A pilot beta-carotene intervention trial with Inuits using smokeless tobacco.

The frequency of exfoliated cells with micronuclei (MNC) was used to estimate the genotoxic effect of smokeless tobacco (snuff) on the oral mucosa and to follow the response to the administration of beta-carotene (180 mg/week, given twice weekly in 6 capsules of 30 mg each). The pilot trial was carried out with Inuits in Gjoa Haven, Northwest Territories, Canada. Their traditional diet, which is rich in caribou and seal meat and liver but low in vegetables and fruits, leads to "normal" serum levels of retinol (447 ng/ml in non-users of tobacco and 463 ng/ml in tobacco users) but low levels of beta-carotene (57 ng/ml for non-users of tobacco and 47 ng/ml for users). Prior to the twice-weekly administration of beta-carotene, the frequency of MNC was 1.87% +/- 0.92 (n = 23) in the mucosa of the lower gingival groove where the tobacco was usually kept. It decreased significantly (P less than 0.001) to 0.74% +/- 0.42 following the 10-week oral administration of beta-carotene capsules. The frequency of MNC did not change significantly in the group receiving a placebo and in snuff users who received no treatment over the 10-week trial period. The size and morphological appearance of the typical snuff-related, whitish, wrinkled patches of the mucosa where the tobacco was kept was not affected by the 10-week treatment with beta-carotene. Similarly, no reduction was observed in the frequency of anucleated, exfoliated mucosa cells. Beta-carotene appears to be an efficient inhibitor of MNC in the oral mucosa of snuff users who do not suffer from any vitamin A deficiency and who have "normal" levels of retinol.