Cross-sectional studies have suggested an association between glycaemic index (GI) or glycaemic load (GL) and serum lipids. However, no prospective studies have been performed.

To examine whether GI or GL was associated with subsequent changes in serum lipids.

Prospective study with 6 years of follow-up. Overall dietary GI and GL of each participant were assessed from diet history interviews.

Population-based study.

Three hundred and thirty-five healthy men and women aged 35–65 years selected randomly from a larger sample of Danish adults.

In men GI was directly related to changes in total cholesterol (ΔTC), regression coefficient (β) = 0.0044 (95% confidence interval (CI): 0.0008–0.0081) and GL was positively related to changes in low-density lipoprotein cholesterol (ΔLDL), β = 0.1554 (95% CI: 0.0127–0.2982). Furthermore, the relationship between GL and ΔTC was modified by age, being particularly strong for the younger men (P = 0.02). In women the relationship between GI and ΔLDL was modified by age and was stronger for younger rather than older women (P = 0.01). A tendency for a similar interaction was seen for GI and ΔTC (P = 0.09). Associations between GL and ΔLDL and GL and ΔTC were inverse for women with body mass index ≥ 30 kg m−2 (P = 0.03 and 0.04, respectively).

This is the first study to demonstrate that dietary GI and GL are related to 6-year changes in serum lipid levels. However, associations were weak and generally confined to subgroups.