Nutrition & Health   > Beans


'Lowly legumes' offer lasting legacy
By Bob LeRoy, RD, MS, EdM -- Nutrition editor for Vegetarian Voice


Among cultivated staple-food plants throughout history, the legume may validly be dubbed "aristocracy." And yet, we have lost track of much of the value of legumes in the cuisines, daily diets and convenience foods offered worldwide.


Beans and peas -- devalued in ignorant pronouncements by nutrition professionals and government agriculturists throughout the 1900s -- seem widely regarded as charisma-lacking foods, described half in jest as "lowly," even by chefs who may better grasp their true worth.


Some say the legume needs a gourmet revival; others in the vegetarian movement or food business seem to think all legumes have vanished except for the "Almighty Soy," the single weapon with which meat and dairy may be overcome.


But, delicious, nutritious legumes are many and have much to brag about.


Agricultural Breakthrough


Cultivation of beans and peas was one of the most revolutionary agricultural breakthroughs ever. Root systems of leguminous plants develop nodes which harbor staggering numbers of nitrogen-fixing bacteria -- organisms which bring in nitrogen from the air itself, making it available for the plant's use.


Unlike nearly all cultivated crops, which deplete the soil of nitrogen (a key element for the growth process), bean and pea plants actually bolster the soil's nitrogen content. This remarkable attribute has:


• enabled beans to grow in some soils where nitrogen deficiency would have doomed other crops;


• provided some soil rehabilitation through seasonally alternating legumes and other crops; and


• even allowed soil-sparing systems of interplanting different crops in the same row (practiced in various Native-American cultures with corn, beans and squash).


Powerhouses of Protein


The one nutritional attribute of legumes that has not remained a secret in this century has been their abundant protein content. Based on this, the U. S. Department of Agriculture long ago admitted beans and peas to the "Meat Group" of its Basic Four Food Groups. Of course, legumes have a group all their own in the New Four Food Groups released by Physicians Committee for Responsible Medicine.


All legumes seem to derive 20 to 44 percent of their calories from protein (except for the peanut, at 16.3% due to its uniquely high fat content). This is daunting in view of recommendations by nutrition authorities in nearly all nations that only 8 - 10 percent of total calories in the diet need come from protein.


A vegetarian can effortlessly achieve an average of at least 8 - 10 percent protein, just by eating non-legume vegetables, grains and fruits -- thus in fact, it is very possible to get TOO MUCH protein, if one eats a large amount of legumes!


For those people who are getting enough food to eat, it is not necessary to "combine proteins" in order to get ENOUGH protein. However, it is well known that eating foods of distinctly different amino acid makeup (within some reasonable span of hours) will allow the body to use the protein and nitrogen content of those foods to a greater, more efficient extent for true protein functions (tissue, hormone and enzyme building, etc.).


So, less of the protein will then be shunned off to be used inefficiently by the body as "fuel" -- and potentially stored as fat -- along with the processing of the useless nitrogen wastes which burdens the liver and kidneys.


The main way people achieve this beneficial protein complementation is by eating foods that are high in the amino acid lysine when compared to sulfur-containing amino acids PLUS foods that are high in sulfur-containing aminos when compared to lysine. Higher- lysine foods include legumes, green leafy vegetables, and cabbage-family vegetables. Higher-sulfur-amino foods include barley, corn, millet, oats, rye, wheat -- and the high-fat sesame seeds, almonds, Brazil nuts, walnuts, and sesame, flax, pumpkin and sunflower seeds.


Legumes have been humanity's best "lysine bargain" throughout history -- yielding the most food lysine per cost of agricultural production, and doing this via foodstuffs that can easily be stored year around. Not so for green leafy and cabbage-family vegetables, which are otherwise the champions of vegetarian nutrition. Not coincidentally, beans and peas have been staple-food fixtures alongside foods they "complement" in countless human societies, for example:


  • beans + corn (many Native-American/Latin-American cultures)

  • chickpeas + wheat and/or sesame (Middle East)

  • peanuts + millet (much of Africa)

  • peas + oats (western Canada)

  • one of the several daals + one of the various grains such as rice, wheat, barley, etc. (India) (- Ed.)


Far More Than Protein


The nutritional importance of legumes extends far beyond the realm of protein, and beyond the obvious fact that legumes, grains and starchy vegetables have provided the human race's staple sources of complex carbohydrates (from which the great majority of calories should come, according to ALL nutrition authorities).


Though most people think of vitamin pills or nutritional yeast when the words "B complex" are mentioned, beans and peas throughout human history have been crucial sources of the full range of B vitamins other than B12.


Major B vitamins like thiamine, riboflavin, niacin, pyridoxine, pantothenic acid and biotin are well supplied by the entire legume family. Niacin-rich peanuts act much like a niacin supplement, and probably gave protection from pellagra to those African peoples who traditionally used them with grains.


But what are the best B complex supplements? Sprouted legumes! The sprouting process manufactures plentiful new B vitamins (but probably not B12). Only cabbage-related dark greens (kale, collards, etc.) offer as much B vitamin content per calorie as do good-quality sprouted beans... and no foods compare to home-grown sprouts in providing so much in B vitamins for so little dollar cost.


Eating sprouted legumes also helps avoid some inevitable concerns about taking commercial supplements: Why take a dose so much higher than what a human could consume from natural foods in a day; and why allow unwanted excesses of irrelevant nutrients to jeopardize delicate balances among nutrients in the body (as with the huge amounts of phosphorus in yeast products, normally almost devoid of calcium).


Legume sprouts (except alfalfa sprouts, which I discourage using) are also a very useful source of vitamin E, an antioxidant nutrient. Among unsprouted legumes, the few that have more than a tiny amount of fat also supply notable amounts of vitamin E or essential unsaturated fatty acids: high-fat soybeans and peanuts, and medium-fat (19.5% of calories) chickpeas.


Calcium Absorption


Magnesium, zinc and iron are amply provided in beans and peas in general, and calcium occurs in much smaller amounts. For all these minerals, absorbability is partly limited by some binding to phytate phosphorus. Both sprouting and fermenting (the latter exemplified by making tempeh from whole soybeans) are effective in breaking down much of the phytate and thereby increasing the amount of these minerals which the body can use.


Soybeans contain more calcium than do other legumes; their calcium-to-calorie, calcium-to-phosphorus and calcium-to-protein ratios are similar to those of chickpeas or navy beans. Despite their phytate and unusual calcium-bindable oxalate content, they show, in some studies, about twice as much calcium absorbability as other common unsprouted beans. This absorption rate is only half to three-quarters' that of the "calcium champions" (kale, collards and related greens) and broccoli, and soybeans can't compare to any of these in terms of calcium ratios... but it points to theoretical usefulness for soy as a calcium source.


Soy or no soy, an epidemiological look at any society where beans and peas are among the staples, and dairy products are not consumed, reveals that osteoporosis is conspicuously absent!


Balanced Iron


On the other hand, absorbability of iron from soybeans seems poor (though improved in fermented soy products such as tempeh), and this has been traced to binding by soy protein as opposed to phytate or oxalate... a problem apparently not shared by other legumes.


Still, epidemiological studies of cultures using soybean products heavily and animal products minimally (e.g. the massive, recent Study Of Diet And Disease In China) have not found iron deficiency to be a public health problem.


Balanced diets comprised of natural vegetarian foods -- without mega-dosing or iron supplements -- seem easily to find iron's happy medium: avoiding anemia caused by iron deficiency, and avoiding iron excess which, various studies show, can promote free radical formation and undermine the health of the heart.