Kevin Klatt, PhD, RD

If you're reading this expecting me to either endorse or stand in opposition to high-protein diets, turn back now. In nutrition, it's difficult to make a simplistic recommendation out of the mounds of scientific literature that exists on a topic - I can't imagine the stress that the Food and Nutrition Board of the Institute of Medicine (IOM) is under while making population-level recommendations. Protein is probably the most well studied of the macronutrients, from a physiological and biochemical perspective - the worldwide obsession with ensuring adequate 'complete' protein intake enveloped a lot nutritional sciences research in the 1900's. From this research, we learned a lot about amino acid metabolism/catabolism and understand the basic needs of most humans. It's known now that it's not necessary to only eat complete proteins, and that eating a combination of plant foods can provide all of the amino acids - hence, vegetarians not completely wasting...

That title is half a fiber joke and half pointing to the need for a Nutrition Fact Check website (similar to the politics version ). Fiber also happens to be a great way to slow down digestion, to reduce the surge of blood sugar following a higher carbohydrate meal and maintain satiety for longer (1). I see/hear a lot of things about Glycemic Index and many of them are not factual, misguided or simply untrue. The most common myth I've heard lately is that all whole grains have the same Glycemic Index value as processed grains (it varies a lot, some do , some don't - see below). Besides the fact that one should be using the Glycemic Load and ditching the Glycemic Index, it's hard to substantiate those rumors - I don't like to call out web sites, simply type into google "whole wheat same GI as white wheat" if you want to see the numerous websites passing around this myth. If you would like a reliable source regarding general Glycemic Indices, try this Ha...

If you don't already follow Marion Nestle's blog @ foodpolitics.com, I'd highly recommend checking it more frequently. Her perspective on socio-political issues is a nice counter-point sometimes. In perusing her blog, I came across an action notice by the FDA. The FDA will be studying the effects that nutrient claims have on consumer attitudes and responses. I find that this goes quite nicely with my most recent post on Isolated Nutrients and how the food industry likes to manipulate nutrient content to glorify the healthful components of their products. The FDA notes that it's stance "...  does not encourage the addition of nutrients to certain food products (including sugars or snack foods such as [cookies] candies, and carbonated beverages).  "  The FDA will be giving 15 minutes web-based interviews to 7500 individuals that reflect the U.S. Census data regarding gender, SES, age, education, ethnicity, etc. They will be using mock snacks, candy and carbo...

Part 1 focused much more on the types of folate, how they get into cells, and the genetic variants that effect folate-related enzymes and their activity. All fine and dandy background information - Folate's most interesting role, to me, is in its variable effects on genomic methylation aka Epigenetics. Quick background on genomic methylation - different CpG dinucleotides/islands/shores located throughout the genome have the potential to be methylated. This, alongside histone modifications, are responsible for cell type-specific expression patterns, X inactivation in females, silencing of transposable elements and some of the inter-individual variations in expression levels of different proteins that are not explained by coding sequences/other environmental stresses. The thinking is that the methyl groups inhibit transcription factor binding and subsequent expression rates. NOTE: tissues are extremely heterogeneous organs, filled with multiple cell types - methylation levels are e...

A new Nature article came out the other day that addresses a major question in the story of lactase persistence, one of the strongest gene-culture-selection interactions: did hunter-gatherer populations adopt dairy'ing or did dairy'ing cultures migrate and replace these HG populations? I really love this type of research, not only for its profound insight into the past but also the interdisciplinary team that participated in elucidating these facts. I often find myself thinking I need to be a biochemist/molecular biologist/genomicist/bioinformatician to answer all the  questions I have about nutrigenomics - but in this effort alone, there were anthropologists, paleogeneticists, bioarchaeologists, mathematicians, and archaezoologists. To solve the issue of dairying's origins, researchers looked at the bone remains - since calves need to be killed earlier than a cow raised for slaughter, looking at a bone's age can give insight into whether individuals in the time per...

The Biochemistry Folic acid is probably my favourite vitamin, right next to choline (you caught me - i love methyl donors). Folic acid is one of the water soluble B-vitamins, B9. Folates are actually a family of related compounds that are some modified form of pteroylglutamic acid. We generally hear about folate in terms of folic acid, which is the form found in folate supplements. Folates are modified by being reduced, methylated or through varying numbers of glutamate residues on their tails. Dietary folates are mainly folylpolyglutamates, containing four to seven glutamic acid residues - some folylmonoglutamates (the most bioavailable) may be present in food because most animals/plants contain gamma-glutamyl hydrolase; however, cooking destroys the activity of this enzyme. Upon absorption by enterocrytes, the enzyme gamma-glutamyl hydrolase hydrolyzes these folylpolyglutamates to folylmonoglutamates. One reason that folic acid supplements are much more bioavailable than dietary fol...

I find the story of amylase to be quite interesting, partly because it's a less understood nutrigenetics story compared to lactase. To look at amylase, we must first understand it's substrate, starch. Starch is the polysaccharide storage form of plants - it is homologous to human's storage of glucose as glycogen. Starches are made of two types of glucose polymers - amylose and amylopectin. The enzyme, amylase, is able to catalyze the hydrolysis of starch (at the interior positions), yielding maltose and maltotriose from amylose, and maltose, glucose and dextrins from amylopectin. These are further degraded by isomaltases to provide an energy substrate for the body. Amylase provides a lot of insight into human evolution because of its varied copy number across human populations. 5 genes on Chromosome 1 encode for amylase: AMY1A,B,C and AMY2 A andB (1). AMY1 is our gene of interest, because of its increased copy number - It is believed that the human salivary amylase gene...

The moderate viewpoint always seems to be most truthful, from my experiences. This is especially true in nutrition. I have read articles by MDs stating that nutrition isn't a big issue and there's no evidence showing that fruits and vegetables lead to long life. I have also read alternative health providers stating that eating a raw vegan diet will stave away every ailment known to man. I find this polarized view to be quite vexing - and part of the reason that I'm interested in the intersection of genetics and nutrition. There is definitely no questioning that people benefit from increasing their consumption of nutrient dense foods - getting back to nature is definitely a good thing in a secure food environment; choosing minimally processed foods increases the amounts of vitamins, mineral, antioxidants and phytonutrients that you'll get. It's not all about genetics; people don't become obese due to some genetic defect alone - there needs to be a calorically r...

The term anti-nutrients seems to come up a lot when considering ancestral diets, and for those trying to eat a diet more in line with this concept. For one, I don't think antinutrients is truly the best of describing these plants compounds - calling phytic acid or lectins 'antinutrients' automatically assumes that they are bad in all forms and all concentrations. You'll hear me say this a lot - Nutrition is Toxicology. There is nothing that is inherently bad for you, in and of itself. It depends on the quality, quantity, and form. Don't get me wrong, phytic acid may be something you want to consider, especially if you're a vegetarian with low iron, but it's also been looked at as having anti carinogenic effects (1) - there is definitely not enough of a body of research to draw any overwhelming clinical significance out of this, but there's at least a hint that it's not all bad (phytic acid will probably get its own post later). Anywho, let's ...

It'd be impossible to discuss nutrition and genetics without discussion human milk consumption and lactose (in)tolerance. This example is iconic in that it has huge evolutionary and nutrition implications. From an evolutionary perspective, lactase persistence's relatively widespread distribution is largely due to the success of the agricultural revolution. Milk provides an excellent source of calories, nutrients, animal based amino acids and, often not considered, hydration to any species that can consume it. For most humans, and mammals in general, milk is food for infants. Following weaning, there is low digestive capacity of lactose, and for humans, milk consumed in a non-fermented form in excess of 500mL can be quite uncomfortable. There is potentially good evolutionary reason for this loss of lactase persistence: lactase is able to digest some glycosides found in plants, such as berries and nightshade plants, that would allow for the release of cyanides and other toxic s...

It should be pretty obvious but I nearly forgot to make this post - defining nutrigenetics and nutrigenomics Nutrigenetics: This is, in my opinion, more of the clinical definition. Nutrigenetics seeks to understand the interplay between the genome, variant alleles and nutrition and this interplay's effect on health and athletic performance. Nutrigenomics: This is a broader definition, looking at everything from nutrigenetics to also understanding how gene transcription is affected by nutrients and their metabolites - whether that be by acting directly as a transcription factor, altering the epigenetic state, or by altering the microbiota, which can subsequently alter gene expression. The goal of this discipline: personalized medical nutrition therapy and a greater understanding of human evolution. It's been established that nutrition and the genome interact with each. Nutrition affects gene expression, methylation and acetylation, and nutrient requirements are defined by ...

Here's a link to the talk: http://www.youtube.com/watch?v=BMOjVYgYaG8 I personally don't think this is really a debunking of the paleo diet, as the title claims - and I really don't care to make this blog abut the topic of debunking Paleo either. The Paleo diet seems to have become as diverse as Christianity - with everyone believing the same central dogma (no grains) but fighting over the details (is raw milk paleo? are nuts okay? etc ) - so it's hard to make a generalized statement debunking it. She brings up a lot of good points though, about changes in the diet in the past 10,000 years or so and how much humans have augmented food composition over the years. It's a pretty holistic anthropological viewpoint and better said than I could write up in a timely fashion - enjoy!

Also included in the aforementioned powerpoint presentation that I did was a generalized overview of the hominid diet across the ages. Instead of parsing through the really long post on that, this will be a good review - and contains a bit more temporal data and tool use: Primates – folivorous, frugivorous, insectivores, exudates Australopithecines – 2-4 mya – Similar to primates – bipedal – more humanlike teeth – no evidence of tools- Robustus/bosei- started to include more roots/nuts/seeds/harder to chew foods Homo Habilis – 2.3 mya -first to include scavenged meats/eggs in diet – leap in brain size from Robustus/bosei – tool use – flakes and chopping tools Homo Erectus – first species to leave Africa- 2 mya – much more advanced tool use – use of fire – evidence of cannibalism – potentially hunted small animals Homo Heidelbergensis – descendent of erectus – first hominid to truly hunt large game – brain size getting close to humans – improved tools and subsistence techniq...

A year or so ago I did a powerpoint presentation for a nutrition lab on how past diets are generally reconstructed. I am by no means an expert on the topic (I focused much more on evolutionary genetics and biochemistry in my coursework than bio-archaeology) but here's a brief overview: Primatology - Insectivores – frugivores – folivores – exudates – omnivores – seasonality of food – group dynamics 96% shared base pair sequences between humans/chimps Human brain 3x larger than chimpanzees – consumes about 25% of our calories -   Terrestrial – bipedal – energy expenditure Kleiber's Law – Expensive Tissue Hypothesis Hindgut/Foregut Fermentation – larger colons, smaller intestines comparative anatomy Archaeology - Weapon usage – different for different species – points toward hunting habits Cooking tools – conjectured usage from structure – granules of food particles left - Coprolites – fossilized feces – place in trisodium phosphate for 72 hrs – turns dark brown/...

Primates, Hominids and Their Diets The minutia of this diagram is debated amongst archaeologists and anthropologists. However, the overall point i'm trying to get across is that human evolution happened over a long period of time and had a diverse number of players. Having an understanding of the diet throughout human evolution is of importance if we're going to have a broad understanding of nutrigenetics/genomics. Many factors govern which foods a species will choose for nutrient acquisition: taste, gut morphology, toxic load, seasonality of the environment - just to name a few. It is imperative to take the following information in the context that Homo Sapiens have a much more advanced culture that has allowed for nutrient acquisition from a variety of sources that has made for 'Choice' and 'Preference' to play a much more important role than say, seasonality. What I mean by this is that a chimpanzee may eat largely fruit and leaves but that does not mean...