On 21 June 1941, the German biochemist Otto Warburg was summoned to the New Reich Chancellery, the seat of the Nazi government in Berlin. Dr Warburg, winner of the 1931 Nobel Prize for Physiology or Medicine, had good reason to be panicked. He was of Jewish descent and his relatives in finance were members of one of the world’s most famous Jewish families.


Worse yet for Warburg, he lived with another man, Jacob Heiss, and was rumoured to be a homosexual. That Warburg had survived in Nazi Germany for so long was astounding, but he had recently been evicted from his laboratory. And now he was being called to Nazi headquarters. An unlikely survival story appeared to be coming to an end.

When he arrived, Warburg, a lifelong anglophile, was likely wearing one of the elegant suits he ordered from his tailor in London. Walking through the long marble galleries of the New Reich Chancellery, Warburg’s carefully polished Scottish wingtips would have clacked ominously with each step.

The meeting had been arranged by Viktor Brack, a top official in the Chancellery of the Führer. Though Warburg did not know it, Brack was not merely one more Nazi functionary. He had overseen the operation of the Nazis’ first systematic killing operation, the ‘euthanasia’ programme designed to eliminate disabled people. Brack was the last person someone in Warburg’s position would want to see in June of 1941.

A portrait of Viktor Brack, c1946
Viktor Brack, seen c1946 before he was executed for war crimes, was the architect of the Nazi ‘euthanasia’ programme. In 1941, he summoned Otto Warburg for a meeting to continue his cancer research (Photo by Keystone/Getty Images)

But on that day, Brack, clad in his black SS uniform, had good news for Warburg. The biochemist would not only be allowed to live, he would be allowed to continue working at his institute. It was a strange episode: a Nazi with a direct role in tens of thousands of murders sparing a suspected homosexual with Jewish heritage.

And yet the strangest part of the meeting may have been the timing. Early the next morning, the Nazis would launch Operation Barbarossa, then the biggest military operation in history, a massive assault on the Soviet Union that would change the course of the war. Warburg should have been the very last thing on the mind of the Nazi leadership at that moment.

It was a strange episode: a Nazi with a direct role in tens of thousands of murders sparing a suspected homosexual with Jewish heritage

So why were Nazi leaders thinking about Warburg at such a critical moment for their regime? It wasn’t just Brack, after all. SS leader Heinrich Himmler’s diary shows that he met with Brack to discuss Warburg on that same day, 21 June 1941.

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The answer is that Warburg was studying a condition that the Nazis cared about as much as almost any other: cancer.

Brack, as Warburg later recalled, had given him only one condition: Warburg would have to focus all of his efforts on cancer research. Though there is no direct evidence that Adolf Hitler discussed Warburg’s case that day, later that same night – only hours before the first German tanks rolled into Soviet territory – the Minister of Propaganda Joseph Goebbels’ diary reveals that he and Hitler took a break from planning for the announcement of Operation Barbarossa to discuss new developments in cancer research.

Cancer breakthroughs

Hitler’s interest in cancer was personal. He had been a teenager when he lost his mother – the only person he seems to have ever truly loved – to breast cancer. From that point on, the disease was almost always in his thoughts.

At one point, the hypochondriacal Hitler was so sure he was dying of cancer that he stopped what he was doing and began to write out his will. That he might soon die of cancer, he said in 1932, made it all the more urgent for him to “finish the gigantic tasks” he had in mind.

At one point, Hitler was so sure he was dying of cancer that he began to write out his will

Hitler and other Nazi leaders embraced quackery of all kinds, but they had good reason to trust in the cancer research of Otto Warburg. Warburg’s father, Emil, was a celebrated physicist who had worked with Albert Einstein; Otto had served in the German military during World War I and only returned home to Berlin after Einstein sent him a letter urging him to save himself for the sake of German science.

Given these influences, it was natural for Warburg to think about biology through the lens of energy. And so when he turned his attention to cancer in the early 1920s, he wasn’t interested in the mangled chromosomes of cancer cells or the theory that cancer was caused by microbes. He wanted to understand how cancer cells derived the energy to support their rapid growth.

What Warburg found would revolutionise cancer research in the following decades. Cancer cells, it turned out, do not eat glucose (blood sugar) like other cells. While healthy cells derive most of their energy by burning nutrients with oxygen, cancer cells generate much of their energy without oxygen, through the process we know as fermentation. It’s the same biochemical process that, when carried out by microorganisms, gives us so many of our favourite foods – from beer and wine (alcoholic fermentation), to cheese and yoghurt (lactic acid fermentation).

A group of scientists gathered for the Solvay Conference in 1911, including Marie Curie, Albert Einstein and Otto Warburg's father Emil
Science ran in Otto Warburg's family: his father Emil (seated fifth from left) was a celebrated physicist who worked alongside Marie Curie (seated second from right) and Albert Einstein (standing second from right). Einstein implored Warburg to leave the army to rejoin academia (Photo by © Hulton-Deutsch Collection/CORBIS/Corbis via Getty Images)

It was already known at the time that human cells could ferment glucose. It was thought to be an act of last resort, though, a backup generator when there was not enough oxygen to run a cell’s power stations, the mitochondria.

But the cancer cells in Warburg’s glass vessel didn’t seem to care how much oxygen was available. They were ravenous for glucose and they fermented it, Warburg wrote, like “wildly proliferating torula yeasts”.

Under Nazi protection

Cancer wasn’t Warburg’s only area of interest – he also revolutionised the fields of photosynthesis and cellular respiration – but it would remain central to his research until the end of his life.

It wasn’t that Warburg was a great humanitarian, either. On the contrary, he was famously arrogant and narcissistic. When he learned he had won the Nobel Prize in 1931, Warburg’s first response was, “It’s about time.”

It was this tremendous self-regard that made him such a unique character in Nazi Germany. Warburg refused to leave Germany in the first half of the 1930s when he still had the chance, in part because he couldn’t stand the thought of the Nazis telling him what to do.

When Warburg learned he had won the Nobel Prize in 1931, his first response was, ‘It’s about time’

Warburg repeatedly pushed back against the Nazis in the first years under their rule. He banned his employees from making the Nazi salute or hanging the Nazi flag at his institute. On one occasion, a company of storm troopers arrived at the institute and ordered his assistants to leave for the day to take part in a mandatory Nazi march. Warburg declared that he “would burn his institute” before following the command. The storm troopers left without Warburg’s assistants.

In 1934, Warburg sent a memo to Max Planck, a grandee of German science, suggesting that Nazi regulations needed to be rewritten to exempt someone in his position. He even suggested the specific language for the revised regulations.

Warburg, to be sure, was in a better position than most Jewish scientists in Nazi Germany. His institute was supported by the Rockefeller Foundation, and he had influential friends who repeatedly came to his aid when he got into trouble.

But Warburg was convinced that it was Hitler’s fear of cancer that ultimately saved him, and he was likely correct. After Brack told Warburg that he could remain at his institute, the Nazis went out of their way to protect the scientist, even allowing him to relocate to a country mansion when bombs began to fall near his institute in the Berlin neighbourhood of Dahlem.

Scientific suspicion

After the war, Warburg’s story would take another surprising turn: his groundbreaking research on how cancer cells fuel their growth was almost entirely ignored, as cancer scientists turned their attention to DNA and genetic mutations.

It didn’t help that many western scientists were suspicious of how Warburg had managed so well in Nazi Germany, nor that he was making more and more outrageous statements about cancer.

In December, 1950, Warburg told a gathering of Nobel laureates that the cancer cell’s transition to fermentation was caused by an inability to use oxygen properly. He then added that it was the only thing his fellow Nobel laureates needed to know about the biology of cancer. All the rest, he declared, was “garbage”.

Warburg died in 1970. By the start of the 21st century, his name was no longer included in popular cancer textbooks. But, even after his death, Warburg’s story would see new plot twists. In the late 1990s, a small number of cancer researchers found that their search for cancer genes had led them directly back to Warburg and the energy processes he had studied.

The past decade, in particular, has seen a renaissance in the study of the metabolism of cancer cells. Though contemporary researchers don’t necessarily agree with all of Warburg’s ideas, they do tend to agree with his larger arguments: that cancer is a metabolic disease as much as a genetic disease and that the way a cell takes up and processes food is fundamental to what the disease is and how it originates.

Today, the study of cancer metabolism is leading to new drugs and to a rethinking of how our diets contribute to cancer. Warburg’s unlikely survival story, it seems, may yet have a few more chapters.

Three other Jewish scientists in Nazi Germany

Hans Krebs

The Jewish Nobel Prize-winning metabolism researcher who trained by Otto Warburg’s side, Krebs was fired from the University of Freiburg after the Nazis assumed power in 1933. Krebs fled to England with the tools Warburg had devised to continue his study. Just a few years later, he used them to discover the famed Krebs cycle, and revolutionised our understanding of metabolism.

Otto Meyerhof

A friend and research collaborator of Warburg, Meyerhof shared the 1922 Nobel Prize for Physiology or Medicine with British physiologist AV Hill. Meyerhof was yet another brilliant Jewish scientist who found his life in jeopardy under the Nazis. In 1938, he escaped Germany for France, then when the Nazis invaded France he made a dangerous trek across the Pyrenees.

Fritz Haber 

The Nobel laureate and famed architect of Germany’s gas warfare programme during World War I, Haber had his own institute in Dahlem, not far from Warburg’s. After leaving Germany in 1933, the Jewish-born Haber remained mystified. “I never did anything, never even said a single word, that could warrant making me an enemy of those now ruling Germany,” he wrote to a colleague in December 1933.

Sam Apple is a journalist and author of Ravenous: Otto Warburg, the Nazis, and the Search for the Cancer-Diet Connection (Liveright, 2021)


This article was first published in the July 2021 issue of BBC History Revealed