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EATING less might help prevent or delay the development of cancer.

This tantalising conclusion comes from a theoretical study based on the idea
that fast-growing cancer cells need more calories to survive than healthy ones.
So far, there have been no clinical trials to show if it works.

Obesity and eating an unhealthy diet are thought to raise people’s risk of
developing cancer. David Eichler of Ben Gurion University in Be’er Sheva,
Israel, decided to investigate whether limiting the amount of food you eat to
only what is necessary could have a direct effect on cancer cells.

He developed a mathematical model that simulates how cell populations grow
when they have to compete for a limited supply of energy. Under such conditions,
normal cells multiply more slowly, he found. But fast-growing abnormal cells of
the kind that are often found in some cancers died off. Such cells require a
disproportionate amount of energy to reproduce at such a high rate, Eichler
says.

“Cells with a really strong energy need have a dilemma,” he says. “Either
they have to not grow faster than the rest of the body or they’ll die by trying
to reproduce faster than the limited energy supply will allow them to.” This
suggests that eating minimal, yet adequate, amounts of food might help cancer
patients starve their tumours.

Circumstantial evidence suggests that this can happen in real patients. In
1993, researchers at Tulane University in New Orleans, Louisiana, followed 23
patients with pancreatic cancer who adopted a moderately low-calorie, high-fibre
diet. On average, these patients lived for a year and a half, whereas those on
unchanged diets died after six months. In 1998, researchers from the National
Cancer Institute in Bethesda, Maryland, found that obesity coupled with
high-calorie diets increased the risk of people getting pancreatic cancer.

Clinical trials are now needed to find out if low-calorie diets could help
cancer patients. “We don’t know if we can improve the efficacy of our cancer
therapy if we put people on different dietary regimens,” says Steven Clinton, a
cancer physician and researcher at the Ohio State University in Columbus, Ohio.
“We need to do the studies.”

But he thinks the idea is intriguing. In 1999, he and his colleagues found
that rats on a reduced-calorie diet had smaller prostate cancer tumours than
rats that ate all they wanted. The tumour cells died faster, and there were
fewer and smaller blood vessels feeding them. The cells also produced less of a
growth factor called VEGF, which stimulates the formation of blood vessels.
“It’s very clear that diet restriction will inhibit the growth of the tumour,”
says Clinton.

Eichler’s model only applies to cancers in which tumour cells replicate
faster than normal cells. Cancers are also defined by other biological phenomena
such as cells not undergoing programmed cell death, or apoptosis. And the model
assumes that cancer cells absorb nutrients from what’s available in their
micro-environment, says Clinton. That’s not always the case.