Many parents agonize over sending a healthy lunch to school with their children — will he eat carrots? Is there enough protein in this meal? Will she trade her sandwich for a cupcake? Yet an astonishing number of sack lunches may be more than unhealthy — they may be unsafe to eat.

According to a new study by researchers at The University of Texas, over 90 percent of home-prepared lunches sent to school with preschoolers reach unsafe temperatures before lunchtime. This is true even of lunches that include an ice pack.

Researchers visited nine Texas preschools and used noncontact temperature guns to collect data from a sample of over 700 children’s lunches. They determined that although 45 percent of preschoolers’ lunches contained at least one ice pack, 88 percent of all lunches were at room temperature an hour and a half before lunchtime.

Moreover, of those lunches containing perishable items, such as cheese, meat and vegetables, less than 2 percent were stored at a safe temperature, and over 90 percent of the total lunches, including some that contained multiple ice packs, reached unsafe temperatures.

The ideal temperature for food storage is below 40 degrees or above 140 degrees Fahrenheit. Between those temperatures, bacteria grow easily, increasing the risk of food-borne illnesses. The researchers recommend packing at least two ice packs in children’s school lunches to ensure that lunches stay at a safe temperature.

Some parents have criticized this research, however. Most criticism has fallen into one of two categories: Questioning the importance of the research (“I grew up on sack lunches and never got sick” — an important point considering that the researchers don’t specify how long it takes for harmful levels of bacteria to grow on food stored in the unsafe temperature zone), or questioning the researchers’ choice to study the topic at all (“I don’t need graduate research to tell me the importance of keeping food cool”). This second type of criticism may be a moot point considering that only 45 percent of lunches contained an ice pack.

It’s also been pointed out that other research in the last few years shows children exposed to certain types of bacteria and viruses at a young age have an increased immune system response later in life, as well as lower rates of allergies. Could it be that worrying less about food storage temperatures is beneficial to children in the long run?

What do you think? Will this research change the way you pack your children’s school lunches?