Nuts and seeds have multiple uses beyond simple snacks or breakfast toppings. They can be transformed into non-dairy, soy-free milks, quick cheeses, fermented cheeses, flours and used in raw desserts or baked goods as part of a gluten-free flour blend.
That said, nut and seeds are high in anti-nutrients and nut or seed products should not form a staple of the diet. Anti-nutrients in nuts and seeds include gut-damaging lectins, mineral-binding phytates, protein-binding tannins, enzyme inhibitors and inflammatory polyunsaturated fatty acids (PUFAs) in the form of omega-6 if taken in excess. This type of fat oxidizes readily due to its unstable chemical structure and is metabolized in the body to products that generally mediate inflammatory responses. Comparative studies have shown that dietary intake of omega-6 : omega-3 ratio under 4:1 is contributive to health in reducing the risk of many of the chronic diseases. However, high nut consumption tends to skew the ratio in favor of omega-6.
Apart from the inherent anti-nutrients, nuts and seeds are also susceptible to aflatoxin contamination. Aflatoxins are a group of toxic and carcinogenic metabolites produced by strains of the Aspergillus mold. It can cause liver cancer by inducing changes at the DNA level. The most frequently contaminated products have been reported as peanuts, tree nuts (almonds, Brazil nuts, pecans, pistachio nuts, and walnuts) and oilseeds. A comparative study on Iranian tree nuts (pistachio and peanuts) reported that salt-roasted nuts had higher levels of aflatoxin than raw nuts. In addition, that study highlighted the varying degree of contamination of the same type of nut depending on the country of origin. Storage conditions such as temperature, humidity and transporting methods may influence the levels of aflatoxin contamination.
Below is a table of common nuts and seeds that stock my pantry, and their respective fatty acid profile, omega-6-to-omega-3 ratio, and phytic acid levels. Click on the headers to sort the data in ascending order.
Fatty acid profile and phytate in nuts and seeds.
Legend: SFA: saturated fat; MUFA: monounsaturated fat; PUFA: polyunsaturated fat; O6: omega-6; O3: omega-3; *peanut is a legume. Calculations are based on data obtained from USDA Nutrient Database.
|Name||SFA (%)||MUFA (%)||PUFA (%)||O3 (mg per oz)||O6 (mg per oz)||O6:O3||Phytate
(g per 100g)
From the table, it can be seen that among the nuts, walnuts and macadamia nuts have the most favorable O6:O3 ratio, 4:1 and 6:1 respectively. However in absolute values, walnuts have markedly high levels of overall PUFA and thus is not the “alpha” nut in my opinion. PUFAs are susceptible to oxidative damage, a main cause for many chronic diseases. Among the seeds, chia and flax emerge superior, with an inverted O6:O3 ratio of 1:3 and 1:4 respectively. However, it must be noted that plant-derived O3 is in the form of alpha-linolenic acid (ALA), which is not as efficiently absorbed as the marine-derived O3 eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA).
With regards to phytate, seeds appear to be higher in phytic acid compared to nuts.
Most nuts and seeds should be kept to a minimum on a healthy diet to minimize exposure to the anti-nutrients and aflatoxins. Choose raw nuts and source them from reputable and certified suppliers or companies. When consuming nuts, it is paramount to prepare them properly. Soaking in saltwater reduces the amount of phytic acid and inactivates enzyme inhibitors, and fermentation reduces lectin levels substantially, which are reduced further by cooking. However as nuts and seeds have high fat content, it is better to keep them raw as cooking may oxidize the PUFA. To learn how to activate nuts and seeds properly, head over to the techniques section: soaking and sprouting.