A Passion for pulses and satiety: where are we headed?

What is the relationship between pulses and satiety?

If the word “pulse” brings only a heartbeat to mind, it’s time to change it up – pulses are also known as the dried seeds of the legume family, including the familiar chickpea, lentil, dried pea, and dried bean. Touting an excellent source of plant-based protein, dietary fibre, complex carbohydrates, vitamins, and minerals, they can complement almost any dish from being a starchy side to a protein-packed main attraction.

In addition to their nutrient-packed profile, pulses have also been investigated for their potential to increase satiety – otherwise known as the process that inhibits further eating, reduces hunger, and produces feelings of fullness after a meal has finished [1].

With unique nutritional traits including slowly digestible carbohydrates, protein-starch complexes, and anti-nutrients such as phytate, all thought to be able to slow down digestion and delay hunger [10], it’s no wonder that pulses have been studied for their ability to increase satiety and decrease food intake as a result. With global rates of overweight and obesity and their associated chronic diseases on the rise, pulse consumption has great potential to be an important front-line dietary strategy to assist with body weight management.

What does the current pulse and satiety literature say?

While the relationship between pulses and satiety seems plausible, results from short-term human clinical trials have been mixed [2]. From stacking different types of whole pulses up to foods such as pasta [11,12,13] to substituting wheat flour with pulse flour in breads [4,6,7,8], studies have produced a wide array of evidence.

Select pulse varieties in whole, fraction (fibre and protein), and flour form, when compared to select control foods, have been shown to increase satiety through an increase in self-reported appetite sensations such as fullness, hunger, and desire to eat, while some have also been shown to decrease food intake at a later test meal – typically an ad libitum buffet or pizza meal served three hours after pulses are consumed. However, variation in the variety, form, and amount of pulses consumed, the type of control food used, and whether foods are matched for energy (calories) or available carbohydrate make results hard to compare among studies.

Overall, the most recent meta-analysis of the available short-term human clinical trials within the pulse and satiety literature found that while pulses were able to increase satiety, they weren’t able to translate those effects to a decrease in food intake later in the day [9].

Where can we go from here?

With only 13% of Canadians consuming pulses on any given day [14] despite being a world leader in pulse production [15], it is clear that even if research advances to prove that pulses can indeed increase satiety and decrease food intake, these low consumption rates could act as a barrier. Since these benefits can only be achieved if pulses are actually being consumed, finding ways to encourage Canadians to consume pulses is vital.

In one of the most recent human clinical trials found in the pulse and satiety literature, Erickson & Slavin (2016) replaced ice cream with a red lentil puree within a fruit smoothie [3]. While they did not find significant differences in satiety or food intake between the two smoothies, this could have been due to differences in their macronutrient profiles – while the lentil puree provided additional protein and fibre, the ice cream was higher in fat – or even the differences in texture, with the ice cream smoothie being thicker than the lentil smoothie [3]. Nevertheless, this ingredient substitution strategy hints at where the research may be headed in light of these low consumption rates.

Human clinical trials are currently being conducted at the University of Guelph to determine the effects of replacing the more commonly consumed ingredients of all-purpose wheat flour and white rice with lentils within familiar food matrices of muffins and chilies on satiety and food intake in healthy adults (ClinicalTrials.gov ID: NCT03128684) with the hope of further investigating this ingredient substitution strategy, with results planned to be published late 2018.

Overall, it is clear that additional research is needed that takes into consideration the low pulse consumption rates in Canada as well as the variation seen amongst the current literature. Luckily, Health Canada (2012) has produced a draft guidance document for satiety health claims on food [5], providing direction for future studies to consider in order to ensure consistency among the upcoming pulse and satiety literature in Canada.

Take-home messages

• Pulses have a unique nutritional profile with potential to support body weight management through an increase in satiety.
• Pulse consumption has been shown to increase satiety and reduce food intake with mixed results, but variation among human clinical trials make results hard to compare.
• Pulses and satiety warrant continued research with an emphasis placed on functional foods to increase consumption rates.