Mongongo nuts

Just recently Raphi had a very interesting and very thought provoking chat with Herman Pontzer.

They touched upon honey and the Hadza but didn't mention mongongo nuts and the !Kung San people.

So I will. I might get back to honey in another post.

Mongongo nuts are a major problem for the ROS hypothesis of obesity.

The !Kung San people live on the edge of the Kalahari Desert, as do mongongo trees. The nuts are freely available, storable and edible cooked or raw. They sound quite nice. They go by several names, Manketti nut is the one used in this paper:

Characterization of Schinziophyton rautanenii (Manketti) nut oil from Namibia rich in conjugated fatty acids and tocopherol

With a linoleic acid content just over 30%, and frequently providing a large proportion of the !Kung San people's calories, they should cause obesity, by the ROS hypothesis. If you read the abstract and look at the commas very carefully it almost suggests that the LA is actually conjugated linoleic acid but absolutely doesn't confirm this in the fine print of the full text. With the locations specified for double bonds at 9 and 12 this really is your normal, common-or-garden LA.

So the !Kung should be obese and/or hungry. And they're not.

How come? Another 30-ish% of the fatty acids in the nuts are from alpha eleostearic acid, a triple double bond isomer of alpha linolenic acid. This really is a conjugated fatty acid with double bonds at 9, 11 and 13. Conjugated means the double bonds alternate with single bonds. For ordinary PUFA there are two single bonds between each double bond.

Alpha eleostearic acid is something of a wonder drug, curing everything from cancer to whatever you fancy. It also is very easily converted (by rats at least) in to conjugated linoleic acid (CLA), presumably by hydrogenating the 13 double bond to give cis-9, trans-11 CLA:

Alpha-eleostearic acid (9Z11E13E-18:3) is quickly converted to conjugated linoleic acid (9Z11E-18:2) in rats

CLA is, undoubtedly, a weight/fat loss drug. I glossed over it when it was reported in this paper

Comparison of dietary conjugated linoleic acid with safflower oil on body composition in obese postmenopausal women with type 2 diabetes mellitus

but it seems to be real as in

Isomer-specific effects of conjugated linoleic acid (CLA) on adiposity and lipid metabolism

The CLA/safflower paper was using 6.4g of mixed CLA isomers per day, on a high linoleic acid background (by definition, the subjects were type 2 diabetics with BMI >30, ie LA intoxicated), and got steady weight loss over 18 weeks from this small supplement.

Eating a 1000kcal portion of mongongo nuts would give around 30g of alpha eleostearic acid to convert to CLA. Subsisting on primarily mongongo nuts might supply twice that. Sixty grams of eleostearic acid being converted to just under 60g of cis-9, trans-11 CLA might be enough to offset the LA content.

The situation for the !Kung San seems quite unique and I can't quite imagine any other nut providing an almost year round supply of high fat calories. Any examples gratefully received. In temperate climates nuts are very seasonal and largely supply linoleic acid.

Peter

Addendum from Tucker via twitter; it's not completely clear how important mongongo nuts really are to the !Kung:

Mongongo: The ethnography of a major wild food resource

however there will always be a roughly 1:1 ratio of LA to CLA precursor when they are consumed, in whatever quantities.