Common side effects of nutritional supplements can vary widely depending on the ingredient. Some individuals may experience gastrointestinal distress, such as bloating or diarrhea, particularly with high doses. Allergic reactions are also possible with certain ingredients. Fatigue or headaches can occur due to energy-boosting supplements, especially if misused. It’s essential to research and consult healthcare professionals before beginning any supplement routine. Additionally, not all supplements are necessary or beneficial for everyone, and whole food sources should be prioritized for meeting nutritional needs.