Food Components to Enhance Performance An Evaluation of Potential Performance-Enhancing Food Components for Operational Rations (1994) / Chapter Skim
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19. Choline: Human Requirements and Effects on Human Performance
19. Choline: Human Requirements and Effects on Human Performance
Pages 381-406
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From page 381... ...
Several mechanisms can explain how these effects are mediated. Acetylcholine synthesis can be influenced by the availability of choline; it is an important neurotransmitter controlling such diverse neural Unctions as memory and control of muscle Unction.
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From page 382... ...
. DIETARY SOURCES OF CHOLINE Calculations of dietary choline intake are based on estimates of the free choline and phosphatidylcholine contents of foods (Engel, 1943; Food and Nutrition Board, 1973; McIntire et al., 1944; Weihrauch and Son, 1983; Zeisel et al., 1986~.
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From page 383... ...
. Plasma choline concentrations in fasting subjects vary from 7 to 20 ,uM, with the plasma of most adult human subjects having concentrations of 10,uM, whereas plasma phosphatidylcholine concentrations are approximately 1-1.5 mM (Aquilonius et al., 1975; Sheard et al., 1986; Zeisel et al., 1980, 1991~.
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From page 384... ...
(Finkelstein et al., 1982; Mudd and Poole, 1975; Wong and Thompson, 1972~. Methionine is regenerated from homocysteine in a reaction catalyzed by betaine:homocysteine methyltraIlsferase, in which betaine, a metabolite of choline, serves as the methyl donor (Finkelstein et al., 1982~.
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From page 385... ...
, and phosphatidylcholine is a required component of VLDL (Yao and Vance, 1988, 1989~. Healthy humans fed a choline-deficient diet for 3 weeks developed biochemical changes consistent with choline deficiency (Zeisel et al., 1991~.
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From page 386... ...
The lipid emulsions used to deliver extra calories and essential fatty acids during parenteral nutrition contain choline in the form of phosphatidylcholine (a 20 percent emulsion contains 13.2 ~mol/ml) , and humans treated with parenteral nutrition required 1,000-1,700 ,umol (approximately 800-1,360 mg)
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From page 387... ...
When supplemental choline (in the form of lecithin) was administered during parenteral nutrition in humans, plasma choline levels returned to normal, and the incidence of hepatic dysfunction and steatosis diminished (Buchman et al., 1992~.
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From page 388... ...
A temporal dissociation between choline administration and effects on brain acetylcholine synthesis and release has been observed (Trommer et al., 1982~. The choline taken up by the brain may first enter a storage pool (perhaps the phosphatidylcholine in membranes)
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From page 389... ...
, changes in the cardiac rate have not been observed in healthy humans treated with choline. The urinary bladder muscle is also controlled by parasympathetic cholinergic neurotransmission.
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From page 390... ...
are generated. These second messengers activate protein kinase C (PKC)
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From page 391... ...
. The action of PLC triggers the next event in the signal cascade, which is the activation of protein kinase C (PKC; serine-threonine kineses)
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From page 392... ...
Choline Phospholipids and Signal Transduction The hydrolysis of phosphatidylcholine (PtdCho) occurs in response to a range of agonists, some of which activate PtdCho-specific PLCs and phospholipase D (PLD; PLD generates phosphatidic acid and choline)
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From page 393... ...
Choline and Carcinogenesis Choline deficiency is an excellent example of how choline can influence PKC signal transduction. Choline is the major dietary source for labile methyl groups, and its metabolism is interrelated with methionine and folate metabolism; choline deficiency depletes all of these methyl donors (Zeisel, 19901.
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From page 394... ...
Perturbed PKC signal transduction may lower the threshold dose of carcinogen needed to initiate the development of cancers. CONCLUSIONS AND RECOMMENDATIONS · Choline is an essential nutrient for humans and can affect human performance via multiple mechanisms.
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From page 395... ...
Pieri 1985 Chronic dietary choline modulates synaptic plasticity in the cerebellar glomeruli of aging mice.
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From page 396... ...
Ament, and C.D. Eckhert 1992 Lecithin increases plasma free choline and decreases hepatic steatosis in long-term total parenteral nutrition patients.
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From page 397... ...
26:18-23. Federation of American Societies for Experimental Biology 1975 Evaluation of the Health Aspects of Choline Chloride and Choline Bitartrate as Food Ingredients.
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From page 398... ...
Hannun. 1992 Activation of protein kinase C by oleic acid.
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From page 399... ...
and V.L. Stevens 1989 Modulation of protein kinase C and diverse cell functions by sphingosine- a pharmacologically interesting compound linking sphingolipids and signal transduction.
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From page 400... ...
1988 Influence of dietary choline availability and neuronal demand on acetylcholine synthesis by rat brain.
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From page 401... ...
Cawley, and S Rothermel 1989 Acute choline supplementation in vivo enhances acetylcholine synthesis in vitro when neurotransmitter release is increased by potassium.
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From page 402... ...
I think the consequence of reducing dietary cholesterol is concurrently to reduce dietary choline. My question is, what is the down side of giving people 3 grams of choline per day as opposed to the gram or gram and a half that they are getting now?
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From page 403... ...
There is preliminary evidence, and not very strong evidence, that activation of protein kinase C may be involved in the translocation and activation of the glucose transport system of the skeletal muscle, and so it would be very interesting to look to see whether there is a defect in the glucose transport system in choline-deficient animals. STEVEN ZEISEL: I would be glad to study this.
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From page 404... ...
If part of efficacy has to do with the fatty acid constituents, you would want to know the difference. One thing I did mention, right from the story of total parenteral nutrition, is that there is a study from Emory University that came out a couple of months ago in which they showed that patients treated with nonnal intravenous solutions with lipid emulsions developed fatty liver and liver dysfunction.
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From page 405... ...
The other thing we did was to run people 5, 10, 15, and 20 miles. There was not a linear drop in plasma choline levels with distance.
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