Posted 16 July 2019
Scientists looked at 16 supplements and found most were useless when it came to heart health and longevity — even vitamin D, iron, and multivitamins
Julia Naftulin , Business Insider US
Jul 14, 2019, 12:22 PM
- A new study, published June 8 in Annals of Internal Medicine, further suggests that investing in supplement pills and powders won’t reduce your risk of heart-related disease or lengthen your life.
- Researchers looked at more than 100 prior studies including 16 kinds of supplements and found that only two types, folic acid and omega-3, helped reduce people’s heart-related disease risks.
- Supplements that combined vitamin D and calcium were found to increase a person’s risk of stroke.
There’s plenty of evidence that suggests stocking up on vitamin supplements to stay healthy is a waste of money, if not harmful to health, and a robust new study adds even more weight to that argument.
The meta-analysis, published on June 8 in Annals of Internal Medicine, included 105 previous studies and looked at how 16 different types of supplements (like vitamin D and folic acid) and eight eating habits (including the Mediterranean diet and reduced salt intake) affected people’s risk of developing cardiovascular disease, heart attack, stroke, and coronary heart disease, as well as their risk of dying from any cause over the given period. All the studies included were randomised controlled trials, the strongest study design out there.
Researchers found that 14 of the 16 supplements were, on the whole, ineffective at reducing heart-related disease risks or lowering the risk of dying from any cause. These supplements were: antioxidants, B-carotene, vitamin B complex, multivitamins, vitamin A, vitamin B6, selenium, niacin, vitamin C, vitamin E, vitamin D, vitamin D with calcium, calcium, and iron.
The only supplements that seemed to be beneficial for reducing heart-related disease risks were folic acid, which was associated with a reduced stroke risk, and omega-3, which was linked to a reduced risk of myocardial infarction, or heart attack. A low-sodium diet was also connected with a lower stroke risk, but no other diets seemed to affect disease risk.
“This study can help those who create professional cardiovascular and dietary guidelines modify their recommendations, provide the evidence base for clinicians to discuss dietary supplements with their patients, and guide new studies to fulfill the evidence gap,” the study authors wrote.
Vitamin D and calcium, when combined in one supplement, increased stroke risk
Most of the supplements had no effect, either positive or negative, on disease risk. But vitamin D and calcium, when combined, actually increased stroke risk.
A previous study, published in April 2019, also found that these two supplements could have potentially harmful effects. Researchers found that people who took vitamin D supplements without have a diagnosed vitamin D deficiency had greater risks for cancer and death than people who didn’t take any vitamin D supplements.
They also found that people who took calcium supplements were more likely to develop cancer, but that eating foods high in calcium had no effect on cancer risk. Researchers were unable to pinpoint exactly why this was the case, but theorise that the excess calcium from supplements increases hormone production.
The new study had some limitations, like that many of the former studies researchers analyzed focused on specific populations, such as all Chinese people. That means their findings can’t be generalised to everyone, or even all Americans, since lifestyle factors and diets differ between the two countries.
Two doctors not associated with the study said that these new findings offer important insights, but more research needs to be done. “Unfortunately, the current study leaves us with the same foggy conditions that we started with,” Dr. Amitabh C. Pandey and Dr. Eric J. Topol wrote in their editorial review. “Until these conditions clear, it would be reasonable to hold off on any supplement or diet modification in all guidelines and recommendations.”
Effects of Nutritional Supplements and Dietary Interventions on Cardiovascular Outcomes: An Umbrella Review and Evidence Map
Safi U. Khan, MD; Muhammad U. Khan, MD; Haris Riaz, MD; Shahul Valavoor, MD; Di Zhao, PhD; Lauren Vaughan, MD; Victor Okunrintemi, MD, MPH; Irbaz Bin Riaz, MD, MS; Muhammad Shahzeb Khan, MD; Edo Kaluski, MD; M. Hassan Murad, MD; Michael J. Blaha, MD, MPH; Eliseo Guallar, MD, DrPH; Erin D. Michos, MD, MHS
The role of nutritional supplements and dietary interventions in preventing mortality and cardiovascular disease (CVD) outcomes is unclear.
To examine evidence about the effects of nutritional supplements and dietary interventions on mortality and cardiovascular outcomes in adults.
PubMed, CINAHL, and the Cochrane Library from inception until March 2019; ClinicalTrials.gov (10 March 2019); journal Web sites; and reference lists.
English-language, randomized controlled trials (RCTs) and meta-analyses of RCTs that assessed the effects of nutritional supplements or dietary interventions on all-cause mortality or cardiovascular outcomes, such as death, myocardial infarction, stroke, and coronary heart disease.
Two independent investigators abstracted data, assessed the quality of evidence, and rated the certainty of evidence.
Nine systematic reviews and 4 new RCTs were selected that encompassed a total of 277 trials, 24 interventions, and 992 129 participants. A total of 105 meta-analyses were generated. There was moderate-certainty evidence that reduced salt intake decreased the risk for all-cause mortality in normotensive participants (risk ratio [RR], 0.90 [95% CI, 0.85 to 0.95]) and cardiovascular mortality in hypertensive participants (RR, 0.67 [CI, 0.46 to 0.99]). Low-certainty evidence showed that omega-3 long-chain polyunsaturated fatty acid (LC-PUFA) was associated with reduced risk for myocardial infarction (RR, 0.92 [CI, 0.85 to 0.99]) and coronary heart disease (RR, 0.93 [CI, 0.89 to 0.98]). Folic acid was associated with lower risk for stroke (RR, 0.80 [CI, 0.67 to 0.96]; low certainty), whereas calcium plus vitamin D increased the risk for stroke (RR, 1.17 [CI, 1.05 to 1.30]; moderate certainty). Other nutritional supplements, such as vitamin B6, vitamin A, multivitamins, antioxidants, and iron and dietary interventions, such as reduced fat intake, had no significant effect on mortality or cardiovascular disease outcomes (very low– to moderate-certainty evidence).
Suboptimal quality and certainty of evidence.
Reduced salt intake, omega-3 LC-PUFA use, and folate supplementation could reduce risk for some cardiovascular outcomes in adults. Combined calcium plus vitamin D might increase risk for stroke.
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