Here's what snopes has to say: http://www.snopes.com/food/warnings/butter.asp
Origins: This compilation began circulating on the Internet in June 2003, often under the title "Butter vs. Margarine
Surprisingly enough, there is a fair bit of truth to it. According to the latest findings in the medical world, margarine can increase the risk of heart disease, depending upon the type of fat contained in the spread. Previously, the dietary villain in the development in the development of coronary disease was presumed to be saturated fat, but new evidence points the finger to trans fat (also known as trans fatty acids). Although butter has its own set of dietary shortcomings, it does not contain trans fat.
In 1994, Harvard University researchers reported that people who ate partially hydrogenated oils, which are high in trans fats, had nearly twice the risk of heart attacks as those who consumed much less of the substance. Several large studies in the United States and elsewhere, including the Nurses' Health Study conducted by researchers at the Harvard School of Public Health, have also suggested a strong link between earlier death and consumption of foods high in trans fat.
Trans fats occur naturally in small amounts in some foods, including meat and dairy products, but most trans fats in the American diet are formed when vegetable oils are chemically changed to give them a longer shelf life. Cookies, potato
chips, baked products, and the like are particularly loaded with trans fats.
The Food and Drug Administration, the National Academy, the National Heart, Lung, and Blood Institute. and the American Heart Association all recommend consumers limit their intake of trans fat wherever possible. Moreover, the federal government has insisted that by 2006 all food labels disclose how much trans fat products contain.
Until that labelling change comes into effect, consumers should be wary of any foodstuff that makes mention of containing "hydrogenated" or "partially hydrogenated" ingredients. They should also not make the mistake of assuming saturated fats are now good for them or no longer pose any danger to their health. This is not a time to be wallowing in butter.
Those still tussling with the "butter versus margarine" controversy, or who just want to know how their margarine stacks up against others might find the following comparison chart informative. Numbers given in grams refer to how many grams of each particular type of fat there are per tablespoon of that brand. (A tablespoon of butter or margarine contains 14 grams.) Numbers given as percentages represent the impact of one tablespoon of that spread on the recommended daily allowance of that substance. Margarines sampled were of the "tub" variety. (The same margarines in "stick" form had consistently higher numbers.)
Total Fat Saturated Polyunsaturated Monounsaturated
Butter 11g (17%) 7g (36%) 0 0
I Can't Believe It's Not Butter 10g (15%) 2g (10%) 4.5g 4.5g
I Can't Believe It's Not Butter Light 5g (8%) 1g (5%) 2.5g 1.5g
Parkay 8g (13%) 1.5g (8%) 4g 2g
Fleischmann's 9g (14%) 1.5g (10%) 4g 3g
Blue Bonnet 7g (14%) 1.5g (10%) 3g 2g
Imperial 7g (10%) 1.5g (7%) 3g 1.5g
Country Crock (Shedd's Spread) 7g (10%) 1.5g (7%) 3g 1.5g
Because butter is an animal product, it contains cholesterol, amounting to 30 mg per tablespoon or 10% of the USDA recommended daily allowance. Margarines, because they are non-animal products, do not.
The preceeding chart says nothing about which margarines contain trans fats or how much because this information is not yet included on product labels.
Although a great deal of the information given in the e-mail is valid, one bit of intelligence is nothing more than hyperbole tossed in by the author in an effort to make his point more strongly. The claim that some comestible is but a "single molecule away" from being a decidedly inedible (or even toxic) substance has been applied to a variety of processed foods, but that type of statement (even if it were true) is essentially meaningless. Many disparate substances share similar chemical properties, but even the slightest variation in molecular structure can make a world of difference in the qualities of those substances.
Barbara "gold standard" Mikkelson: 2003