Although vitamin C is known correctly for its cancer preventing qualities, fat in your stomach can alter it so that it forms certain cancer causing chemicals, according to a report published in the journal Gut.

In this study, the scientists looked at the impact of both lipids (fat) and ascorbic acid (vitamin C) on nitrite chemistry in the proximal (upper) stomach. This part of the stomach is especially vulnerable to pre-cancerous alterations and tumor growth, say the writers.

Nitrates can turn into nitrosamines - cancer causing compounds. Nitrates are present in the human saliva, as well as in some preserved foods. Nitrates turn into nitrosamines more easily in acidic conditions, such as the environment in the stomach. Usually, vitamin C converts nitrite into nitric oxide, thus inhibiting the formation of nitrosamines.

The scientists replicated the conditions of the proximal stomach. They then measured the formation of nitrosamines, oxygen and nitric oxide. In the absence of lipids vitamin C reduced the levels of two nitrosamines by a factor of between 5 and 1,000, while completely inhibiting the production of the other two.

The scientists then added 10% fat and found that vitamin C turned nasty. Rather than inhibiting the production of nitrosamines, it boosted it between 8 and 140 fold.

Fat stays around in the proximal stomach for quite a while after a meal. It also makes up a substantial amount of the cells lining the stomach, explain the writers.

When vitamin C reacts with nitrite in acid it forms nitric oxide. However, the nitric oxide can diffuse into fat; react with oxygen to form nitrosamine-generating chemicals.

The authors say their findings may be relevant to the recent observations that vitamin C supplements fail to lower cancer risk.

"Fat transforms ascorbic acid from inhibiting to promoting acid-catlysed N-nitrosation"
Emilie Combet, Stuart Paterson, Katsunori Iijima, Jack Winter, William Mullen, Alan Crozier, Tom Preston and Kenneth E. L. McColl
Online First Gut 2007; doi: 10.1136/gut.2007.12857
Click here to view abstract online

N.B. This footnote has been added after we received several e-mails explaining the same: This article equates ascorbic acid with vitamin C. Ingested by itself, ascorbic acid can actually CAUSE oxidative damage. The fact is that ascorbic acid is only the PRESERVATIVE part of naturally occurring vitamin C. Naturally occurring vitamin C contains other phytochemicals that do provide a protective effect against cancer. Raw organic broccoli is an excellent source of fully complexed vitamin C. To equate ascorbic acid alone with vitamin C is inaccurate and dangerous.

Written by: Christian Nordqvist