Berries improves glycemic response to bread or sugar


Jacob Schor, ND, FABNO
www.DenverNaturopathic.com
May 31, 2013

Three papers have changed the way I look at raspberry jam. And strawberry jam. They would also change my view of lingonberry, bilberry, cloudberry and also chokeberry jam as well except I don’t recall ever tasting them.

These threes studies were all conducted by Riitta Törrönen and colleagues at the University of Eastern Finland, a country apparently blessed with all sorts of juicy berries. Few of us would have predicted the results reported in any of these studies.

In the most recent study, published just this past April, Törrönen investigated the effect of eating berries with bread, either white or rye. In the two earlier studies the berries were combined with sugar. In all the effect on glycemic profiles was measured.

Let’s review these in chronological order. The two earlier studies were published in May and September of 2012. 

The May study measured the impact of a combination of berries and sucrose (white sugar) on postprandial insulin, serum glucose and glucagon-like peptide 1. Twelve subjects were randomized, into a single-blind, placebo-controlled crossover study in which two test meals were consumed on separate days. One meal was a berry purée (150 g) made of bilberries, blackcurrants, cranberries and strawberries with 35 grams of added sucrose. The ‘control meal’ was 35 grams of sucrose dissolved in water. The berries significantly improved the glycemic profile over the sugar water; plasma glucose and serum insulin concentrations were all lower at 15 min, and higher at 90 min. The berry mixture also reduced the maximum increases in glucose and insulin concentrations and improved the glycemic profile. Glycemic control was improved by adding berries to sucrose. 

The second study in Törrönen’s series was published in September 2012. Twenty healthy women participated in this randomized, controlled, crossover meal study. They consumed either blackcurrants or lingonberries (150 g served as purées) or blackcurrant or lingonberry nectars (300 mL) with 35 grams of added sucrose. Sucrose alone (35 g in 300 mL water) was used as a reference. 

Again, compared with sucrose alone, adding berries to sucrose resulted in lower glucose and insulin concentrations during the first 30 min and a slower decline during the second hour and a significantly improved glycemic profile. Berries prevented the sucrose-induced late postprandial hypoglycemic response and the compensatory free fatty acid rebound. Nearly similar effects were observed with the sugar and berry nectars. The improved responses were evident despite the higher content of available carbohydrate in the berry and nectar meals. 


In the most recent study published just this past April 2013, subjects participated in 3 randomized, controlled, crossover, 2-hour meal studies. They consumed white bread (WB) or rye bread (RB), both equal to 50 grams of available starch, with 150 g whole-berry purée or the same amount of bread without berries as reference. 
In study 1, WB was served with strawberries, bilberries, or lingonberries and in study 2 with raspberries, cloudberries, or chokeberries. In study 3, WB or RB was served with a mixture of berries consisting of equal amounts of strawberries, bilberries, cranberries, and blackcurrants.

Eating Strawberries, bilberries, lingonberries, or chokeberries with white bread significantly reduced the postprandial insulin response. So did eating the mixed berry puree with either white bread or rye bread. Both strawberries and the mixed berry puree significantly improved the glycemic profile of both breads (about 40% for the white bread and about 20% for the rye). When white bread is consumed with berries, less insulin is needed for maintenance of a normal or even slightly improved postprandial glucose metabolism. Even the insulin profile to rye bread, which is initially better than white bread’s, is improved.



These three studies tell us that combining berries to sugar or astarch containing food improves the glycemic profile.

The term the term glycemic profile is actually a bit obscure and I confess to only vaguely understanding it until I read these papers. The glycemic profile system was developed by Liza Rosén, doctor in applied nutrition at Lund University in Sweden. It is a specific measuring system used to describe the blood glucose response. It goes beyond the low glycemic index concept we are familiar with. Glycemic profile is “… defined as the duration for the incremental post-prandial blood glucose response divided with the blood glucose incremental peak (min/mM).” 

In simpler words, the GP is based on the graph of the rise and fall of postprandial blood glucose. Glycemic profile scores reflect the appearance of this graph’s curve. The flatter the curve, the better the glucose profile and the higher it is scored. The best scores are for blood sugar curves that are even and reasonably low. High scores describe when blood sugar rises slowly and evenly after a meal and then drops down slowly. Low scores describe sudden spikes and rebound drops into hypoglycemia. Taking these variations into account provides a more accurate prediction of a person’s response to a particular meal, how long their energy is sustained after eating or conversely how soon they will crash.

“A food with a high GP indicates that the energy lasts longer. The absolute best situation is if the product has a low GI and high GP. This means it’s a really good product! One example is boiled rye kernels, which have a GI of 73 (where 100 is the GI of white wheat bread) and a GP of 94. In the same study, boiled wheat kernels had a GI of 68 but a GP of 51. The results suggest that the rye kernels produce a more stable blood sugar profile”, says Liza Rosén. 

This GP system added to glycemic index scores may be a more accurate predictor of your response to meals. Flattening out the sudden spikes in glucose level and insulin production may have more value in preventing and treating metabolic syndrome than glycemic indexes alone. High glycemic profile foods may keep people feeling ‘full’ longer increasing satiety. 

Törrönen’s studies taken together should leave us fairly certain that adding berries to either sugar or bread will actually improve glycemic control. 

Berries provide significant amounts of polyphenols that are linked to a wide array of health benefits. Yet patients, particularly those with blood sugar problems, are often resistant to our suggestions to eat berries in quantity or with frequency out of fear that the berries contain sugar. These studies provide the data to respond to this concern. While berries may contain some sugar, they contain other chemicals that change they way the body responds, slowing the rise in blood sugar, so that neither the sugar in the berries nor the starches eaten with them are quite as bad for you as they might normally be. 

Adding berries to a high carbohydrate breakfast such as corn flakes or oatmeal should lessen the mid-morning hypoglycemic crash these meals often trigger. Adding berries to a pastry do something more than making it look pretty.

Does this mean that bread eaten with jam is better than plain bread alone? Not exactly, but almost; if the jam were made from berry puree without further added sucrose, then yes, apparently it would yield a better glycemic profile. Would a sugar-sweetened berry jam on my morning toast be better than no jam at all? This is where it gets complicated.




References:

1. Törrönen R, Sarkkinen E, Niskanen T, Tapola N, Kilpi K, Niskanen L. Postprandial glucose, insulin and glucagon-like peptide 1 responses to sucrose ingested with berries in healthy subjects. Br J Nutr. 2012 May;107(10):1445-51. doi: 10.1017/S0007114511004557. Epub 2011 Sep 20.

2. Törrönen R, Kolehmainen M, Sarkkinen E, Mykkänen H, Niskanen L. Postprandial glucose, insulin, and free fatty acid responses to sucrose consumed with blackcurrants and lingonberries in healthy women. Am J Clin Nutr. 2012 Sep;96(3):527-33. doi: 10.3945/ajcn.112.042184. Epub 2012 Aug 1.

3. Törrönen R, Kolehmainen M, Sarkkinen E, Poutanen K, Mykkänen H, Niskanen L.J Nutr. Berries reduce postprandial insulin responses to wheat and rye breads in healthy women 2013 Apr;143(4):430-6.

4. Rosén LA, Silva LO, Andersson UK, Holm C, Ostman EM, Björck IM. Endosperm and whole grain rye breads are characterized by low post-prandial insulin response and a beneficial blood glucose profile. Nutr J. 2009 Sep 25;8:42. doi: 10.1186/1475-2891-8-42.

5. http://www.lunduniversity.lu.se/o.o.i.s?news_item=5628&id=24890

6. Rosén LA, Silva LO, Andersson UK, Holm C, Ostman EM, Björck IM. Endosperm and whole grain rye breads are characterized by low post-prandial insulin response and a beneficial blood glucose profile. Nutr J. 2009 Sep 25;8:42. doi: 10.1186/1475-2891-8-42.