Causes of Weakness in Legs. Weakness in the legs can be caused by many conditions and diseases. Weakness means there is less strength in the muscles than there should be. Some people mistake fatigue as weakness, but technically in the medical world, they aren't the same. People with the flu or cancer, for example, may say they feel weak when they're referring to sluggishness.
1 (Outside of the body, Lactobacillus acidophilus is the probiotic that is found in some yogurts.). 2  Foods that contain probiotics include: some juices and soy drinks, fermented and unfermented milk, buttermilk, some soft cheeses, miso, tempeh, kefir, kim chi, sauerkraut, and many pickles.
(Source 2 below). Another method of taking in probiotics is through fermented foods, such as sauerkraut, miso, kimchi, or any other fermented food you can purchase or make yourself. Milk kefir and water kefir are excellent sources of probiotics that can be consumed daily.