A review of 57 trials suggests that when dairy is consumed may matter as much as the type, with whey taken before meals showing the clearest short-term benefit for glucose control.
A new review in Nutrients suggests that milk and dairy are not all metabolically alike, and that timing and formulation may matter as much as the food itself for people with type 2 diabetes and prediabetes. Drawing on 57 randomised controlled trials, the review found that broad increases in dairy intake tended to produce mixed, mostly neutral effects on long-term blood sugar markers, while more targeted approaches, particularly whey protein taken before meals, were more likely to blunt short-term glucose spikes.
The authors examined studies of fluid milk, yoghurt, kefir, fortified dairy drinks and isolated proteins, with outcomes including fasting glucose, HbA1c, insulin resistance and post-meal hormone responses. The review, which was published in Nutrients, reflects a wider debate in diabetes nutrition: dairy has long been associated in some observational research with a lower risk of type 2 diabetes, especially yoghurt and low-fat products, yet the evidence from intervention trials has been far less consistent.
One of the clearest signals in the new review came from whey protein preloads, meaning whey consumed before eating. Across several trials, amounts of roughly 15g to 50g taken before a meal improved post-meal glucose control, although the best dose and timing remain uncertain. In one study involving adults with type 2 diabetes, a 50g whey preload taken 30 minutes before breakfast cut overall post-meal glucose exposure by 28% and increased insulin and GLP-1 responses, a hormone that helps the body release insulin after eating. Other studies found that some fortified or fermented products, including certain yoghurt drinks, improved glycaemic measures, although those benefits may have come from added vitamin D, calcium or bacterial cultures rather than from dairy alone.
The review also found that the longer-term picture remains unsettled. Several trials showed no meaningful change in HbA1c, the key measure of average blood sugar over about three months, when people simply increased dairy intake to three or more servings a day. A small number of studies pointed in other directions, including one 12-week trial in which a whey-enriched breakfast lowered HbA1c by 0.89 percentage points, but other experiments did not replicate that effect. The authors say the most promising results may come from specific products used in a structured way, rather than from a general instruction to eat more dairy.
That caution matters because the review’s authors emphasised that the trials were often short, small and varied in design. Most lasted only four to 24 weeks, and many were not large enough to settle questions about durability, sex differences or real-world use. The researchers also said future studies should test how whey preloads might interact with newer diabetes medicines, including GLP-1 receptor agonists, which can already cause gastrointestinal side effects. For now, the review points to a practical but limited conclusion: dairy should not be treated as a single category, and some forms, used at the right time, may help reduce post-meal blood sugar rises without replacing established diabetes treatment.
Disclaimer: This content is for informational purposes only and is not intended to be a substitute for professional medical judgment, advice, diagnosis, or treatment.
