Dietary supplements have no effect on mortality risk

For the general population, supplementation does not reduce the risk of death from cardiovascular disease or cancer, concludes a large cohort study.

"People should aim to get adequate nutrition through a healthy and balanced diet rather than relying on supplements," said lead author Zhang Fang Fang, MD, PhD, Tufts University, Boston, Massachusetts Medscape Medical News in an email.

An exception was the taking of a lycopene supplement, which seemed to reduce the risk of CVD and cancer mortality.

However, the study also revealed that taking a supplement could be detrimental: taking calcium supplements in high doses seemed to increase the risk of dying from cancer.

The study was published online on April 8, 2019 in the Annals of Internal Medicine.

"Since more than half of Americans take dietary supplements to improve their overall health, stay healthy or improve specific health conditions, it is important to evaluate the effect that dietary supplements might have. have on the risk of mortality, "commented Zhang.

In the study, the use of dietary supplements over the last 30 days was analyzed in 30,899 adults who participated in six cycles of the National Health and Nutrition Survey (NHANES) from 1999 to 2000 and from 2009 to 2010.

The intake of nutrients from foods and supplements was also analyzed in 27,725 participants who provided one or two valid information on the recall of a diet every 24 hours.

The team ranked nutrient intake as being "inadequate" – defined as being the total intake of nutrients from foods and supplements less than the estimated average need – or as "sufficient" "when nutrient intake was at levels specified in the Dietary Reference Intakes. The nutrient abuse was determined by comparing the absorption of participants with levels greater than the maximum tolerable absorption.

Study participants who reported taking dietary supplements had an average age of 50.7 years, while the average age of those who did not take dietary supplements was 42.8 years (P <0.001).

"More than half of participants (51.2%) reported using dietary supplements in the last 30 days and 38.3% reported using MMV (multivitamins and minerals) supplements," commented Zhang. colleagues.

The most commonly used vitamin supplements included vitamin C (used by 40.3% of participants), vitamin E (used by 38.6%) and vitamin D (used by 37.6%).

The most commonly used mineral supplements were calcium (used by 38.6%), zinc (34.5%) and magnesium (33.3%).

In general, participants who took supplements had higher total nutrient intakes for the 25 nutrients tested compared to non-users. Even when nutrient intake from supplement use was reduced, foods for 23 nutrients were still higher than for users without supplements, the researchers said.

Interestingly, however, more than half of the participants had inadequate intake of vitamin D, vitamin E, choline, vitamin K and potassium. Less than 5% of all respondents consumed what investigators determined to be an "excess" of consumption for all nutrients except niacin.

"During a median follow-up of 6.1 years, 3616 deaths were recorded, including 945 CVD deaths and 805 cancer deaths," the researchers reported.

After multivariate adjustment, no dietary supplement, with the exception of lycopene, was associated with a lower mortality risk. Lycopene reduced the risk of all-cause mortality by 18% and the number of cancer deaths by 54%.

Nutrients from food

The researchers then began to understand the effects of nutrient intake from foods compared to the same intake of nutrients from the supplements.

At first, they found that people with adequate vitamin K and magnesium intake had a lower risk of all-cause mortality, while those with sufficient vitamin A, vitamin K, copper and zinc intake had a lower risk of dying from the disease. CVD.

However, "when sources of nutrient intake were assessed, the lesser all-cause mortality associated with adequate vitamin K and magnesium intake was limited to that from food [while] the lowest CVD mortality was associated with adequate vitamin A, vitamin K, zinc and copper (…), limited to that of food, "observe Zhang and his colleagues.

Importantly, excessive calcium intake was associated with a 62% higher risk of cancer death. This risk was limited to high-dose calcium supplements of 1,000 mg / day or more, and not to calcium intake from food, the team noted.

At the same time, the researchers also noted that vitamin D supplementation at doses greater than 10 μg / day – or around 400 IU / day – was associated with an increased risk of all-cause mortality and cancer .

However, this effect was observed only in participants with sufficient vitamin D levels, defined as a serum 25-hydroxyvitamin D level greater than or equal to 50 nmol / L, and not in participants with serum 25-hydroxyvitamin D less than 50 nmol / L.

"Thus, using vitamin D supplements at 400 IU / day or more can have adverse effects in people with no evidence of vitamin D deficiency," Zhang observed.

"For people with low vitamin D status, vitamin D supplements have no benefit or harm," she added.

Zhang pointed out that if a patient suffered from a health problem that could lead to malabsorption of nutrients in foods or following specific dietary habits and practices, he or she could have nutritional deficiencies that required treatment with dietary supplements.

She also warned that it was important for doctors to ask questions about the use of dietary supplements in cancer patients, as some dietary supplements, such as antioxidants, may interfere with treatments that are not recommended. they are about to receive.

"Thus, patients with nutritional deficiencies can be assessed separately according to their needs," she suggested.

However, for the general population, Zhang pointed out that foods are usually the most important source of nutrients and that doctors should advise patients accordingly.

Elizabeth Kantor, MD, of the Memorial Sloan-Kettering Cancer Center in New York, said, "People should discuss decisions regarding the use of dietary supplements with their health care providers."

Zhang did not reveal any relevant financial relationship, although one of his co-investigators did so; see the publication for information. Kantor has not revealed any relevant financial relationship.

Ann Intern Med. Posted online April 8, 2019. Summary

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