Once considered a fringe science, circadian rhythms have more recently made their way into mainstream consciousness.
His book Life Time: The New Science of the Body Clock, and How It Can Revolutionize Your Sleep and Health, is a best seller.
Our understanding of the importance of sleep and our circadian rhythms has improved markedly over the past few years, Foster tells Jim Mora.
“I certainly remember in the ‘80s people coming in saying I've done another all-nighter. And they’d be getting a slap on the back, almost heroic, and that sleep was some sort of illness that needed a cure.”
We've discovered over the past decade the vital role of sleep for memory consolidation and broader cognitive benefits, he says.
“It's not just the laying down of facts, but it's playing with information, we can actually come up with innovative solutions to complex problems after a night of sleep.
“Some very recent studies have shown that whilst we sleep, there's this sort of clearance system, called the glymphatic system, which is getting rid of toxins including a misfolded protein, beta amyloid, which is associated with the development of dementia and Alzheimer's.”
Although poor sleep isn’t going to cause dementia or Alzheimer's, if you're at risk of those diseases, then it could be an additional risk factor, he says.
“We do know that in some people, poor sleep in the middle years is a risk factor for dementia in later years.
“The quality of our sleep essentially defines the quality of our wake, and we need to take it seriously.”
The fact that society is not embracing the science of circadian rhythms represents an immense squandering of resources, he says.
“If we think about timed drug taking, for example, we now know that drugs will have different effects at different times of the day.
"So, there's some very important studies that have come out showing that if you take your anti-hypertensives before you go to sleep, before you go to bed, and rather than first thing in the morning, over a 10 year period, you can halve the risk of stroke.
"Now, why is that? It's because between six and 12 noon, there's a huge circadian driven rise in blood pressure.”
That window is called the 'death zone' in some fields, he says.
“If you take your tablets before you go to bed, they have a long half-life, so they're hanging around and they will blunt that sharp rise in blood pressure first thing in the morning,
“And if you take them in the morning, then of course, at the time you've taken the drug, it gets into the circulation, it has its effects, you’re past that major window of vulnerability.”
Similar results have been seen in cancer drug therapy, he says.
“Really quite extraordinary data. In some studies from the States, in ovarian cancer, the same drug, two different times, and same concentration, and after a five year period, 45 percent of one group was still alive, but 10 percent in the other group - so same drug, same concentration, different time, hugely different effects.”
If you discovered a drug that reduced your chances of death as a result of certain cancers, you’d be off to “Stockholm getting a Nobel Prize”, he says.
“But we can do it now, with the knowledge that we have.”
A third of our lives are asleep and much of our biology is regulated by the clock, Foster says. This has implications for a range of health interventions.
“If we think about our biology, to make our biology work, we've got to do the right stuff at the right time.
"We've got to get our organs ready, and we've got to get them ready in time and space. And it's the circadian system that gives this this temporal structure to our entire world.”
Recent understanding of that internal clock has been an “extraordinary success” in biology and neuroscience, he says.
“What's been discovered is that there are a bunch of clock genes, and they're turned on, they produce their clock proteins.
“And those proteins then go into the nucleus, turn off their genes, those proteins are then degraded. And then the genes can make more protein.
“So, you have this sort of cycle, this 24-hour cycle of protein production, and then degradation.”
That happens in every cell in the body, he says.
“That's just completely awesome. You have a master clock in the brain, but it's then coordinating billions and billions of individual cellular clocks scattered through the organ systems of the body, which ultimately deliver our rhythmic behaviour.
“And subtle changes in some of those clock genes and their proteins have been associated with morningness and eveningness. So, in a sense, by the contribution to our genes, our parents are still telling us what time to get up.”