The science is in: Processed food is addictive, can make you extremely unhappy and will prematurely kill you. How did this happen? And how have food manufacturers been able to deceive the world about these facts? Dr. Robert Lustig has written a new book, “The Hacking of the American Mind: The Science Behind the Corporate Takeover of Our Bodies and Brains,” in which he explains how and why this occurred.

He is perhaps most well-known for his brilliant research into sugar and obesity, and his previous book, “Fat Chance: Beating the Odds Against Sugar, Processed Food, Obesity and Disease,” was a New York Times Best Seller. Lustig is an emeritus professor of pediatrics in the division of endocrinology at the University of California, San Francisco, and a member of the Institute for Health Policy Studies. Since the last time I interviewed him, he’s also completed a master’s in public health law.

The Genesis of ‘Hacking of the American Mind’

The motivation for “The Hacking of the American Mind” began some 30 years ago, while still a postdoctoral fellow in neuroscience at Rockefeller University. There, he learned about the interaction between dopamine and serotonin in the brain. At the time, only basic correlational data existed, but there appeared to be a very specific interaction going on between these two neurochemicals.

“As I was researching the data for ‘Fat Chance,’ four years ago, it became very clear that the data had come in on the role of diet and behavioral health,” Lustig says. “In addition, we also now had neuroimaging studies. I realized everything was falling into place — that this issue, dopamine and serotonin, was actually at the core of what had now become our depression and opiate crises.

At the same time, I was giving Psychiatry Grand Rounds at a U.S. medical school in 2014. The woman who ran their outpatient treatment program took me on a tour of their facility. She was a recovered addict herself. She said something to me that was so jarring. She said, ‘When I was shooting up, I was happy. What my new life has brought me is pleasure.’

I thought to myself, ‘That’s wrong. That’s exactly turned around.’ But I didn’t say anything to her. I went home and talked to some psychiatry friends. They said, ‘Oh yeah, a lot of people seem to get addicted with this concept in mind.’ I said, ‘Well, there’s a book there.’ That was the genesis of this book.”

Why Processed Food Diets Fuel Depression

Tryptophan, which is the precursor for serotonin, is one of the rarest amino acids in our diet. But it’s a mistake to think the answer to depression is as simple as taking tryptophan to boost serotonin. The reason for this is because most of the tryptophan is converted to serotonin in your gut, and it does not freely travel into your brain. Lustig explains:

“Tryptophan is the only amino acid that can be converted into serotonin. Tryptophan is the rarest amino acid in our diet. Eggs have the most. Certain poultry and other avian species have some [tryptophan]. There’s very little in vegetables. Obviously, carbohydrates have virtually no tryptophan whatsoever.

It’s actually pretty hard to get tryptophan into your body to start with. Take processed food on top of that, then it’s even harder because it tends to be tryptophan-depleted. [Moreover], 99.9 percent of the tryptophan you ingest either gets turned into serotonin in the gut for your gut’s purposes, or it goes into your platelets to help your platelets help you clot. [So] very little tryptophan actually gets to the brain.

Top that off with the fact that tryptophan has to share an amino acid transporter with two relatively common amino acids: phenylalanine and tyrosine, which, by the way, are the precursors for dopamine. You can see that the more processed food you eat, the more dopamine you will make because you will have the precursors for that.

They will actually crowd out the ability to get tryptophan across the blood-brain barrier … Yet, serotonin is the nidus of contentment, of happiness. It explains why diet is so problematic … ”