This is because vitamins and minerals are most potent when they come from food.
In foods, they come with many other beneficial nutrients, including hundreds of carotenoids, flavonoids, minerals, and antioxidants that aren't found in most supplements.
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University of Cambridge, Department of Public Health & Primary Care, Strangeways Research Laboratories, Worts Causeway, Cambridge CB1 8RN In the past, vitamins and minerals were used to cure deficiency diseases. Supplements today are used with the goal of reducing the risk of chronic diseases whose origins are complex. The use of dietary supplements has increased in the United Kingdom in recent decades, which has contributed to the intake of nutrients in the population, but not necessarily to the proportion of the population that is not optimally nourished; therefore, it does not reduce the proportion below the estimated average requirement and could increase the number of people at risk of an intake above the safe limits. The nutrient intake of the supplement can be objectively controlled using circulation biomarkers.
However, the researcher's influence on the way supplements are grouped and the way nutrient intakes are quantified can lead to different conclusions regarding their nutrient contribution, associations with biomarkers in general, and dose-response associations specifically. The diet may be sufficient in micronutrients, but it lacks a balanced food intake. Since public health nutritional guidelines are expressed in terms of food, there is a possibility that there is a discrepancy between the nutrient-oriented supplement and the quality of the dietary pattern. To promote health, current public health messages only advocate supplements in specific circumstances, not in populations with optimal nutrition.
This article aims to describe the methodology for evaluating dietary supplements in the context of observational research and to characterize the heterogeneity among supplement users. A secondary objective is to focus on the role of supplements in nutrient distribution, circulating biomarkers, and diseases, using a variety of examples that illustrate their (in) efficacy in public health. All of the assessment instruments listed above, except for the biomarkers, require the researcher to make assumptions regarding the nutrient composition of the supplement. Pre-structured questionnaires will assume a predetermined nutrient composition.
Open questionnaires, such as those used in the NDNS (32.3) and in the Norfolk branch of the European Prospective Investigation into Cancer (EPIC-Norfolk) study (3), may be more specific, but they will also be based on the labels printed on the packaging of dietary supplements and, therefore, on the possibility of transcription errors in the labels (3). The packaging may contain errors, the supplement may have been kept under poor storage conditions, or the supplement may contain “surpluses”, mainly for vitamins, and taking into account safety limits, in the range of 5 to 100% of the label value (36, 3). All of these factors mean that what is “on the label” does not accurately reflect what is contained in the dietary supplement and, therefore, is a less accurate (or even biased) measure of the supplement's nutrient intake (at least attenuating any association between nutrient intake and the biomarker or disease). For these reasons, a long-term process has been proposed and developed to develop a composition table based on analytical data (38.3, DRV, dietary reference value; LRNI, lower intake of reference nutrients; EAR, estimated average requirement; RNI, reference nutrient intake; SUL, higher safe level).
Supplement intake shifts the distribution of exposure to nutrients to the right; however, nutrient sufficiency, in most cases, can only be obtained from food sources. The (small) reduction in the proportion of people at risk after including supplements depends on the nutrient, but also on the grouping of supplements. There is a slightly greater risk of exceeding the upper limits when supplementation is included (among those who use that nutrient in supplement form). The supplemented nutrients are capable of increasing the plasma concentrations of the respective nutrients, in particular vitamins and fatty acids.
Supplements in pharmaceutical doses may have high correlations between intake and biomarker; however, dose-response associations indicate saturation. A biomarker can be influenced by many other factors (see, for example, Proc Nut Soc McMillan); in addition, this does not automatically mean that higher circulating concentrations indicate better health or functionality, since circulating biomarkers may not reflect the storage or efficacy of the nutrient in an organ. Since nutrients can be derived from a variety of (potentially fortified) foods and not necessarily from foods recommended for public health, it can be argued that food intake could be a better marker of optimal intake than of nutrient intake. For example, the median TNI for vitamin C, expressed as a percentage of the RNI, was 18.5% and 19.7% in men aged 19 to 64 and over 65, respectively, and 19.2% and 20.9% in women (3).
Unlike fruit and vegetable consumption, the UK diet meets 30% and 40% of the 5-a-day guidelines for both men and women aged 19 to 64 and over 65, respectively). The role of multivitamins in the past was partly considered as a means of compensating for poor dietary choices (7); or, when, after various considerations, the likely benefits outweighed the harms of using supplements (9). However, as observed in the meta-analyses described above, its use has not been successful in preventing diseases or premature death in populations. Potentially, since foods contain more than just vitamins and minerals on their own, and dietary patterns in general play an important role in health (.
How do you tip the balance between food and supplements? Supplements continue to be consumed by an increasing proportion of the population, so it is necessary to control their contribution to diet, health and disease. Traditionally, essential nutrients have been studied in relation to health and, although micronutrient deficiencies are still prevalent in the UK population, relatively high nutrient intake may not be an indicator of healthy food choices, as reflected in the low consumption of fruits, vegetables and fish in national surveys. Resolving unhealthy dietary patterns with micronutrient supplements is too narrow a solution. Today, public health nutrition guidelines consider the role of the nutrient, its food source, and its place in the diet to optimize the diet.
The current role of supplements in this context seems to be restricted to certain age groups, life circumstances, or diseases with poor nutrient absorption (7,10). The challenge of observational research methodology is to evaluate and describe nutrient intake, as well as diet as a whole, in the general population and to clarify the role, if any, of nutrient supplements in the primary prevention of diseases. I would like to thank Professor Kay-Tee Khaw and Professor Ailsa Welch for their supervision during my doctoral studies. I thank the staff at Elsie Widdowson Laboratories for answering questions about the use of the NDNS data sets and Angela Mulligan for reading the draft manuscript.
When evaluating the association between nutrient intake (from both food sources and supplements) and a biomarker, Block et al. A clear intervention, then still in the form of food, alleviated symptoms and cured diseases such as lime (26%), scurvy, unpolished rice (beri beri beri) and cod liver oil (26%) rickets. Even the American Academy of Pediatrics encourages children who are generally healthy to meet their daily nutritional needs with food alone. Consuming vitamins and minerals beyond what your body needs won't increase your energy or protect you from disease.
The Dietary Guidelines for Americans say that your nutritional needs should be met primarily through diet, although you can supplement with vitamins if your needs can't be met with food alone. The Vitamin and Mineral Expert Group (EVM) defines the safe upper level (SUL) as “an intake that can be consumed daily throughout life without significant health risk”, according to available evidence (3) and refers only to intake from supplements. When you replace whole foods with supplements, you lose the dietary components that benefit your health but are not yet fully understood. Once the nutrient intake of supplements has been evaluated, they can be added to the dietary intake to obtain the TNI.
For example, the role of vitamin D and calcium are closely related, as is the role of folate and vitamin B12. Significant reductions were observed in mortality (9%), cancer mortality (13%), but particularly in stomach cancer (21%) when supplemented with ß-carotene and vitamin E and 26% selenium. Supplement intake shifts the distribution of nutrient exposure to the right; however, nutrient sufficiency, in most cases, can only be obtained from dietary sources. Taking into account the variation in the use of supplements in Europe (30.3), supplements vary in the contribution they make to food intake and in the proportion of the population at risk of not meeting sufficient DRVs. So, while the need to take a vitamin probably means that you're interested in living a healthy lifestyle, a vitamin supplement itself may not help you lead that lifestyle.
In the Vitamin And Lifestyle (VITAL) cohort (VITAL) (5), the adjusted correlations between supplement intake and the biomarker were 0.69, with a significant linear trend in N-tiles (P. .