Chocolate consumption and cardiometabolic disorders: systematic review and meta-analysis

To the Editor. Comment on “Chocolate consumption and cardio-metabolic disorders: systematic review and meta-analysis1”: a role for unrecognised vitamin D content?
Marion Rowe1, Senior Laboratory Scientific Officer, Peter M Timms1, Consultant Biochemist, Barbara J Bouche2r, Professor of diabetes
1 Department of Clinical Biochemistry, Homerton University Hospital Foundation Trust, Homerton Row, London E9 6SR, UK .2 Centre for Diabetes, Bart’s & The London School of Medicine & Dentistry ,Blizard Institute, Queen Mary University of London, Newark Street, London E12AT, UK

Enjoyment of chocolate may become a less guilty pleasure in the light of this meta-analysis reporting reductions by at least a third in the risks of ‘any cardiovascular disease’ and of stroke in prospective studies of chocolate consumption over 8-16 years, especially with consumption of dark chocolate1. This risk reduction was not abolished by adjustment for recognised risk factors for cardiovascular disease including unspecified ‘dietary factors’. Chocolate is thought to have anti-inflammatory and anti-atherogenic effects that have been suggested to be due to contained polyphenols and flavinoids2. We wonder, however, whether fat-soluble vitamin D might be present in chocolate and contributing to these beneficial effects, since it has both anti-inflammatory and anti-atherogenic effects and, furthermore, better baseline repletion is associated prospectively with reductions in cardiometabolic risk factors. 3-5. In the 1930s, vitamin D2 was reported to be present in cacao beans on bio-assay but only after they had been undergone fermentation and been dried in the sun, the vitamin D being thought to be synthesised by invading moulds,6,7 since vitamin D is well known to be formed in yeasts and fungi under the influence of UVB from sunshine. However, cacao shells [nibs] and cacao butter are also reported to contain sterols [at 6-8% and 0.3-0.4% respectively] that develop anti-rachitic activity when irradiated with UVB, and the total vitamin D content of prepared cacao beans has been reported to be comparable to that found in natural cod-liver oil. Cacao beans are used in chocolate manufacture and nibs are also used in making some dark chocolate. Furthermore, winter feeding of cows with dried cacao bean shells in the winter increased the anti-rachitic effects of their butter to match that seen in the summer7. We have, therefore, analysed an especially high coca dark chocolate currently on sale in the UK using modern methodology [Liquid chromatography coupled with triple quad mass spectrometry]. Vitamin D2 was present at 1.042 microgram per gram, providing at least 1000 IU per ounce [25 G]; thus, anyone eating dark chocolate at 1-2 oz/day is getting at 1000-2000 IU of vitamin D2/day which is rather more than the recommended daily amount of vitamin D [600 IU/day] recently advised for adults by the Institute of Medicine in the US8. Buitrago-Lopez et al. report adjustment for ‘dietary factors’ [including caffeine] does not reduce the effects of chocolate consumption.1 However, can the authors say whether the beneficial effects of high chocolate intake that they report persist after adjustment for the vitamin D content of the chocolate eaten, since vitamin D could be contributing to the dose-dependent reductions in cardiovascular disease [CVD] risk reported with higher chocolate consumption. If adjustment for vitamin D content does reduce or abolish the association it would support the suggestion that improving vitamin D repletion could contribute to reduction in CVD risks9, supporting the rationale for carrying out adequate trials of vitamin D supplementation for CVD prevention.

References
1. Buitrago-Lopez A, Sanderson J, Johnson L, Warnakula S, Wood A, Di Angelantonia E, Franco OH. Chocolate consumption and cardiometabolic disorders: systematic review and meta-analysis. BMJ (2011) 343:d4488. doi: 10.1136/bmj.d4488.
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6. Knapp AW, Coward KH. Vitamin D activity of cacao shell: i. the effect of the fermenting and drying of cacao on the vitamin D potency of cacao shell. (1935). ii. The origin of vitamin D in cacao shell. Biochem J. (1935) 29:2728-35
7. Kon SK, Henry KM. The effect of feeding cacao shells to cows on the vitamin D content of butter (milk). Biochem J (19935) 29:2051-6
8. Ross AC, Manson JE, Abrams SA, Aloia JF, Brannon PM, Clinton SK et al. The 2011 report on dietary reference intakes for calcium and vitamin D from the Institute of Medicine: what clinicians need to know. J Clin Endocrinol Metab. (2011) 96:53-8
9. Judd SE, Tangpricha V. Vitamin D therapy and cardiovascular health. Curr Ther Hyperten. (2011) 13:187-91