Gosh, get your head out of the gutter
If you make nuts a regular part of your breakfast routine—whether they’re incorporated into granola, baked into muffins, or scattered on top of waffles—you might think you’re ahead of the nutritional curve. After all, nuts are a solid source of protein, fiber, and healthy fats, not to mention vitamins and minerals like iron, zinc, selenium. And they’re ready to eat straight out of the package—aren’t they? Not according to a bevy of health bloggers who claim that nuts are practically worthless unless you soak them before you eat them. I first learned about soaking nuts from a colleague a few years ago, and I found myself going down an internet rabbit hole on the topic not long afterwards.
Nuts, I learned from a number of thinly sourced blog posts, contain not only the aforementioned nutrients but also an indigestible form of phosphorous called phytic acid or phytate. Phytate ostensibly binds to iron, zinc, magnesium, calcium, and other minerals, making it impossible for people to absorb these nutrients. The only way to break down the phytic acid in nuts, according to these health bloggers, is to soak them in salt water for 12 to 24 hours and then dehydrate them in a food dehydrator or a very low oven to make them crispy again.
This rationale for soaking nuts sounds scientific, but is it? None of the blog posts I found that advocate the method linked to any studies supporting the hypothesis that phytic acid is robbing humans of nuts’ many nutrients. However, many of them cited a book called Nourishing Traditions: The Cookbook That Challenges Politically Correct Nutrition and the Diet Dictocrats, the subtitle of which didn’t do much to dispel my suspicion that nut soaking was not rooted in nutritional science. I decided to reach out to a few nutritionists and food scientists to ask if soaking nuts is really necessary for most nut-lovers.
The short answer: Phytic acid really does bind to minerals in plant foods, but nobody really knows if soaking nuts makes them healthier for humans. “There is very little in the scientific literature on the effects of soaking (nuts or other foods) on nutrient availability,” explained David Baer, a research leader at the USDA’s Human Nutrition Research Center in Beltsville, Maryland, in an email. What research does exist concerns the effects of soaking on the phytic acid content of whole grains and beans, not nuts. It’s very possible that soaking reduces phytic acid levels in nuts just as it does in grains and beans, but no one’s carried out a study to find out for sure.
It’s also possible that soaking could have the ironic effect of reducing mineral levels in nuts. “I would argue you are also likely to lose water-soluble nutrients by soaking the nuts,” speculated Richard Mattes, distinguished professor of nutrition science at Purdue University. Again, the only way to find out is to test the pre- and post-soaking levels of both phytic acid and crucial minerals in nuts, which hasn’t been done in a well-designed, peer-reviewed study.
Despite the lack of research on soaking nuts, scientists do know that people can absorb at least some nutrients from raw, unsoaked nuts. “With unsoaked nuts, there are papers in the literature that show that after consumption, mineral and vitamin concentrations in blood do increase,” summarized Baer. “Could they increase more if the nuts were soaked? Maybe, maybe not.” And there’s evidence that people who consume lots of phytic-acid-rich foods end up with gut bacteria that can break down phytic acid, freeing up minerals for absorption. So if you eat a lot of nuts, grains, and legumes, your microbiota might already have figured out a way to counteract the phytic acid in them.
So the unsatisfactory bottom line when it comes to soaking nuts is that your mileage may vary. If you currently find nuts difficult to digest, it probably can’t hurt to try soaking them to see if soaked nuts are easier on your digestive system. But there’s simply no empirical evidence that most people will benefit nutritionally from soaking nuts—especially people who have access to a wide variety of other mineral-rich foods, like meat, fish, and green vegetables. Unless you’ve been diagnosed with a zinc, iron, or other mineral deficiency, you’re probably absorbing minerals just fine from the nuts you’re eating.
But there might be another reason to soak nuts: It makes them taste better. After I went down the aforementioned rabbit hole of thinly sourced blog posts, I tried soaking the cashews, almonds, walnuts, and Brazil nuts I put in the homemade muesli I usually eat for breakfast. The results were so good that soaking has become a habit for me. As soon as I bring nuts home from the bulk aisle, I put them in a large bowl, cover them with warm tap water, and stir in about a tablespoon of salt. After letting them soak overnight, I drain them, rinse them well with fresh tap water, spread them on a baking sheet, and let them dry out for 12 to 24 hours in a 175-degree oven. (I’ve found that the cashews and Brazil nuts usually take a few hours longer to dry out fully than the almonds and walnuts.) Nuts that have been given this treatment have a perfectly crisp texture, a slightly salty flavor, and a warm, toasty aroma. Whether or not it’s more nutritious than it used to be, my muesli has never tasted better.