Many articles recommend you get all your nutrients from food, but I agree with Dave Asprey, founder of BulletProof, and his article Why Getting Your Nutrition Only From Food is A Bad Idea.  

When asked 'can't I get all I need from foods?', my general response is 'only if you eat a lot of whale blubber!'  Most people need at least 4000 IU/day of vitamin D. Salmon has about 400 IU/serving... are you going to eat 10 servings a day?  Milk has 400 IU/quart--let's see now, that's 2 1/2 gallons of milk a day!  

With vitamin D the common line is "you will have plenty vitamin D as long as you drink milk and get outside 15 minutes a day." That does not seem to be working for the average American, as the average vitamin D level is 24 ng/ml* (60 nmol/L), well below the recommended 40-60 ng/ml (100-150 nmol/L). (*NHANES data 2001-2010)

From 2009-2011 we asked about food in our questionnaire. We analyzed what foods, if any, were making people vitamin D replete. We wrote a paper in 2013 on the topic which concluded most people need more than food to reach a vitamin D level greater than 40 ng/ml (100 nmol/L). They either need supplements or purposeful, regular, non-burning sun exposure. See below for more detail.

For Omega-3 Index levels which we are tracking in the D*action+Omega-3 project, we do not yet have enough data on our project to come to a conclusion on food changes. However, we reviewed a paper that did increase Omega-3 Index through a change in diet by substituting more Omega-3 rich foods for normal rations. As more people join D*action+Omega-3 we will be able to show you some information you might use as a guide about how to get to the recommended index level (above 8%) with food, supplements or both.

Onwards!