In the conversation about the dismal state of Americans’ health, the cost of healthful food comes up a lot. If produce were cheaper, we would all eat better, and that would lead to less disease.

Would that actually work?

I’ll start by saying there is muddy water galore here. The case starts with the uncertain proposition that decreasing prices will increase the consumption of foods that even rich people don’t eat much of. It moves on to the uncertain proposition that eating slightly more of these foods will have a significant impact on public health. Along the way, it is clouded by people’s inability to remember what they eat, the difficulty connecting diet to health, and problems of researchers generating data on their own projects.

If you want a guarantee, the saying goes, buy a toaster.

A toaster, this ain’t. But there is interesting, relevant research. Let’s take a look.

First, we have to consider whether lower prices will get people to eat more vegetables. (And this theoretical subsidy isn’t for the farmer, but for the consumer.) Economics is pretty clear that a price decrease on almost anything will increase demand, but it’s hard to know by how much.

This problem is compounded when it comes to vegetables. Buoyed by good intentions and reduced prices, you buy a nice assortment of vegetables. Do all of them make it to your dinner table? In the world of full-price vegetables, that answer is a resounding “sometimes,” given that about half of the produce in this country is wasted, with much of that loss coming at the household level. We have all done the crisper-to-compost walk of shame. If people buy more, will they eat more?

Studies of produce subsidies show varying results. A 2013 review of the research concluded that, yes, subsidies do change behavior. It’s worth noting, though, that not all studies find a change. A small study done in Palo Alto, Calif., published last year, found that a subsidy increased purchase but not consumption. An Australian study from 2016 found that participants reported increased consumption, but purchase data didn’t reflect it. Likewise, a study of the Supplemental Nutrition Assistance Program (SNAP, the program formerly known as food stamps) participants in Massachusetts found a self-reported increase in fruit and vegetable consumption, but the expenditures on participants’ electronic benefit cards did not match the reported increase.

Parke Wilde, an agricultural economist at Tufts’s Friedman School of Nutrition Science and Policy and a co-author of the paper reporting the study, floats two possible explanations. The first is simply that people aren’t very good at remembering what they ate. The second is what he calls the “persuasion effect.” Not all fruits and vegetables were covered by the subsidy, and it may be that participants were eating other produce as well.

Wilde favors that second explanation, but anyone evaluating the research essentially has to guess. And that is one of the difficulties of studying the impact of price on what people eat, as opposed to, say, what they drive or wear or hang on their walls. It is easy to track sales but hard to track consumption.

The preponderance of the evidence seems to indicate that a decrease in price is likely to increase purchasing, and that, in turn, will probably increase consumption, at least a little. The USDA estimates that a 10 percent price drop would drive a 2 to 5 percent increase in consumption. A recent study attempting to model the impact of produce prices on health (Wilde is a co-author of the study) concluded that the increase would be larger: about 14 percent.

The model goes on to predict that the 14 percent increase would prevent or postpone about 150,000 deaths from cardiovascular disease by 2030. That would be about 1 in 61, since 610,000 people die of heart disease every year. (It is America’s No. 1 killer.)

The researchers acknowledge that they are working with imperfect evidence, something Marion Nestle, a professor of nutrition, food studies and public health at New York University, explains: “We know from correlational evidence that people who eat more fruits and vegetables are healthier than those who do not. We also know that fruits and vegetables are sources of vitamins, minerals, antioxidants and fiber, and are low in calories – all good things.” Nevertheless, trying to prove that eating more produce would improve health is a job she calls “difficult, if not impossible.” Absent absolute proof, though, the consensus on the healthfulness of produce makes eating more of it “a sensible idea.”

While it is unlikely that this adds up to the kind of justification that would drive that population-wide 10 percent subsidy (which would cost something in the range of $10 billion a year), there are much-smaller-scale, privately funded programs finding other ways to get the job done.

Wholesome Wave is a nonprofit organization working on several fronts to bring affordable produce to underserved communities. In its Fruit and Vegetable Prescription Program, it partners with health-care providers who write “prescriptions” that amount to $1 per day (for each person in the household) toward the purchase of produce. Results are positive, but modest – participants lose, on average, a couple of pounds, and eat an additional half-serving of produce per day (self-reported). A lot of participants drop out, and it is only fair to note that the research is compiled by people who have an interest in the program’s success.

But there is an aspect of these programs that defies data. I talked with Michel Nischan, chief executive of Wholesome Wave, and Pam Hess, executive director of the Arcadia Center for Sustainable Food and Agriculture, which sends Mobile Markets stocked with fresh local produce to neighborhoods in the District not well served by traditional supermarkets. Both of them have made it their business to tackle some of the most difficult, intractable, costly, life-destroying problems we face as a society: obesity and poor nutrition, and the diseases that attend them.

We can all say for sure that some people are helped by these programs – not just by the kale but also by the very idea that someone is paying attention. Someone is trying to fix the imbalance that has left some of the most vulnerable among us with so few good options for decent food.

Both Hess and Nischan stress the importance of measuring the health impact, because if we can reduce the $3.2 trillion we spend annually on health care just a bit, it would pay for a lot of vegetables. (The $10 billion it would cost to reduce everyone’s produce cost by 10 percent is one-third of 1 percent of that total.) But each person helped is more than a data point. Nischan talks about “the impact our programs have on real lives and real people, people who have every reason to be hopeless and feel despair. I’ll never stop, because of the human contact.”