, on average, about 22 teaspoons of added sugar a day. The American Heart Association recommends that women consume no more than about six teaspoons, or 100 calories, of added sugars each day. Men should limit their intake to 150 calories or nine teaspoons. Children should only consume three teaspoons a day. A single 12-ounce soda contains eight teaspoons of sugar or 130 calories.

Mice were fed a diet comparable to a healthy human diet. Some were given added sugar equivalent to three cans of soda a day — a diet similar to that of 13 to 25 percent of the US population.

The new study on sugar consumption offers a more realistic picture of its effects than previous research. Instead of giving mice sugar in doses substantially higher than humans would ever consume, mice were fed a diet comparable to a healthy human diet. Some were given added sugar equivalent to three cans of soda daily — a diet similar to that of 13 to 25 percent of the US population, making the results more directly applicable to humans.

Researchers studying the health effects of sugar and other nutrients often use mice as subjects. Not only are there ethical issues involved in offering a diet with nutritional excesses or deficiencies to humans, the shorter life span of mice means that long-term effects show up much more quickly.

Females fed the sugary diet died at nearly twice the rate of the female mice in the control group which were not fed extra sugar. Males fed sugar did not exhibit normal territorial behavior, and produced fewer offspring. Mice did not become obese, nor did they show any significant metabolic changes over the course of the 32-week experiment.

This study offers new evidence that the amount of sugar consumed by millions of people in the US is harmful to health, even when weight is not an issue. The researchers recommend that the safe level of sugar intake be lowered.

Sugars which occur naturally in fruits, vegetables, low-fat dairy foods, and whole grains don’t need to be avoided. They are part of a healthy diet.

The study is published in Nature Communications.