Overstated Associations Between Fructose and Nonalcoholic Fatty Liver Disease
Bibliographic record
Abstract
To the Editor: The conclusion made by O'Sullivan et al (1) may be unjustified. Proper adjustment for energy is imperative. Although the residuals method (2,3) is valid for the energy-adjustment of nutrient intake, it does not completely adjust for total energy intake. To isolate the effect of a nutrient, the convention is to add total energy to the nutrient residual model (2,3). Important confounding from energy has been observed in the effects of fructose. In a series of systematic reviews and meta-analyses of controlled feeding trials, we found that fructose did not have an adverse effect on markers of nonalcoholic fatty liver disease (NAFLD) (4) or related risk factors (5–10) in comparisons matched for energy. A consistent signal for harm, however, was seen in imbalanced comparisons, in which excess energy from fructose is added to diets compared with diets without the excess energy (4–8). Thus, the effects of fructose appear attributable more to excess energy than fructose. Other confounders associated with NAFLD, absent in the models, include saturated fat, dietary fiber, and physical activity. Although not significantly associated with NAFLD in their univariate models, this does not rule out important residual confounding (2,3), especially because the authors themselves have already shown that a Western dietary pattern is associated with a greater risk of NAFLD in this same cohort (11). Contradictory findings further complicate the matter. Across the total cohort (n = 592), a significant negative association was shown with fructose and NAFLD by liver enzymes (alanine aminotransferase [ALT]), an established marker in the diagnosis and management of NAFLD (12). The positive association with fructose and NAFLD by liver ultrasound was only seen in the obese subset (n = 28). Given the small sample size, there is a real chance this association represents a noncausal false-positive association. To understand whether fructose is independently associated with NAFLD, these results need to be tested in other prospective cohort studies with appropriate adjustments on biopsy-proven NAFLD. To move beyond associations, high-quality randomized trials on biopsy-proven NAFLD are needed.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.023 | 0.120 |
| Meta-epidemiology (narrow) | 0.002 | 0.001 |
| Meta-epidemiology (broad) | 0.004 | 0.002 |
| Bibliometrics | 0.002 | 0.002 |
| Science and technology studies | 0.002 | 0.002 |
| Scholarly communication | 0.004 | 0.004 |
| Open science | 0.006 | 0.001 |
| Research integrity | 0.014 | 0.018 |
| Insufficient payload (model declined to judge) | 0.007 | 0.004 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".