They also need to be sure that their products offer some nutritional value so that customers don’t have to go elsewhere to meet their vitamin needs. But the very processing that’s necessary to create long shelf lives destroys vitamins, among other important nutrients. It’s nearly impossible to create foods that can sit for months in a supermarket that are also naturally vitamin-rich.

Luckily for manufacturers, the early days of the packaged foods industry coincided with the advent of synthetic vitamins, which made it possible to simply replace any vitamins that processing had destroyed. This fortuitous timing meant that manufacturers never had to publicly admit the nutritional inferiority of their products.

Instead, they were free to make claims about the benefits of enrichment and fortification without acknowledging why the addition of synthetic vitamins was necessary to begin with. And once they began to recognize the enormous profits that synthetic vitamins could help them achieve, they never looked back. Today, it would be easy to blame food marketers for using vitamins to deceive us into buying their products. But our blindness is largely our own fault. Rather than challenge the companies that make these foods, we’ve entered into a complicit agreement with them: They depend on us to buy their products, and we depend on the synthetic vitamins they add to those products to support eating habits that might otherwise leave us deficient. The problem with this approach to nutrition is not that there’s anything inherently wrong with synthetic vitamins — it’s the shortsighted nutritional philosophy that our obsession with vitamins encourages. Sure, our easy access to synthetic vitamins means that we’re no longer likely to die from acute vitamin deficiency diseases. But extra vitamins do not protect us from the long-term “diseases of civilization” that are currently ravaging our country, including obesity, heart disease and Type 2 diabetes — many of which are strongly associated with diet.

Indeed, natural foods contain potentially protective substances such as phytochemicals and polyunsaturated fat that also are affected by processing, but that are not usually replaced. If these turn out to be as important as many researchers suspect, then our exclusive focus on vitamins could mean we’re protecting ourselves against the wrong dangers. It’s as if we’re taking out earthquake insurance policies in an area more at risk for floods.

And adding back vitamins after the fact ignores the issue of synergy: how nutrients work naturally as opposed to when they are isolated. A 2011 study on broccoli, for example, found that giving subjects fresh broccoli florets led them to absorb and metabolize seven times more of the anticancer compounds known as glucosinolates, present in broccoli and other cruciferous vegetables, than when glucosinolates were given in straight capsule form. The researchers hypothesized that this might be because the whole broccoli contained other compounds that helped people’s bodies put the anticancer chemicals to use.

And yet we refuse to change our eating habits in the ways that would actually protect us, which would require refocusing our diets on minimally processed foods that are naturally nutrient-rich.

Instead, we use the presence of synthetic vitamins in so many of our foods as justification to continue to eat whatever we want, and seek to fill any remaining gaps via pills. This isn’t true just for people who exist on junk food: The popularity of dietary supplements and vitamin-enhanced processed “health” foods means that even those of us who try to do right by our health are often getting it wrong.

While the recent debate over dietary supplements is important, we mustn’t let it distract us from an even more fundamental question: how we’ve allowed the word “vitamin” to become synonymous with “health.” If we actually thought about this, we’d be forced to admit that the allure of vitamins has hijacked our common sense. And we’d realize a consequential paradox. Synthetic vitamins are now required to keep us healthy — but they also enable us to eat ourselves sick.