Blood biomarkers
None of the people in the study had cancer at the time of treatment, however Karmazin's team looked at the levels of certain proteins called carcinoembryonic antigens. These chemicals are found in the blood of healthy people at low concentrations, but in larger amounts these antigens can be a sign of having cancer.

The team detected that the levels of carcinoembryonic antigens fell by around 20 per cent in the blood of people who received the treatment. However, there was no control group or placebo treatment in the study, and it isn't clear whether a 20 per cent reduction in these proteins is likely to affect someone's chances of developing cancer.

Karmazin says the team also saw a 10 per cent fall in blood cholesterol levels. "That was a surprise," he says. This may help explain why a study by a different company last year found that heart health improved in old mice that were given blood from human teenagers.