Independent report

Fortifying foods and drinks with vitamin D: glossary

Published 23 May 2024

Applies to England

Numbers (0 to 9)

25-hydroxyvitamin D (25(OH)D)

25-hydroxyvitamin D (25(OH)D) is a metabolite of vitamin D produced in the liver from vitamin D. It circulates in the blood and is the principal indicator of total exposure to vitamin D, reflecting vitamin D supply from skin synthesis and the diet.

C

Cholecalciferol

Cholecalciferol is another name for vitamin D3.

Confidence interval

A confidence interval shows the range of values, which is likely to include the true estimate.

D

Dose-response relationship

Dose-response relationship refers to the intensity of response to size of dose.

E

Efficacy trials

Efficacy trials test whether interventions work under optimal, highly controlled conditions.

Effectiveness trials

Effectiveness trials test whether interventions work in real-world settings.

Ergocalciferol

Ergocalciferol is another name for vitamin D2.

F

Forest plot

A forest plot is a graphic representation of results from studies in a meta-analysis, showing direction and magnitude of effect, and the confidence intervals.

Fortification

Fortification is addition of nutrients to foods during the manufacturing process.

G

Gene expression

Gene expression is the process by which a gene is turned on to produce the specific biological molecule encoded by the gene.

Genetic polymorphism

Genetic polymorphism is natural variation in a gene, DNA sequence or chromosome.

Grey literature

Grey literature describes a wide range of different information produced outside of traditional commercial and academic publishing and distribution channels. This can include information such as reports, government documents, white papers and evaluations published by organisations across government, academia, business and industry.

H

Heterogeneity

Heterogeneity is used generically to refer to any type of significant variability between studies contributing to a meta-analysis that renders the data inappropriate for pooling. This may include heterogeneity in diagnostic procedure, intervention strategy, outcome measures, population, study samples, or study methods.

The term heterogeneity can also refer to differences in study findings. Statistical tests can be applied to compare study findings to determine whether differences between the findings are statistically significant. For example, significant heterogeneity between estimates of effect from intervention studies suggests that the studies are not estimating a single common effect. In the presence of significant heterogeneity, it is more appropriate to describe the variations in study findings than to attempt to combine the findings into one overall estimate of effect.

The I² statistic estimates the proportion of the variance in study estimates that is due to heterogeneity.

Heterogeneous

Heterogeneous means varied in content.

High performance liquid chromatography

High performance liquid chromatography is an advanced type of liquid chromatography that is performed under high pressure (see definition of ‘Liquid chromatography’ below in this glossary). This reduces the time of separation and increases efficiency.

I

Idiopathic infantile hypercalcaemia

Idiopathic infantile hypercalcaemia is a condition characterised by high concentrations of calcium in the blood.

L

Liquid chromatography

Liquid chromatography is an analytic technique that separates a mixture into its individual chemical components.

Liquid chromatography-mass spectrometry

Liquid chromatography-mass spectrometry is an analytical technique that combines liquid chromatography and mass spectrometry.

Liquid chromatography with tandem mass spectrometry

Liquid chromatography with tandem mass spectrometry is an analytic technique that combines liquid chromatography and tandem mass spectrometry.

M

Mass spectrometry

Mass spectrometry is an analytical tool for separating ionised molecules according to their mass-to-charge ratio.

Mean difference

Mean difference is the absolute difference between the mean value in 2 groups in a trial.

Meta-analysis

Meta-analysis is a method of statistical synthesis that is used in some systematic reviews, where the results from several studies are quantitatively combined and summarised. By combining results from all relevant studies, meta-analyses provide more precise estimates of the effects of an intervention than those derived from the individual studies included in a review.

Metabolites

Metabolites are intermediates and products of chemical reactions in the body.

Microarray

A microarray is a laboratory tool used to analyse large numbers of genes or proteins at one time.

N

Normocalcaemic hyperparathyroidism

Normocalcaemic hyperparathyroidism is a condition characterised by serum calcium concentrations within the normal range and elevated parathyroid hormone concentrations.

P

Placebo

A placebo is an inactive substance prepared to resemble the active product under investigation in a study.

R

Radioimmunoassay

Radioimmunoassay is an antibody-based method used to measure the concentration of substances.

Random-effects model

A random-effects model is a statistical model in which both within-study sampling error (variance) and between-studies variation are included in the assessment of the uncertainty (confidence interval) of the results of a meta-analysis.

Randomised controlled trial

A randomised controlled trial is a type of study in which participants are randomly assigned to 2 (or more) groups to test a specific intervention or treatment. One group (experimental or treatment group) receives the intervention being tested, while the other group receives a placebo (control group) for a specific duration.

Reference nutrient intake

Reference nutrient intake is the amount of a nutrient that will be adequate to meet the needs of 97.5% of the population.

Rickets

Rickets is a disorder of the growth plates of infants and children that affects skeletal development. The most common cause is insufficient vitamin D (vitamin D deficiency rickets), calcium or phosphate during growth, which leads to pain, softening and weakening of the bones, and characteristic deformities of the long bones.

Risk of bias

Risk of bias relates to the quality of a study. A bias is a systematic error or deviation from the true results of a study. It is caused by inadequacies in the study design or execution.

S

Safe intake

Safe intake is set for some nutrients if there is insufficient reliable data to set dietary reference values. It represents a level or intake range at which research shows there is no risk of deficiency and below a level where there is a risk of undesirable effects.

Sarcoidosis

Sarcoidosis is a rare condition that causes small patches of swollen tissue, called granulomas, to develop in the organs of the body.

Study power

Study power is a measure of the extent to which a study is capable of discerning differences or associations that exist within the population under investigation.

Study power may be increased by increasing sample size.

Subgroup analysis

Subgroup analysis is an analysis that is repeated for a subset of participants (such as male or female or age group) or for a subset of studies.

Systematic review

A systematic review is a method of identifying, appraising and synthesising research evidence. The aim is to evaluate and interpret all the available research on a specific review question, using a predefined protocol. Systematic and explicit methods are used to minimise bias.

Researchers define the objectives in advance and they specify the methods to be used at each step, including:

• search criteria to identify all relevant studies
• eligibility criteria for study inclusion
• application of established standards to appraise study quality
• methods for extracting, synthesising and reporting study findings

A systematic review may also include meta-analyses.

T

Tandem mass spectrometry

Tandem mass spectrometry is an analytical technique that involves multiple steps of mass spectrometry.

Tolerable upper intake level

Tolerable upper intake level (UL) is the highest average daily intake of a nutrient that is likely to pose no risk of adverse effects to almost all individuals in the general population. As intake increases above UL, the potential risk of adverse effects may increase.

U

Ultraviolet radiation

Ultraviolet radiation is part of the electromagnetic spectrum emitted by the sun with wavelengths of around 100 to 400 nanometres (nm). Sub-regions of ultraviolet radiation spectrum have been defined according to transmission in human tissue and potential health effects. These are:

• ultraviolet A (UVA) covers the range 315 to 400nm
• ultraviolet B (UVB) covers the range 280 to 315nm
• ultraviolet C (UVC) covers the range 100 to 280nm

V

Vitamin D2

Vitamin D2 is a form of vitamin D. Also known as ergocalciferol. It is formed in fungi and yeast by UVB exposure of the steroid ergosterol.

Vitamin D3

Vitamin D3 is a form of vitamin . Also known as cholecalciferol. It is synthesised in the skin of humans by the action of sunlight containing UVB radiation.