Oh dear. Well, let's summarise a little and see what can be gleaned from the sources so far.
I created an
online spreadsheet (including an
HTML version) which collects information from scientific journals. It contains three pages - the albumin, globulin, prolamin and glutelin composition of buckwheat and rice; prolamin content of various grains as quoted by Dr. Peter Osborne; and a list of references.
The primary source of information is
Food Chemistry although other sources have also been identified. I was not able to locate all of them and add the results this quickly but maybe others can join in.
The numerical results were written down exactly as quoted by the references and the relevant journal article was also given. Some sources identify the individual grain species (well, let's call them grains though buckwheat is not) - others merely give value ranges for groups of species. That is also clearly spelt out. In the case of rice, fairly non-descript names were published (e.g., PR-106) so I also added descriptions based on the appearance of the grain (e.g., coarse medium length). These come from the relevant sources as well.
Dr. Osborne defines gluten as any protein that belongs to either the family of prolamins or glutelins (is this an unassailable statement?). So the fraction values in those two groups are of importance to this investigation.
The first thing that immediately jumps out is that rice is very high in glutelin content. In fact, this is the bulk of the total proteins and is several times that of buckwheat. On the other hand, buckwheat appears to be mainly composed of albumin and has a higher prolamin content.
Now, I can't make a determination whether glutelins are more "evil" than prolamins - perhaps a medical professional can express an opinion. It's interesting, however, that people who withdraw rice from their diet, see an improvement in overall health. Can this be caused by a reduction in the intake of glutelins...?
When it comes to prolamins, buckwheat does indeed look worse for wear based on the sources quoted. Rice seems to be very low in prolamins - and the values are much smaller than what Dr. Osborne is giving us. So I see a discrepancy here already.
Moreover - there is a discrepancy between various studies themselves! So who is right? Well, you could look at averages - as zlyja mentioned, but one of the sources explains this as follows:
Xiaona Guo said:
Table 1 shows the Kjeldahl nitrogen and the protein
content of fractions from defatted tartary buckwheat
flour. Albumin was the predominant protein fraction
(43.8%) followed by glutelin (14.6%), prolamin
(10.5%), and globulin (7.82%).
This is in disagreement with earlier reports (Imai & Shibata, 1978;
Pomeranz,1983; Tahir & Farooq, 1985; Wei et al., 2003). Imai
and Shibata (1978) reported 40–77% albumin and globulin,
0.7–2.0% prolamin, and 23–59% glutelin and residual
protein for commercial buckwheat flour.
Pomeranz (1983) reported that buckwheat protein was composed
of about 80% albumin and globulin. Tahir and Farooq
(1985) found that the proportions of albumin plus globulin,
prolamin, glutelin, and residual protein were 38–
44%, 2–5%, 21–29% and 28–37%, respectively, for 4
buckwheat species.
Wei et al. (2003) reported that proportions
of albumin, globulin, prolamin, and glutelin
were 16.8–30.3%, 4.96–21.6%, 3.08–7.01%, and 11.5–
16.0%, respectively, for four buckwheat species.
Fractionation of plant proteins on the basis of solubilities
in different solvents is only an estimation of the protein
composition. Different extraction methods and various
species may lead to greatly different results.
Table 1 also shows the nitrogen content of the protein fractions.
The globulin content was the lowest (7.82%) but its protein
content was the highest (92.9%).
Makes sense. The variability of results is due to the differences in plant material, the methods used - and the experimental error. This is my first criticism of Dr. Osborne's statement about the prolamin content of rice. I would like to see his sources, too.
But hey, after seeing the results, I gave away all my rice. Gonna see what happens - the last rice meal I had was on Friday and I am already less mucousy and my back pain is gone. Though that is not a very scientific statement because I eat other foods as well and ate less during the weekend due to the confusion about this topic.
The next direction could be - what are prolamins and what are glutelins? What are their individual effects on the human body? Are there differences in the ways those proteins act on the human body within each group - i.e., do all prolamins act in the same way; are some less harmful than others? (It's this generalisation that bothers me, actually).
Going further, can some people be more sensitive to prolamins as opposed to glutelins - and vice versa. Could that explain the different reactions to buckwheat and rice. Are people with IBS, therefore, more sensitive to prolamins and tolerate glutelins better? The picture may be more complicated than we think and this is the reason for my Q to the C's.
Laura said:
Puhleeeeeeeeze don't tell me I can't have buckwheat!!!
LOL - no kidding. I think this is one of those cross-roads questions and we can either be totally committed to eliminating prolamins (which indeed means no grains or buckwheat and going Palaeolithic) - or we may be able to identify cases where moderated consumption is OK.
After reading these articles, I am convinced that buckwheat consumption is very beneficial to the human body, though there are a few catches which we may be able to correct with appropriate supplements or enzymes. Have a look at this:
Composition and technological properties of the flour and bran from common and tartary buckwheat
G. Bonafaccia, M. Marocchini, I. Kreft
Food Chemistry 80 (2003) 9–15
Two types of buckwheat are used around the world:
common buckwheat (Fagopyrum esculentum) and tartary
buckwheat (Fagopyrum tataricum). Which one is
used depends on the production zone. Generally, in
Europe, USA, Canada, Brazil, South Africa and Australia,
the more common buckwheat is grown.
The same is true in most Asian buckwheat growing countries, for
example Japan, Korea, and the central and northern
parts of China. Tartary buckwheat (Lin, Tao, & Li,
1992) is grown and used in the mountainous regions of
southwest China (Sichuan).
In northern India, Bhutan, and Nepal both types are known,
tartary buckwheat being grown in more harsh climatic conditions.
Many buckwheat flour products are quite similar.
Buckwheat pasta is used in Italy (pizzoccheri), in Japan,
as soba and in Korea and China as extruded noodles and
‘‘cats’ ears’’; also there are buckwheat pizza and ‘‘polenta’’
type buckwheat porridge (zganci in Slovenia, sterz
in Austria, soba-gaki in Japan). The products change
their name according to the area in which they are
produced.
In Europe, buckwheat has been grown for centuries
and is now, alongside spelt wheat (Bonafaccia, Galli,
Francisci, Mair, Skrabanja, & Kreft, 2000), one of the
most important alternative crops, suitable for ecological
growing, without the use of artificial fertilizers or pesticides.
It is used for flour and groats products in central
and eastern Europe (Kreft, 1994).
For many years, cultivation of buckwheat declined, but recent interest in old,
traditional foods and a re-evaluation of typical regional
products, has led to a resurgence in its cultivation. Buckwheat
products are known for their resistant starch
(Skrabanja, Laerke, & Kreft, 1998; Skrabanja, Liljeberg,
Kreft, & Bjo¨ rck, 2001) and as an important source of
antioxidative substances (Kreft, Bonafaccia, & Zigo,
1994; Kreft, Skrabanja, Ikeda, Ikeda, & Bonafaccia, 1996;
Kreft, Knapp, & Kreft, 1999; Nagai, Sakai, Inoue, Inoue,
& Suzuki, 2001; Park et al., 2000; Watanabe, 1998), trace
elements (Ikeda & Yamashita, 1994), and dietary fibre
(Steadman, Burgoon, Lewis, Edwardson, & Obendorf
2001).
Buckwheat proteins have a high biological value,
but relatively low true digestibility (Skrabanja, Nygaard,
& Kreft, 2000).
Buckwheat protein products have been
associated with preventative nutrition. In experimental
animals they suppress gallstone formation better than soy
protein isolate (Tomotake, Shimaoka, Kayashita,
Yokoyama, Nakajoh, & Kato, 2000). They are associated
with retardation of mammary carcinogenesis by lowering
serum estradiol, and with suppression of colon carcinogenesis
by reducing cell proliferation (Kayashita, Shimaoka,
Nakajoh, Kishida,&Kato, 1999; Liu et al., 2001).
...and this one...
Effect of processing on buckwheat phenolics and antioxidant activity
Ilkay Sensoy, Robert T. Rosen, Chi-Tang Ho, Mukund V. Karwe
Food Chemistry 99 (2006) 388–393
Phenolic compounds in buckwheat have been shown to
possess antioxidative activity (Halosava et al., 2002). Tian,
Li, and Patil (2002) have identified four main flavonolglycosides
in methanol extracts, namely, rutin, quercetin,
kaempferol-3-rutinoside, and a trace quantity of a flavonol
triglycoside. Watanabe (1998) has isolated catechins along
with rutin in buckwheat. Buckwheat was cultivated as a rutin
source but later was discontinued due to the discovery
of other highly concentrated sources of rutin such as dimorphandra,
which is a legume plant. Rutin has been shown
to exhibit antioxidative, antihemorrhagic, and blood vessel
protecting properties (Baumgertel, Grimm, Eisenbeib, &
Kreis, 2003).
Several researchers have investigated health benefits of
buckwheat. According to Prestamo, Pedrazuela, Penas,
Lasuncion, and Arroyo (2003) buckwheat could be used
as a prebiotic food because it was found to increase lactic
acid bacteria in rat intestine. Kim et al. (2003) claimed that
buckwheat grain extract could be used in the treatment of
allergic inflammation. Buckwheat has been shown (Kawa,
Taylor, & Przybylski, 2003) to reduce the serum glucose level
in rats due to high content of D-chrio-inositol (D-Cl), a
component of an insulin mediator.
Proteins in buckwheat flour do not have any toxic prolamins
to Celiac patients (Aubrecht & Biacs, 2001; Im,
Huff, & Hsieh, 2003). Buckwheat protein suppresses gallstone
formation and cholesterol level more strongly than
soy protein isolate (Kayashita, Shimaoka, & Nakajyuh,
1995; Tomotake et al., 2000). Protein digestibility of whole
buckwheat grain is relatively low (<80%) due to high content
of crude fiber and tannin, a protease inhibitor (Ikeda,
Sakaguchi, Kusano, & Yasumoto, 1991; Pandya, Smith,
Yarwood, Gilroy, & Richardson, 1996).
Interestingly, buckwheat has been recognized as a common food allergen
in Korea and Japan (Park et al., 2000; Tanaka et al., 2002;
Taylor & Hefle, 2001) but not in North America where
milk, egg, peanut, tree nut, fish, shellfish, soy and wheat
are at the top of the list of allergies, probably due to less
popularity of buckwheat products
So it looks like there is this digestibility dimension to buckwheat as well and, perhaps, that's what's causing problems in some people. There may even be differences based on ethnic background. Sorry, the details escape me right now but isn't there a protocol to aid digestion of foods by adding certain amino acids? Could anyone comment on that?
And there is this:
Xiaona Guo said:
3.4. In vitro pepsin digestibility
Table 3 shows in vitro pepsin digestibility of defatted
tartary buckwheat flour protein fractions and other food
proteins.
Protein digestibility may be affected by two
types of factors: exogenous factors (protease inhibitors,
phytic acid, polyphenols and tannin) and endogenous
factors (protein structure) (Duodu, Taylor, Belton, &
Hamaker, 2003).
The digestibilities of defatted tartary
buckwheat flour protein fractions (from high to low)
were: albumin > globulin > prolamin and glutelin.
Compared with isolated protein of wheat germ and soybean,
tartary buckwheat flour fractions had relatively
lower digestibility. In addition to some antinutrients,
the lower digestibility of these fractions might be affected
by structural properties but the mechanism influencing
this needs to be studied further.
Others made a comment in this thread that gluten contamination in buckwheat flour could be the real cause of digestive discomfort. I think it's a fair comment and I wonder if it's possible to find a product for gluten testing of food. Does anyone know if such a thing exists? I would love to have something like that at home - my seeds are marked as "gluten free" but not the flour so it would be interesting to check.
Anywhoo, that's where this thread is at. It's not all as clear as we would like it to be and I would be weary of anyone making general statements about prolamins. I got rid of rice from the house and will give the updated protocol a go. Although, it would be nice to clear up this quandary - if buckwheat has prolamins and it is also found to be OK through testing - then not all prolamins are harmful, right?
Unless, it is wrong - in which case the Paleolithic diet will be the way to go...
That's what I get for not reading carefully! Thanks for pointing that out. Kind of inspires me to make sweet potato flour, actually!
