A second review, in BMJ Open, by researchers from two UK universities, the University of Leeds and University of Surrey, looked at the nutrition content of yogurt from UK supermarkets, and concluded that reformulation is warranted, given that fewer than 9% and only 2% of the children’s products surveyed, were low enough in sugar to earn ‘green’ in UK front-of-pack labeling.
The study noted that dairy is a significant contributor to the intakes of free sugars by children and adults, adding that diets high in free sugars are now unequivocally linked to obesity and dental caries.
The UK study was a cross-sectional survey of yogurt products available in UK supermarkets in November 2016.
Yogurts were taken from five UK retailers and placed into eight categories: children’s, dairy alternatives, dessert, drinks, fruit, flavored, natural/Greek style and organic. A database of product information for 921 unique products was created and analyzed.
The total sugar, fat, protein, calcium and energy contents were highly variable across categories, and the ranges were extremely broad.
Although lower than the dessert category, the medians (range) of the total sugar content of children’s (10.8 g/100 g (4.8–14.5)), fruit (11.9 g/100 g (4.6–21.3)), flavored (12.0 g/100 g (0.1–18.8)) and organic (13.1 g/100 g (3.8–16.9)) yogurt products were all well above 10 g/100 g, and represented more than 45% of total energy.
Only two out of 101 children’s yogurt and fromage frais products surveyed qualified as low sugar (≤5 g/100 g). Natural/Greek yogurts had dramatically lower sugar contents (5.0 g/100 g (1.6, 9.5), largely lactose) than all other categories.
While low-fat (<3 g/100 g) products had less sugar and energy than higher fat yogurts, 55% (285 of 518 low-fat yogurts) contained between 10 g and 20 g sugar/100 g. Within the children’s category, fromage frais had higher protein (5.3 g/100 g (3.3, 8.6) vs 3.2 (2.8, 7.1); p<0.0001) and calcium contents (150 mg/100 g (90, 240) vs 130.5 mg/100 g (114, 258); p=0.0015) than yogurts.
The researchers said the study highlights other challenges and mixed messages for consumers due to marketing and packaging. Many products suggested for children’s lunches on supermarket websites were very high-sugar desserts (from jelly to dairy based) rather than yogurt or fromage frais.
The authors said retailers could play a positive role in promoting health by establishing boundaries for inclusion in lunch box recommendations. Furthermore, portion sizes for children’s yogurts varied enormously and were often identical to adult portion sizes.
Reformulation is likely to be challenging, the researchers argued, because as well as being a sweetener, added sugar in foods acts as a bulking and coloring agent, and the use of sugar in foods is dictated by physical and chemical properties that are difficult to substitute.
Also, consumers ‘liking’ for yogurt is correlated positively with sweetness. They pointed to a French study where sugar was measured when 204 French subjects were given natural yogurt, and added sugar to make it their preferred sweetness. On average, participants added 13.6 g of sugar to their yogurts, more than the content of many commercial sweetened yogurts.
So, how to reduce sugar?
The US study, by researchers at the Department of Food, Bioprocessing and Nutrition Sciences, Southeast Dairy Foods Research Centre at North Carolina State University and the National Dairy Council, looked at current methods of sugar reduction for dairy foods.
The US researchers noted replacing sugar can have negative effects, making substitution difficult. And while natural non-nutritive sweeteners are popular, particularly for label appeal, many consumers still prefer the taste of artificial non-nutritive sweeteners.
They also said sweet taste perception can be affected by the texture of the food matrix and the presence of fat.
The sugar-reduction techniques considered include hydrolysis of lactose, ultrafiltration and direct reduction.
Role of Sweeteners
As both the US and UK researchers noted, sugar has many roles in foods; it makes foods more palatable, and is a bulking agent, adds viscosity, enhances flavor, provides texture, adds color, is a preservative, and inhibits protein coagulation.
Sugar acts as a bulking agent for many foods. When sugar is replaced or reduced, another bulking agent, such as insoluble fiber or polydextrose system, is often required.
However, when sucrose is replaced with a bulking agent, the bulking agents also contribute calories to the product and may negate the original purpose of removing the sugar. For example, maltodextrin is a common sugar replacer and bulking agent and it contributes the same amount of calories as sugar (4 kcal/g).
Natural and artificial sweeteners
Sweeteners can be divided into two categories: natural and artificial.
According to the authors of the US study, currently there are many FDA-approved natural nutritive sweeteners, two natural non-nutritive sweeteners, and seven FDA-approved artificial sweeteners, with more being developed.
Natural nutritive sweeteners provide energy in the form of carbohydrates. Examples include fructose (found in honey and agave), lactose (found in milk), and sucrose (table sugar). Sugar alcohols are natural nutritive sweeteners that have similar sweetness intensity to sucrose but contribute fewer calories due to slower and incomplete absorption in the intestine.
An example of a sugar alcohol that can be metabolized without insulin is lactitol or isomalt.
Stevia (Stevia rebaudiana) and monk fruit are natural non-nutritive sweeteners that can be extracted from plants, dried and used as sweeteners.
Artificial sweeteners are not found in nature and are synthesized. The first artificial sweetener, saccharin, was approved by the FDA in 1958, and the most recent artificial sweetener approved by the FDA was Advantame in 2014.
The researchers stated artificial sweeteners can be synthesized from a natural source: for instance, sucralose is derived from sucrose but because it is derived or synthesized from sucrose, the sweetener is no longer considered natural.
They also stated when addressing sugar and calorie reduction, artificial sweeteners have more desirable taste profiles and when only flavor is considered (blind tasting), foods and beverages sweetened with artificial sweeteners generally score better than natural non-nutritive sweeteners.
Consumers have shown interest in natural sweeteners but many refuse to compromise on taste, as the food must have a desirable flavor, they added. Contrary to this, many consumers still will choose a “naturally sweetened” product over an “artificial” labeled product.
The authors cited other factors: there is a large cost difference between natural and artificial sweeteners; and stability is another factor, as many artificial sweeteners cannot be used in certain applications due to heat or pH instability.
Lactose hydrolysis has been investigated as a sugar reduction alternative because hydrolysis of 70% of the lactose in milk increases the sweetness of milk or yogurt to the same degree as adding 2% sugar.
Lactose hydrolysis of natural lactose in milk has also been investigated as a means of sugar reduction in yogurt.
Ultrafiltration is a well-established method for decreasing lactose in milk; it is a pressure-driven process that separates compounds in milk by molecular weight, and is widely used in the dairy industry for lactose removal and can be used for sugar reduction.
Direct reduction of sugar is a method for a gradual reduction of sugar consumption, whereby the sugar content of dairy products is slowly and progressively reduced so consumers will gradually get used to the lower sugar concentrations without noticing a difference.
Because consumers desire sweet taste, sugar substitution is a preferred method among sugar reduction techniques to preserve a sweet taste. Currently, many different types of sweeteners are available for sugar substitution but issues include sugar substitution being very product specific.
The authors also looked at the different methods currently available for sweetening ice cream, frozen yogurt, yogurt, and flavored milks, concluding that progress is being made to make products acceptable to consumers.
They said that, currently, substitution of sugar using non-nutritive sweeteners has been the most successful approach for sugar reduction but direct reduction of sugar and lactose hydrolysis methods show promise, adding that there are a variety of methods manufacturers can use to reduce sugar and still produce high-quality products to help reverse the negative health effects with high sugar consumption.
Source: Journal of Dairy Science
Invited review: Sugar reduction in dairy products
H.R. McCain, S. Kaliappan M.A. Drake
Source: BMJ Open
Evaluation of the nutrient content of yogurts: a comprehensive survey of yogurt products in the major UK supermarkets
Moore JB, Horti A, Fielding BA