Michael Pollan says broccoli is better than any supplement — here's why

• Michael Pollan has been studying America's unhealthy food system for nearly two decades.
• Vegetables are some of his favorite foods.

It's no secret that Michael Pollan loves plants. He's been encouraging folks to eat more real food — especially veggies — for nearly two decades.

Pollan, the author of "The Omnivore's Dilemma" and "In Defense of Food," said that vegetables can function as preventive medicine — and they provide more health benefits than taking pricey supplements.

"It's much better to get your vitamins from food," Pollan told Business Insider. His latest documentary, "Food, Inc. 2," was released in theaters Friday.

"Our bodies evolved to get nutrients from food, not from pills," he said. "So it's no wonder that supplements generally don't work unless you have a very specific deficiency."

Many doctors, nutritionists, independent supplement researchers, and leading longevity experts agree with him.

Itching to add a new supplement to your diet? Try broccoli.

A family of cruciferous vegetables called brassicas, also known as cole crops, provide a ton of health-boosting benefits, Pollan said.

Brassicas are some of the stockiest, crunchiest plants you can find in the grocery store and include cabbage, collard greens, kale, cauliflower, broccoli, and Brussels sprouts. They're great for improving circulation and blood flow and can help prevent a number of age-related diseases.

Scientists believe that broccoli and other brassicas contain sulfur-based chemicals called glucosinolates, which give these veggies their bitter flavor. When we chop, chew, and digest cruciferous veggies, these potent chemicals break down into bioactive compounds that may help prevent some forms of cancer. But squeezing this compound into a pill isn't the same as consuming it in whole food.

"When they identified this compound and then they put it in a supplement, it did not have the same effect," Pollan said.

Studies have consistently shown that the bioavailability of nutritional supplements — the amount of nutrients our bodies absorb — can vary widely, from basically zilch to toxic. Because supplements aren't well-regulated, it's often hard to know what you're getting, and it can be near impossible to tell whether the supplements you take are helping you or doing more harm than good.

But we already have lots of evidence of the long-term health benefits of eating more fresh vegetables like broccoli. People who do tend to have fewer strokes, healthier hearts, less belly fat, a lower chance of developing type 2 diabetes, and less cognitive decline, and scientists don't think that's a coincidence.

"There are things we don't understand about the structure of food and the relationship of the chemicals within the food that is very important," Pollan said.

Pollan pops one supplement: a multivitamin

In addition to his veggie-rich diet, Pollan does take a multivitamin, "but that's it," he said.

Recent research has suggested that a daily multivitamin might be marginally beneficial for older adults' working memory.

Scientists still generally agree that no supplement can match a good diet and exercise routine in helping to prevent many chronic diseases.