Despite the similar-sounding names, lactate and lactose aren't actually similar chemicals. Though both can occur in foods, including dairy products, they're not used by the same way in the body. Further, if you're lactose intolerant, that doesn't mean that you will have trouble processing lactate or eating lactate-containing foods.
Lactate is a negatively charged molecule formed from a compound called lactic acid. Some bacteria make lactate when they metabolize sugars. Humans also produce lactate as a byproduct of metabolism, though only under certain conditions. Specifically, says Dr. Gary Thibodeau in his book "Anatomy and Physiology," you make lactate when your cells process sugars for energy in the absence of oxygen, such as when you're engaging in a hard sprint or power efforts during exercise.
Lactate in Food
Lactate can occur naturally in some foods, and in other cases, it's added. Fermented foods like sourdough bread and yogurt contain lactate naturally. This is because these foods are manufactured by allowing bacteria to convert a certain amount of the sugar in the dough or dairy into lactate, yielding a sour flavor and change in texture. Because lactate changes a food's acidity, it can make it hard for pathogenic bacteria to grow in the food. As such, lactate is sometimes added to foods as a preservative.
Unlike lactate, lactose is a sugar. While it's possible for humans, other animals and bacteria to convert lactose to lactate through the process of fermentation, the chemicals have little in common. You take in lactose any time you consume milk or other dairy products. An enzyme called lactase, which occurs in your intestines, digests lactose into smaller molecules that you absorb into your bloodstream and can use for energy, say Drs. Reginald Garrett and Charles Grisham in their book "Biochemistry."
Some people don't produce enough lactase to digest lactose effectively. This is referred to as lactose intolerance. If you're lactose intolerant, consuming dairy causes you to experience a variety of uncomfortable gastrointestinal symptoms, including bloating and cramping. If you're lactose intolerant, you have to avoid lactose-containing foods. Alternately, you can take a lactase supplement when you consume dairy. You do not, however, need to avoid foods with natural or added lactate.