Well, yes and no... so much depends on the individual - diet, age, existing illnesses, medication use, pregnancy, smoking, stress levels etc.
Many people aren't eating nutrient dense diets, so a multi can fill nutritional gaps, though it is not a substitute for good food. However, for vegans, people on low calorie diets, people with multiple food allergies / sensitivities, the elderly, high alcohol intake, women on the oral contraceptive pill, those with chronic stress, very fussy eaters - then a multivitamin almost becomes a necessity.
Dr Andrew Saul (editor of Orthomolecular.org) has compiled 19 studies that show a strong correlation between vitamin use and the reduced risk of cancer and heart disease.
The Journal of the American Medical Assoc (JAMA) published 2 reviews in 2002, that were based on 30 years worth of scientific papers looking at vitamins and chronic disease. BOTH reviews ended up recommending daily multivitamin supplementation for all adults, based on the accumulated evidence.
Multivitamins are also extremely safe to take - compared to prescription drugs, they pose little to no risk. The US National Poison Data System reported ZERO deaths from any vitamin supplement (2010), however, 37,485 people died (2009 statistics from the US Centres for Disease Control) from prescription drugs. While I believe prescribed medications have their place, I worry that polypharmacy (too many different medications), accidental overdoses, incorrect prescribing, and multiple side effects are a high cost to pay.
If you aren't confident that your diet is nutritionally sound and meets your individual requirements, then an appointment with Christine can help sort this out. Some consideration is given to supplements, but not to the exclusion of a wholesome, fresh, unprocessed diet that meets your individual requirements.