The one food-related ingredient which he aggressively avoids are trans-fats. Being a doctor and all, he's unusually familiar with all the relevant studies and whatnot. Some fats (I discovered to my surprise) are as important as Vitamin C to your health; thus the designation "Essential Fatty Acids," of which the "Omega-3s" are the most well known. Other fats (there are two kinds: fatty acids, and cholesterols) are also part of the entire "food in, life goes on" system of digestion.
Plant fats are almost always runny liquids, aka oils. Animal fats are usually cholesterol solids: grease, butter, lard, and other things commonly called "fat." A few decades back, animal fats were decreed "fata non grata." So the food industry created margarine: plant oils converted to solids by adding extra hydrogen bonds. Presto! Thus Crisco was born. It's just like lard, but made from low-cholesterol plant fat! Yay!
But adding hydrogen bonds to some (partially hydrogenated) or all (fully hydrogenated) of the linking sites of some molecule of fat makes it a different fat. If you hydrogenate alpha-linolenic acid (an Omega-3) or any other fat that your body has a specific use for, you've converted it into a "junk" fat. Not all forms of fat have specific assignments in your body, and any extra "good" fat, and all "junk" fat, will be treated like, well, Fat! The classic "nine calories per gram eat and grow large" aspect of fat that dieters are so dreadfully familiar with.
So, some 'natural' fats (although not all!) are also nutrients. No hydrogenated trans-fats are nutrients.
It gets worse. There is some evidence that a trans-fat version of a nutritive fat might be picked up by the same cellular mechanisms that process "good" fat into various important chemicals with long fancy names. If it does this, then it will sort of "jam" the normal mechanisms, taking up a slot that should have gone to a useful fat, but getting stuck part-way through the process since it isn't really the fat that it appeared to be. So trans-fats might merely be junk fat, or they might actually interfere with your ability to metabolize essential fats, causing even the good fat to just go right to your hips or wherever instead of being turned into prostaglandins, thromboxanes, and leukotrienes. [No, I don't know what they're for, but not having enough is a Bad Thing.]
All right, so I don't treat my body/my temple with quite the same reverence as my husband. I still buy and eat Hamburger Helper even though it's got some partially hydrogenated oil in it (in addition to the un-runny-ness, hydrogenated oils are far more resistant to oxidation; they won't go rancid in a box like a natural oil). But I did throw out the partial can of butter-flavor Crisco, and the margarine I had for cooking 'cause it's so much cheaper than butter.
All well and good, but for one little flaw. Chocolate Chip Cookies require their fat content to be half butter, half Crisco. I swapped in all butter ("hey, it's all fat") but that makes them too flat! And I'm not about to compromise on my cookies! So I told my sweetie "I'm sorry, but for this one recipe, butter or natural plant oils won't do. The cookies must have shortening. Trans-fats must come back."
Of course, the recipe calls for Crisco because it's a substitute for the real ingredient: lard. So here I am at the store, shopping for Crisco ("Hmm. Cute little round can, or butter-shaped stick?"), and I spot, right next to them . . . lard! Lookie there! A little tub of lard! Perfect!
Oh. My. God.
Lard and Hydrogenated Lard
BHA, Propyl Gallate and Citric Acid
Added to Help Protect Flavor
They hydrogenated the lard!!!!
They hydrogenated the lard!
They hydrogenated the lard.
What the hell?