The North/South Ireland Food Consumption Survey: vitamin intakes in 18-64-year-old adults.

OBJECTIVE

To estimate vitamin intakes and assess the contribution of different food groups to vitamin intakes in adults aged 18-64 years in Ireland as estimated in the North/South Ireland Food Consumption Survey. Intakes are reported for retinol, carotene, total vitamin A, vitamin D, vitamin E, thiamin, riboflavin, pre-formed niacin, total niacin equivalents, vitamin B6, vitamin B12, folate, biotin, pantothenate and vitamin C. The adequacy of vitamin intakes in the population and the risk of occurrence of excessive vitamin intakes are also assessed.

DESIGN

Food consumption was estimated using a 7-day food diary for a representative sample (n=1379; 662 men and 717 women) of 18-64-year-old adults in the Republic of Ireland and Northern Ireland selected randomly from the electoral register. Vitamin intakes were estimated using tables of food composition.

RESULTS

In general, the percentage of the population with vitamin intakes below the average requirement (AR) was low. Mean daily intake of total vitamin A was below the AR in 20.2% and 16.6% of men and women, respectively, and mean daily intake of riboflavin was below the AR in 12.5% and 20.6% of men and women, respectively. Mean daily folate intakes were below the AR for folate in 11.2% and 6.6% of women aged 18-35 years and 36-50 years, respectively. Only 2.2% of women aged 18-35 years and 5.2% of women aged 36-50 years achieved the recommended folate intake of 600 microg day(-1) for women of reproductive age for the prevention of neural tube defects. A high proportion of the population has a low dietary vitamin D intake and is largely dependent on sunlight exposure to maintain adequate vitamin D status. Except for pre-formed niacin, the 95th percentile intake of vitamins did not exceed the tolerable upper intake level (UL) for any group and was much less than the UL for most vitamins. Although 20.8% of men and 6.3% of women exceeded the UL for pre-formed niacin (which is 35 mg, based on nicotinic-acid-induced flushing), the large contribution of meat and fish to the intake of niacin (as nicotinamide) suggests that the risk of overexposure to nicotinic acid is much lower than this and is probably solely related to supplement use. A small proportion of men (4.0%) and women (1.2%) aged 51-64 years had retinol intakes that exceeded the UL (3000 microg) and while the 95th percentile intake of women in the 18-50 year age group was well below the UL, 1.5% of 18-35-year-old and 2.4% of 36-50-year-old women had mean daily retinol intakes above the UL. About 2.0% of women had intakes of vitamin B6 that exceeded the UL (25 mg). There were significant differences by age and sex in nutrient densities of vitamin intakes between men and women and between age groups, which may be explained by differences in consumption of particular food groups as well as different patterns of supplement use.

CONCLUSION

Nutritional adequacy of the population for most vitamins was good. Folate intake in women of childbearing age is not meeting current recommendations for the prevention of neural tube defects. The public health significance of the relatively high proportion of men and women with inadequate intakes of vitamin A and riboflavin and with low dietary intakes of vitamin D is unclear and should be investigated further. With the possible exception of niacin (flushing) and vitamin B6 (neuropathy), there appears to be little risk of the occurrence of adverse effects due to excessive consumption of vitamins in this population, based on current dietary practices.