If I had to choose one food catagory that would have the most impact on your health, I would have to say fermented foods.
Let me explain: health-wise, everything begins with the health of the gut. The gut is your entire gastrointestional system from your mouth all the way down and out. The quality of the food you choose and the health of your gut will determine the health of your entire body.
Some of us begin life pretty well - mom eats pretty well while pregnant with us, she has a natural birth with minimal intervention, breastfeeds us, and feeds us pretty good food. Others start out at a disadvantage. Mom might not have availabilty to good nutrition, maybe there are complications with the pregnancy and/or birth leading to a c-section, and then perhaps she is unable to nurse us.
When babies are born naturally, they swallow the normal, beneficial vaginal bacteria that start a healthy gut environment. These probiotics promote a natural balance of pH and normal gut flora to help with digestion of food, assimilation of nutrients, and immune factors. If that step is bypassed via c-section, then baby's immune system is already at a disadvantage.
Eating fermented foods is a delicious, cost-effective way to inoculate your gastrointestinal tract with the health-promoting, beneficial bacteria you need to obtain proper nutrition and fight off dis-ease. Even if you are on a limited budget and can't afford a probiotic supplement, you can always choose healthier, more nutrient-dense food. Raw milk kefir, miso, kombucha, raw saurkraut and kim chee are just a few examples of delicious ways to get your gut restored so you can continue to build robust health.
Here are some websites to start learning:
Fermented Food Recipes
The Benefits of Fermented Foods
List of Fermented Foods & Vegetables that Can Heal Your Gut