Walnut Nutrition Facts: Omega-3 ALA, Brain Health, and Antioxidants

One ounce of raw walnuts delivers 185 calories, 18.5g of fat (13.4g polyunsaturated, including 2.5g of ALA omega-3), 4.3g of protein, 3.9g of carbs (1.9g fiber), and over half the daily value of copper and manganese. Despite their calorie density, walnuts have earned a place in virtually every evidence-based dietary pattern—Mediterranean, MIND, DASH, and even low-carb plans—largely because their fat profile and phytonutrient content produce measurable gains in cognitive function, lipid profiles, and inflammation markers.

This guide draws every number from USDA FoodData Central (English walnut, raw, NDB 12155) and explains what those numbers mean for your brain and heart.

Walnut Nutrition Facts (per 1 oz / 28g, raw)

Nutrient	Amount	% Daily Value*
Calories	185 kcal	9%
Total Fat	18.5 g	24%
— Saturated Fat	1.7 g	9%
— Monounsaturated Fat	2.5 g	—
— Polyunsaturated Fat	13.4 g	—
— of which ALA Omega-3	2.5 g	167%
Carbohydrates	3.9 g	1%
— Dietary Fiber	1.9 g	7%
— Sugars	0.7 g	—
Protein	4.3 g	9%
Copper	0.45 mg	50%
Manganese	0.97 mg	42%
Magnesium	45 mg	11%
Vitamin E (gamma-tocopherol)	0.91 mg	6%
Folate	28 µg	7%

*Daily Values based on a 2,000-calorie reference diet (FDA). Individual needs vary.

Walnuts Are the Only Common Nut Rich in ALA Omega-3

Why ALA matters

Alpha-linolenic acid (ALA) is an essential omega-3 fatty acid—meaning your body cannot synthesize it and must obtain it from food. Walnuts are unique among nuts: a single ounce provides 2.5g of ALA, meeting 167% of the National Institutes of Health’s recommended daily intake for adults (1.6g for men, 1.1g for women). In comparison, almonds, hazelnuts, and pistachios contain negligible amounts.

The EPA/DHA conversion limitation

Plant-based omega-3 in the form of ALA is not directly equivalent to the long-chain omega-3 fatty acids EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) found in fatty fish and algae. The body converts ALA to EPA and DHA, but the process is inefficient—most research suggests only 8–12% of dietary ALA converts to EPA, and less than 5% to DHA. Genetic variation, sex (women convert better than men), and competing linoleic acid intake all influence conversion rates. This means eating walnuts is a valuable ALA source but should not replace fish or algae supplementation if your goal is to reach therapeutic EPA/DHA levels.

Anti-inflammatory potential

Despite the conversion bottleneck, ALA has independent health benefits. Research in the American Journal of Clinical Nutrition shows ALA intake inversely correlates with inflammatory markers (CRP, IL-6) and is associated with lower cardiovascular mortality. The anti-inflammatory effect likely stems from ALA itself, not just its conversion products.

Brain Health Research: PREDIMED, Walnuts and Healthy Aging, and Cognition

The Walnuts and Healthy Aging (WAH) study

In 2020, Sala-Vila and colleagues published a landmark study in Nutrients examining the cognitive effects of walnut consumption in older adults with subjective cognitive decline (SCD). Over 24 weeks, participants randomized to consume 1 ounce of walnuts daily (vs. an energy-matched control) showed:

• Improved memory, particularly in word-recall tasks
• Faster processing speed (reaction time on cognitive batteries)
• Better selective attention

The magnitude of improvement was modest but clinically relevant—comparable to the cognitive gains seen in some pharmaceutical interventions for mild cognitive impairment. Brain imaging (fMRI) in a subset of participants showed increased activity in regions associated with memory consolidation.

PREDIMED trial and cardiovascular-cognitive link

The PREDIMED trial, one of the largest Mediterranean-diet intervention studies, included walnuts as a key component in the walnut-supplemented arm. Participants who consumed walnuts showed not only improved lipid profiles and lower cardiovascular event rates but also better cognitive performance in secondary analyses. The link is mechanistic: cardiovascular health (blood flow, endothelial function) directly supports brain oxygenation and neuroplasticity.

The polyphenol and vitamin E angle

Much of the cognitive benefit likely originates from walnuts’ high polyphenol content, especially ellagic acid and its metabolites. A 2019 review in Advances in Nutrition noted that polyphenols cross the blood-brain barrier, reduce neuroinflammation, and support mitochondrial function in neurons. Vitamin E (particularly gamma-tocopherol, which is abundant in walnuts) acts as a free-radical scavenger in the brain, protecting lipid-rich neuronal membranes from oxidative damage.

Polyphenol Antioxidant Profile and Anti-Inflammatory Effects

Walnuts are among the most polyphenol-rich nuts, containing 450–1,900 mg of phenolic compounds per 100g (dried weight), depending on variety and growing conditions. Common polyphenols include:

• Ellagic acid and ellagitannins: metabolized by gut bacteria into urolithin A and urolithin B, which show promise in preclinical models for reducing neuroinflammation and promoting mitochondrial autophagy
• Gallic acid: a phenolic acid with antioxidant and antimicrobial properties
• Catechin: a flavonoid also found in green tea, linked to improved EGFR-signaling in brain tissue

The total antioxidant capacity of walnuts (measured by ORAC or TEAC assays) is comparable to that of fresh berries, making them a practical year-round source of antioxidant compounds for people who don’t eat fresh berries daily. In-vitro studies show walnut extracts suppress pro-inflammatory cytokine production (TNF-α, IL-6) in activated immune cells—evidence that supports but does not yet prove the anti-inflammatory effect in humans.

Raw vs. Roasted: Storage, Rancidity, and Heat Damage

Raw walnuts: pros and cons

Raw walnuts retain the full spectrum of heat-sensitive polyphenols and lipase enzymes. However, the high polyunsaturated fat content (~77% of total fat) makes raw walnuts vulnerable to oxidative rancidity—especially if exposed to light, heat, or air for extended periods. A single walnut with visible off-color or sour smell indicates oxidation and should be discarded.

Storage strategy for raw walnuts: keep in an opaque, airtight container in the refrigerator or freezer. Frozen walnuts maintain quality for 1–2 years; refrigerated, 6–12 months; at room temperature (above 70°F), only 2–4 weeks.

Roasted walnuts: the trade-off

Roasting walnuts (typically at 160–180°C for 10–15 minutes) inactivates lipase and other enzymes, dramatically extending shelf life to 6–12 months at room temperature. Roasted walnuts are significantly less prone to rancidity and taste more pleasant to most consumers. The downsides:

• Heat-sensitive polyphenol loss: roasting can reduce some phenolic compounds by 10–30%, depending on roasting temperature and duration. Light roasts preserve more antioxidants than dark roasts.
• Advanced glycation end products (AGEs): high-heat roasting creates small amounts of AGEs (glycation products like acrylamide), compounds implicated in chronic inflammation and aging. However, the AGE content in roasted walnuts remains far below levels in heavily fried or charred foods.

Practical takeaway: both raw and roasted walnuts are nutritious. Choose based on your storage conditions and taste preference. If you buy raw walnuts, use them within a month or freeze them. If you prefer convenience and longer shelf life, choose lightly roasted varieties (avoid heavily darkened batches).

Portion Size and Daily Intake

One ounce of walnuts—equivalent to 14 walnut halves—is the gold standard serving size used in major clinical trials and recommended by the American Heart Association (AHA). This portion:

• Provides 185 calories and 2.5g ALA omega-3
• Fits within fat-intake guidelines for most populations (fits 23–35% of energy from fat)
• Delivers 50% DV of copper and 42% DV of manganese
• Is easy to eyeball or pre-portion (14 halves per small container)

Higher intakes (1.5–2 oz per day) have been tested in some studies without adverse effects and are safe for people actively managing their overall calorie and fat intake. They are not necessary for health and may displace other foods if calories are restricted.

When Walnuts Might Not Fit Your Diet

• Tree nut allergy: walnuts are tree nuts and pose a severe anaphylaxis risk for people with tree nut allergies. A tree nut allergy does not automatically mean peanut allergy (peanuts are legumes), but cross-reactivity varies. Consult an allergist.

• Very low-fat diets (e.g., Ornish, Pritikin, <10% energy from fat): one ounce of walnuts alone uses 16% of a 1,800-calorie diet’s fat budget. These diets are rarely recommended today but are relevant for specific cardiac rehabilitation programs.

• High FODMAP sensitivity (IBS, SIBO): walnuts are low in FODMAPs and are safe for most people on a low-FODMAP diet. However, eating large quantities (>2 oz) of any nut at once can cause digestive distress in sensitive individuals due to fiber and fat load.

• Oxalate-sensitive individuals (chronic kidney disease stage 3–5, or history of calcium oxalate stones): walnuts contain ~32 mg of oxalate per ounce—a moderate amount. People on strict oxalate restriction should count walnuts as part of their daily oxalate budget and confirm with their nephrologist that the amount is safe.

The Bottom Line

One ounce of raw walnuts: 185 calories, 2.5g of ALA omega-3 (the only common nut with significant omega-3), 450–1,900 mg of polyphenols, and roughly 50% of the daily value for copper. Daily walnut consumption (1 oz/day) is supported by cardiovascular, cognitive, and inflammatory-marker research, particularly the PREDIMED trial and Walnuts and Healthy Aging study. The main caveats are that ALA converts to EPA/DHA inefficiently, tree nut allergies require strict avoidance, and the high calorie and fat density demands portion awareness. For people without allergies who can tolerate nuts, walnuts are among the most evidence-backed nuts available.