The number of people following a plant-based (PB) diet has increased in recent years. This has led to concerns regarding vitamin D intake, as natural dietary sources of vitamin D are primarily animal based1 and cross-sectional studies have reported lower intakes amongst vegetarians and vegans2. Some PB foods, primarily dairy alternatives, are now fortified with vitamin D. Whilst vitamin D is synthesised in the skin following exposure to UV light, this does not happen in the autumn and winter months in areas of northern latitude (such as the UK). Hence, dietary supply of vitamin D becomes particularly important. This study aimed to investigate whether it is possible to maintain dietary vitamin D intake when transitioning to a PB diet, through careful choice of PB alternatives.

A subset of 4-day diet diaries, from 81 women (72 Caucasian and 9 South Asian, mean age 52±12 y) living in South East England, was randomly selected from those collected for the D-FINES study (Vitamin D, Food Intake, Nutrition and Exposure to Sunlight in Southern England, 2006–2007; FSA funded Project N05064, NHS REC 06/Q1909/1)3 and analysed for vitamin D intake. No subjects followed an entirely PB diet at baseline. Data modelling was carried out to substitute animal-based foods with equivalent amounts of PB alternatives. For dairy products, the equivalent fortified PB alternatives were chosen. Meat, fish and eggs were replaced with equivalent amounts of protein from PB sources, such as lentils and tofu, as no fortified direct alternatives were found. The diaries were then re-analysed. Pre- and post-substitution intakes were compared by paired t test, and ethnic groups by independent t test.

There were no differences in Vitamin D intake between ethnicities either at baseline (p=0.087) or post-substitution (p=0.361). Vitamin D intake increased in the South Asian group post-substitution (from 2.4±1.3 to 4.3±1.8 µg/day, p=0.002), with no change observed in the Caucasian group (3.6±2.0 to 3.7±1.8 µg/day, p=0.660). There was no difference between vitamin D intake pre- and post-substitution overall (3.5±2.0 and 3.8±1.8 µg/day respectively, p=0.222). Twenty cases decreased by ≥1 µg/day, all in the Caucasian group, with the largest decrease being from 9.6 to 2.2 µg/day.

This study demonstrates that it is possible to move to a PB diet, whilst maintaining existing dietary patterns, without a reduction in vitamin D intake, but it is largely dependent on dairy intake in the original diet, as no meat/fish substitutes in the UK are currently fortified. It also requires care when choosing PB dairy substitutions as many, including organic options, are not fortified. Mean daily intakes, both pre- and post-substitution, were substantially below the recommended intake of 10 µg/day4, suggesting that supplementation may be necessary, particularly during winter months.

This work is funded by the UK Biotechnology and Biological Sciences Research Council (BBSRC); with funding by the BBSRC Institute Strategic Programme Food Microbiome and Health BB/X011054/1 and its partner project BB/X020029/1.
Benedik, E.  (2022) Int J Vitam Nutr Res 92, 118–125
Crowe, F.  L. et al. (2011) Public Health Nutr 14, 340–346
Darling, A. L. et al. (2013)  Osteoporosis International 24, 477–488
SACN vitamin D and health report - GOV.UK. (2016) [Available  at: https://www.gov.uk/government/publications/sacn-vitamin-d-and-health-report]

The number of people following a plant-based (PB) diet has increased in recent years. This has led to concerns regarding vitamin D intake, as natural dietary sources of vitamin D are primarily animal based^1^ and cross-sectional studies have reported lower intakes amongst vegetarians and vegans^2^. Some PB foods, primarily dairy alternatives, are now fortified with vitamin D. Whilst vitamin D is synthesised in the skin following exposure to UV light, this does not happen in the autumn and winter months in areas of northern latitude (such as the UK). Hence, dietary supply of vitamin D becomes particularly important. This study aimed to investigate whether it is possible to maintain dietary vitamin D intake when transitioning to a PB diet, through careful choice of PB alternatives.

A subset of 4-day diet diaries, from 81 women (72 Caucasian and 9 South Asian, mean age 52±12 y) living in South East England, was randomly selected from those collected for the D-FINES study (Vitamin **D**, **F**ood **I**ntake, **N**utrition and **E**xposure to **S**unlight in Southern England, 2006–2007; FSA funded Project N05064, NHS REC 06/Q1909/1)^3^ and analysed for vitamin D intake. No subjects followed an entirely PB diet at baseline. Data modelling was carried out to substitute animal-based foods with equivalent amounts of PB alternatives. For dairy products, the equivalent fortified PB alternatives were chosen. Meat, fish and eggs were replaced with equivalent amounts of protein from PB sources, such as lentils and tofu, as no fortified direct alternatives were found. The diaries were then re-analysed. Pre- and post-substitution intakes were compared by paired _t_ test, and ethnic groups by independent _t_ test.

There were no differences in Vitamin D intake between ethnicities either at baseline (p=0.087) or post-substitution (p=0.361). Vitamin D intake increased in the South Asian group post-substitution (from 2.4±1.3 to 4.3±1.8 µg/day, p=0.002), with no change observed in the Caucasian group (3.6±2.0 to 3.7±1.8 µg/day, p=0.660). There was no difference between vitamin D intake pre- and post-substitution overall (3.5±2.0 and 3.8±1.8 µg/day respectively, p=0.222). Twenty cases decreased by ≥1 µg/day, all in the Caucasian group, with the largest decrease being from 9.6 to 2.2 µg/day.

This study demonstrates that it is possible to move to a PB diet, whilst maintaining existing dietary patterns, without a reduction in vitamin D intake, but it is largely dependent on dairy intake in the original diet, as no meat/fish substitutes in the UK are currently fortified. It also requires care when choosing PB dairy substitutions as many, including organic options, are not fortified. Mean daily intakes, both pre- and post-substitution, were substantially below the recommended intake of 10 µg/day^4^, suggesting that supplementation may be necessary, particularly during winter months.

_This work is funded by the UK Biotechnology and Biological Sciences Research Council (BBSRC); with funding by the BBSRC Institute Strategic Programme Food Microbiome and Health BB/X011054/1 and its partner project BB/X020029/1._
1. Benedik, E.  (2022) _Int J Vitam Nutr Res_ 92, 118–125
2. Crowe, F.  L. _et al._ (2011) _Public Health Nutr_ 14, 340–346
3. Darling, A. L. _et al._ (2013)  _Osteoporosis International_ 24, 477–488
4. SACN vitamin D and health report - GOV.UK. (2016) [Available  at: https://www.gov.uk/government/publications/sacn-vitamin-d-and-health-report]

OC106 - The effect on habitual dietary vitamin D intake of changing to a plant-based diet.

Unique to the new Congress (previously the Summer Conference) is that you will have greater opportunity to engage with more nutrition science than ever before. In 2024 the core programme will be delivered by the Irish Section of The Nutrition Society, supported by the Science Committee. The theme of these symposia will be ‘new data – focused approaches and challenges’. Outside of the core programme you will have the chance to hear the latest research from the Society’s partner organisations, universities, the private sector and more, on a diverse range of research.