While I agree with the concept of moving subjects from heavily processed, nutrient empty foods such as Lean Cusines®, to more natural foods like nuts, this approach can still result in problems. It is all too common for many to over-do their nut intake, leading to plateaus in weight loss, acne, digestive issues and other problems.
But lets first define what exactly qualifies as a nut, since there are some common misnomers among the general populace.
Nuts: Acorn/Oak, almond, Brazil, candlenut, chestnuts, coconut, hazelnut, filbert, kola, macadamia, pecan, pili, pine, pistachio, soynut, walnut.
Not Nuts, But Actually Legumes: Peanuts, cashews.
The technical difference between the two is as follows: a nut contains one seed, or at most, two. This is in direct contrast to a legume, which contains multiple seeds. Nuts also differ by having a single seed in the shell, whereas legumes contain multiple nuts within a larger case. There are also scientific differences, especially in regards to how nuts and legumes are digested, what elements they contain (such as saponins), and how they may or may not provide energy to your body efficiently, and in what form.
But lets first make the argument FOR nut consumption. Nuts are recommended because of their omega-3 content, which helps to work against inflammation. They are also recommended for their high content of monounsaturated fatty acids, which help lower cholesterol and stabilize blood sugar levels. Nuts contain fat, protein and carbohydrates, as well as antioxidants, like vitamin E. No doubt that in place of processed food snacks (of any kind) or foods such as grains or dairy, nuts come out on top.
However, omega-3 and monounsaturated fatty acids are not all that are found within a nut. Nuts also contain very high levels of omega-6 (an inflammatory element) and PUFAs, or polyunsaturated fatty acids, which are something you will mostly want to avoid. Nuts also contain phytic acid, in higher amounts than even grains. Phytic acid binds to minerals in foods and stops your body from absorbing them. Bad news.
Anecdotal accounts of overconsumption, indigestion and acne are also all very common, when dealing with nuts. Besides fruit, many people turn to nuts as their new fix, or replacement for junk food. Because nuts are calorically dense, and come in jars (which many people eat straight out of) they promote overconsumption very easily. A smarter solution is to eat your nuts in individual servings, or in bags.
Nuts are also extremely high in omega-6, as previously mentioned. Below you will find the worst balance of omega-3 to 6 (Brazil nuts) and ending with the best (macadamia nuts).
Brazil Nuts 416:1, Hazelnuts 42:1, Almonds 27:1, Walnuts 10:1, Macadamia Nuts 1:1
As we start our journey into the compounds and elements present in nuts, we start with selenium. Selenium is a trace mineral, but it is vital to healthy glutathione (master antioxidant) function. Simply eating 2 Brazil nuts per day has been scientifically proven to significantly raise selenium status. Since they are also the worst in terms of omega-3 to 6 ratio, eat small quantities of Brazil nuts, not giant servings.
Another interesting compound found in nuts, is the form of vitamin E found in walnuts. Instead of having this antioxidant vitamin in the alpha-tocopherol form, which is most commonly seen, walnuts instead have it in the gamma-tocopherol form. This form has been proven to be significantly beneficial for heart disease protection.
Macadamia nuts, which should be your go-to nut, have the most beneficial omega-3 to 6 ratio, as well as providing a good source of manganese. Manganese is important for skin, as it is required to make an enzyme called prolidase. This is needed to make collagen. Collagen, as most probably know, is an important component of healthy skin. You may have also read about manganese superoxide dismutase (MNSod) which is an antioxidant famous for protecting against UV damage. Manganese is an important part of forming this compound as well.
Hazelnuts, despite their less-than-optimal 42:1 omega-6 to 3 ratio, do contain a number of interesting compounds as well. They are another nut high in manganese, as well as being high in copper, which is needed for iron absorption. They are also the highest of any nut in folate content. Hazelnuts contain a large amount of proanthocyanidin, which has been proven to fight against reactive oxygen species, and to consequently help fight against cellular damage and aging.
Almonds are the most commonly consumed nut among healthier citizens, and with good reason. Falling somewhere in the middle of omega-3 to 6 ratios, almonds contain a number of other beneficial compounds, as well. Vitamin E, a potent antioxidant, as mentioned earlier, is contained within almonds. What is also present, is magnesiun, potassium, biotin, manganese and copper. A somewhat unique element to almonds alone, is the presence of riboflavin, or vitamin B2. This vitamin plays a vital role in being a co-factor for glutathione reductase, an important version of the master antioxidant glutathione.
What happens when we overconsume nuts? Well, for starters, this is likely to put us in a positive energy balance, which, based on the first law of thermodynamics, means you will start to put on body fat. Since nuts are inherently high in inflammatory omega-6, you will hypothetically start to become inflamed, as well. Though small-to-normal amounts of nuts can be beneficial, overconsumption will likely lead to problems.
By default, you are also likely undereating other sources of nutrients, such as vegetables, or dense sources of protein, like grass fed beef. Nuts are meant only as a small ticket item, not a main course. You can also be ODing on vitamins, such as too much vitamin E from almonds. A simple guide to nut intake can be found here, though I disagree with some of their choices.