Our science staff is trying to lead a more scientific life in 2018. Throughout the week, we’ll be writing about our resolutions for the new year. Here’s the second entry, on Tom Brady’s fitness empire.

I am done with testimonials from professional athletes. I’ve spent the last year and a half reporting and writing a book about exercise recovery, and what I’ve learned is that advice from elite athletes is often cluttered with pseudoscientific explanations for their stupendous results. The problem is that gifted athletes don’t necessarily know how they got that way. Or, in the words of David Epstein, author of “The Sports Gene,” “Just because you’re a bird doesn’t mean you’re an ornithologist.”

Take New England Patriots quarterback and five-time Super Bowl champion Tom Brady, for instance. He’s still playing at 40, a geriatric age in the NFL. What keeps him performing at such a high level all these years? It could be that he’s blessed with a strong arm and a sturdy frame, or that the Patriots’ strong offensive line has (mostly) protected him from sacks and related injuries.

But Brady has his own theories. He attributes his athletic longevity to a list of 12 principles outlined in his best-selling 2017 book, “The TB12 Method.” (Twelve is an important number to Brady; it’s not only the number on his jersey, but also the brand on the many products he sells to his fans.) The TB12 principles include generic advice like “feeling better — that’s the key” and “balance and moderation in all things.”

Moderation in all things, that is, except when it comes to water. “Sometimes I think I’m the most hydrated person in the world,” Brady writes after advising readers to drink at least one half of their body weight in ounces of water every day. “At 225 pounds, that means I should be drinking 112 ounces a day, minimum,” he says. If you don’t drink enough, he claims, you decrease the oxygen in your bloodstream, build up toxins in your cells and create an “unhealthy inner environment,” whatever that means. (Brady also contends that “the more hydrated I am, the less likely I am to get sunburned,” a claim disputed by scientists.)

Water alone isn’t enough, though. Brady also relies on TB12™ Electrolytes, “a natural mineral concentrate that enable athletes to turn any liquid into a hydrating sports drink enriched with 72 trace minerals extracted from sea water.” (Curiously, the product packaging lists only 17 ingredients.) Who doesn’t love guzzling sea-water extract?

Electrolytes, though, aren’t anything special. They’re simply salts and minerals. “They’re brilliant marketing,” exercise scientist Tamara Hew-Butler at Oakland University told me. Sodium and potassium are the major ones we need, and your body maintains stores of them that it can tap into as needed to protect your body’s normal functioning. “You have a lot of redundancy in the feedback systems to protect their levels,” she said. Unless you’re exercising continuously in excess of 18 hours or more, you normally make up for any loss through the food you eat in your next meal. Despite all the hoopla about their presence in sports drinks and fancy bottled waters, there’s no need to take them in supplements or some special formula.

Drinking excessive amounts of water when you’re not thirsty isn’t just dumb, it’s dangerous, because it can produce a potentially fatal condition called hyponatremia, or “water intoxication.” Despite the marketing campaigns of bottled water makers and sports drink manufacturers, there’s no good science to show that athletes or anyone else needs to drink beyond thirst, which is your body’s natural way of telling you to drink, just like hunger means you need to eat. But there’s plenty of good evidence that drinking too much can kill you. Hyponatremia happens when the blood becomes dangerously diluted, which can lead to symptoms that look a lot like dehydration — such as fatigue, headache, confusion and weakness. In the most serious cases, it can provoke brain swelling, coma and even death. I have been unable to find a single case of a football player collapsing and dying from dehydration on the field, but at least two high school football players have died from hyponatremia. Yet Brady says that underhydration is a greater problem than overhydration.

But wait — there’s more! Brady also recommends a restricted diet that, among other things, avoids nightshades and favors “alkaline” foods, which he says, without presenting any evidence, reduce inflammation. (The diet is apparently outlined in greater detail in the TB12 Nutrition Manual, which sells for $200.)

For every bit of advice, there’s a product for sale. In addition to the electrolytes and rollers and stretchy bands, there’s a protein powder that he just happens to sell, and a brain training app that you can subscribe to for $14 a month (or $96 for a year).

Brady credits his athletic longevity to something called “muscle pliability,” a term invented by his “body coach,” Alex Guerrero, a man twice investigated by government regulators for misrepresenting himself as a doctor (he’s not) and falsely asserting that one supplement he was shilling had been clinically tested and proven to cure cancer, Parkinson’s, AIDS and other diseases and that another, which Brady once endorsed, could prevent concussions.

What’s muscle pliability? “Pliability is the name Alex and I give to the training regimen he and I do every day. Using his hands and elbows, Alex performs targeted, deep-force muscle work to lengthen and soften every muscle of my body, as I rhythmically contract and relax that muscle,” Brady writes in his book. It may sound like massage, but Brady insists it’s something different. (The best part of inventing your own word is that you can make it mean whatever you want it to.) “The goal of pliability is to reeducate your brain-body connection, which continually sends messages to your muscles to stay long, soft, and primed,” he writes, adding that you can think of it as the “new ‘warm-up’ and ‘cool-down.’”

The book illustrates a series of exercises and self-massages that Brady promises will make muscles less tight, dense, stiff and injury-prone. Do the muscle pliability exercises in his book do what they advertise? It’s hard to say, because the only evidence provided is Brady’s testimonials, and there’s no actual scientific research on this stuff. “I don’t know what they’re trying to say with that,” said Keith Baar, a physiologist who studies muscles and exercise at the University of California, Davis. University of Kentucky muscle physiologist Tim Butterfield told me that he’d never heard the term pliability used in muscle research. To test Brady’s claims yourself, you’ll have to buy some TB12 vibrating foam rollers or, better yet, hire a TB12-certified body coach. “I want to make it very clear that the best method of achieving optimal pliability is through a certified TB12 body coach,” Brady writes.

Maybe he really believes in this stuff, but after reading all 303 pages of Brady’s book, I can’t help noticing how much of his recommendations sound like advertising. For every bit of advice, there’s a product for sale. In addition to the electrolytes and rollers and stretchy bands, there’s a protein powder that he just happens to sell, and a brain training app that you can subscribe to for $14 a month (or $96 for a year).

Brady has faced criticism for his association with Guerrero, and Patriots coach Bill Belichick is reported to be distancing his team from the disgraced guru, but it’s easy to see what Brady sees in the guy. Brady might well be the greatest quarterback in NFL history, and Guerrero has taught him how to turn that on-field résumé into an off-field wellness empire.

CORRECTION (Jan. 3, 2018, 2:38 p.m.): An earlier version of this story missidentified sodium and potassium as molecules. They are ions when serving as electrolytes in the human body and also exist in elemental form.

CLARIFICATION (Jan. 4, 2018, 4:45 p.m.): This article has been updated to make clear that potassium and sodium are ions when serving as electrolytes in the body.