Category: Nutrition

Posted on

Food composition

The new issue of the Journal of Food Composition and Analysis has reviews of food composition activities in both Latin America and Oceania. I only have access to the abstracts, but I know that in the Pacific a lot of attention is being paid to differences in nutrient composition among varieties of crops like banana, pandanus and giant swamp taro. This is something that might be of interest to the authors of a third paper in the same issue of the journal. They look at differences in micronutrient composition within different cereal species in Mali but fail to mention this varietal dimension. They ascribe the differences to climate and ecology — at least in the abstract. Important, of course, but surely not the whole story. I’m going to try to get hold of the paper.

LATER: So it looks like what they did is collect various different samples of fonio, say, in each of several distinct eco-geographic zones and pool the samples collected in each zone for analysis. Nothing in the paper about trying to collect material with similar varietal names or anything like that. So any differences due to environment will be confounded with genetic variation. Seems to me like an opportunity missed, at best.

Posted on

More on iron

As coincidence would have it, just a few days after Jeremy blogged about iron deficiency and what could be done about it, Dienekes’ Anthropology Blog flagged a paper on the diversity that exists among human populations in their predisposition to this problem. More specifically, the paper is about hemochromatosis ((Christopher Naugler. Hemochromatosis: A Neolithic adaptation to cereal grain diets. Medical hypotheses. 2007/08/10.)), an hereditary disorder that causes body tissues like the liver to absorb and store more iron than “normal.”

The hypothesis advanced by the author is that the condition arose in Neolithic farming communities as an adaptation to the lower levels of iron in a cereals-based diet as the shift from more iron-rich hunter-gatherer diets accelerated. Highlighting the complexity of nutritional issues, however, is the fact that prevalence of the guilty allele is lower in the Mediterranean and Near Eastern than in northern European agrarian regions, possibly because of the higher dietary intake of vitamin C down south — vitamin C assists in iron uptake. Such interactions are one reason why nutritional silver bullets are unlikely to exist.

Posted on

Rusty conclusions about iron deficiency

Iron deficiency anaemia is a big problem. WHO estimates that about 2 billion people — that’s roughly one in three — lack enough iron in the diet. And the consequences are grave for health and the economies of developing countries. So of course people are focused on ways to combat iron deficiency. Two hog the limelight: supplementation by adding iron to the diet and biofortification, breeding to add more iron to the staples that make up the diet. A recent paper in The Lancet reviews the story of iron deficiency and how to treat it. ((Michael B Zimmermann and Richard F Hurrell, Nutritional iron deficiency, The Lancet, 370 (9586), 11 August 2007-17 August 2007, Pp 511-520.)) Perhaps not surprisingly, the study concludes that “targeted iron supplementation, iron fortification of foods, or both, can control iron deficiency in populations”. And yet, having said that “dietary iron bioavailability is low in populations consuming monotonous plant-based diets,” the authors do not appear to have seriously considered the idea of trying to attack that monotony instead. Maybe enriching and diversifying those plant-based diets to include more dark green leafy vegetables and more pulses would be as effective, with additional benefits in other realms. But that kind of intervention isn’t nearly as glamorous, and gets little attention.

Of course, it could be that solving the problem of iron deficiency will just give rise to other difficulties. Another paper suggests that iron deficiency protects us against some of the epidemic contagious diseases that have hitched along as people crowded together in agriculturally-fed cities. ((S Denic and M Agarwal, Nutritional iron deficiency: an evolutionary perspective. Nutrition. 2007, 23:603-14. Epub 2007 Jun 20.)) Maybe iron deficiency — at least in moderation — is a good thing?

Posted on

All cows are not equal

Cows produce milk, right? Its qualities vary among breeds, with creamy Jersey milk at one end and that skimmed milk cow at the other. And the quantity varies within a breed, which is how we got to the monster lactation machines that are the modern Friesian. But until this morning I had no idea that there was a distinct difference in the type of milk produced by cows within a breed.

Apparently, the major protein in milk, beta-casein, comes in two different forms, called A1 and A2 (original, huh). Some cows have both forms of casein in their milk, some only A1 and some only A2. (Students of genetics will want to know the ratios. I can’t seem to find them.) The A2 corporation, which has registered and trademarked A2 milkâ„¢, says that the A2 form is the original, and that at some point in the past a mutation produced A1. It also hints strongly that as a result, pure A2 milk is better for you. There seems to be some evidence floating around out there, but none of it is overwhelmingly positive.

Anyway, one can determine which cows produce what milk with a simple DNA test, and this morning’s awakening came from a report about the first dairy farm in the US to separate the milk from its A2 cows. A dairy company in Lincoln, Nebraska has started to market A2 milk in the US. To say they are cagey about the exact health claims they are making for this premium priced product would be the understatement of the week.

“To say there is no controversy over this would not be correct,” said Timothy Thietje, CEO of The Original Foods Company, a Nebraska-based marketer of A2 Milk.

“But to say there’s a substantial body of evidence both in terms of science and the response from people who use the product is correct.”

Right.

All this started in New Zealand and Australia, where the milk is marketed without the approval of the milk boards; what would all those other farmers do? But could this, just possibly, be a case in which reducing diversity might be good for you?