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Extra protein failed to build muscle in cancer patients whose inflammation was already high
Protein advice for cancer patients is given as a single number for everyone. Tracking 50 people with colorectal cancer found that what their blood was doing beforehand largely decided whether it worked.
- Muscle response to extra protein varied enormously between people.
- An inflammatory marker measured before starting explained much of that variation.
- About 27 extra grams of protein a day was where gains began to appear.
- More may be needed by people whose inflammation is higher.
- A post hoc analysis of 50 patients, so it generates a hypothesis rather than settling one.
Losing muscle during cancer is not a side issue. It predicts how well someone tolerates treatment, how likely they are to be admitted to hospital, and how long they live.
The standard response is protein. Eat more of it, usually expressed as a target per kilogram of body weight, the same figure handed to everyone.
An earlier trial suggested that pushing intake up did increase muscle in people with colorectal cancer. What it also showed, less prominently, was that some people gained a great deal and others gained nothing.
The question behind the averages
Writing in The American Journal of Clinical Nutrition, the investigators went back into their own trial to ask why the responses differed so much.
They had measurements taken before anyone started: inflammatory signals, hormones, and the individual amino acids circulating in the blood. The question was whether the starting state predicted who would respond.
What predicted the response
It did, and substantially. At six weeks, most of the variation in muscle response was accounted for by a handful of baseline measurements together with how much extra protein someone actually managed to eat.
The inflammatory signal interleukin-6 was central to it. Higher inflammation at the start, less muscle gained from the same additional protein.
By twelve weeks the model explained considerably less, which is what usually happens as other influences accumulate over a longer period. The early signal was the strong one.
Why this makes biological sense
Building muscle from food is not passive absorption. It is an active process that has to be switched on, and inflammatory signaling appears both to interfere with the switch and to promote breakdown at the same time.
So the protein arrives and the machinery meant to use it is being suppressed. Eating more of a raw material does not help when the factory is running slow.
Elevated IL-6 blunts the anabolic capacity of protein support, as the authors put it.
The number that came out of it
Positive muscle change appeared at a daily protein increase of about 27 grams, and the authors add that higher amounts may be needed in patients whose inflammation is higher.
That is roughly the protein in a large chicken breast, or two substantial servings of dairy. It is a useful anchor precisely because it is expressed as an increase rather than a target, which is easier for a patient to act on than a figure per kilogram.
It should still be treated as a signpost. This is 50 people in a post hoc analysis, and a threshold derived from a small dataset is the kind of number that shifts when someone tries to reproduce it.
What the study cannot support
Post hoc analyses look for patterns after the fact, in data collected to answer a different question. They are the right way to generate a hypothesis and the wrong way to confirm one.
Fifty patients is also few for a model with several predictors, which is a situation where models tend to fit the specific people in the dataset better than they fit anyone else.
And this was colorectal cancer specifically. Colorectal cancer is cancer that develops in the tissues of the colon or rectum, and whether the same interference operates in other cancers, or in the milder inflammation of ordinary aging, is untested.
Why it is worth acting on anyway
Because the current advice ignores the variable this study says matters most.
A single protein target handed to every patient assumes they will all respond similarly. This suggests they will not, that the ones who need muscle most may be the ones least able to build it, and that measuring inflammation before giving nutritional advice would tell you something you currently do not ask.
People also ask
What did the analysis find?
Among 50 patients (mean age 57 years) whose baseline cytokines were elevated, protein intake rose 22% by 6 weeks and 29% by 12 weeks, but lean soft tissue response varied widely. At 6 weeks, 77% of that variation was explained by baseline interleukin-6, insulin and specific amino acids together with change in protein intake (P = 0.021). Positive lean tissue change occurred at a daily protein increase of 27 g.
What is lean soft tissue?
Body tissue that is neither fat nor bone, which is mostly muscle. It is measured here by a scan rather than by weight, because total weight cannot distinguish muscle from fat or fluid.
What is interleukin-6?
A signaling molecule the immune system releases during inflammation. It is often elevated in cancer, and it is one of the signals thought to drive the muscle loss that accompanies advanced disease.
Why would inflammation block the effect of protein?
Because building muscle from dietary protein is an active process, and inflammatory signaling appears to interfere with it while simultaneously promoting breakdown. Eating more protein does not help if the machinery that uses it is being suppressed.
Is 27 grams a recommendation?
No. It is the point in this small dataset where lean tissue began to move in a positive direction, and the authors note more may be needed when inflammation is higher. It is a signpost for future trials rather than a dose to follow.
Does this apply to healthy people taking protein supplements?
Not directly. Everyone here had colorectal cancer and elevated inflammatory markers. Whether the same interference operates at the milder inflammation of ordinary aging is an open question this study cannot answer.
What should a patient with cancer do about protein?
Nutrition during cancer treatment is managed alongside the treatment itself, and a dietitian attached to the oncology team is the right person to ask. This is general information rather than medical advice.