Nutrition labels list total fat and saturated fat. But when you subtract the saturated fat from total fat, what remains? Is it unsaturated fat? But some labels that include unsaturated fat still don’t add up. Is that because of rounding?
Besides saturated, there’s unsaturated and monosaturated. Mono is the most likely to be left off of a nutrition label. And yes, rounding can be at play sometimes, too. Not everything has monosaturated fat in it.
I think you mean monounsaturated (as opposed to polyunsaturated). “Monosaturated” does not really mean anything in this context.
Of course, monounsaturated fat is still unsaturated, but it may be (I do not know) that nutrition labels use “unsaturated” loosely, to refer to to polyunsaturated fats only.
It may also be that there are other more complex lipids such as cholesterol present, that do not fit neatly into the saturated, monounsaturated, polyunsaturated categories.
Or as Frogurt suggests, rounding errors.
doh, yeah, that’s what I meant. Too tired to type correctly.
Unsaturated comes in two types, monounsaturated and polyunsaturated. They’re not required to spell out the fat content of these types, and frequently don’t.
FWIW, ‘saturated’ means that it’s a long, straight chain of single-bonded carbons that are totally saturated with hydrogen. ‘Monounsaturated’ means that at one joint of the long chain of carbons, two of the carbons share a double bond, meaning that you could theoretically add a couple more hydrogens to that molecule, so it’s not totally saturated with them. ‘Polyunsaturated’ means that there’s more than one place in the chain where this double bond happens, so you could add lots more hydrogens. Saturated fats pack more tightly, because they don’t have any double bonds that force them to kink up; this makes them solid at room temperature, which is a handy way to know if a fat is mostly saturated or not. (Butter? Saturated. Olive oil? Unsaturated.)
The OP is cursed.
I have never seen a label that lists “unsaturated fat”. Either it lists only total fat and saturated fat (sometimes total fat only, on smaller packages), or it lists those two plus polyunsaturated fat and monounsaturated fat. I suspect that grouping them together as “unsaturated fats” is not accepted by the FDA.
Where it gets complicated is with trans fat. Many people think trans fat is a separate, fourth category of fat, and labeling encourages this misconception. Trans fat is unsaturated, and may be either monounsaturated or polyunsaturated (or perhaps a combination of the two). But because of concerns about trans fat intake, it now appears on labeling. So far I have only seen “all four” fats on a label when the trans fat is zero. If that value was non-zero, it would be quite confusing. I do also see the combination of total fat, saturated fat, and trans fat, without the other two.
I had understood that trans fats were always polyunsaturated, having as a necessary but not sufficient condition that the number of unsaturated sites be even.
No. Trans (and its converse, cis) simply refers to the sort of kink that the double bond produces in the hydrocarbon chain. It is entirely possible for there to be trans monounsaturated fats. (It is also possible in principle to have polyunsaturated fats that are a mixture of trans and cis, but I do not think they commonly occur in practice, because naturally produced double bonds in the chains are normally cis, and trans unsaturated fat is generally made by artificial hydrogenation of saturated fats.)
That’s bad.
Sometimes the labeling will say 0% trans fats, but if you read the ingredients, you may find partially hydrogenized fat of one kind or another (which is a trans fat). FDA allows the label to advertise 0% if the ingredients contain 0.5% or less. So, sometimes the totals will not add up because of the rounding down to 0%.