It is a traditional Jewish birthday greeting: “May you live to be 120.” And so far, only one person in all of history is officially recorded as having made it that far.

But now a doctor tells The Post that living a full, healthy life to 120 will be attainable — starting this decade.

Dr. Ernst von Schwarz believes that rapid advances in stem cells mean living and even working far beyond current expectations is entirely within humanity’s grasp and that 150 will be normal by the end of the century.

The only downside: stem cells will not work alone. If you want to benefit, now is the time to start eating healthily and exercising regularly.

And, he warns, it might be too late for some — 30 is when you really need to change your life.

“I believe that we can create prolongation of life,” von Schwarz tells The Post. “Probably within a couple of years people can live to 120, 150 years if not longer than that.

“And not just as bed-bound non-communicating individuals, but really as active individuals who can participate in social life, professional life and have a quality of life. Because that’s the goal.”

The provocative claim may seem to stretch credulity.

The only person acknowledged officially as living past 120 was France’s Jeanne Calment, who died in 1997, aged 122 years and 164 days — and even that record has been questioned, with theories circulating that Calment’s daughter was actually posing as her.

But von Schwarz is throwing his full weight — as a triple board-certified internist, cardiologist, and heart transplant cardiologist at Cedars Sinai Medical Center, the David Geffen School of Medicine at UCLA, and the Heart Institute of the Southern California Hospital — behind the idea that a healthy 120 years can be our allotted span.

There is, he says, a quiet revolution going on inside medicine.

“In the last few years, we have shifted from what we call reactive medicine to what we now call regenerative medicine using mainly stem cell therapies,” von Schwarz explains.

“Even though stem cells are not FDA-approved, that’s the future of medicine where we are able to repair damage. And by repairing damage we can prolong life, or even reduce certain processes of aging.”

Von Schwarz makes the claim in a new book, “Secrets of Immortality,” which picks up where his previous one, “The Secret World of Stem Cell Therapy,” leaves off.

He is also prescribing stem cells himself. Celebrities clamor for Dr. von Schwarz’s anti-aging facials before the Oscars and Emmys. 

While he wouldn’t disclose his patients’ names, his book publicist touts his supporters as including Frank Stallone, Jeff Fahey, Lisa Gastineau, Josie Davis, Drea De Matteo, and Fabio.

“We inject stem cells into their face, and they glow,” he says. “The process repairs superficial skin damage and regenerates collagen in the face. After a few days, they look 5 to 10 years younger.”

Von Schwarz is no stranger to the celebrity scene: his wife is actress Angela Oakenfold, the ex-wife of DJ Paul Oakenfold.

The couple also infamously bought Hollywood’s notorious Alfred Rosenheim Mansion for $3.2 million. 

The Tudor-style house was prominently featured in the first season of “American Horror Story: Murder House,” and has been subsequently nicknamed the “Murder House.”

Brushes with fame aside, the stem cell pioneer says that they have more significant uses than just for superficial applications.

“Stem cells can repair an arthritic knee, they can create hair regrowth and they can repair some damage in the brain. One injection takes less than half an hour with no recovery time, versus surgery.”

That, he says, will only be the start. “Stem cells can repair an arthritic knee, they can create hair regrowth and they can repair some damage in the brain. One injection takes less than half an hour with no recovery time, versus surgery.”

Stem cells are the “master cells” of the body, ready to become blood, skin, hair — any of the parts that make us. Naturally occurring, they are responsible for regenerating the body.

But what von Schwarz, and many other doctors, see as the future of medicine is harvesting them to go further than nature does.

Large numbers of clinical trials are under way but so far the FDA has only approved one therapy, for blood cancer patients, and warns that rogue practitioners have put people’s lives a risk by offering bogus stem cell cures.

Von Schwarz says that stem cells will be proven to FDA standards.

“Stem cell therapy is considered to be the most important discovery in modern medicine, likely bigger than the discovery of penicillin or the detection of the tuberculous bacteria,” von Schwarz says in his book.

And he has been watching the scientific research avidly. “We have treated patients with neurodegenerative diseases such as Parkinson’s or MS or even strokes and have seen a significant improvement of their mobility and mental capacities.

“We are not interested in creating a population of senior citizens with bed-ridden conditions like dementia who are unable to feed themselves. We want to increase the health span to enable people to work out and be active in their communities up to high ages. That’s all doable nowadays.”

He has also used them himself, including treating his arm and shoulder pain, which was flaring up due to nerve degeneration.

“Two years later, I’m completely asymptomatic from a single injection, and I can exercise.”

There is, however, the thorny issue of sourcing stem cells, which are salvaged from biological tissue.

“They come from donors, usually from placenta tissue, [umbilical] cord blood, and from what we call Wharton’s jelly,” von Schwarz says. “After birth, this material is usually discarded, and labs buy that material.”

The doctor is quick to point out that these are not embryonic stem cells. “That’s not allowed in this country. And from an ethical and religious point of view, of course, I would never consider that.”

Stem cell therapies, of course, are only available now to the wealthy, and unless or until the FDA approves them, that will remain the case.

Von Schwarz is adamant that stem cells are not miracle cures: patients who want to benefit have to put the work in too, with a Mediterranean diet, exercise, and ending toxic habits like smoking. 

“A healthy diet can prolong life,” he says and cites a study linking the consumption of processed foods to rising levels of colon cancer among 20- and 30-year-olds.

Exercise is a big factor, too. “The recommendation is to exercise five days a week with a minimum of 150 to 300 minutes per week, which is 30 to 60 minutes a day of what we would call moderate intensity exercise.

“A more recent study… showed that if you do double the recommended amount, you can further prolong your life for another seven years.”

The doctor suggests getting serious at age 30 when our aging process starts. “In order to turn the clock backward, we have to start early.

“We know that with lifestyle modification and reduction of risk factors like high blood pressure, cholesterol, and diabetes, we can reduce cardiovascular death by 90% and prolong life.”

However, the other question is, even if this is all possible, would you want to live to 120?

Von Schwarz does not advocate for actual immorality, despite the name of his book. “People have been looking for ways to live forever since the beginning of time,” he says.

“I don’t believe that we are destined to achieve immortality. I’m a strong believer that there has to be something after our earthly existence. I find it fascinating to come from a scientific viewpoint to address these issues.”

But, he says, he wants people to live without disease. “I want people to know is there’s hope,” he says.

“There are treatment options for conditions where even five years ago we thought there was nothing we could do. We want to increase health span, not just only numerical life.”