Effect of different protein sources on satiation and short-term satiety when consumed as a starter

Abstract

Background: Because the source of protein may play a role in its satiating effect, we investigated the effect of different proteins on satiation and short-term satiety.

Methods: Two randomized single-blind cross-over studies were completed. In the first study, we investigated the effect of a preload containing 20 g of casein, whey, pea protein, egg albumin or maltodextrin vs. water control on food intake 30 min later in 32 male volunteers (25 ± 4 yrs, BMI 24 ± 0.4 kg/m(2)). Subjective appetite was assessed using visual analogue scales at 10 min intervals after the preload. Capillary blood glucose was measured every 30 min during 2 hrs before and after the ad libitum meal. In the second study, we compared the effect of 20 g of casein, pea protein or whey vs. water control on satiation in 32 male volunteers (25 ± 0.6 yrs, BMI 24 ± 0.5 kg/m(2)). The preload was consumed as a starter during an ad libitum meal and food intake was measured. The preloads in both studies were in the form of a beverage.

Results: In the first study, food intake was significantly lower only after casein and pea protein compared to water control (P = 0.02; 0.04 respectively). Caloric compensation was 110, 103, 62, 56 and 51% after casein, pea protein, whey, albumin and maltodextrin, respectively. Feelings of satiety were significantly higher after casein and pea protein compared to other preloads (P < 0.05). Blood glucose response to the meal was significantly lower when whey protein was consumed as a preload compared to other groups (P < 0.001). In the second study, results showed no difference between preloads on ad libitum intake. Total intake was significantly higher after caloric preloads compared to water control (P < 0.05).

Conclusion: Casein and pea protein showed a stronger effect on food intake compared to whey when consumed as a preload. However, consuming the protein preload as a starter of a meal decreased its impact on food intake as opposed to consuming it 30 min before the meal.

Figure 1

Test session timeline for Experiment 1. Subjects arrived at 8h15 in the morning and completed a baseline questionnaire to assess their state of well being and whether they were fasted on the day of the session. They then completed motivation-to-eat ratings. At 8h35 subjects consumed the preload within 5 min accompanied by 50 ml of water or just the water preload (250 ml), and rated their satiety feelings. Between 8h40 and 9h10, subjects continued to complete satiety ratings. At 9h10, subjects measured their plasma blood glucose after they completed the satiety ratings questions. Immediately after, they consumed an ad libitum meal. Once finished (9h30), the subjects completed 2 further sets of satiety questionnaires. They also measured their plasma glucose at different time-intervals.

Figure 2

Energy intake (Mean + SEM) from the ad libitum meal 30 min after the preload. The respective means are embedded in the columns. *Significantly different from water at P < 0.05. Energy intake from the ad libitum meal was significantly lower after the casein and pea protein preloads compared to water control (P = 0.02; 0.04 respectively).

Figure 3

Combined satiety score ratings (Mean ± SEM) before and after consumption of the preload. The CSS ratings were significantly higher after the casein and pea protein preloads compared to the other preloads (P < 0.05). CSS was the lowest after the water control while the ratings were the same after albumin, whey and maltodextrin but higher than the water control (P < 0.05).

Figure 4

Left: plasma glucose response to the ad libitum meal consumed 30 min after the preload (Mean ± SEM). Right: plasma glucose response area under the curve (AUC) (Mean + SEM). Bars with different superscripts are significantly different at P < 0.05. The response after the maltodextrin preload was not included in the analysis since it is 100% carbohydrate and resulted in a pre-meal baseline value that was much higher and incomparable to the protein and control values. Plasma glucose response to the ad libitum meal was significantly lower when whey protein was consumed as a preload compared to the other preloads (P < 0.001).

Figure 5

Cumulative energy intake (Mean + SEM) from both the preload and ad libitum meal. The respective means are embedded in the columns. Bars with different superscripts are significantly different at P < 0.05. Cumulative energy intake, calculated as the preload + the ad libitum meal, was significantly higher after all three protein preloads compared to the water control (P < 0.05).