Aspartame and its effects on health
http://www.100md.com
《英国医生杂志》
EDITOR—Lean and Hankey's editorial provoked excited responses on bmj.com from nutritionists, wellness experts, and journalists that showed an often simplistic and selective approach to evidence.1
Mercola talks about "flooding the brain" with amino acids, presupposing that aspartame causes excessive rises in plasma concentrations of phenylalanine that then cross the blood-brain barrier. Plasma phenylalanine rises to 80-120 mmol/l after a protein meal such as a glass of the "natural substance" milk, about the same as after a dose of 34 mg aspartame per kg body weight (about 28 canned drinks sweetened with aspartame consumed at once); current consumption data show that average daily intake is less than 1% of this and maximum intake less than 10%.2
Briffa thinks that aspartame metabolism produces methanol toxicity. According to the US Food and Drug Administration, to cause toxicity in humans, 200-500 mg methanol per kg body weight is needed to produce sufficient amounts of its metabolite, formate (federal register 1984). This corresponds to drinking 600-1700 cans of diet soft drink at once, an amount not achieved after a dose of 200 mg aspartame per kg body weight.3 In long term studies formate production is balanced by excretion, so blood concentrations of formate do not change. Briffa quotes data on formaldehyde accumulation in animals when little aspartame was ingested but not a study in primates that describes the normal conversion of formaldehyde to formate and its inclusion in the one-carbon folate pool, eventually forming S-adenosylmethionine.4 The appearance of around 1% of the radiolabelled carbon in protein, DNA, or RNA could be explained by the rapid flux of carbon through S-adenosylmethionine or other folate dependent reactions into these molecules and tissues. This flux reflects methanol from any source (fruit juice, pectin, or aspartame) and is normal biochemistry, not a toxic event.4
The European Commission's Scientific Committee on Food recently reviewed both science and clinical evidence and gives an update on the safety of aspartame.5
Nick Finer, consultant in obesity medicine
Addenbrooke's Hospital, Cambridge CB2 2QQ nf237@medschl.cam.ac.uk
Competing interests: NF is medical adviser to Ajinomoto.
References
Electronic responses. Aspartame and its effects on health. bmj.com 2004. http://bmj.bmjjournals.com/cgi/eletters/329/7469/755 (accessed 27 Jan 2005).
French Food Safety Agency. Assessment report. Opinion on a possible link between the exposition to aspartame and the incidence of brain tumours in humans. Maisons-Alfort: French Food Safety Agency, 2002. www.aspartame.org/pdf/AFSSA-Eng.pdf (accessed 28 Dec 2004).
Stegink LD, Filer LJ. Effects of aspartame ingestion on plasma aspartate, phenylalanine and methanol concentrations in potentially sensitive populations. In: Tschanz C, Butchko HH, Stargel WW, Kotsonis FN, eds. The clinical evaluation of a food additive. Assessment of aspartame. Boca Raton, FL: CRC Press, 1996: 87-113.
Tephly TR. Comments on the purported generation of formaldehyde and adduct formation from the sweetener aspartame. Life Sci 1999;65: 157-60.
Commission of the European Communities, Health and Consumer Protection Directorate-General. Opinion of the Scientific Committee on Food: update on the safety of aspartame. Brussels, 4 December 2002. (SCF/CS/ADD/EDUL/222 Final.) www.food.gov.uk/multimedia/pdfs/aspartameopinion.pdf (accessed 28 Dec 2004).
Mercola talks about "flooding the brain" with amino acids, presupposing that aspartame causes excessive rises in plasma concentrations of phenylalanine that then cross the blood-brain barrier. Plasma phenylalanine rises to 80-120 mmol/l after a protein meal such as a glass of the "natural substance" milk, about the same as after a dose of 34 mg aspartame per kg body weight (about 28 canned drinks sweetened with aspartame consumed at once); current consumption data show that average daily intake is less than 1% of this and maximum intake less than 10%.2
Briffa thinks that aspartame metabolism produces methanol toxicity. According to the US Food and Drug Administration, to cause toxicity in humans, 200-500 mg methanol per kg body weight is needed to produce sufficient amounts of its metabolite, formate (federal register 1984). This corresponds to drinking 600-1700 cans of diet soft drink at once, an amount not achieved after a dose of 200 mg aspartame per kg body weight.3 In long term studies formate production is balanced by excretion, so blood concentrations of formate do not change. Briffa quotes data on formaldehyde accumulation in animals when little aspartame was ingested but not a study in primates that describes the normal conversion of formaldehyde to formate and its inclusion in the one-carbon folate pool, eventually forming S-adenosylmethionine.4 The appearance of around 1% of the radiolabelled carbon in protein, DNA, or RNA could be explained by the rapid flux of carbon through S-adenosylmethionine or other folate dependent reactions into these molecules and tissues. This flux reflects methanol from any source (fruit juice, pectin, or aspartame) and is normal biochemistry, not a toxic event.4
The European Commission's Scientific Committee on Food recently reviewed both science and clinical evidence and gives an update on the safety of aspartame.5
Nick Finer, consultant in obesity medicine
Addenbrooke's Hospital, Cambridge CB2 2QQ nf237@medschl.cam.ac.uk
Competing interests: NF is medical adviser to Ajinomoto.
References
Electronic responses. Aspartame and its effects on health. bmj.com 2004. http://bmj.bmjjournals.com/cgi/eletters/329/7469/755 (accessed 27 Jan 2005).
French Food Safety Agency. Assessment report. Opinion on a possible link between the exposition to aspartame and the incidence of brain tumours in humans. Maisons-Alfort: French Food Safety Agency, 2002. www.aspartame.org/pdf/AFSSA-Eng.pdf (accessed 28 Dec 2004).
Stegink LD, Filer LJ. Effects of aspartame ingestion on plasma aspartate, phenylalanine and methanol concentrations in potentially sensitive populations. In: Tschanz C, Butchko HH, Stargel WW, Kotsonis FN, eds. The clinical evaluation of a food additive. Assessment of aspartame. Boca Raton, FL: CRC Press, 1996: 87-113.
Tephly TR. Comments on the purported generation of formaldehyde and adduct formation from the sweetener aspartame. Life Sci 1999;65: 157-60.
Commission of the European Communities, Health and Consumer Protection Directorate-General. Opinion of the Scientific Committee on Food: update on the safety of aspartame. Brussels, 4 December 2002. (SCF/CS/ADD/EDUL/222 Final.) www.food.gov.uk/multimedia/pdfs/aspartameopinion.pdf (accessed 28 Dec 2004).