HealthExtended periods of hunger and malnutrition were the biggest danger to their health - at least for the poorer people. Fairytales of the Middle Ages still describe the way to recognize royalty at first sight is by their size and strength. This is not improbable: People who came from a rich family never had to go hungry and could develop better physically.
The drafty and damp houses would often promote illnesses affecting the joints. A lot of people probably suffered from eye infections as well, because of the smoke filled houses.
Most Germanic people had bad and worn down teeth, because the grain mush often contained rock particles and dust from the stone mill. In addition, caries were very common.
Birth control and abortions were (in contrast to Rome) unknown among the Germanic people, which usually led to continuous pregnancies for most women after they entered into marriage.
Because of the constant shortage of food it was common up to the middle ages to kill off weak, sick or crippled children after they were born: Another mouth to feed, that could not contribute to the food, would have forced the others to go hungry.
A lot of people died during childhood, but many lived till the age of about 40. Only a very few reached old age. (Even around 1850 only 7% of the population reached an age of 60 years or higher.)
Different from today's Europe, young people made up the vast majority of the population.
Young people, who had their strength and health seemed to have been rather energetic: Plutarch reports that when the Cimbrians invaded Italy, they were running around naked in the snow and they would sit on their shields sliding down steep slopes. Instead of crossing the Etsch river by boat or bridge, they tried to dam the river: Like Titans they would drag whole trees with their roots still attached and huge boulders, down to the riverbanks - 'solely to show off their strength and bravery to the Romans'.
(The Roman soldiers were indeed impressed and panicked after seeing this show of strength by their enemies. They deserted their camp and ran away. Their commander Catulus could not stop his men and had to flee with them.)