Grains; beyond gluten and carbohydrate

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When snooping around the internet looking for trouble information to add to my anti-healthy eating guidelines war chest, I occasionally stumble upon articles that are interesting but perhaps not a lot of use. That is, until you mine their references. Then you might strike gold.

The start of last week saw me on the road presenting my take on nutrition to a couple of different groups. Explaining to these individuals the argument against sugar is easy – nearly everyone will accept that sugar isn’t good for us. Arguing a case against vegetable oils, whilst not quite as easy, is still accepted, especially when couched in the terms of butter versus margarine. And I think, for the most part, unless there is a large Asian contingent in the audience, most Kiwi’s struggle to understand the difference between traditional fermented sources of soy and that which is used in commercial food production. But the two biggest stumbling blocks in the “paleo sales-pitch” remain the cases for saturated fat and against grains.

Fortunately, I had a few papers pulled for me prior to my trip to keep me entertained on the planes and in the airport lounges. These papers proved rather useful in my presentations, highlighting a case against grains…

From a 1999 paper titled Bioactive antinutritional peptides derived from cereal prolamins: A review… Despite cereals providing most of the energy and protein for many cultures around the world (wheat [mainly bread], rice, and maize supplying three-quarters of total cereal production; barley, sorghum, oats, and millets the remaining quarter);

…nutritional quality of these cereals is relatively poor due to their low total protein contents and to their unbalanced composition of essential amino acids…

Not only cereals grains have a poor nutritional value for healthy individuals, but some cereals may also induce widespread primary and secondary intolerances, thus becoming “non tolerated” or “toxic” under particular, although rather frequent, conditions. Peptides originating from digestion of wheat protein or of other “toxic” cereals in the human gastrointestinal tract are responsible for both primary and secondary intolerances.

The first audience that I read the above passage to were genuinely shocked to hear, via a research paper, that grains offer poor nutrition, and indeed may even be toxic, such is the powerful programming that is the “choose heart healthy whole grains” mantra.

Whilst the above paper went on to focus mainly on the gluten-type fractions within grains, the following paper focused on the lectin, wheat-germ agglutinin (WGA)…

Antinutritive effects of wheat-germ agglutinin and other N-acetylglucosamine-specific lectins

Wheat-germ agglutinin has been shown to have anti-insect activity, presumably for the same reasons that it is toxic to higher animals. So, given this toxicity to insects, it was thought that if this WGA lectin could be genetically added to plants, then we could increase the insect-resistance of these plants. The only stumbling block to this theory is that, upon ingestion of these same plants by higher animals, this WGA causes damage to their small intestines.

To test the extent of this damage, and with comparison to lectins from kidney beans and soya beans, the authors fed rats relatively high doses (7g/kg) of pure lectin. The inclusion of lectins in the diet significantly depressed the growth of the rats in this study, particularly those rats fed the WGA. This stunting in growth was put down to a less efficient digestion of protein, retaining less of the ingested protein, and higher faecal losses of nitrogen.

WGA was also a potent growth factor for the gut, significantly thickening the lining of the small intestine and thus adding to the nutritional cost of the gut tissue (building and maintaining a thicker gut lining is nutritionally and metabolically expensive, and a thicker gut lining will make digestion and absorption of nutrients more difficult. The effects of WGA were not, however, limited to the gut. It appears that WGA can be taken up by the cells lining the gut (enterocytes) and transported to the systemic circulation.

The consequences of this systemic absorption, according to these authors in 1993, are not known. However, they had this to say;

However, as the lectin appeared to be fully active and fairly stable against proteolytic breakdown, its potentially harmful effects on both metabolism and health need to be explored, particularly when diets containing WGA are fed for extended periods of time.

So, if we are eating WGA-containing foods within staples of the diet (e.g. bread), and as such are likely to be consumed at moderate levels over many decades, then we might want to know what effect they potentially have on our health. One main area of concern highlighted by the researchers was the significant effect of WGA on causing enlargement of the pancreas and atrophy of the thymus. Compared to controls, the rats fed WGA had ~18% increase in their pancreas mass and a ~20% reduction in thymus mass.

The consequences of the continuous stimulation of the pancreas, particularly in the long term, may be harmful for both of its vital exocrine and endocrine functions. Moreover, as one of the previously shown toxic effects of dietary PHA [kidney bean lectin] is due to its interference with the functioning of the immune system, it is of special concern what effects the systemically-absorbed WGA may have on the gut and the body’s immune systems. The thymus atrophy observed in rats fed with diets containing WGA may be particularly damaging for the proper functioning of the immune system.

Given the importance of the pancreas to the likes of digestive enzyme production and blood glucose regulation, one would think that this might be an important area of focus. Add to this the atrophy of the thymus, an important organ in the regulation of immune function, and one can begin to see how grains, such as wheat, containing these lectins and immunoreactive compounds, might just trigger metabolic issues that are independent of their carbohydrate content (making them unsafe starches versus what we might consider “safe starches“).

Now we need to be cautious interpreting such research given that it was on rats, and was with what might be considered very high doses of purified lectin. At 7g/kg, it would be like feeding myself 560g of purified lectin every day. WGA is present in staple foods derived from cereals at a concentration of about 300mg per kg of wheat bran (the authors state that they would need the concentration to be 10g/kg within the plant to be effective against insects).

This is a MASSIVE concentration difference. As such, I’m not likely to suffer acutely from the toxic effects of WGA. But one of my questions regarding this sort of thing, is what is the effect when small amounts are consumed day in, day out, for decades? Maybe I won’t consume enough WGA-laden bread to trash my pancreas and thymus in a year, or 5 years. But what happens when I start eating wheat-based products from aged two, for 10 years; 20 years; 30 years? Then what starts to happen? Even a modest dose of 100mg per day soon adds up to 365000mg put through the system over a decade. Does spacing the toxin over such a prolonged period make a difference? I don’t know the answer, but I have my suspicions (driven heavily by confirmation bias, of course).

It is not unexpected that at this low natural level, particularly when also diluted with other food ingredients, no toxic effects of WGA have been observed. However, the nutritional evaluation of the effects of pure WGA at the dietary inclusion of 7 g/kg clearly showed that the lectin reduces the utilization of dietary proteins, induces wasteful growth of both the small intestine and the pancreas, causes thymus atrophy and depresses the growth of rats. Moreover, it is particularly worrying that detectable amounts of functionally- and immunochemically-intact WGA are transported across the intestinal wall and may reach the systemic circulation. The long term effects of this systemic absorption of WGA on immune function, metabolism and health are unknown. Thus, the general use of WGA in edible parts of crop plants as a natural insecticide is not without dangers for potential consumers and its safety may still have to be established.

As if the potential for WGA to potentially trash your pancreas and thymus isn’t enough, it looks as though WGA can also exhibit insulin-like activity…

Insulin-Like Activity of Concanavalin A and Wheat Germ Agglutinin-Direct Interactions with Insulin Receptors

Some interesting lines from this paper…

In this report, we demonstrate that very low concentrations of these plant lectins have profound insulin-like effects on metabolic processes of isolated fat cells, and that they can interact directly with the cell surface receptors for insulin in these cells.

Concanavalin A and wheat germ agglutinin are plant proteins that can bind to specific carbohydrate determinants on the surface of mammalian cells, and they can agglutinate various normal and neoplastic animal cells.

Low concentrations of wheat germ agglutinin enhance the specific binding of insulin to receptors of fat cells and liver membranes. Higher concentrations of this plant lectin, as well as of concanavalin A, competitively displace the binding of insulin to receptors in these tissues.

Concanavalin A and wheat germ agglutinin are also as effective as insulin in reversing epinephrine-induced lipolysis in fat cells.This antilipolytic property, which does not depend on the presence of glucose in the medium, is not mediated by effects on membrane transport. The plant lectins are effective in concentrations as low as those that demonstrably activate glucose transport.

In English, these plant lectins appear to have the ability to instruct your liver and fat cells to undertake certain functions in the same way that insulin otherwise would, but without the presence of glucose to drive this (as might otherwise be expected with insulin). Importantly, these lectins are as effective as shutting down the breakdown of fat within fat cells. Not ideal, I would have thought.

One of the things that concerns me, is the thought that these lectins can competitively inhibit insulin. That is, they can push insulin out of the way and occupy the receptors that insulin itself should otherwise occupy. This might have the effect of blocking a necessary action of insulin in some tissues and/or enhancing the effect of insulin in others (similar in a way to what it is thought plant-derived phytoestrogens might do with oestrogen receptors). It does make me wonder whether these lectins have the ability to block certain cells from taking up nutrients under the influence of insulin, whilst simultaneously enhancing the uptake of nutrients into other cells, e.g. increased glucose and fat uptake into liver and fat cells.

So let’s summarise. We know that grains are a poor source of nutrition and easily replaced by more nutrient-dense foods. We know that they can contain immuno-reactive proteins, such as gluten. We know that they can also contain lectins, and in the case of the lectin wheat-germ agglutinin, we know that this can avoid digestion and end up in systemic circulation, where, possibly, we might see effects on the hormonal and enzymatic function of organs such as the pancreas and on immune-regulating organs such as the thymus. We also see that there is potential for these lectins to also have insulin-like activity. All of these effects are seemingly independent of the carbohydrate content of the source foods they are found in.

Of course, this is all speculation on my part. Most of the studies in this area are either on non-human animals at doses beyond what might be realistically consumed in the human diet, or are performed on isolated tissue cultures and cell lines. Those limitations notwithstanding, it is tempting to suggest that perhaps some of these factors are at play in real people in the real world. Perhaps, in susceptible individuals, we see the development of metabolic issues related to, amongst other things (such as PUFA and fructose intake), the specific effects of grains?

Perhaps the metabolic damage that components within grain-based foods cause precede overweight and obesity? Simply adding carbohydrate into the mix, whilst not doing a broken metabolism any favours, isn’t the root cause of the damage. But once that damage is done, the normal regulatory systems that might have otherwise coped with an influx of glucose are significantly impaired – perhaps with a state of permanence?

So many questions without immediate answers. But trying to connect the dots and seeing what picture you can come up with is part of the fun of an inquisitive mind, isn’t it?

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Post-script: I received a tweet asking whether cooking destroys WGA, as mentioned by Mat Lalonde at the Ancestral Health Symposium last August. Mat may indeed by far more up-to-date on this issue than the studies I have referenced here allows me to be, however the 1993 BJN states;

Due to the heat stability of WGA and its resistance to proteolytic breakdown, this same consideration applies also to the expression of the WGA gene in the leaves of crop plants (e.g. maize) which are used as winter feed for cattle in many countries.

So, from the above statement at least, that WGA is stable to cooking and survives digestion. This isn’t to say that more traditional slow cooking methods do not reduce the concentrations of such lectins, but then slow cooking is rarely used in either industrial food processes or within the modern home.

I’d also like to comment on the idea of creating transgenic plants that have had their insect resistance artificially jacked up, as is the idea in the WGA paper. I can think of nothing more catastrophic to the long-term viability of the ecosystem than having plants, which may be an insects main source of food, be able to wipe out large numbers of insects with all the flow on effects from there. If we require large volumes of crops to be protected in such ways in order to feed large numbers of humans (and of course, make someone lots of money in the process), then the human numbers are the troublesome side of the equation – not the insects. It is this use of WGA, rather than any health problems is may cause in individuals, that scares me the most.