Does sugar cause cancer? If one has cancer, does sugar contribute to its growth? This has been a debatable question for a very long time, but unfortunately there are no simple answers to it. The question has merit, but at the same time it is fueled largely by misinterpreted science.
Usually, when there’s sufficient oxygen, healthy cells
utilise that to convert glucose (a basic sugar) into energy by the process of
aerobic respiration. And when the oxygen is low, the cells use an alternative
process, anaerobic respiration, to generate energy from sugar, but not nearly
as much as aerobic respiration. Thus, it is safe to say that anaerobic
respiration is less efficient fort energy production, and not the first choice
for a healthy cell.
Nearly a century ago, a German scientist Otto Warburg
hypothesised that cancer cells primarily use anaerobic respiration for energy
even when oxygen is sufficient (1, 2). This means that the cancer cells require
lot more glucose to generate energy. This came to be known as the Warburg
effect. This made scientists wonder if cancer is fuelled by more sugar, perhaps
one can prevent cancer by not eating sugar. There have been several studies that
have tried to establish this connection. Scientists have observed a small
increase in the risk of colorectal cancer with increasing intakes of
carbohydrate, sucrose or fructose in men. However, this was not statistically significant,
and they also did not find any association of cancer with women (3). It was
hypothesised that increased sugar causes hyperinsulinemia (high insulin levels)
which further promotes colon cancer progression (4). But the authors of a 2014 study
failed to establish a direct and substantial link between sugar and colon cancer
(5), where other factors apparently increased cancer risk, like smoking.
Since Warburg’s time, the actual causes of cancer have been
discovered. Researchers have uncovered genetic mutations as a primary cause of
cancer. Cells also attain malignancy through epigenetic changes, a mechanism
that alters expression patterns and cellular signalling pathways. This has been
established in a number of studies where human cancer cells harboured epigenetic
abnormalities (6-8). Thus, the causes of cancer are complex.
Interestingly, while the link between sugar and cancer has
been challenged, it is also worth noting that people with type II diabetes are
prone to cancer (9). One explanation could be that in type II diabetes, insulin
is unable to carry glucose to the cells effectively. As a result, pancreas
produces more and more insulin and this results in hyperinsulinemia. Importantly,
besides maintaining blood glucose levels, insulin stimulates cell growth, and
this can trigger abnormal cell growth leading up to cancer. Recently, scientists
at American Chemical society meeting 2019 reported a study to explain how this
could possibly happens (10). They looked at the connection between heightened
blood glucose and DNA damage, resulting in genome instability and cancer. They realized
that chemically modified DNA bases occurred more frequently in diabetes
inflicted rodents compared to the normal ones. The reason for this was that in
this model, one of the proteins that were downregulated is directly responsible
for activating DNA repair genes, establishing the link between diabetes and cancer.
This discussion though remains incomplete without a mention
of obesity and cancer. High consumption of sugar leads to obesity, which affects
growth, metabolism (like insulin resistance) and reproductive cycles. These signals
trigger the cells in our body to divide more often than required and can lead
to cancer (11, 12). The International Association for Research on Cancer has
agreed that obesity causes cancer and has suggested people to keep a check on
Nevertheless, the fact remains that there are no conclusive
studies which have linked sugar consumption to cancer directly. The body
digests our consumed foods and converts everything to glucose that is
eventually used by cells. So, even if one restricts sugar consumption, it will
not necessarily inhibit the growth of a tumour, because the tumour will be able
to access sugar anyway. The bottom line is that it is okay to consume sugar, in
moderation, and from natural sources. And the occasional indulgence is simply
unlikely to increase your chances of getting cancer.
O., Versuche an überlebendem carcinom-gewebe. Klin Wochenschr 1923;2:776-7. 3.
O., über den stoffwechsel der carcinomzelle. Naturwissenschaften 1924;12:1131
DS, Fuchs CS, Liu S, Willett WC, Colditz GA, Giovannucci E., Dietary glycemic
load and risk of colorectal cancer in the Women’s Health Study., Cancer
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E., Insulin, insulin-like growth factors and colon cancer: a review of the
evidence. J Nutr. 2001 Nov; 131(11 Suppl):3109S-20S.
Wang, et. al. Sugars, sucrose and colorectal cancer risk: the Fukuoka
colorectal cancer study. Scand J Gastroenterol. 2014 May; 49(5): 581–588.
SB, Jones PA., A decade of exploring the cancer epigenome – biological and
translational implications. Nat Rev Cancer. 2011 Sep 23; 11(10):726-34.
J, Esteller M., Cancer epigenomics: beyond genomics. Curr Opin Genet Dev. 2012
Kelly TK, Jones PA., Epigenetics in cancer. Carcinogenesis. 2010 Jan;
Fierz Y, Vijayakumar A, LeRoith D. Type 2 diabetes and cancer: what is the
connection? Mt Sinai J Med. 2010 Mar-Apr;77(2):197-213
Antara is a computational biology researcher at the University of Groningen. She also freelances as a science writer for Science LinX,that engages the public in the research conducted by the University. Prior to that, she studied biomedical science and bioinformatics from New Delhi. Outside of work, she enjoys organising scientific and cultural events, singing and is a travelling enthusiast.