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Wednesday, 15 August 2012

Footnotes in Support of the Thiamine Hypothesis of Obesity

Some footnotes in support of the Thiamine Hypothesis:

From The Penguin Encyclopaedia of Nutrition, by John Yudkin:

"The reduction in the prevalence of beri-beri in some countries, such as Japan, has come about by a general improvement in living standards, which as always has been accompanied by a reduced proportion of cereal in the diet, and an increased proportion of other foods. In addition, some governments have introduced legislation requiring a lesser degree of milling of the rice, but this is not always enforced, and the people still prefer the whiter polished rice they have been used to. Nor has there been much success in persuading people to parboil rice if they have not traditionally used it in this form. The addition of thiamine to rice has also been attempted by some countries, but this too is difficult to enforce in the poorer countries.

[The imported rice which we buy in New Zealand is not fortified, and vitamins are sprayed on fortified rice and easily lost in washing and cooking. Only in the USA and Canada does the fortification of rice appear to be, though not mandatory, very pervasive] 

Although beri-beri is usually found in people whose staple food is polished rice, it does occur, although rarely, in other circumstances. It has been seen, for example, in areas where there has been a high dependence on bread made with highly-milled and unfortified wheat flour."

From Principles of Biochemistry 1954 (1973 edition)

"The sparing action of lipid was thought to reflect a lesser metabolic demand for thiamine, but since the thiamine pyrophosphate (TPP) content of the tissues of animals fed a high-lipid diet is considerably higher than that of animals on a high-carbohydrate diet, the lipid may in some manner protect thiamine from destruction.

Nutritional surveys indicate that for much of the American population the thiamine intake is marginal; few adults consume more than 0.8 mg/day, and many eat appreciably less. Thiamine intake can be augmented relatively cheaply by increased use of peas, beans, and enriched or whole-wheat bread, as well as by improved cooking practices. Prolonged cooking of peas and beans with soda results in destruction of as much as 60% of the original thiamine content, and excessive cooking leaches the water-soluble thiamine from many foodstuffs."


In a 1994-1995 survey, the mean intake of thiamine by American adults had more than doubled, to about 2 mg/day, with the lowest percentile near the older figure of 0.8 mg/day, and the highest at around 4 mg/day (this was from food alone, vitamin supplements were not included; today, energy drinks, vitamin enriched chewing gum, and vitamin water would also be boosting the intake): http://www.nap.edu/openbook.php?record_id=6015&page=466

Conclusion:

There is a difference in thiamine status between East and West, and a difference between the Western past, even the recent past, and the Western present, which is consistent with optimal thiamine status being a factor in the "obesity epidemic".
Marginal thiamine status has the potential to be an important confounder when evaluating associations between the proportional carbohydrate content of different diets and obesity rates.

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