- Helping bodily processes has a positive impact on an animal / an animal 's health
- A human is a kind of animal
- Hence, helping bodily processes has a positive impact on a human

- Helping bodily processes has a positive impact on a human
- Digestion is a kind of bodily process
- Hence, helping digestion has a positive impact on a human

- Helping digestion has a positive impact on a human
- Bacteria can help digest food in humans
- So, some bacteria have a positive impact on humans by helping digestion

- Some bacteria have a positive impact on humans by helping digestion
- If something has a positive impact on something else then that something is good for that something else
- So, some bacteria are good for humans by helping digestion

- Some bacteria are good for humans by helping digestion
- Digestion is when stomach acid breaks down food
- Hence, some bacteria are good for humans by helping to break down food

Therefore, some bacteria are good for humans by helping to break down food
Q: In what way can bacteria be good for the human body?
Context:
- Helping bodily processes has a positive impact on an animal / an animal 's health 
- Digestion is a kind of bodily process 
- A human is a kind of animal 
- Bacteria can help digest food in humans 
- If something has a positive impact on something else then that something is good for that something else 
- Digestion is when stomach acid breaks down food