Does linoleic acid in tissue increase the risk of skin cancer?
There are preliminary indications that higher linoleic acid levels are associated with a higher melanoma risk, but the evidence is too thin and inconsistent to justify avoiding linoleic acid. Those concerned about skin cancer would benefit more from ensuring adequate vitamin D intake and protection against UV radiation.
In an Australian study, melanoma patients had higher proportions of polyunsaturated fatty acids in their subcutaneous fat tissue than healthy individuals. A small Italian study found that the highest linoleic acid intake was associated with a more than twofold higher melanoma risk, but the statistical trend fell just short of significance (p=0.061). Both studies are small and can only demonstrate an association, not causation.
For basal cell carcinoma and squamous cell carcinoma, the two most common forms of skin cancer, a large Australian study with ten years of follow-up found no clearly elevated risk at higher linoleic acid intake. The small associations that were found were attributed by the researchers themselves to chance. A study examining blood levels of fatty acids showed that high omega-6 (including linoleic acid) in the blood was not associated with greater signs of early UV damage in the skin, while high omega-3 was actually associated with less of that damage.
Omega-3 fatty acids appear to play an opposite role: higher intake was linked in an American study to a lower likelihood of squamous cell carcinoma, though again without statistically conclusive evidence. Vitamin D and dietary carotenoids were associated with a lower melanoma risk; linoleic acid played no role in that study.
On balance, the picture is mixed. Small studies suggest a link between linoleic acid and melanoma, but larger studies do not find that link for other skin cancers. No study has been able to demonstrate cause and effect. It is not clear whether linoleic acid itself raises the risk, or whether it is a marker for a particular dietary pattern.
The answer rests on a handful of small studies without an experimental design, in which participants were not randomly assigned to groups. The two studies that found an elevated melanoma risk with linoleic acid each had between 59 and 100 participants; both found just-below-significant results. The larger Australian study with over a thousand participants and ten years of follow-up found no effect for other skin cancers. None of the sources is a systematic summary of multiple studies.
Does being overweight increase my risk of cancer, and if so, which types?
Excess weight increases your risk of at least 13 types of cancer, including uterine, colorectal, breast and liver cancer. Losing weight reduces that risk, although it remains unclear whether all methods of weight loss are equally effective for immune defence against cancer.
Does eating a lot of sugar increase my risk of cancer?
Drinking large amounts of sugar-sweetened beverages is associated with a noticeably higher risk of certain cancers, particularly early-onset colorectal cancer and liver cancer. The association is observational, but consistent enough to make reducing soft drinks and fruit juice a concrete point of attention.
Does working with pesticides increase your risk of cancer?
Working with pesticides is associated in multiple studies with an increased risk of several types of cancer, including bladder, bowel, and blood cancers. Avoiding unprotected contact is sensible, especially if you are pregnant or planning to become pregnant.
Does having type 2 diabetes increase your risk of certain cancers?
Type 2 diabetes increases the risk of several cancers, including liver, pancreatic, uterine and colorectal cancer. If you have diabetes, it is worthwhile to discuss with your doctor whether closer attention to early detection or lifestyle improvement is appropriate for you.
Does alcohol increase your risk of cancer, even with one drink a day?
Yes, even one drink a day increases the risk of certain cancers, particularly breast and colorectal cancer. There is no safe lower threshold; drinking less or stopping reduces your risk immediately.
Does eating heavily heated or charred food increase your risk of cancer?
Heavily heated or charred meat likely increases the risk of certain types of cancer, although the associations in humans are associative. By not charring meat and varying cooking methods, you can substantially reduce your exposure to these substances.