Insufficient consumption of fruits and vegetables is a well-known dietary problem today; many try to make up for it by taking supplements. Dietary supplements are being consumed under the belief that they are an easy way to get the essential nutrients for our body. However, new research has suggested that vitamins and supplements may not be enough to keep you healthy.
This study has been conducted by a research team from Tufts School of Medicine (USA) and published in the scientific journal Annals of Internal Medicine. The study reports that sufficient intake of certain nutrients from food is linked to a lower risk of cancer and all-cause mortality. Conversely, nutrients from supplements are not associated with a reduced risk of death; in fact, some supplements may actually increase mortality risk.
According to the research, the problematic supplements were specifically calcium and vitamin D. Doses of calcium that exceeded 1,000mg (milligrams) per day were tied to a high risk of death from cancer. Similarly, vitamin D supplements, taken by people who do not have vitamin D deficiency, were connected to an elevated likelihood of death from all causes, including cancer.
“As potential benefits and harms of supplement use continue to be studied, some studies have found associations between excess nutrient intake and adverse outcomes, including increased risk of certain cancers,” said lead author Prof Fang Fang Zhang, from Friedman School of Nutrition Science and Policy at Tufts University. “It is important understand the role that the nutrient and its source might play in health outcomes, particularly if the effect might not be beneficial.”
The research was conducted using data from 27,000 US adults aged 20 years and older to explore two relationships—whether adequate or excess nutrient intake was linked to all-cause mortality; and whether results changed if the nutrients came from supplements instead of food. For each nutrient, scientists calculated the daily supplement dose by combining the frequency with the product information for each ingredient, the amount of the said ingredient per serving and its unit. The assessment was based on participants’ dietary intake of nutrients from food using 24-hour dietary recalls and mortality outcomes through the National Death Index through 31 December 2001.
The phase of the study that examined the impact of nutrients on death risk revealed three associations, viz., sufficient intake of magnesium and vitamin K were linked to a lower risk of death; sufficient intake of vitamin K, vitamin A and zinc were tied to a lower cardiovascular disease risk of death; and excess calcium intake was connected to a higher likelihood of death by cancer. When nutrients from food were compared to nutrients from supplements, the results showed the first two associations were due to nutrients from food rather than nutrients from supplements. While no adverse effect of calcium intake from food was noted, excess calcium intake from supplements was linked to an increased risk of death from cancer. In addition, supplements had no effect on the risk of death in people with low nutrient intake from food.
“Our results support the idea that, while supplement use contributes to an increased level of total nutrient intake, there are beneficial associations with nutrients from foods that aren’t seen with supplements,” Prof Zhang said. “This study also confirms the importance of identifying the nutrient source when evaluating mortality outcomes.” She further added that it is important to understand the effect that a nutrient and its source might play on health and mortality outcomes, especially when it is not beneficial.
The research team has noted some limitations of the study, including the duration for which use of dietary supplement was studied. The team are also aware that, since the prevalence and dosage of dietary supplement was self-reported, there is certainly a possibility of recall bias. The authors believe that this study has only pointed out a possible cause and further research on this possible connection will be necessary.
