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Walnuts are tree nuts of the genus Juglans. Technically, they are stone fruit, not true nuts. Once picked, walnuts need to be stored properly or they are susceptible to insect or mould infestation, producing aflatoxin (a potent carcinogen). They are best stored at low humidity, below 25°C. The nut meat is used as a high-protein food and walnut oil as a salad dressing but its low smoke point limits its use for frying.
Walnuts contain high protein (15 per cent), high fibre (7 per cent) and high fat (65 per cent). Micronutrients are lutein, zeaxanthin, a range of B vitamins (with high levels of B6 ) and minerals, particularly manganese (163 per cent RDA), magnesium, phosphorus, potassium and zinc.
The fat profile shows high polyunsaturated omega-3 fatty acids with alpha-linolenic acid (14 per cent), linoleic acid (58 per cent) and 13 per cent oleic acid (omega-9). Polyphenols are the main active ingredients, with seven phenolic compounds including ferulic acid, vanillic acid, coumaric acid, myricetin and juglone.
Walnuts also contain ellagitannins, betulinic acid and beta-sitosterol. Phytosterols, tocopherols and squalene are present as well. Based on serving size, walnuts are the seventh-largest source of total polyphenols of all common foods.
In traditional medicine, walnuts were used for a wide variety of ailments: to treat worms and helminths, for diarrhoea, sinusitis, stomach aches, arthritis, asthma, eczema, scrofula, skin disorders, diabetes mellitus, anorexia, thyroid dysfunction, cancer and infectious disease.
Walnuts Nutrient Chart
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There have been many studies conducted on the therapeutic activity of walnuts (and other nuts) on the cardiovascular system. They have been shown to lower total cholesterol and the LDL fraction, trigylcerides and the ApoB marker, while increasing the protective HDL and antioxidant defense systems. Higher doses give better results. They also lowered blood pressure in people without diabetes.
The anti-inflammatory effect reduces the risk of atherosclerosis development in human aortic endothelial cells. Walnut derivatives have also been shown to reduce the oxidation of LDLs, thus lowering the risk of atherosclerosis. Walnuts have protective properties in cardiovascular disease in overweight humans with visceral adiposity (weight collecting around the abdomen) — a known risk factor for cardiovascular disease and metabolic syndrome.
Comparing walnuts with fatty fish, research has shown each regulates different components of cholesterol metabolism. The polyunsaturated fats of walnuts lowered LDL and total cholesterol levels in people with high blood fats and the fatty fish lowered triglycerides and raised HDL cholesterol.
Overall, the high walnut diet showed better results than the high fish diet in regulating cholesterol as well as improving antioxidant capacity.
Improves Brain Health
Yes, walnuts look like the brain, contain polyunsaturated fat like the brain and are often thought of as ‘brain food’, but does science support this claim? Preliminary research has found that walnut extracts appear to have anti-inflammatory effects on brain cells. In addition, another study found a diet rich in antioxidant foods such as berries, grapes, and walnuts may enhance cognitive and motor function in ageing. These are promising results, so eating walnuts may, in fact, be of benefit to brain health.
The anti-inflammatory and antioxidant ingredients of walnuts improve neurological function, increasing signalling, neurogenesis (development of new neurons) and reduction in the amyloid plaques involved in dementia, thus being neuroprotective. Walnuts have been shown to assist in the maintenance of brain health and cognitive function in the ageing.
Despite the high-fat, energy-dense content of walnuts, the high protein and dietary fibre components contribute significantly to the feeling of satiety. Along with the high levels of micronutrients, the net effect is that walnuts have an inverse association with higher levels of consumption (one handful daily is ideal) and lower body weight, helping prevent both obesity and type 2 diabetes.
Metabolic syndrome & diabetes
Regular consumption reduces the risk of the development of metabolic syndrome and type 2 diabetes due to its anti-inflammatory and antioxidant properties.
People with diabetes have twice the risk of heart disease compared to those that don’t.Research has shown that if people with diabetes include walnuts in their diet their blood cholesterol improves, insulin levels are reduced and blood vessels are more relaxed, proving walnuts are cardioprotective.
Improves Gut Health
Beneficial changes in gut microbial communities were shown on the ingestion of walnuts. In rat studies, increased levels of Lactobacillus were measured. Walnuts are prescribed for chronic constipation, intestinal toxaemia, giardia, portal congestion and haemorrhoids.
Green black walnut hulls have been used as a traditional medicine to expel parasites, worms and a variety of pathogenic organisms inhabiting the gut. The juglone component has shown antimicrobial, antiparasitic effects, which, when combined with its laxative activity assist in removing these organisms.
Improves Liver Function
Walnut consumption reverses nonalcoholic fatty liver. It’s said that three things are necessary for a healthy liver: walnuts, coffee and oily fish.
Anti Cancer Properties
The proteins from walnuts showed antiproliferative activity against cancer of the prostate and breast as well as melanoma and leukaemia. Walnuts have been shown to afford partial protection from colon cancer, possibly due to the beneficial changes to the gut microbiome.
Ellagic acid from walnuts is protective against UVA (sun-related) skin cancer by reducing DNA damage in skin cells. Various studies have shown that walnuts improve pathways related to cancer initiation, development and progression.
Buying and StorageTips
When choosing nuts, look for crisp, plump kernels with light skin colour. If buying walnuts in the shell, select clean nuts free from cracks and holes. To keep nuts in the best condition, store them in an airtight container in the refrigerator or freezer. Nuts can be refrigerated for up to 4 months and frozen for up to 6 months. Return nuts to room temperature before eating.
To get the most nutrients from walnuts and take away the mouth dryness it’s best to activate them by soaking in filtered water with a little salt for 4–12 hours then draining them before consuming.
- Tapsell LC, et al. Including walnuts in a low-fat/modified-fat diet improves HDL cholesterol-to-total cholesterol ratios in patients with type 2 diabetes. Diabetes Care 2004;27(12):2777–83.
- Ma Y, et al. Effects of Walnut Consumption on Endothelial Function in Type 2 Diabetics: A Randomized, Controlled, Cross-Over Trial. Diabetes Care. 2010;33(2):227–32.
- Tapsell LC, et al. Long-term effects of increased dietary polyunsaturated fat from walnuts on metabolic parameters in type II diabetes. Eur J Clin Nutr. 2009;63(8):1008–15
- Noakes M. The role of protein in weight management. Asia Pac J Clin Nutr. 2008;17(S1):169–71.
- Sabate J, et al. Does regular walnut consumption lead to weight gain? British Journal of Nutrition 2005;94(5):859–64.
- Willis LM, et al. Walnut Extract Inhibits LPS-induced Activation of Bv-2 Microglia via Internalization of TLR4: Possible Involvement of Phospholipase D2. Inflammation. 2010;33(5):325–33.
- Joseph JA, et al. Grape juice, berries, and walnuts affect brain ageing and behavior. J Nutr. 2009;139(9):1813S–7S.
- Kalgaonkar S, et al. Differential effects of walnuts vs almonds on improving metabolic and endocrine parameters in PCOS. Eur J Clin Nutr. 2011 Mar;65(3):386–93.
- Vanden Heuvel JP, et al. Mechanistic examination of walnuts in prevention of breast cancer. Nutr Cancer. 2012;64(7):1078–86.
- Nagel JM, et al. Dietary walnuts inhibit colorectal cancer growth in mice by suppressing angiogenesis. Nutrition. 2012 Jan;28(1):67–75.
This content is accurate and true to the best of the author’s knowledge and does not substitute for diagnosis, prognosis, treatment, prescription, and/or dietary advice from a licensed health professional. Drugs, supplements, and natural remedies may have dangerous side effects. If pregnant or nursing, consult with a qualified provider on an individual basis. Seek immediate help if you are experiencing a medical emergency.