4 truths about supplements that are not discussed enough
Supplements are often considered quick-fix pills that can be taken just in case. That probably explains why one of the most common questions dietitians get is, “What supplement do you recommend?”. Dietitians generally take a food-first approach, meaning diet change comes before supplementation. But wait, why food first when there are so many convenient options out there? Here are 4 things that are underlooked about supplements.
You can overdose from good nutrients
Most healthy people take nutrient supplementation just in case they don’t get enough nutrients from their everyday diet without knowing some nutrients can have adverse effects in high doses, such as vitamins A and E. Nutrient intake that is above the recommended Upper Limit (UL) can lead to adverse effects such as metabolic dysregulation or even increases the risk of diseases. Botanical ingredients, which are popular and widespread on the market, in large doses can give extra stress to our livers as opposed to the common belief of liver detox.
Risk of polysupplementation
Besides overdosing, polysupplementation is very common. Polysupplementation means taking multiple supplements at the same time. This is completely fine under medical supervision to correct dysregulations, but there are risks in voluntary polysupplementation. Most supplement products are formulated with multiple ingredients and nutrients. It is easy to take various supplements with the same ingredient, which puts you at risk of overdosing. Moreover, polysupplementation without supervision introduces the risk of undesired effects from nutrient-nutrient or nutrient-medication interactions.
Mixed outcomes in general health
Even though the supplement industry often puts a promising line on supplement package, the effects of taking a supplement for general health is mixed. In scientific research, general health is usually measured in all-cause mortality (general risk of death) and disease specific-mortality (risk of dying from a specific group of diseases). Studies have found very mixed (protective, neutral and harmful) effects on all-cause, cardiovascular diseases (CVD) and cancer mortality (1-5§). Some nutrients showed both protective and harmful effects in different studies, suggesting the impact of supplements on general health is really not clear yet.
§ Brief summaries of cited studies:
Schwingshack et al. (2017) performed a systematic review and meta-analysis examining dietary and supplement nutrient intake and risk of diseases and death (1). The result suggested that vitamin E and folate supplementation reduces cardiovascular disease (CVD) risks, and many nutrients (Vitamin C, D, K, selenium, zinc, magnesium, EPA) have no effect on CVD and cancer risk. In contrast, vitamin A and beta-carotene increase cancer and all-cause mortality rate.
Chen et al. analysed data from over 30,000 US adults in 2019 (2). Results suggested that vitamin A & K, magnesium and zinc can reduce all-cause and cardiovascular disease mortality, but only limited in dietary intake (not from supplements), and excessive calcium intake (associated with supplement use) increase cancer mortality.
Hua et al. (2023) examined supplement effects in over 8000 US adults with diabetes (3). The data suggested that general supplementation has no effect on mortality risk. However, some amino acid supplementation may lower all-cause mortality.
Hua’s colleague, Lam, analysed data from over 30000 UK adults with cancer in 2023 (4). Vitamin supplements have a small decrease in cancer mortality, while non-vitamin-non-mineral supplements may lower cancer and all-cause mortality.
Messerer et al.(2008) investigated supplements and the risk of all-cause, cancer and CVD mortality in nearly 39,000 middle-aged to older Swedish men. They found that multivitamin, vitamin C, E and fish oil do not affect all-cause, cancer and CVD mortality. The result also alerted that smokers with regular supplement use are 46% more likely to develop cancer. Supplementation is only beneficial in those with inadequate dietary intake.
Food can replace supplements most of the time, but supplements can never replace food
As the name “supplement” suggests, they should be used on top of something (diet). From a general health perspective, a healthy balanced diet can meet all nutritional and health needs, but it is extremely difficult to get a balanced nutrient from supplements.
An observational study highlighted that while vitamin A & K, magnesium and zinc can potentially reduce all-cause and CVD mortality, the benefits are only found in dietary nutrient intake but not supplements (2). Another study showed supplement benefits are only found in those with inadequate dietary nutritional intake, not those with a balanced diet (5). This suggested that we should prioritise diet quality to gain health benefits and only use supplements when adequate intake is hard to achieve, such as vitamin B12 for strict vegans.
Key Messages
It is safest to take supplements according to professional advice.
Follow instructions when taking supplements and avoid taking extra supplements “just in case”.
The claimed health benefit of a supplement might not be the whole picture.
One supplement that works for your friend does not necessarily work for you.
Supplements cannot replace food. Always aim to have a balanced diet first, then seek professional advice on supplements if it is hard to achieve, e.g. B12 for strict vegans.
References
Schwingshack L, Boeing H, Stelmach-Mardas M, Gottschalk M, Dietrich S, Hoffmann G, Chaimani A. Dietary supplements and risk of cause-specific death, cardiovascular disease and cancer: A systematic review and meta-analysis of primary prevention trial. Adv Nutr.2017;8(1):27-39
Chen F, Du M, Blumberg JM, Chui KKH, Ruan M, Roger G, Shan Z, Zeng L, Zhang FF. Association between dietary supplement use, nutrient intake and mortality among US adults: a cohort study. Ann Intern Med.2019;170(9):604-613
Hua R, Lam CS, Chu N, Yang A, Chow E, Cheung YT. Association between dietary supplement use and mortality among US adults with diabetes: a longitudinal cohort study. Nutr & Metab.2023; 20:33
Lam CS, Koon HK, Loong HHF, Chung VCH, Cheung YT. Association of dietary supplement use with the all-cause and cause-specific mortality in patient diagnosed with cancer: a large prospective cohort study in UK Biobank. Eur. J. Nutr.2023;62:879-889
Messerer M, Håkansson N, Wolk A, Åkesson A. Dietary supplement use and mortality in a cohort of Swedish men.Br. J. Nutr.2008;99(3):626-31
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