Nutritarians or people whose diet consists mainly of foods rich in nutrients, are at a huge advantage vs others when it comes to their immune system.  When foods are refined a lot of their nutrient content is removed (especially true in the case of refined flour), reducing their ability to help the body withstand attacks from free radicals and other sources of dna damage (phytochemical nutrients resist free radicals which in turn protects against damage to the dna nucleus and dna methylation).

Phytochemicals (naturally occuring chemical compounds found in plants) are so effective that in the distant past, they were the mainstream drugs used to treat all kinds of diseases.  Paxitacel is a widely used and effective immune-disease fighting drug derived from tree bark phytochemicals.

Key vegetables:  Broccoli, cabbage and brussel sprouts are especially powerful against diseases affecting the immune system.  Isothiocyanates (ITC's) remove carcinogens and repair defects.  They are found most notably in the cell walls of the wasabi, horseradish, radish, brussels sprouts and mustard plants;  Myrosinase in the cell wall forms the itc's in the mouth as people chew the vegetable.  More specifically ITC's inhibit the enyzmes which oxidize polycyclic aromatic hydrocarbons into forms that cause dangerous mutations to develop (out of control cell growth).  ITC's can even destroy mutated tumor cells (apoptosis) that other treatments are ineffective against.  Mushrooms have unique tumor fighting properties;  Lectins and angiogenesis inhibitors inhibit enzymes needed for blood vessel growth (without that there's no tumor growth).

Want to lose weight ?  Then eat more nutrients !   Studies show that people eating a high nutrient diet desire less calories.  There are many explanations for why that's the case;  In certain vegetables it's their starch content that causes people to feel full and gain less weight (the body doesn't easily break down and store starch as fat meaning it just goes through the body). 

What if you don't like the taste of all those healthy vegetables ?  Well, taste buds develop for foods you eat more of meaning that simple changes to your diet, made on a regular basis will inevitably lead to a preference for those healthier foods.  Major grocers like Carrefour are making it easier to access natural foods (in 2011 the grocery chain offered a much bigger selection of organic products than it did in 2008;  Now at 1968 up from 1236/1586 in 2007/2008).

Have kids ?  Make phytochemical-rich foods a part of their daily diet early on since studies show that when dna damage starts occuring at a younger age, chances of developing lupus and other autoimmune diseases later in life go up.