The results by Montonen et al. (1) regarding the potential role of dietary antioxidants in the prevention of type 2 diabetes are of considerable interest. The authors identify β-cryptoxanthin as a preventive factor, regardless of adjustment for other potential confounding factors, and point out that data support the hypothesis that “a sufficient intake of antioxidants plays a role in type 2 diabetes prevention.”
Although the follow-up time and number of subjects are considerable, the nutritional and public health relevance on a population basis is uncertain, at least concerning β-cryptoxanthin. The authors report that dietary intake is on average <4 μg β-cryptoxanthin/day in both groups, with the lowest and highest quartiles <0.3 to >4.2 μg/day. However, regardless of the value obtained for the risk ratio (0.58 [95% CI 0.44–0.78]), these data should be interpreted in practical terms.
In developed countries, β-cryptoxanthin is mostly provided by citrus fruits, (2,3) and, after these major contributors are considered, dietary β-cryptoxanthin intake may be easily assessed, making misclassification of individuals unlikely, especially when considering extreme centiles. Also, β-cryptoxanthin content in fresh orange and mandarin is 120–1,300 μg/100 g (3,4). Thus, assuming the lowest end of this range, intake of β-cryptoxanthin in the highest quartile in Montonen et al.’s study (∼5 μg/day) would be equivalent to the consumption of <5 g fresh orange or mandarin per day, which is less than one-twentieth of a standard portion.
In other European countries, median β-cryptoxanthin intake is 0.45–1.36 mg/day (2,3); the southern countries have higher intakes than those in the north, a difference that is also observed in their serum levels (5). Because there is a biological correlation between β-cryptoxanthin intake and serum concentrations, it is reasonable to assume that the lower the intake the lower the serum concentrations.
Considering these facts, in our opinion, it is very difficult to imagine any potential beneficial effects associated with the intake of such low amounts of β-cryptoxanthin as those reported by Montonen et al. (1), even when the statistical evidence is strong. Where nutritionally relevant population-based recommendations are concerned, we should not forget the multifactorial nature of the disease and that people, in the real world, consume foods and diets.
