“It is better to eat a healthy diet than to take a lot of supplements.”
True. The micronutrients in food come in the perfectly designed package of a whole food item in which they act synergistically; they do not appear in isolation. They are more readily available to and more easily metabolized by the body. And you are less likely to take in toxic levels of any nutrient.
That said, I recommend testing of vitamin D levels. I take vitamin D3 except for during the summer, because living in the Northern hemisphere, I do not get enough sunlight exposure.
CoQ10 is important in energy production in cells, and is the a supplement I recommend to every adult, especially those taking statins or birth control pills since these medications deplete CoQ10 in the body. We get very little of this nutrient in our diet and it is slowly depleted as we age.