The rise in popularity of overnight oats is rooted in food preparation techniques that have been around for many centuries. Soaking legumes, grains, and seeds is similar to other techniques like sprouting and fermenting. The idea common to all of these is to improve the nutritional quality of the food in question, thereby optimizing the health effects these foods have on the body.Traditionally, cultures were attuned to the positive effects that soaking, sprouting, and fermenting had on the foods prepared for consumption.

When discussing the health benefits of a specific food, it is important to consider factors that go beyond the nutrient composition of the food. The way the food is prepared will change the structure of the food and thereby change the journey of the food in the body (along with other factors such as chewing, hormonal factors, and other elements that go beyond the scope of this article).

The Science Behind Soaking

Whole grains and legumes are seeds which are designed by nature to pass through the body undigested in order to be planted and propagated. There are certain compounds, called phytates, within the seed which stop the seed from sprouting until it is in the optimal environment to do so. When consumed in this form, the phytates interfere with the digestion process and inhibit the body from absorbing some essential minerals such as zinc, iron, and calcium. Phytates lower the bioavailability of these minerals and are thus considered “anti-nutrients”.

Bioavailability refers to the amount of a nutrient from a food that is absorbed and used by the body for healthy functioning. If a mineral has a low bioavailability in a specific food, this means that most of the mineral leaves the body unused. An easy way to reduce the amount of phytates is by soaking legumes, grains, and seeds in water. Soaking is a way to jump-start this sprouting process, rendering the minerals more available to be used by the body for healthy functions.

However, the amount of phytate reduction will vary depending on the food, the length of soaking, and the pH of the liquid. Let’s take the example of oats since oats are a popular breakfast cereal in the western world. Oats contain a high level of phytate and it is preferable to soak the oats in an acidic liquid (vinegar and water) or sprout the oats in order to significantly reduce the phytate content. This doesn’t necessarily mean that eating oats that are not sprouted is unhealthy. It is important to note that rolled oats contain fewer phytates because a part of the bran (which contains most of the phytates) is removed during the rolling process. If your diet is well balanced with a variety of different whole foods, you are most likely getting optimal nutrition. If you are unsure, consulting with a nutritionist is a great way to ensure you are getting what you need for your body.

Benefits of Soaking Grains, Seeds, and Legumes

The benefits of soaking grains, seeds, and legumes are not limited to those discussed above. Here are all the ways you can benefit from this simple technique:

• Reduces preparation and cooking time ²
• Softens texture (ie. overnight oats) ²
• Improves digestibility ^{1, 2, 3}
• Reduces phytates ^{3, 4, 5}
• Increases bioavailability of iron, zinc, and calcium ⁵
• Increases magnesium, manganese, and copper content (legumes and millet) ²
• Reduces gas-producing compounds ²

Soaking has been a suggested technique that reduces phytic acid, greatly improves digestibility, and allows your body to absorb more nutrients from various whole foods that may be a regular part of your diet.

Other Benefits of Soaking Oats

Oats have been known to stabilize the blood sugar, lower cholesterol, and improve bowel regularity due to the presence of a fibre called beta-glucan when cooked in water. However, the rise in popularity of overnight oats comes with certain other health benefits when it comes to digestion. When the oats are soaked in water, the texture softens and starches begin to break down, making it easier on the body to digest. Eating the overnight oats uncooked also increases the amount of resistant starch, which elicits a prebiotic effect on the gut microbiota and helps to regulate your blood sugar. By regulating your blood sugar, this means that your energy levels will remain more stable and you will feel full for a longer period of time after eating.

1. Agnoli, C., et al. "Position paper on vegetarian diets from the working group of the Italian Society of Human Nutrition." Nutrition, Metabolism and Cardiovascular Diseases 27.12 (2017): 1037-1052.
2. Fardet, Anthony. "A shift toward a new holistic paradigm will help to preserve and better process grain products’ food structure for improving their health effects." Food & function6.2 (2015): 363-382.
3. Gibson, Rosalind S., and Christine Hotz. "Dietary diversification/modification strategies to enhance micronutrient content and bioavailability of diets in developing countries." British Journal of Nutrition 85.S2 (2001): S159-S166.
4. Gibson, Rosalind S., Leah Perlas, and Christine Hotz. "Improving the bioavailability of nutrients in plant foods at the household level." Proceedings of the Nutrition Society 65.2 (2006): 160-168.
5. Gibson, Rosalind S., et al. "A review of phytate, iron, zinc, and calcium concentrations in plant-based complementary foods used in low-income countries and implications for bioavailability." Food and nutrition bulletin 31.2_suppl2 (2010): S134-S146.
6. Larsson, Marie, et al. "Improved zinc and iron absorption from breakfast meals containing malted oats with reduced phytate content." British Journal of Nutrition 76.5 (1996): 677-688.
7. Sandberg, Ann-Sofie. "Bioavailability of minerals in legumes." British Journal of Nutrition 88.S3 (2002): 281-285.
8. Vadivel, Vellingiri, and Hans K. Biesalski. "Effect of certain indigenous processing methods on the bioactive compounds of ten different wild type legume grains." Journal of food science and technology 49.6 (2012): 673-684.
9. Wolever, Thomas MS, et al. "Glycaemic and insulinaemic impact of oats soaked overnight in milk vs. cream of rice with and without sugar, nuts, and seeds: a randomized, controlled trial." European journal of clinical nutrition 73.1 (2019): 86.