100% fruit juices may raise cancer risk
*Supplements do not protect from heart disease, early death, study finds
A new observational study finds a link between the consumption of sugary drinks, including 100% fruit juices, and the risk of cancer.For some time now, researchers have been linking sugary drinks with a wide range of health risks.
Obesity, type 2 diabetes, and cardiovascular disease are only some of the conditions that previous studies have associated with sweetened drinks. Some studies in rodents have suggested that the added sugar in soft drinks can drive the spread of cancer and fuel tumor growth.
Now, new research further explores the link between sugary drinks and cancer. The observational study, appearing in The BMJ, finds an association between a high intake of sugary drinks and cancer.
Eloi Chazelas, from the Sorbonne Paris Cité Epidemiology and Statistics Research Center in France, is the first author of the study. Chazelas and team examined the links between the intake of sugary drinks and various forms of cancer in 101,257 French adults aged 42 years, on average. The researchers obtained the data from the NutriNet-Santé study.
The drinks they examined included “sugar-sweetened beverages” such as soft drinks, syrups, fruit drinks, 100% fruit juices without any added sugar, milk-based sugary drinks, sports drinks, and energy drinks. The researchers also considered artificially sweetened drinks, that is, “all beverages containing nonnutritive sweeteners, such as diet soft drinks, sugar-free syrups, and diet milk-based beverages.”
Using 24-hour online food questionnaires, the researchers assessed the participants’ consumption of 3,300 different kinds of foods and drinks. Furthermore, clinical observation of the participants continued for up to nine years. During this time, the researchers looked at the risk of “overall, breast, prostate, and colorectal cancer.”
Also, a major review has found most nutritional supplements offer no protection against early death. Experts found that multivitamins, fish oil, and antioxidants are among the products taken by millions of people, which make no difference to mortality rates. A team of academics at West Virginia University in the United States (U.S.) analyzed 277 trials, involving a combined one million people, to determine the effects of 16 different nutritional supplements and eight dietary interventions.
They found the majority made no difference to mortality or cardiovascular disease. Multivitamins, selenium, vitamin A, vitamin B6, vitamin C, vitamin E, vitamin D and iron had no significant effect on either early death or cardiovascular disease Multivitamins, selenium, vitamin A, vitamin B6, vitamin C, vitamin E, vitamin D and iron had no significant effect on either early death or cardiovascular disease
Some 34 percent of adults take vitamins and supplements every day – driving a market that has grown six percent in five years is now worth an annual $37 billion globally. But experts are increasingly skeptical about the worth of the pills, with many pointing out that supplements do provide a short cut to a healthy diet and can never replace real food.
The researchers, writing in the Annals of Internal Medicine journal, found some supplements provided a degree of protection against specific health problems. Folic acid, for example, showed some protection against stroke. And omega-3 fatty acids, which are present in fish oils, protected against heart attacks.
Chazelas and colleagues accounted for potential confounders, including age, sex, education, hereditary risk of cancer, and lifestyle factors — such as smoking behavior and exercise patterns. Over the follow-up period, 2,193 people developed cancer for the first time; they were 59 years old at the time of diagnosis, on average. Among all these cases were 693 of breast cancer, 291 of prostate cancer, and 166 colorectal cancers.
The analysis revealed that for a daily increase of 100 milliliters in the intake of sugary drinks, the risk of overall cancer rose by 18 percent, and the risk of breast cancer increased by 22 percent. When the researchers analyzed the risk for 100 percent fruit juices separately, these also elevated the risk of overall cancer and breast cancer. However, the study found no links with colorectal cancer or prostate cancer.
By contrast, diet drinks did not increase cancer risk. The scientists explain that people who consumed diet drinks did so in very small amounts, so they suggest interpreting this particular result with caution. Chazelas and colleagues also lay out the strengths and weaknesses of their research.
First, the “large sample size and its detailed and up-to-date assessment” of the drinks consumed to strengthen the results, write the researchers. However, the findings may not be widely generalizable, as the study cohort is not representative of the wider population, they continue.
“Since the participants of the NutriNet-Santé cohort were more often women,” they say, “with health-conscious behaviors and higher socio-professional and educational levels than the general French population, this might have resulted in a lower cancer incidence compared with national estimates.”
Other limitations include the inability to determine causality and potential measurement biases. However, the authors speculate that sugary drinks may raise cancer risk because the sugar affects visceral fat, blood sugar, and inflammatory markers — all of which previous studies have correlated with higher cancer risk.
The researchers conclude: “These data support the relevance of existing nutritional recommendations to limit sugary drink consumption, including 100% fruit juice, as well as policy actions, such as taxation and marketing restrictions targeting sugary drinks, which might potentially contribute to the reduction of cancer incidence.”
But the Annals of Internal Medicine journal found multivitamins, selenium, vitamin A, vitamin B6, vitamin C, vitamin E, vitamin D, and iron had no significant effect on either early death or cardiovascular disease. The researchers also found dietary interventions, such as the Mediterranean diet, rich in vegetables, olive oil and fish, made no difference to mortality or heart health.
Surprisingly, reducing fat did not cut heart disease and cutting salt levels did cut death rates, but not heart problems. Experts last night welcomed the findings but said the study could not provide the whole story. Victoria Taylor, the senior dietitian at the British Heart Foundation, said: “Studies on dietary approaches are very difficult to conduct and may vary widely in their approaches and definitions of the interventions.
“It would also be all but impossible to carry out a research trial where you carefully controlled the diets of thousands of people over many years.”
Prof. Susan Jebb of the University of Oxford, said: “This review confirms the vast majority of previous research that has failed to find benefits of most nutritional supplements.
“It finds no good evidence that vitamin and mineral supplements are associated with a reduction in premature death or in cardiovascular disease.“Except to prevent or correct specific deficiencies (example Vitamin D), or in specific circumstances such as folic acid supplements in early pregnancy to prevent neural tube defects, there is generally good agreement that dietary supplements should not be recommended to the general population.” But she disagreed with the assertion that cutting fat or salt does not benefit health. “The suggestion that dietary interventions have no benefit does not reflect the totality of the evidence,” she said.
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