Body metabolism, including digesting and assimilating the food we eat, normally and naturally produces acid toxic organic waste; making good elimination - such as from bowels and kidneys - a key element in ph balance. Overacid body chemistry is seen by some researchers as the "signal" for the microorganism activity described in Part 9 of this discussion - "How Does It Work? - Unconventional Concepts of Illness & Health You May or May Not Have Considered".

Although foods that are not acid in their natural state produce acid waste products during the apparantly normal course of metabolism, some will be MORE ACID-FORMING and some less so depending on how and how much they're processed before eating. And, remarkably, some ACID foods CAN become just the opposite when digested and metabolized properly.

Examples:

Alfalfa --- very possibly the #1 Alkaline food --- typically available fresh for human consumption only as sprouts (which should ideally be grown at home from untreated seeds rather than bought not-so-fresh in supermarkets). Mature Alfalfa leaves are usually available dried as tea (or in tablets that may be more convenient provided the binder used to hold the tablet together does not exacerbate an already-sluggish elimination problem). Some people like the tea better mixed with Peppermint Tea.

Citrus fruits --- ALONE --- not eaten with other foods or sugar or salt or... (you get the idea). Some folks find drinking the juice of half a lemon in a glass of "non-chemicaled" water first thing in the morning about thirty minutes before breakfast very helpful. I know what you're thinking --- citrus is commonly the most acid food there is. But used ALONE it seems to trigger the very opposite in reaction with body chemistry; orchestrated, apparantly by the liver and other glands and organs involved in the body's ph balance.

All "flesh foods" (meats, etc.) are more acid-forming than fruits and vegetables. Pork is usually the most acid; fish --- especially if gently broiled, baked or steamed rather than deep fried --- is probably the least.

Grains --- Corn seems to be the most acid-forming. Oats and Millet the least. Observant farmers of yesteryear who plowed with horses or mules noticed evidence of this from observing their animals' reaction to the summer heat.

Legumes (beans, peas and their "cousins") --- Lima beans have the reputation for being the least acid-forming --- especially the less starchy (not white) varieties. Followed by lentils and garbanzos, if memory serves. (You probably should consult a better "authority" on the last two.)

FRESH RAW fruits and vegetables are almost always less acid-forming than canned or otherwise processed. Even less-so than gently steamed.

Not a food --- but definitely a factor: Negative emotions --- from anger and resentment to grief and despair (and everything in between) --- produce acid reactions, also; while over-acid body chemistry, in turn, often induces negative emotions. Thus the old observations that "Laughter is good medicine", and "Whatever happens, you mustn't lose your sense of humor".

An interesting note from Nicole ---
http://nutrition.answers.com ---
July 11, 2013:
------------ "I'm trying to sift through the innumerable claims of the foods you should include in a nutritious diet to come up with a definitive list of 5. Although I've come across a lot more specific research lately, I'm still looking for resources that give detailed, rather than flippant, reasons to eat certain foods over others."

I don't know of any such specific nutritional research, but if there were, I strongly suspect it would indicate there ARE no such 5 foods --- or any other number of such SPECIFIC foods --- but, rather, that all the presently known NUTRITIONAL ELEMENTS necessary for life are to be found in the entire group of foods indigenous to any part of the earth.

As far as I can tell, these sites ---
http://www.health.gov/dietaryguidelines/
http://www.nutritionevidencelibrary.gov/ = http://www.nel.gov/
http://ods.od.nih.gov/factsheets/list-all/
--- (which you've probably already tried) all appear to focus on food GROUPS, as do most other reputable dietary guidelines.

The modern world seems to have the idea that life is an accident, and that our supposedly highly intelligent society must sift through the "rubble" and bring some sort of order to the "chaos"; when actually, life must have been highly organized when it began, since reliable evidence strongly indicates it cannot exist any other way.

While many scientists rather loosly and glibly admire the DESIGN in nature (and courts of law debate whether or not the expression should be taken literally to imply INTELLIGENT design --- and consequently an intelligent Designer) an impressive number of reputable biologists, biochemists, and related researchers are finding serious evidence that life and everything else about the physical universe was indeed meticulously designed with great precision. [ I'd be happy to send you links to condensed reports on some of their backgrounds and research if you're interested.]

This perspective would indicate there may indeed be one particular TYPE of food that IS absolutely necessary for good health --- UNPROCESSED food --- in it's natural state --- and, that we need to learn better ways of cooperating with nature rather than trying to "remodel" the earth and it's "furnishings" and other resources.

I look forward to seeing the results of your research!

They're virtually the same biologically. All come from plants called "legumes". The seeds of those plants are sometimes called "pulse". Traditionally, in English-speaking cultures, the round ones are peas and the oval or kidney-shaped ones are beans. Of course, not everybody follows custom. So Mung beans - the traditional Oriental bean sprouts - are almost as perfectly round as ball-bearings before they're soaked and sprouted (they become oval as they sprout); while "Black-Eyed Peas" - at least that's the Southern U.S. name for them - are quite kidney-shaped. Not surprisingly, some cultures call them "Black-Eyed BEANS".

And then there are chick PEAS - also called "Garbanzo BEANS". With their rough, uneven blob-shape, they don't quite fit either description do they? But they're the same plant family - with a flavor and texture as unique as their shape.

Finally, to round out the ambiguity, there are Lentils. Not usually referred to as beans OR peas - just "lentils". Still legumes or pulses.

But, as the famous quotation goes: "What's in a name?" In this case what is important is the high-quality protien and other very similar nutrition all of them contain. Try some. Search any of the above names followed by RECIPES and explore new worlds. Or visit the following websites for more in-depth biology of the subject.

https://www.quora.com/Vegetables-Whats-the-difference-between-a-pea-and-a-bean?share=1

https://www.quora.com/Are-yellow-peas-same-as-garbanzo-beans/answer/Anne-Hinkle