THE SEEDS OF ILL HEALTH
Part 3: Toxins in cereals
But does it matter that cereal grains are nutrient deficient when we can make up their shortfall by combining them with foods from other sources? The answer is: Yes it does matter, for cereals also contain other antinutrients — toxic substances that also have to be allowed for.
Like all living things, plants have no desire to become the food source of another species. Their whole raison d'Ítre is to survive and reproduce. Their evolution has determined that they do this by the development of defence mechanisms which deter the insects and animals that would eat them. Many plants also provide their seeds with substances which ensure the survival of the seed and subsequent seedling until it can synthesise its own protective compounds.
Cereal grains are no exception. They contain a whole cocktail of chemical protectants that may be either outright toxic, antinutritional or uncomfortable to a predatory animal. For example, wheat grains can lie buried in the soil for several years before they finally sprout. This demonstrates how very successful are the toxic properties of the bran coating in warding off soil microbes. Bran is extremely durable and resistant to breakdown by organic action.
Of course, these don't always work. Insects, birds, and other animals have evolved to cope with these substances and, by so doing, are able to consume cereals with few if any adverse effects. We, unfortunately, have not. Like all primates, our species evolved in the tropical forest; our food would have been from broad leafed plants, and that is what our gut was initially adapted to cope with. Cereals are quite different. Although a few species of primates have been seen to eat grass and grass seeds under certain conditions, this behaviour is quite rare. We, like all other primates have had little time to develop a resistance to the toxic compounds found in cereal grains. For this reason, when the energy from cereal grains reaches fifty percent or more of the daily caloric intake, many of us suffer severe health consequences.
The main sources of ill health due to higher levels of cereal grain consumption are:
- Phytic acid found in bran, which binds to minerals, inhibiting their absorption.
- Lectins which also decrease intestinal absorption of many key nutrients.
- Protease inhibitors, which inhibit the metabolism of dietary proteins
- Alpha-amylase inhibitors, which prevent starch digestion and are known to be prominent allergens.
- Alkylrescorcinols, which suppress growth and cause kidney damage.
- Molecular-mimicking proteins: amino acid sequences that have the same structural form as a variety of amino acid sequences in body tissue and can cause auto-immune diseases.
Genetic changes to the human gut
But, you might suggest, we have been eating cereal grains for several thousand years. Isn't it possible that we could have adapted to their use by now?
Not really. The timeframe since we began to cultivate cereals is actually very short in evolutionary terms. It is possible that some adaptation could have taken place in the five-hundred or so generations since grains were first used in northern Africa, but time frames within northern Eurasia, for example, are of the order of no more than one-hundred generations, and in some others — Inuit, northern Scandinavians, Icelanders, Siberians, Native Americans — as few as three or even one generation.
If those who had had more time to adapt had been able to do so, there should be measurable differences between their guts and enzyme systems and those with a more recent history of grain use. But anatomical and physiological studies among and between various racial groups indicate that there are few differences in the basic structure and function of the gut. Thus it is reasonable to assume that there has been insufficient evolutionary experience since the advent of agriculture to create large genetic differences among human populations in their ability to digest and assimilate various foods.
The complete re-arrangement of gut and the evolution of new enzyme systems capable of handling such new food types is, therefore, quite unlikely to have occurred in humans in the short time period since the advent of agriculture.
Where there has been some adaptation is in an increased ability to digest disaccharides: the milk sugar, lactose, and sucrose, (table sugar). Although insulin is not a direct component of the gastrointestinal tract, there is substantial evidence to indicate that populations without a long history of carbohydrate use are more prone to high levels of insulin in the blood as a result of the unaccustomed high intakes of carbohydrates and the resultant high blood glucose levels. These peoples are much more prone to the consequences: type-2 diabetes mellitus, obesity, hypertension and coronary heart disease.
So while there has been some adaptation to dietary sugars, the same is not true of the starches found in cereals. There is no apparent difference between human groups in their ability to deal with the harmful effects of the antinutrients in cereals regardless of their genetic background. And no human can digest and assimilate the energy contained in bran.
What this all means is that except for the evolution of certain enzymes to digest simple sugars and perhaps changes in some genes involving insulin sensitivity, the human gut remains relatively unchanged from Palaeolithic times — when we did not eat cereals. And that, in turn, means that we should be very circumspect about how much of them we eat today.
If that weren't enough, pretty much all of the above is also applicable to legumes: beans, particularly soya, and other pulses.
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Last updated 31 March 2010