The FastDay Forum

I saw an article about this in the Times this morning. The on line link to the Times article is not free but I found this Daily Mail one. As some one with a sweet tooth it makes some sense to me. What do others think?

http://www.dailymail.co.uk/sciencetech/article-2593081/How-Atkins-Gene-slim-Enzyme-saliva-begins-breakdown-starchy-food-like-chips-crisps-rice.

Thanks for the link. Very interesting.

[carorees]

I had a look at the scientific literature and found that they think that a high carb diet may have exerted evolutionary pressure for more copies of the amy1 gene:

http://www.ncbi.nlm.nih.gov/pubmed/17828263

Nat Genet. 2007 Oct;39(10):1256-60. Epub 2007 Sep 9.
Diet and the evolution of human amylase gene copy number variation.
Perry GH1, Dominy NJ, Claw KG, Lee AS, Fiegler H, Redon R, Werner J, Villanea FA, Mountain JL, Misra R, Carter NP, Lee C, Stone AC.
Author information
Abstract
Starch consumption is a prominent characteristic of agricultural societies and hunter-gatherers in arid environments. In contrast, rainforest and circum-arctic hunter-gatherers and some pastoralists consume much less starch. This behavioral variation raises the possibility that different selective pressures have acted on amylase, the enzyme responsible for starch hydrolysis. We found that copy number of the salivary amylase gene (AMY1) is correlated positively with salivary amylase protein level and that individuals from populations with high-starch diets have, on average, more AMY1 copies than those with traditionally low-starch diets. Comparisons with other loci in a subset of these populations suggest that the extent of AMY1 copy number differentiation is highly unusual. This example of positive selection on a copy number-variable gene is, to our knowledge, one of the first discovered in the human genome. Higher AMY1 copy numbers and protein levels probably improve the digestion of starchy foods and may buffer against the fitness-reducing effects of intestinal disease.

and that people with more copies of the gene appear to handle carbs better:
http://www.ncbi.nlm.nih.gov/pubmed/22492122

J Nutr. 2012 May;142(5):853-8. doi: 10.3945/jn.111.156984. Epub 2012 Apr 4.
High endogenous salivary amylase activity is associated with improved glycemic homeostasis following starch ingestion in adults.
Mandel AL1, Breslin PA.
Author information
Abstract
In the current study, we determined whether increased digestion of starch by high salivary amylase concentrations predicted postprandial blood glucose following starch ingestion. Healthy, nonobese individuals were prescreened for salivary amylase activity and classified as high (HA) or low amylase (LA) if their activity levels per minute fell 1 SD higher or lower than the group mean, respectively. Fasting HA (n = 7) and LA (n = 7) individuals participated in 2 sessions during which they ingested either a starch (experimental) or glucose solution (control) on separate days. Blood samples were collected before, during, and after the participants drank each solution. The samples were analyzed for plasma glucose and insulin concentrations as well as diploid AMY1 gene copy number. HA individuals had significantly more AMY1 gene copies within their genomes than did the LA individuals. We found that following starch ingestion, HA individuals had significantly lower postprandial blood glucose concentrations at 45, 60, and 75 min, as well as significantly lower AUC and peak blood glucose concentrations than the LA individuals. Plasma insulin concentrations in the HA group were significantly higher than baseline early in the testing session, whereas insulin concentrations in the LA group did not increase at this time. Following ingestion of the glucose solution, however, blood glucose and insulin concentrations did not differ between the groups. These observations are interpreted to suggest that HA individuals may be better adapted to ingest starches, whereas LA individuals may be at greater risk for insulin resistance and diabetes if chronically ingesting starch-rich diets.

This fits nicely with the observation that some individuals seem better able to handle carbs than others and the idea that we can be divided into 'hunters' and 'farmers' such that people who cannot handle carbs well have a genome more like our ancient hunter gatherer ancestors whereas those who are able to cope with carbs have a genome that has been adapted to cope with the higher carb content of our more recent farmer ancestors.

Finally, I found this useful study suggesting that you might be able to make a guess as to how much amylase your saliva makes and hence how many copies of the gene you have by comparing how quickly your saliva dissolves starch:
http://www.ncbi.nlm.nih.gov/pubmed/20967220

PLoS One. 2010 Oct 13;5(10):e13352. doi: 10.1371/journal.pone.0013352.
Individual differences in AMY1 gene copy number, salivary α-amylase levels, and the perception of oral starch.
Mandel AL1, Peyrot des Gachons C, Plank KL, Alarcon S, Breslin PA.
Author information
Abstract
BACKGROUND:
The digestion of dietary starch in humans is initiated by salivary α-amylase, an endo-enzyme that hydrolyzes starch into maltose, maltotriose and larger oligosaccharides. Salivary amylase accounts for 40 to 50% of protein in human saliva and rapidly alters the physical properties of starch. Importantly, the quantity and enzymatic activity of salivary amylase show significant individual variation. However, linking variation in salivary amylase levels with the oral perception of starch has proven difficult. Furthermore, the relationship between copy number variations (CNVs) in the AMY1 gene, which influence salivary amylase levels, and starch viscosity perception has not been explored.
PRINCIPAL FINDINGS:
Here we demonstrate that saliva containing high levels of amylase has sufficient activity to rapidly hydrolyze a viscous starch solution in vitro. Furthermore, we show with time-intensity ratings, which track the digestion of starch during oral manipulation, that individuals with high amylase levels report faster and more significant decreases in perceived starch viscosity than people with low salivary amylase levels. Finally, we demonstrate that AMY1 CNVs predict an individual's amount and activity of salivary amylase and thereby, ultimately determine their perceived rate of oral starch viscosity thinning.
CONCLUSIONS:
By linking genetic variation and its consequent salivary enzymatic differences to the perceptual sequellae of these variations, we show that AMY1 copy number relates to salivary amylase concentration and enzymatic activity level, which, in turn, account for individual variation in the oral perception of starch viscosity. The profound individual differences in salivary amylase levels and salivary activity may contribute significantly to individual differences in dietary starch intake and, consequently, to overall nutritional status.

Fascinating stuff! Thanks for bringing it to my attention!

Do you think that means the HA people are more efficient at storing carbs as fat? I'm fasting today or I would be getting out the cornflour and having a chew! I can't decide if it is better to be HA or LA. I suppose the risk of insulin resistance in the LA group makes it undesirable

[carorees]

Do you think that means the HA people are more efficient at storing carbs as fat? I'm fasting today or I would be getting out the cornflour and having a chew! I can't decide if it is better to be HA or LA. I suppose the risk of insulin resistance in the LA group makes it undesirable

I believe that insulin resistance is the cause of obesity, particularly the dangerous visceral obesity so it's HA all the way!

It is also interesting in that the development of high amylase and also the ability to digest lactose in humans puts paid to the idea that we should all eat like paleolithic man (the paleo diet). In fact, some of us should but some of us have evolved since then

Re the cornflour...I did find this: http://www.ncbi.nlm.nih.gov/pubmed/15501494

Physiol Behav. 2004 Oct 30;83(1):81-91.
The role of alpha-amylase in the perception of oral texture and flavour in custards.
de Wijk RA1, Prinz JF, Engelen L, Weenen H.
Author information
Abstract
The role of salivary alpha-amylase in odour, flavour, and oral texture sensations was investigated in two studies in which the activity of salivary amylase present in the mouth of human subjects was either increased by presenting custards with added alpha-amylase or decreased by presenting custards with added acarbose, an amylase inhibitor. For starch-based vanilla custard desserts, amylase resulted in increased melting and decreased thickness sensations, whereas acarbose had the opposite effect, i.e., decreased melting and increased thickness. Other affected attributes included creamy mouth feel, creamy after feel, and fatty after feel. Creaminess, which is considered to be a highly desirable food quality, decreased by as much as 25% with added amylase and increased by as much as 59% with added acarbose. Neither additional amylase nor acarbose affected sensations for a nonstarch-based carboxy methylcellulose (CMC) vanilla custard dessert. This indicates that the effects of amylase on viscosity-related sensations of starch-based custards, such as perceived melting and thickness, are caused by amylase-induced breakdown of starch. Partial Least Square (PLS) analysis indicated that the effects of amylase and acarbose on perceived creaminess are not only driven by their effects on perceived melting and thickness, but also by their effects on perceived flavour.

I'm quite tempted to make custard tonight and compare tasting notes with my naturally v skinny husband! Or perhaps I should wait until the weekend when my cousin who has T2D is visiting so I can compare the v skinny with insulin-resistant phenotypes and see where I fit in!!!

Oh my gosh,i' ll have to come back to this another time when i feel more with it..
Its going WAY over my head today xx

Wow! This is fascinating! I've been flirting with Type 2 Diabetes for several years now and had gestational diabetes when I had my daughter at age 38 (my weight when I got pregnant was about what it is now--133 lbs). My weight (and midriff/belly) is way down from what is was last year, so it will be interesting to see the glucose numbers when I go for annual checkup and blood work.

I will have to figure out how to do a little test on myself and my husband to see where I come out on this. Let us know how yours comes out, Carol.

Can someone post an "idiot's guide" test? I'd love to try out the theory with hubs and daughter but don't know where to start. Thank you x

[carorees]

you could try this:
http://rbascienceunveiled.blogspot.co.u ... a.html?m=1
but you'd have to cut the time down enough so the saliva from a low amylase producer hadn't had time to digest the starch. I'd guess to quite a short time if you think about how long food stays in our mouths. Maybe 1 min? And you'd need to ensure the same amount of bread and saliva, and that the timing was accurate. Seems possible but not easy. And where does one get iodine these days?

[carorees]

Actually this looks much easier! Just add a timer! http://www.thenakedscientists.com/HTML/ ... f-enzymes/

[carorees]

And this got me thinking: I posted some months back about a study that showed people who eat fast are more likely to be overweight. Perhaps slow eaters keep the food in their mouths longer and so if they are a low amylase producer the food is in the mouth long enough for the amylase to work.

I can remember doing the bread chewing when I was at school. Also something to do with iodine but I think we used potatoes for that one. We still don't know how long HA/LA should take. Maybe you have the perfect control with your skinny husband carorees

This is fascinating. I just read an article on starch & resistant starch & its impact on gut flora and digestion on Marks Daily Apple today. There was something in there about enzymes & insulin resistance too. Lots of connections here - thanks as usual for the great info everyone. As soon as I process it & figure out how it might apply, I'll try it.