Remember when Margarine was healthy and Butter was unhealthy? Yeah...well we discovered trans fats (Margarine baaaaaad) and Omega-3s (Butter gooooood). (And we discovered this within the last 10 years, too).
You may want to avoid getting your nutritional information filtered through the dairy farmers of America. <_< Just checked the margarine in my fridge and it has Omega-3s but no trans fat.
Also, while trans fats are indeed bad, they're only about as bad as saturated fats, which are unavoidable in butter. Although to be fair, the margarines that have them (usually the ones trying to imitate butter) are indeed shit.
Hm, Margarine's improved since the last time I looked at it, then.
Or at least my patchwork understanding of nutrition history is that in the 60s it was mostly hydrogenated vegetable oils (hydrogenation generally causing trans fats) and it was advertised as more healthy than butter specifically because it avoided certain kinds of fats they thought were good to avoid (including Omega-3s).
According to wikipedia, Margarine these days is a mixture of milk and vegetable oil. So...yes: anything with milk in it is going to have some of the same stuff as butter; and naturally, now that we know Omega-3s are good, you can do "added omega-3s" if desired (the same way my orange juice has added Vitamin-D...which is good because I'm a vampire and avoid sunlight).
Nutrition is actually brutally uncomplicated according to most people in medicine I've talked to. We know very well what people need more of (fruits/vegetables, fibre in general) and less of (saturated fat, refined sugar, sodium) compared to the average North American diet.
Hm, good to know. Probably should work on my sodium....
I find all the distracting fad diets immensely frustrating, as such; by contrast they are usually based on little to no scientific evidence (such as the one Trips linked) and often flaunt what evidence we do have. And the publication of such diets is distracting for people who honestly want to live healthier and will usually key onto such diets over the things they don't want to hear (sorry, that sweet/salty food you love is actually bad for you and should only be eaten once a week).
In defence of seemingly stupid oddball diets...my parents did the Atkins diet, which I thought was stupid at the time. They said that because they did this diet they were eating a lot more vegetables (the kind of carbohydrates the plan does allow) and fewer things like crackers and cookies (the kind of carbohydrates the plan does not allow). The actual protein intake the Atkin diet is known for? ...Well they still ate exactly the same meat dishes (which already met Atkins requirements), just surrounded them with vegetables instead of their old choices. From all I've read this is...actually a significant dietary improvement. And indeed their health did improve. So...sure, a plan that advertises itself as "remove carbohydrates" sounds completely retarded, but it actually knew what it was talking about...mostly.
As for the caveman diet...I bet their refined sugar and sodium intake is very low. It was clear from the article that they do eat vegetables. Saturated fats...depends on what kind of animal they eat, and how they prepare it (you can cut away fat). Notably, organ meat (which they eat) is probably fairly light on fat (since fat tends to lay right below the skin as a layer of insulation, not inside the organs). So...in all likelihood it's actually a relatively healthy diet (outside of fasting...).