Why would drinking only one cup of coffee cause me to feel nauseous, nervous, anxious & jittery? thanks.

Try decaffeinated: It may be that you are more sensitive to caffeine. If using decaffeinated coffee does not cause the symptoms, you will know. For good health - Have a diet rich in fresh vegetables, fruits, whole grains, milk and milk products, nuts, beans, legumes, lentils and small amounts of lean meats. Avoid saturated fats. Exercise at least 150 minutes/week and increase the intensity of exercise gradually. Do not use tobacco, alcohol, weed or street drugs in any form. Practice safe sex.