People soak walnuts to reduce bitterness, soften their texture, and wash away compounds that can interfere with mineral absorption. The practice, sometimes called “activating” nuts, has roots in traditional food preparation, though the actual nutritional benefits are more modest than many wellness sources claim.
Tannins and Bitter Flavor
The most noticeable reason to soak walnuts is taste. Walnut skins contain tannins, the same astringent compounds found in red wine and strong tea. These tannins give raw walnuts their characteristic bitter, mouth-drying quality. Because tannins are water-soluble, soaking pulls them out of the skin and into the water. A 24-hour soak in cold water is usually enough to remove most of the bitterness. If the water still looks dark after the first soak, you can drain it and repeat with fresh water until it runs clear. The result is a milder, sweeter-tasting walnut.
Phytic Acid and Mineral Absorption
Walnuts, like most nuts and seeds, contain phytic acid. This compound binds to iron, zinc, and calcium in your digestive tract, forming insoluble salts your body can’t absorb. Humans lack the enzyme (phytase) needed to break down phytic acid during digestion, so minerals that are technically present in your food pass through without being used. This is the main nutritional argument for soaking: the idea that water draws phytic acid out and frees up those minerals.
The reality is less dramatic than many health blogs suggest. A 2020 study published in the journal Nutrients tested walnuts soaked for 4 hours in salt water, 12 hours in salt water, and 12 hours in plain water. The differences in phytate concentration between soaked and raw walnuts were small, ranging from a 12% reduction to a 10% increase depending on the method. That’s a far cry from the major reductions often promised. Soaking does reduce phytic acid in grains and legumes quite effectively, but nuts appear to hold onto their phytate more stubbornly.
This doesn’t mean soaking is pointless. Even a modest reduction in phytic acid adds up if you eat nuts regularly, and the texture and flavor improvements are real benefits on their own. But if mineral absorption is your primary concern, pairing walnuts with vitamin C-rich foods (which counteract phytic acid) may be equally or more effective.
Texture and Digestibility
Soaking softens walnuts considerably, which some people find easier to chew and digest. If you’ve ever felt heavy or uncomfortable after eating a handful of raw nuts, the dense, dry texture is part of the problem. Soaked walnuts break down more easily during chewing and in the stomach. This is especially relevant if you blend walnuts into smoothies, sauces, or plant-based milks, where a softer nut produces a creamier result.
Interestingly, the polyphenols in walnuts (the same compounds responsible for some of the bitterness) have been shown to slow carbohydrate digestion by inhibiting starch-digesting enzymes. A study in Food Research International found that walnut polyphenols reduced glucose transport across intestinal cells by up to 59%, which could help blunt blood sugar spikes after meals. So while soaking removes some of these polyphenols to improve taste, you may also be washing away compounds with genuine metabolic benefits. It’s a trade-off worth knowing about, particularly if you eat walnuts partly for blood sugar management.
How to Soak Walnuts
The process is simple. Place raw walnuts in a glass bowl and cover them with enough water that they’re fully submerged with an inch or two to spare. Add about 1 tablespoon of salt for every 2 cups of water. The salt helps draw out tannins and phytic acid and improves flavor. Use warm (not hot) water to start, as hot water can partially cook the walnuts and leave them hard and dry. Soak for 7 to 12 hours, or overnight.
After soaking, drain and rinse the walnuts thoroughly. They’ll be soft, slightly rubbery, and noticeably less bitter. You can eat them this way, but most people prefer to dry them first.
Drying Soaked Walnuts
Wet walnuts spoil quickly. If you don’t plan to eat them immediately, drying is essential to prevent mold. The goal is to get them crispy again without damaging the polyunsaturated fats (including omega-3s) that make walnuts nutritionally valuable. Research on nut drying shows that higher temperatures and longer drying times decrease polyunsaturated fat content while increasing less desirable fat profiles, so low and slow is the way to go.
A food dehydrator set between 95 and 100°F is ideal. At this temperature, walnuts typically take 12 to 24 hours to dry completely. You’ll know they’re done when they snap cleanly and feel crisp rather than chewy or bendy. If you don’t own a dehydrator, your oven on its lowest setting with the door cracked open works, though it’s harder to maintain a consistent low temperature. Staying below 115°F preserves the most heat-sensitive nutrients.
Once fully dried, soaked walnuts keep for several weeks in a sealed container at room temperature, or longer in the fridge or freezer. If they feel even slightly soft or damp, keep drying. Any residual moisture is an invitation for mold.
Is Soaking Worth the Effort?
It depends on why you’re doing it. If you find raw walnuts unpleasantly bitter, soaking is one of the most effective ways to fix that, and the improvement is immediate and obvious. If you eat large quantities of nuts and are concerned about mineral absorption over time, soaking offers a small benefit, though the phytic acid reduction in walnuts specifically is modest compared to what soaking achieves in grains and legumes. And if you use walnuts in recipes where a softer, creamier texture matters, soaking is a practical kitchen technique regardless of the nutritional angle.
The one clear downside is time. Between soaking overnight and drying for up to a full day, you’re looking at roughly 24 to 36 hours of passive preparation. Doing large batches at once and storing them makes this more practical than soaking a handful at a time.