Vitamin D – How Much is Enough?

What Vitamin D Does

Vitamin D is an essential nutrient with a hormone like action helping to maintain the body’s levels of calcium within a normal and healthy range, working together with parathyroid hormone and calcitonin. Via various feedback mechanisms it aides the regulation of calcium through adjusting the absorption within the gut and controlling reabsorption in the kidneys accordingly - but in times of need it can also promote mobilisation of calcium from the skeleton (which acts like a vast storage facility).

It has long been known that deficiency can lead to rickets in infants and children (which has been seen to be on the rise) and osteomalacia in adults. It is also associated with osteoporosis and increased risk of hip fractures – and with a more sedentary population coupled with a decline in dairy intake and thus calcium in the diet this is an issue that can’t be ignored.

More recent research has also looked at vitamin D's role in a variety of other diseases other than bone health though. Mostly through epidemiological evidence many of these studies have highlighted an association of low vitamin D status with cardiovascular diseases, diabetes, some cancers, cognitive decline, depression, autoimmune diseases, pregnancy complications but even before this with foetal programming which in turn may influence all the above. This is not to scare monger (which some of the tabloids do quite well) but more to highlight Vitamin D far exceeds its previous remit of just bone health.

Where does it come from?

Vitamin D is primarily produced naturally when our skin is exposed to ultraviolet B (UVB) radiation from the Sun and this is still believed to be the most efficient way opposed to diet and supplementation. UVB converts 7-dehydrocholesterol precursors into previtamin D3, which spontaneously changes to vitamin D3. (We’re not quite there yet) vitamin D3 then is converted via two hydroxylation reactions into 25-hydroxyvitamin D3(25(OH)D) and its final active form, 1,25-dihydroxyvitamin D3 (1,25(OH)D).  Whereby it is this level of 25(OH)D in the blood which is the most reliable indicator of vitamin D status.

Summary Diagram of Synthesis and Source of Vitamin D

Skin pigmentation, geographical location, time spent outside, sunscreen use, age etc. are all factors in how much vitamin D is produced by the skin (and therefore how much vitamin D is present and active in the body) before we take any supplements. Dietary intake also varies greatly whereby supplementation to many products comes in the less active form (D2). Individual requirements also range greatly whereby being widely debated amongst clinician’s and scientists as more and more data acknowledges the potential detrimental effects of low status with limited to no data highlighting adverse impacts at high levels. This so far has provided little clarity to the public other than hearing ‘something needs to be done’ and ‘recommendations and current guidelines need increasing’ however, on a practical basis what does this really mean?

Who is at Risk?

Well firstly let’s establish who is at risk - an unpublished review undertaken by Kings College, London in the 1990s (at the request of DH) confirmed that the problem of vitamin D deficiency and rickets, when occurring, still remained predominantly a problem in Asian populations. Where rickets was identified it was associated with strict vegetarian diets and breastfeeding exclusively without vitamin D supplementation for periods longer than 6-months. Inadequate maternal status during pregnancy is likely to have been the important antecedent factor in such circumstances whilst also considering lack of skin exposure due to cultural dress and darker skin types requiring more UVB radiation to produce the relevant vitamin D precursors needed.

More recently Pearce and Chatham (2010) published in the BMJ an article which highlighted this as an escalating problem. This highlighted the problem of vitamin D insufficiency across the whole UK population. The article cites a survey in which more than 50% of the adult population had insufficiency and 16% had severe insufficiency, and goes on to discuss a large body of observational evidence associating such insufficiency with an increased risk of mortality.

So in summary we see in our text books the answer being – ethnic groups with darker pigmentation, cultural wear as another key factor and institutionalised individuals. However, I think the evidence now firmly suggests we’re ALL potentially at risk, all those in offices stuck inside from 9-5 or beyond, people running around hospital wards working day/nights or on calls and this just highlights a few. So after this tabloid scaremongering where does this leave us?

Vitamin D – Where do we Stand?

This is directly taken from an expert review published via NICE 2010

“There is consensus that levels below 25nmol/L (10ng/ml) qualify as ‘deficient’ but beyond this there is currently no standard definition of ‘optimal’ 25(OH)D levels.  Some sources suggest that levels above 50nmol/L (30ng/ml) are ‘sufficient’, while 70–80nmol/L (28 32ng/ml) is ‘optimal’.”

Vitamin D Dietary Recommendations

In the UK and USA

(SACN 2007, IOM 2010) respectively

Adult population	-*	600 IU/day (15µg)
Elderly and risk of osteoporosis	400 IU/day (10µg)	800 IU/day (20µg)
Pregnancy, breastfeeding**	400 IU/day (10µg)	600 IU/day (15µg)

*assumes adequate sunlight exposure

**reiterates consideration of supplementation to meet individual and foetal demands

Highlighting the difference between current guidance from the UK and USA is really the tip of the ice berg in terms of the Vitamin D debate and as to how potentially these should be changed in the future. For those who want to delve a bit deeper should definitely check out further information which can be found at www.vitamindcouncil.org which is a non profit organization with vast information regarding Vitamin D and health who would argue these ‘conservative’ guidelines. However, SACN, 2007 and IOM, 2010 guidance are great resources too for references and other information.  

Dietary Sources to Boost Levels

Placing this debate aside, whilst not only sat in an artificially lit room but with the added joys of a British Summer (yes...its cloudy and raining outside, so I shall be sat here for the remainder of the day) leaves me to conclude with what can be done from a dietary point of view.

Good sources to integrate into your diet include:

• Oily fish e.g. salmon, mackerel, sardines, tuna which can provide 200-400 IU = 5-10µg per portion
• Fortified foods, e.g. margarines/spreads/dairy products which can provide 60 IU = 1.5µg per tbsp
• Fortified breakfast cereals contain up 80 IU = 2µg per serve (check labelling, but for example Kelloggs will be fortifying all products by July 2012)
• Egg yolks - serving of 2 would provide 80 IU = 2µg

Key Points to Remember

Spending 15-20 minutes outside in sunshine 2-3 times each week without suncream (if appropriate). Encourage children to play outside and increase your outdoor activities by walking or gardening BUT remember in the UK we can only synthesise Vitamin D in the Spring/Summer months to think about your diet!

Try including a #FishyFriday in your household and enjoy oily types of fish regularly (at least 1-2/week) e.g. salmon, trout, mackerel, herrings, sardines and tuna.

Choose a breakfast cereal with added vitamin D (not all cereals are fortified so check the label)

If pregnant or breastfeeding consider daily supplementation and for children under age of 5 (utilising healthy start FREE vitamins scheme www.healthystart.nhs.uk)

Good resources to check out which provide guidance and factsheets:

Scientific Advisory Committee on Nutrition (SACN)

Institute of Medicine (IOM)

Vitamin D Council

BDA

Healthystart.NHS

BBQ Season Awaits: Some Food for Thought

Marinades

Think of some fun and flavoursome marinades and invest some time into this....overnight always works best if you can (although if needed – some little tips can cut the need for this amount of time)

Marinades not only add flavour, but can help to keep meats moist, tender and help to create an extra texture with the added bonus of being healthier (dependant on what you use of course). There are some mainstay ingredients in marinades (acid + base) to often provide some acidity thus aiding tenderness and to max out on flavour – these may include: lemon, limes, dried spices, chillies, mustard, garlic, onions, differing vinegars and alcohol in the form of wine/beer/whiskey AND a base in the form of oil like rapeseed/sunflower or yoghurt– take your pick!

However, note – adding too much acidic mix will actually toughen meats opposed adding to the tenderness

So back to the fun - this is your chance to be adventurous and see what combination works for you and your family/friends. I always start with a base as if making a salad dressing then add the right acid mix dependant on the meat in question. My preferred base would include rapeseed/sunflower oil as they tolerate the heat better than olive oil and let your flavour combination truly come through!

Here are just some ideas to start but there are MANY MANY more out there:

Lamb: garlic, oregano, thyme, mint, red wine vinegar (marinade overnight preferably or 2hrs min)

Chicken: citrus juice (lemon/lime/orange), cayenne pepper, chillies, honey, mustard, various spices – cumin/turmeric/garam masala (marinade between 1-4hrs)

Beef: red wine, crushed peppercorns, horseradish, olive oil, Worcestershire sauce, soy sauce, stout, ale, beer (marinade overnight preferably or 2hrs min)

Salmon/Prawns: garlic, onion, chillies, paprika, soy sauce, ginger, brown sugar (marinade for a max of 30min to 1 hr)

Tips:

• Score the meat to maximise the surface area that is in contact with the marinade and to help penetrate the flavours
• Invest in sandwich bags or some good tupperware to let the marinade do its stuff – this makes it easier to tuck in the fridge and to transport to the BBQ when needed.
• Befriend your local butcher – not only for the good of local business...but for more selfish reasons – getting the best deals on meat, utilising their skills of deboning cuts of meat and maybe utilising their vacuum packing machine with the addition of your own marinade (no harm in asking)

Don’t Forget Your Veggies

Don’t forget to not only compliment your BBQ with some side salads/veggies – but why not make one of the star dishes a veggie option too?! One of my all time favourites that serves many purposes is stuffed peppers with couscous – you can max out on herbs/spices and then get the warm sweet taste of the BBQ’d pepper! Not only this but corn, aubergine, Portobello mushrooms, and veggie skewers with a honey and mustard dressing work a treat. Some vegetables work well as a last minute addition to the BBQ whereby finishing them off here can provide a great ‘charred’ taste such as asparagus and courgettes.

Tips:

• Using tin foil on the BBQ for veggies if a great way to cook them without over doing the ‘charred’ effect (and also saves washing up)
• Spray the veggies with an oil spray e.g. a couple of squirts of 1kcal spray to ensure healthy moist veggies with even cooking  

Be Safe

BBQ’s are a great chance for some informal dining – but remember all good health and hygiene principles still apply. This is a prime opportunity for the day itself to be ruined....or more likely the days after – yep I’m talking bacteria and undercooking food.  Remember and stick to the following:

Always wash your hands before you start and in between both vegetables and meat prep

Raw and cooked foods should always be handled on separate chopping board

Ensure meat has thawed properly before placing on the BBQ

Use a skewer to check for clear running juices before taking meat off the BBQ

2012 sees many excuses to make the most of the BBQ with Wimbledon, Euro 2012 and the Olympics coming up. So above all enjoy your BBQ experience and see this as a time to experiment with different foods and flavours which can be enhanced by this underused cooking technique.  

Good web sources:

BBC Good Food -  www.bbcgoodfood.com/

Good Food Channel - www.uktv.co.uk/goodfood  

Food Network - www.foodnetwork.co.uk

AllRecipes - www.allrecipes.com