Does linoleic acid in tissue increase the risk of skin cancer?
The available research provides no basis for viewing linoleic acid in tissue as a risk factor for skin cancer; for BCC, several studies even point to a modest protective effect, although the certainty is limited.
Higher levels of linoleic acid in tissue or blood appear to lower the risk of basal cell carcinoma (BCC, the most common form of skin cancer), not raise it. A large Mendelian randomisation study in more than 600,000 people found that genetically higher linoleic acid levels are associated with a 6% lower chance of BCC. Mendelian randomisation is an approach that uses random genetic variation to answer questions of cause and effect more reliably than a conventional observational study.
An Australian prospective study found 25% less BCC in the middle group for linoleic acid intake compared with the lowest group. The researchers themselves note caveats about this finding: they do not rule out that it is partly due to chance. Plasma measurements showed a protective effect only in a specific subgroup with a prior history of skin cancer, and not in the overall group. For squamous cell carcinoma (SCC), the second most common form of skin cancer, the same Australian researchers found no association.
Even less can be said about melanoma. In a small Italian study with 59 cases, an initial signal disappeared entirely after accounting for other factors. No conclusions about linoleic acid and melanoma can be drawn from this.
There are also findings that warrant attention without reversing the overall picture. A cross-sectional study in more than 2,000 women found that higher linoleic acid intake was associated with shorter telomeres, which are the protective ends of chromosomes. Shorter telomeres are linked to accelerated cellular ageing. Whether this mechanism leads to more skin cancer was not investigated in that study, and the association therefore cannot be extrapolated to a cancer risk.
Conjugated linoleic acid, a structurally related compound that is sometimes confused with ordinary linoleic acid, inhibited skin tumours in mice. That is animal research and says nothing about ordinary linoleic acid in humans. Broader review studies from the 1990s also found no epidemiological evidence that polyunsaturated fats, the group to which linoleic acid belongs, promote cancer in humans.
Based on one Mendelian randomisation study (n>600,000), two small to medium-sized observational studies (n=1,322 and n=2,284), one plasma study, one small case-control study (n=59 cases), one animal model study and one older review study. No RCTs or meta-analyses are available for skin cancer and linoleic acid.