There is no single food that can provide all the nutrients needed by the human body, but a healthy diet should include a variety of fresh, plant-based foods that provide a range of nutrients. Here are some of the healthiest foods on Earth, according to various sources:

1. Water: Drink 8 to 12 cups of water daily.
2. Dark Green Vegetables: Eat dark green vegetables at least three to four times a week. Good options include broccoli, peppers, brussel sprouts, kale, and spinach.
3. Whole Grains: Eat whole grains at least two or three times daily. Look for whole wheat flour, rye, oatmeal, barley, amaranth, quinoa, or a multigrain.
4. Beans and Lentils: Try to eat a bean-based meal at least once a week. Try to add legumes, including beans and lentils, to soups, stews, casseroles, salads, and dips or eat them plain.
5. Fish: Try to eat two to three servings of fish a week. Good choices are salmon, trout, herring, bluefish, sardines, and tuna.
6. Berries: Include two to four servings of fruit in your diet each day. Try to eat berries such as raspberries, blueberries, blackberries, and strawberries.
7. Winter Squash: Eat butternut and acorn squash as well as other richly pigmented dark orange and green colored vegetables like sweet potato, cantaloupe, and mango.
8. Soy: 25 grams of soy protein a day is recommended as part of a low-fat diet to help lower cholesterol levels. Try tofu, soy milk, edamame soybeans, tempeh, and texturized vegetable protein (TVP) .
9. Watercress: According to a study, watercress is the most nutrient-dense food in the world, with a total of 100 points in the ranking of the healthiest foods.
10. Spinach: Spinach is one of the healthiest foods on the planet, packed with energy while low in calories. It is also a great source of Vitamins A, Vitamin K, and essential folate.

It is important to note that the more processed a food is, the more likely nutrients are to be destroyed or unwanted nutrients, such as sugar, to be added. Therefore, it is recommended to have a balanced diet that includes plenty of fresh ingredients and is as little processed as possible.