This one's been driving me crazy for years. In the ages before bottled vitamins, people forced to go for long without fruits or vegetables got the vitamin C deficiency disease scurvy. Symptoms include bleeding gums, loosened teeth, sore and stiff joints, slow wound healing, bleeding under the skin, and anemia.
Scurvy always kills unless the deficiency is remedied.
You have to get vitamin C or it gets worse and you die. Note that, while the Encyclopedia Britannica volunteered that last tidbit, it failed to realize that questions arise from it. But there they were, year after year, generation after generation. To be sure, they didn't have a tremendous life expectancy, nor did their adaptation get much beyond bare subsistence. This is by no means a putdown.