It’s an ongoing frustration for many doctors when treating chronic illness: Even effective drugs like beta blockers and insulin won’t work if patients spend the rest of the day eating frozen pizza and cookies.

Now, more and more, patients are leaving the doctor’s office with a prescription not only for the pharmacist but for the grocery store as well.

These nascent programs help treat chronic illness with the most powerful tool available – a healthy diet. And they are having success in helping patients lose weight and be more active, while saving significant money on health care costs.

One of the first such programs started in 2001 in Boston, where patients at a safety net hospital could help themselves to healthy food at an onsite pantry.

In San Francisco, health officials distribute food along with nutrition advice through weekly events at clinics, hoping to reach more people. In northeast and central Pennsylvania, the Fresh Food Farmacy provides 700 patients with produce, cooking demonstrations and diabetes management tips, spending about $3,500 per family but saving on medication, doctor visits and hospital stays.

A new program in Washington, D.C., takes a slightly different tack. Rather than providing the healthy food directly, Produce Rx gives 500 Medicaid patients $20 weekly vouchers to be used at a local grocery store.

The setup allows recipients to pick up their allotment of produce while they are also picking up the rest of their groceries. It also gives those stores reason to carry more produce, something that is often lacking in low-income areas.

Evidence shows patients losing weight and becoming more active, and lowering blood sugar or blood pressure levels.

The savings speak for themselves. The Pennsylvania program estimates it spends about $1,000 per person, but saves $8,000 per person for every point drop in blood sugar. Another found a similar program saved about $1,200 per person per year in health care costs.

Diabetes alone costs the U.S. $240 billion a year. Programs like these spread across the country could take a big bite out of what we spend on diabetes and hypertension, and help people lead more fulfilling lives in the process.

Maine has a somewhat similar initiative in Harvest Bucks, which doubles the value of Supplemental Nutrition Assistance Program benefits, or food stamps, when shopping at a farmers market. It provides healthy food for low-income Mainers, and customers for farmers.

It could work in health care here, too. By spending now on healthy food for low-income Mainers, the state would be avoiding larger costs – along with poorer health outcomes – down the road.

Such a program would also favor farmers, fishermen and other producers of whole, healthy foods over the producers of the unhealthy processed food that makes up most of the American diet – and that is making us sick.

Worldwide, one in five deaths is associated with diets poor in fruit, vegetables and nuts, and high in sugar, salt and trans fat. Simply by eating more of the good foods, Americans could prevent more than 127,000 deaths and save $17 billion in health care costs each year.

It just doesn’t make any sense to only hand out prescription drugs to patients whose diet is killing them anyway, just slower.

When it comes to chronic illness, we shouldn’t direct people only to the pharmacy – we should send them to the farm, too.