Eating vegetables before carbs may only delay blood sugar rise, review finds

A review of 18 trials found that meal sequencing lowered glucose levels briefly, but the effect had disappeared or reversed after two hours, with researchers warning against treating it as a universal fix.

A new analysis from the German Diabetes Centre in Düsseldorf suggests that the order in which food is eaten can alter blood sugar levels, but only for a short period. The review, published in the journal Clinical Nutrition, examined 18 randomised controlled studies and found that eating vegetables before carbohydrates such as pasta or rice was linked to a lower rise in blood glucose at 30 and 60 minutes after a meal. By two hours, however, that advantage had disappeared and had, in some cases, reversed.

According to the centre’s summary of the findings, the average blood glucose level was about 22 milligrams per decilitre lower after half an hour when vegetables were eaten first. Two hours later, it was roughly four milligrams per decilitre higher than in the comparison groups. Insulin followed a similar pattern: it was lower early on, then higher later, suggesting that the body may respond with a delayed hormonal surge to compensate for the slower glucose rise.

The idea, often referred to as “meal sequencing”, has gained traction on social media as a supposedly simple way to curb glucose spikes and support weight loss. But the German researchers caution against treating it as a universal fix. Katharina Kampmann-Gongoll, a nutritional scientist at the German Diabetes Centre, said the effect does not translate into a permanently lower blood sugar level, but instead changes the timing of the glucose and insulin response.

The evidence is also weaker than the headline result might suggest. Ten of the 18 studies reviewed had a moderate risk of bias, while the remaining eight were judged to have a high risk of bias. Many of the trials were conducted in Japan, often involved small groups of young, healthy adults, and used different vegetables and meal patterns, making direct comparison difficult. Alexander Lang, another researcher at the centre, warned that the findings cannot simply be extended to older people or to those with prediabetes or type 2 diabetes.

There are hints of longer-term benefit in people with type 2 diabetes, but they are not strong enough to support a broad recommendation. The review pointed to one study in which the average HbA1c, a measure of blood sugar over the previous two to three months, fell from 8.3% to 6.8% over 24 months, although the participants also ate different amounts of vegetables, leaving open the question of what actually drove the improvement. Michael Roden, the scientific director of the German Diabetes Centre, said meal quality matters, but so does total calorie intake, especially for people who are overweight. For now, the safest conclusion is that food order may influence short-term blood sugar swings, but overall diet, portion size and weight management remain more important for long-term control.