While everyone agrees that it is best to get your daily amount of nutrients from food, we realize that many people find that difficult to do. It takes a good deal of dedication to, first, know what amounts of nutrients you need every day, and, second, actually consume those foods.
Also, there actually are a few nutrients that are very difficult to get enough of in food (Vitamin D, for example).
These are the reasons that supplements can play an important role in maintaining good health.
The following from 2 articles list 7 common deficiencies. The lists are not exactly the same, but the lists have a lot in common.
Missing Nutrients in Your Food
1. Calcium
2. Potassium
3. Fiber
4. Magnesium
5. Vitamin A
6. Vitamin C
7. Vitamin E
Other Important Nutrients
1. Vitamin D
2. Folic acid
3. Iron
4. Vitamin B12
7 Nutrient Deficiencies That Are Incredibly Common
1. Iron deficiency
2. Iodine deficiency
3. Vitamin D deficiency (It is hard to get sufficient amounts through diet alone.)
4. Vitamin B12 deficiency
5. Calcium deficiency
6. Vitamin A deficiency
7. Magnesium deficiency