Final answer:
The four groups of people who should not use supplements are pregnant women, children under 18, individuals with certain medical conditions, and people taking certain medications.
Step-by-step explanation:
The four groups of people who should not use supplements are:
- Pregnant women
- Children under the age of 18
- Individuals with certain medical conditions
- People taking certain medications
Pregnant women need to be cautious with supplements as some can be harmful to the developing baby. Children under 18 may not have fully developed systems to metabolize and process supplements. Individuals with certain medical conditions may have interactions or adverse reactions from certain supplements, and people taking certain medications may experience interference with the effectiveness of their medications.