Vitamin D briefing – Sorting fact from fiction

FACT: In the UK we cannot synthesize vitamin D from sunlight in the months from October to April and therefore everyone needs to take a supplement for those seven months of the year.[1]

The Health Supplements Information Service (HSIS) highlights the continuing concerns around intakes of vitamin D in diets in the UK. Latest data show that around a fifth of adults aged 19 to 64 years have low blood levels of vitamin D.[2] Alongside this, average intakes of vitamin D from food sources alone are less than one-third of the Reference Nutrient Intake[3] (for children aged 1.5 to 3 years and adults aged 65 years and over (29% and 33%, respectively)[4] indicating the importance of dietary supplementation.

SUNLIGHT IS NOT ENOUGH

Nutritionist, Dr Emma Derbyshire, from HSIS says: “It is well known that our bodies use sunlight to make vitamin D. However, evidence shows that the sun is not high enough in the sky between the months of October and April to allow our bodies to make vitamin D from sunlight. This means we need vitamin D from other sources to support our health, particularly bone health.[5] Furthermore, when we do get enough sunshine in the summer months, factors such as air pollution, clothing and sunscreen use can all act as notable barriers to this.”[6]

“A recent report from the Scientific Advisory Committee on Nutrition (SACN) has revised the recommended intakes for vitamin D. In response, Public Health England advises that everyone should supplement their diet with 10 micrograms (µg) a day throughout the winter. Some population groups who are at greatest risk of deficiency are advised to take this amount year-round, as noted below. This is regarded as the average amount needed by most of the population (97.5%) to maintain blood serum vitamin D levels above ≥ 25 nmol/L when UVB sunshine exposure is minimal [7] i.e. throughout the winter months. When blood levels fall below this amount this indicates that an individual may be deficient, though different cut-offs are sometimes used. ”

GROUPS AT RISK OF DEFICIENCY

Dietitian, Dr Carrie Ruxton, from HSIS adds: “It is very difficult to get enough vitamin D from the foods that we eat, mainly because there are so few naturally rich sources. The best source by far is oily fish but two thirds of adults and 90% of teenagers do not eat it regularly. Eggs and red meat also contain useful amounts of vitamin D. Some foods, such as certain breakfast cereals, soya products, some dairy products, powdered milks and fat spreads are fortified with vitamin D. Unfortunately, the amounts added to these products vary and tend not to meet the new recommendation of 10 micrograms.”[8]

Several groups of people in the UK are a greater risk of vitamin D deficiency, including:[9],[10]

children under 5 years of age
people aged 65 and over
people who wear clothing that covers most of the skin
those from ethnic minority groups with dark skin
those who stay indoors for long periods or are housebound
pregnant and breastfeeding women

For those who fall within these at-risk groups, a positive difference to health could be made by taking a daily vitamin D supplement. It is recommended that adults in groups at risk of vitamin D deficiency take 10 μg of vitamin D each day throughout the year.[11]

BONE HEALTH

Vitamin D plays an important role in the regulation of calcium and phosphorus metabolism and, therefore, in bone health. Vitamin D is crucial across all life stages, playing a key role in bone health:[12]

Infancy and early childhood – Vitamin D is needed to meet the demands of rapid growth for healthy skeletal development.
Childhood and adolescence – Vitamin D is needed for bone health during this period of rapid growth when bone accretion (deposition) takes place contributing to peak bone mineral density.
Adults – Vitamin D is needed to maintain healthy bones and prevent osteomalacia (bone softening) which can be presented as muscle weakness and bone tenderness, or pains in the ribs, spine, shoulder or pelvis.
Pregnancy and lactation – Vitamin D supplements (10 μg per day) are currently recommended during pregnancy to ensure that the mother and subsequently her offspring are not deficient in vitamin D.

Whilst the current SACN recommendations for vitamin D are based on bone health, it has been suggested that vitamin D may have a role in other health outcomes, which include reducing the risk of autoimmune diseases, cancers, cardiovascular disease and infectious diseases.[13]

RESPIRATORY HEALTH

A recent meta-analysis published in The British Medical Journal[14] reviewed evidence from 25 randomised controlled trials (RCTs), comprised of data from 11,321 participants. It was found that vitamin D supplementation significantly lowered the risk of acute respiratory infections. Whilst supplementation benefitted all participants, the effects were found to be even stronger amongst those with vitamin D deficiency at baseline.

Dr Emma Derbyshire comments: “This was a high-quality publication with overall findings indicating that vitamin D supplementation, especially during the winter months may be helpful in protecting against severe respiratory tract infections, which affect many of us at that time of year.”

“Other work[15] has shown that vitamin D can act as an adjunctive (supporting) therapy in the treatment of asthma. Current evidence indicates that vitamin D may enhance the body’s response to asthma medication as well as potentially reducing the thickening and constriction that asthma creates in the lungs. In addition, there is emerging evidence[16] that vitamin D supplementation may help to reduce asthma risk in children, though further RCTs are needed to confirm this.”

MENTAL HEALTH

Dr Emma Derbyshire notes: “There is some evidence to indicate that vitamin D may help to support certain aspects of mental health. A meta-analysis,[17] using data from seven trials with a total of 3,191 participants found that vitamin D supplementation was effective in reducing depressive symptoms in those with clinical depression. Whilst further high-quality RCTs are needed these results indicate that vitamin D supplementation could benefit those diagnosed with depression.”

Dr Derbyshire adds “Other work[18] using data from over 100 pregnant women in Michigan found that low vitamin D levels early in pregnancy (at 12 to 20 weeks) was associated with a higher risk of depressive symptoms in early and late pregnancy. Given that around one in six[19] pregnancies is unplanned, raising the vitamin D status of the population as a whole is really important.”

“Further evidence from 25 cross-sectional studies and eight longitudinal studies[20] has found that low vitamin D levels (hypovitaminosis D) may have a role on the way in which mental health problems in children and teenagers develop. RCTs are now urgently needed to study this effect during these important life stages.”

SAFETY

Dr Carrie Ruxton says: “Food supplements sold in the EU, including the UK, must comply with food law making them some of the most regulated food products around. The regulations apply whether the products are in your local pharmacy, or sold on the websites of European companies. This is great news for consumer safety.”

“In contrast, supplements sold on websites by non-EU companies do not necessarily meet the same stringent standards for safety, quality or purity. That’s why it can be risky to use these websites even though you think you’re getting a bargain because the products may be cheaper.”

“I would always recommend that people buy their food supplements, like vitamins, minerals, probiotics, fish oils or botanicals, from their pharmacist, health food store, or from European company websites. That way you get the benefits of these supplements and have peace of mind about the safety and quality.”

“Thanks to our strict food laws, food supplements sold in the UK meet exacting standards for safety and purity, and labelling claims will be compliant with regulations.”

Dr Emma Derbyshire further advises: “When taking vitamin D supplements people should follow Public Health England advice of 10µg per daily for those at risk of vitamin D deficiency. People should not be ‘super-dosing’ and if people have a diagnosed medical condition that may require higher amounts, these should be prescribed by a medical practitioner.”

CONCLUSION

It is clear from dietary surveys that vitamin D shortfalls are common in the UK population. Whilst vitamin D can be obtained from food sources, these are limited and not well consumed by the UK population. The richest dietary source is oily fish, however UK dietary surveys show that this is eaten in only small amounts. Whilst some foods are fortified with vitamin D, this is generally to a relatively low level which is insufficient to make up the 10µg daily intake recommended.

Whilst vitamin D can be made by the body when exposed to sunlight, here in the UK it is not possible for our bodies to do this between October and April as the sun is too low in the sky. Therefore, blood levels of vitamin D drop in the autumn and winter and may become too low to maintain good health. Public Health England advises that everyone should take a food supplement containing 10µg of vitamin D throughout the winter. Those at risk of deficiency should consider continuing to supplement throughout the year.

ABOUT HSIS

HSIS (the Health and Food Supplements Information Service) is a communication service providing accurate and balanced information on vitamins, minerals and other food supplements to the media and to health professionals working in the field of diet and nutrition. Find out more at www.hsis.org.

References:

[1] Scientific Advisory Committee on Nutrition (2016) Vitamin D and Health. pp xi.

[2] https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/551352/NDNS_Y5_6_UK_Main_Text.pdf pp11.

[3] The Reference Nutrient Intake (RNI) is an amount regarded as enough or more than enough for the majority of people

[4] https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/551352/NDNS_Y5_6_UK_Main_Text.pdf pp17.

[5] Scientific Advisory Committee on Nutrition (2016) Vitamin D and Health. pp xi.

[6] Scientific Advisory Committee on Nutrition (2016) Vitamin D and Health. pp xi.

[7] Scientific Advisory Committee on Nutrition (2016) Vitamin D and Health. pp xv.

[8] https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/390394/A5_Vitamin_leaflet_public_FINAL_22_12_14.pdf pp3.

[9] https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/390394/A5_Vitamin_leaflet_public_FINAL_22_12_14.pdf pp4.

[10] https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/537616/SACN_Vitamin_D_and_Health_report.pdf pp.140

[11] https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/390394/A5_Vitamin_leaflet_public_FINAL_22_12_14.pdf pp4.

[12] Scientific Advisory Committee on Nutrition (2016) Vitamin D and Health.pp16-17.

[13] Scientific Advisory Committee on Nutrition (2016) Vitamin D and Health.pp1.

[14] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5310969/

[15] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4514847/

[16] https://www.ncbi.nlm.nih.gov/pubmed/26322509

[17] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4008710/

[18] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4971719/

[19] https://wellcome.ac.uk/press-release/one-six-pregnancies-among-women-britain-are-unplanned

[20] https://www.ncbi.nlm.nih.gov/pubmed/28176022

µg	Microgram a measurement of weight equal to one millionth of a gram (or one thousandth of a milligram). Microgram (µg or mcg) is used for a number of nutrients found in food supplements.
Amino Acid	The building blocks of protein, there are eight essential amino acids which cannot be synthesised within the body and therefore must come from the diet. These are: isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine. In addition arginine and histidine are amino acids required by infants and young children which supports their rapid growth.
Antioxidant	A substance or nutrient which helps to protect our cells from damage caused by free radicals, damaging molecules which are found in pollution and tobacco smoke. Our bodies also produce free radicals as part of the normal biochemistry of living.
Deficiency	A lack of essential macronutrients or micronutrients which results in malnutrition and or disease. This may be the result of inadequate intakes or absorption issues associated with gastrointestinal disease. There are a number of recognised deficiency diseases including (but not exclusively): scurvy (vitamin C deficiency); rickets (vitamin D deficiency); anaemia (iron deficiency, but also deficiencies in B12 and folic acid) and Kwashiorkor (protein deficiency).
DH	The Department of Health is a UK Government department. It has responsibility for nutrition legislation and sets health policy for nutrition.
DHA	Docosahexaenoic acid; one of the key omega-3 fats that provides health benefits
Dietitian	An individual qualified in nutrition and dietetics who can assess, diagnose and treat health issues associated with nutrition and diet. Dietitians are governed by law with a statutory code of practice; they often work within the health service although increasing numbers are also working in a freelance capacity.
EFA	Essential fatty acids (omega 3 and omega 6) cannot be synthesised by the body and must be derived from the diet. EFAs do not provide fuel for energy production and are required for vital biological processes which support growth, development and health.
EFSA	European Food Safety Authority; the European Union food risk management agency which scientifically evaluates safety across all areas of food.
EPA	Eicosapentaenoic acid; one of the key omega-3 fats that provides health benefits.
Fat soluble vitamin	The fat soluble vitamins are vitamins A, D, E and K. Because they are fat soluble these substances can accumulate in the body, often being stored in fat cells, or in the liver. This can create health issues, particularly if intakes have been high for a prolonged period of time. For example, long term high intakes of vitamin D may lead to the laying down of calcium in tissues such as liver and kidneys which can cause nausea and vomiting.
Food supplement	A food supplement is a concentrated source of vitamins, minerals or other substances with a nutritional or physiological effect which is sold in small, measured unit doses.
FSA	The Food Standards Agency is a non-ministerial UK Government department responsible for food safety and food hygiene.
GLA	Gamma-linoleic acid is an omega-6 fatty acid (an essential fatty acid considered to be necessary for human health which must be derived from the diet). GLA is most commonly found in evening primrose oil (EPO), borage or starflower oil and blackcurrant seed oil.
Health claim	A health claim is any claim which states, or implies, that consumption of a specific food will have a beneficial effect on health. Claims may be written, verbal or pictorial.
Herbal medicine (herbal remedy)	A product is considered to be a herbal medicine if the main active ingredient/s are only herbal substances or preparations. Not all herbal products are medicines, some may be food supplements and some may be cosmetics. What determines if a product is, or is not a medicine is complex but generally rests with how the product is presented (i.e. does it make medicinal claims to treat, prevent or cure any disease) and what it does (i.e. does it have a physiological impact on, or alter, any body functions).
Macronutrient	Dietary constituents which are needed in significant amounts, generally protein, fat, carbohydrate, fibre and water.
Malnutrition	Malnutrition is a state in which the deficiency of nutrients such as energy, protein, vitamins or minerals results in measurable adverse effects on the body. Malnutrition may refer to insufficient intake of protein, carbohydrate and fats (macronutrients) which can result in overly low BMI. It may also be insufficient intake of vitamins, minerals and other micronutrients, which can impact on overall health and could include obese individuals with poor diets.
Mg	Milligram is a measurement of weight equal to one thousandth of a gram. Mg is used for a number of nutrients found in food supplements.
Micronutrient	A substance derived from food which is needed in extremely small amounts for the normal growth and development of living beings. Micronutrients are vitamins, minerals and essential fatty acids (omega-3 fats)
Mineral	Inorganic micronutrient essential to health and wellbeing. Minerals are absorbed from soil by plants which are in turn eaten by animals or humans. Minerals may be split into minerals which are needed in relatively high amounts (calcium, phosphorus, magnesium, sodium, chloride and potassium) and trace elements (iron, zinc, cobalt, copper, chromium, fluoride, iodine, manganese, molybdenum, boron and selenium) which are needed in very small quantities.
Multivitamin	A product which contains more than one vitamin, often multivitamins will contain all 13 vitamins although some may contain only the eight B vitamins, or a combination of some of the vitamins and some additional minerals.
NDNS	The UK National Diet and Nutrition Survey is a continuous rolling survey of the dietary habits and nutritional status of adults and children in the UK. The results are used to assess whether intakes of food and nutrients are adequate across different ages and population groups.
NRV	Nutrient Reference Value is the amount set by the European Food Safety Authority (EFSA), primarily to support food labelling, which the majority of the population requires to maintain health. Previously known as RDA
Nutrient	A substance derived from food which provides nourishment to the body and is essential for the maintenance of life and for growth and development.
Nutritionist	Nutritionists generally work for public bodies or governments, although some do work with private clients. They tend to look at large populations to determine risk factors and make dietary recommendations that are applied at population levels. For example, evidence on the incidence of type II Diabetes led public health nutritionists to determine that some populations are more at risk of developing this disease, and to make recommendations for dietary changes to either reduce the risk or manage the disease. However, public health nutritionists do not practice with individual patients.
Omega-3 fats	Essential fatty acids which cannot be synthesised by the body and must be derived from the diet. Primary sources for omega-3 fats are oily fish and fish oil supplements with some also coming from enriched eggs and fortified foods. There are a number of scientifically proven health benefits for omega-3 fats including supporting the health of the eyes, brain and heart, maintaining an appropriate balance of triglycerides in the blood and reducing blood pressure.
Omega-6 fats	Essential fatty acids which cannot be synthesised by the body and must be derived from the diet. Primary sources for omega-6 are vegetable oils such as sunflower and corn oils as well as nuts and seeds. There are a number of health benefits associated with omega-6 fatty acids; they are thought to be beneficial in the management of premenstrual syndrome and in some skin conditions including eczema and psoriasis.
PAGB	Proprietary Association of Great Britain (PAGB) is the UK trade association which represents the manufacturers of branded over-the-counter medicines, self care medical devices and food supplements.
Prebiotics	Foods which promote the growth of probiotics, the beneficial bacteria that inhabit our gut. Prebiotics are generally fibres such as inulin, which our bodies cannot digest and absorb but which provide a food source for probiotics.
Probiotics	Live bacteria (and some yeasts) which inhabit the digestive tract which are viewed as being beneficial to human health. There are thousands of different bacterial strains; some are resident in specific areas of the digestive tract whilst others are transient, simply passing through.
Public Health England (PHE)	Public Health England is an agency of the Department of Health responsible for improving public health. They work with local government, the NHS and non-governmental organisations as well as communicating public health messages to the general public.
PUFA	Polyunsaturated fatty acids (PUFA) are found in nuts, seeds, fish (and fish oil), krill and some algae, small amounts are also found in leafy greens. The omega-3 and omega 6 fats are PUFAs, which are generally associated with health.
RDA	Recommended Daily Amount; previously used terminology for the amount set, primarily to support food labelling, which the majority of the population require to maintain health. Now described using nutrient reference value (NRV)
SUL	Safe Upper Levels of vitamins and minerals were established by the Expert Group on Vitamins and Minerals who published a report in 2003 (https://cot.food.gov.uk/sites/default/files/cot/vitmin2003.pdf). The UK food supplements industry works to the levels set in this report.
Vitamin	Organic micronutrient essential to health and wellbeing. Vitamins cannot be synthesised in sufficient amounts by the animal or human body and must therefore be obtained from the diet. Plants manufacture vitamins which move up the food chain as the plants are consumed by animals or humans. Vitamins can be divided into fat soluble (vitamins A, D, E and K) and water soluble (vitamins B1, B2, B3, B5, B6, B12, biotin, folic acid and vitamin C).
Water soluble vitamin	The B vitamins and vitamin C are water soluble. They are not stored in any significant quantities within the body and are generally either utilised or excreted in the urine. As they are not stored in the body, they tend to have low toxicity and are needed on a daily basis.