Kevin Klatt, PhD, RD

Pigmentation is a great model for teaching evolution and demonstrating the concept of a polygenic trait - there are a number of alleles at different loci at variable frequencies throughout the population.  This variability has been disproportionately seen across a latitudinal cline, with darker skin tones being present around equatorial regions, and a lightening seen as latitude increases. An estimated 88% of total pigmentation variation in humans can be explained by geographic differences; for reference, geography can only explain 13% of craniometric variation, another highly quantitative trait. Considering the recent evolution of modern humans, this drastic geographic distribution in pigmentation has been thought to be the result of strong selective pressures. The major differences in pigmentation are due to the amount and type of melanin synthesized in the melanocytes, and the shape and distribution of the melanosomes, organelles that transport and store melanin . Melanins are...

I'm all for sustainability - I actually ran a Sustainability Living Community in my undergraduate and was involved with a number of sustainability-related groups. The intersect between the food system, nutrition, and the environment has always interested me, and the vast array of opinions on the topic always gets a nice scientific debate going. That being said, there are some efforts that aren't always the best for you. I was at Whole Foods today and saw milk being sold in glass bottles, advertised that it came from a small farm with a nice picture of a happy cow on the front. After having just gone through Vitamins week in the class I teach, photolysis was on my mind. Milk is the highest source of riboflavin for those consuming a typical Western diet. However, riboflavin in milk is particularly susceptible to photolysis - light degrades the biochemical structure of riboflavin (1). Those glass bottles that milk is being sold in may be re-usable and considered better for the...

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...

Alkaline diets have blown up in popularity. The theory is that over a long time, eating more foods that act acidic in the body (not necessarily having to be acidic in its food form outside the body) will lead to a leaching of calcium from the bones to neutralize blood pH. Some foods claimed to acidify the blood are simple starches, sodas (rich in phosphoric acid) and animal products (higher in cysteine/methionine, sulphuric amino acid). The blood sits at a pH of 7.34-7.45 - this is very tightly regulated, because too high or too low a pH can alter the rates of enzymatic reactions, protein structures, etc. You wouldn't make it too long if your pH dropped out of this homeostatic range. This all sounds fine and dandy right? More acid-acting foods, more calcium removed from bone to neutralize this. I've said this before - there isn't always a simplistic logic that allows you to infer anything about health.I've always been very apprehensive to accept this theory, because...