Whether you’re healthy or not, post-meal blood glucose and insulin levels are something that deserve attention.

I previously wrote about how we need to be cognizant of the foods we eat when determining how their calorie and macronutrients contents may affect our health.

Well, what about the way in which foods are eaten?

Veggies (and protein) first

A handful of studies have looked at how food order within a meal affects the blood glucose and insulin responses to that meal. Most of them were conducted in people with type II diabetes, and they compared the effects of eating fibrous vegetables before or after eating starchy carbohydrates.

Blood glucose and insulin levels were reduced by 20–70% and 25–50%, respectively, by simply eating veggies first. Talk about low-hanging fruit.

Two of these studies came out of Saeko Imai’s lab in Japan. The first was a small crossover trial in 15 patients with type II diabetes, and the second was a  crossover trial involving 19 patients with type II diabetes and 21 healthy adults. In both, participants ate a cabbage-tomato veggie salad before a bowl of rice or vice-versa.

The three other studies were conducted by Alpana Shukla from New York’s Weill Cornell Medical College. He wanted to see if similar observations would be made in the American population eating typical Western meals.

I like this guy’s research because each of the studies builds upon one another and answers nuanced questions. His pilot study was pretty simple: have 11 people with type II diabetes eat ciabatta bread and orange juice, followed by skinless grilled chicken breast, followed by a lettuce and tomato salad with steamed broccoli, or the same foods in the reverse order.

In a follow-up study, he then combined the veggies and chicken breast and had 16 patients with type II diabetes eat this before or after the bread and juice. He also had them eat everything combined as a mixed meal. Eating the veggie-chicken combo first reduced the blood glucose and insulin responses by 53% and 25% compared to eating them last, and by 44% and 17% compared to the mixed meal.

Shukla’s most recent publication came out several weeks ago and extended his previous studies into those at risk of developing type II diabetes. The three eating conditions were:

1. Veggies first, then chicken, bread, and juice together,
2. Veggies with chicken, then bread and juice, or
3. Bread and juice, then veggies and chicken.

Compared to (3), both (1) and (2) blunted the blood glucose response by about 38% and reduced the insulin response by 44% (1) and 23% (2).

What about just protein?

Now, all these studies involved eating some vegetables before a starch, sometimes with protein, sometimes without. But what about eating just protein first?

This question was investigated in a crossover trial that looked at the effects of eating boiled mackerel or grilled beef before or after steamed white rice. The researchers recruited 12 patients with type II diabetes, as well as 10 healthy adults.

Both groups experienced reductions in the blood glucose and insulin responses when the meats were eaten before the rice, as compared to afterwards, although statistical significance wasn’t achieved for the healthy folk. Both groups also reduced their C-peptide, indicating less insulin was released by the panreas.

Do these effects play out in the real-world?

Knowing what happens in the three hours after a meal is cool and all, but the real money is whether these effects have an impact on long-term health. Turns out, they do.

In one  randomized controlled trial involving 101 adults with type II diabetes, particiapnts were assigned to a group told to eat veggies first and carbohydrates last in each meal, or to a group that followed the diabetic exchange list recommendations. Both groups dropped their HbA1c after three months, but the veggie-first group kept going thereafter and maintaining a lower HbA1c than the exchange group after two years.

In another study, 20 older adults with type II diabetes underwent an 8-week intervention in which they either did or did not receive advice to eat high-carbohydrate foods after high-protein and high-fat foods during lunch and dinner.

The group told to eat carbs last demonstrated significantly lower post-lunch blood glucose levels (-67%) and glucose variability (-39%) than the control group. It was also the only group to experience reductions in HbA1c (-0.3%), fasting glucose (-14%), post-dinner glucose levels (-60%), and average post-meal blood glucose levels (-11%) after eight weeks compared to baseline. 

Summing up

Eat your veggies first, with protein if you wish. Better yet, just eat your starches last. That is easier to remember.

The improvements in post-meal blood sugar control rival or exceed those seen with add-on drug therapies aimed at regulating post-meal glucose levels. Also, the free-living aspect of the long-term interventions demonstrates that merely giving instructions to consume high-carbohydrate foods at the end of a meal is a pragmatic way of helping people manage their blood glucose levels. 

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