Is cooking with low temperatures safe?

Absolutely. A common misconception about low temperature cooking is that it is unsafe as it involves cooking in lower temperatures that are in the bacterial "danger zone" of 10°C-55°C (50°F-131°F).

In fact, food safety is a function of both time and temperature; a low cooking temperature would be perfectly safe if maintained for long enough to achieve pasteurization.

Generally, food that is heated and served within 4 hours is considered safe (including unpasteurized food), but meat that is cooked for longer to tenderize must reach a temperature of at least 55°C (131°F) within 4 hours and then be kept there, in order to pasteurize the meat.

Unpasteurized food is not dangerous if fresh, high quality ingredients are used with proper hygienic practice. Or else we wouldn't have sushi, rare steak or carpaccio. However, it’s advisable to not serve unpasteurized food to highly susceptible, pregnant or immuno-compromised people.

Sous-vide cooking is safe with good food hygiene practices, purchase of fresh food and adherence to the time-temperature guidelines. Sous-vide cooking is not more dangerous, as these precautions apply to other conventional cooking methods too!