Antioxidant-rich fruit, veg linked to less gullet cancer: study

By Stephen Daniells

- Last updated on GMT

An increased intake of antioxidant vitamins C and E, and
beta-carotene may cut the risk of Barrett's oesophagus, a precursor
to oesophageal cancer, suggests a new study from California.

The antioxidants, linked to fruit and vegetable intake, were associated with risk reductions over 50 per cent in the occurrence of Barrett's oesophagus, according to the new study involving 913 people and published in the American Journal of Gastroenterology .

"This is the first U.S. population-based case-control study that examined the association between intake of antioxidants and the risk of Barrett's oesophagus," wrote lead author Ai Kubo from Kaiser Permanente Northern California.

"The study demonstrated that antioxidant intake was inversely associated with the risk of developing Barrett's oesophagus and that the effects appear to come mainly from dietary sources, rather than from supplemental sources."

Barrett's oesophagus is cause by acid reflux, and although it can occur early in life, most sufferers are in their 40s and 50s.

Although it has been reported to be a precursor to oesophageal cancer, 90 per cent of patients are said to never develop into cancer, and although some speculation as to dietary and drug history, the reason why this is so is not really known.

Kubo and co-authors report the results of the case-control study that included 296 people with Barrett's oesophagus (cases) with 308 controls with gastroesophageal reflux disease (GERD) and 309 healthy controls.

A 110-item food frequency questionnaire was used to quantify dietary and supplemental intakes of antioxidants.

The highest dietary intakes of vitamin C (184 mg/d) and beta-carotene (6.8 mg/d) were associated with a 52 and 44 per cent reduction in Barrett's oesophagus risk than people with the lowest intakes (43 and 1.8 mg/d, respectively).

In addition, the highest dietary intake of vitamin E (19 micrograms/d) was associated with a 75 per cent reduction in Barrett's oesophagus risk than people with the lowest intake (5.4 micrograms per day).

"Our results demonstrated strong associations of overall dietary antioxidant intake as an index: individuals in the highest category of antioxidant index had a substantially lower risk of Barrett's oesophagus compared with those in the lowest category [70 per cent reduction], with a significant trend across the categories," wrote Kubo.

On the other hand, no effect of the antioxidant intake, whether from dietary or total (dietary and supplemental sources), was observed when people with Barrett's oesophagus were compared to GERD controls.

"Consumption of fruits and vegetables was strongly associated with a lower risk of Barrett's oesophagus, which is also strongly associated with antioxidant intake," wrote the researchers.

"These associations were weaker and inconsistent when GERD controls were compared with cases, suggesting that although diet may influence the occurrence of GERD among persons with GERD, it does not substantially influence the risk of Barrett's oesophagus."

Active compounds "The discrepancy between dietary and total intake, as well as the lack of effect of supplement intake among those with low dietary intakes, indicate that the beneficial effects of fruits and vegetables cannot be fully explained by the intake of antioxidants per se ," wrote Kubo.

"There are likely to be other unmeasured compounds in fruits and vegetables that affect the early events in carcinogenesis, or there may be complex interactions among various known and unknown compounds and nutrients affecting the etiology of Barrett's oesophagus."

The researchers indicated that more research was necessary and that future avenues could how dietary changes can modify the risk of gullet cancer.

There are reports that diet may have no effect on later stage tumours.

"To examine whether diet modifies the earlier stages of the oesophageal adenocarcinoma pathway (normal mucosa to GERD to Barrett's oesophagus), [an intervention] study could examine the effects of a diet high in fruits and vegetables for subjects at higher risk of Barrett's oesophagus," they concluded.

Source: American Journal of Gastroenterology Volume 103, Pages 1-10, doi: 10.1111/j.1572-0241.2008.01838.x "Dietary Antioxidants, Fruits, and Vegetables and the Risk of Barrett's Esophagus" Authors: A. Kubo, T.R. Levin, G. Block, G.J. Rumore, C.P. Quesenberry, Jr, P. Buffler, D.A. Corley

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