You are hereHome » Blogs » Dr. Ben Kim's blog How To Make Sure That You Are Getting Enough Vitamin D To receive newly published articles and recipes like this one, stay in touch with us via Straight Leg Raises for Core and Hip Flexor Strength Posterior and Anterior Pelvic Tilt for Improved Core Strength Mobility Routine to Treat Wrist Pain and Stiffness More Natural Health ResourcesIf you’re health conscious, chances are you know a thing or two about vitamin D. You may know, for example, that it’s impossible to enjoy optimal health if you’re low in this nutrient. But getting enough is harder to do than you might think, which is why leading vitamin D expert Dr Michael F. Holick estimates that vitamin D deficiency is “the most common medical condition in the world.” Among other things, vitamin D is needed for mental and emotional health, and for a peak-functioning immune system. There is also a growing body of research demonstrating a link between sub-optimal levels of vitamin D and cancer.
You’ll already know that the best way to get vitamin D is via sunlight. But what you probably know less about is how easy or otherwise that is to do where you live. This article is a mini guide to working that out. I’ve met many health enthusiasts in the UK and similar climates who believe that if they go out jogging in shorts and a T-shirt on a bright winter’s day, that sun exposure will be topping up their vitamin D levels. In the UK we don’t get enough of the kind of sunlight that causes our bodies to manufacture vitamin D under the skin. Only one kind of solar radiation does this: UVB sunlight. Vitamin D is synthesised only when we’re exposed to UVB rays – and unless UVB rays are present it doesn’t matter how warm it is nor how brightly the sun is shining: your skin cannot synthesise vitamin D. “Vitamin D winter” is when no vitamin D production is possible due to the atmosphere blocking all UVB. And what few realise is that in the UK, that winter lasts for at least six months of the year, from October to March inclusive.
In much of the US it lasts for four months, from November to February inclusive (though, as I’ll explain shortly, some experts consider these to be underestimates). Latitude is a measure of distance from the equator, either north or south. Humans evolved in the low latitudes of the tropics, an area of year-round UVB sunlight – that is our ideal environment. Here are a few quick examples to help you understand the connection between latitude and UVB sunlight (the figure after each location is the latitude, either north or south of the equator): New York City – 41 Anywhere north (or south) of 50 degrees. The latitude of the UK? It ranges from 50 to 58, with London at 51 and Aberdeen at 57. So getting enough vitamin D from sunlight is easily done if you live in Miami; impossible if you live in Manchester – unless you make a point of spending time at lower latitudes during the October to March period. If your location isn’t listed above and you want to know its latitude, that couldn’t be simpler: just type into Google the name of the town or city where you live (or the nearest to you) followed by the word latitude.
And depending on whether it’s below 30, 30-40, 40-50, or above 50, you’ll know where you are on the scale above. It is the opinion of Harvard Medical School that, “Except during the summer months, the skin makes little if any vitamin D from the sun at latitudes above 37 degrees north or below 37 degrees south of the equator. People who live in these areas are at relatively greater risk for vitamin D deficiency.”Remember, in the UK we’re at 50 to 58! Sultry Ibiza is at 38, sun-soaked Naples in southern Italy is at 40, and Cannes on France’s balmy Riviera is at 43. Yet Harvard Medical School is not the only credible authority saying that even these Mediterranean locations – much nearer the equator than we are – don’t have the right kind of sunlight year round. In fact, some would tell you that the figures I gave you above understate the lengths of the “vitamin D winters” in the various locations. For example, according to Krispin Sullivan, a certified nutritionist and vitamin D researcher: “In much of the US […]
six months or more during each year have insufficient UVB sunlight to produce optimal D levels. In far northern or southern locations, latitudes 45 degrees and higher, even summer sun is too weak to provide optimum levels of vitamin D.” Sullivan is among the vitamin D experts who say that 30 is the magic number when it comes to latitude and vitamin D production: if we are further from the equator than this, we won’t be meeting our D needs year round from sunlight alone. Vitamin D can be stored in fatty tissue during times of plenty, but when stores are not being regularly replenished, they quickly decline. In one study, submariners with zero UV exposure had vitamin D levels that declined by half in a period of two months. Also, the body is quite limited in how much D it can produce each day and once this threshold is reached, more exposure won’t lead to more D production. So those of us in the UK can worship the sun at every opportunity, and soak it up on a summer holiday in Benidorm, Barbados or Bali, but our stores will have fallen below optimal long before our six-month vitamin D winter is out.
Therefore, we need to have a plan in place for replenishing our vitamin D stores during those months. And if we’re not able to jet off somewhere sunny, the two choices are dietary sources of D (including oily fish such as salmon and sardines) and supplementation. There is no simple answer to this. It depends on how close to the equator you are, and on your skin colour, among other things. If it’s summer where you are (or you’re in the tropics) and you have very fair skin, as little as 10 minutes a day could do it, assuming you are exposing most of your skin to the midday sun (i.e. wearing a bathing suit but no sunblock). You’ll need substantially longer if you’re only exposing hands, arms and face. And the darker your skin, the more sun exposure you’ll need before you’ll synthesise enough vitamin D. Here’s the take-home advice about vitamin D and sun exposure:did you knowIt’s quite common for people to have vitamin D deficiency in winter. In fact, many people lose bone density at this time of year.
Why children and adults need vitamin DChildren need vitamin D for bone growth and development. So do babies developing in the womb. This is because vitamin D helps us absorb calcium.Serious vitamin D deficiency can cause rickets, delayed motor development, muscle weakness, aches and pains, and fractures.Vitamin D deficiency in adults has also been linked to osteoporosis, some cancers, heart disease and diabetes.If women don’t get enough vitamin D during pregnancy, their children might develop neonatal hypocalcaemia (not enough calcium in the blood) or rickets later in childhood.Vitamin D and sunlightYou need sunlight on your skin for your body to make vitamin D. You get about 80% of your vitamin D this way.The amount of sun you need depends on where you live in Australia and the time of year.But no matter where you live, you have to be careful about how much sun you get on your skin. Too much sun can lead to sunburn, skin damage and even skin cancer.The picture below shows how much sun should be enough to help your body make vitamin D, without putting your skin at risk of sun damage.
Image courtesy of Cancer Council Australia. Other factors affecting how much sun you need People with naturally very dark skin need 3-6 times more sun to make vitamin D than the amount fair-skinned people need.It’s important to note that there is no conclusive Australian or New Zealand data on how much sun children need for good levels of vitamin D.To get more information and advice about how much sun is right for you, speak with your GP. Spending too long in the sun isn’t good for your skin, so it’s important to use sun protection.During summer, especially between 10 am and 4 pm, make sure your child stays safe in the sun with sunscreen, a hat, sunglasses, clothing that keeps the sun off and access to plenty of shade.Vitamin D and foodMost children won’t get enough vitamin D from food alone.But food with lots of vitamin D can add to the vitamin D your child gets from sunshine. Foods naturally containing vitamin D include fresh fatty fish (salmon, herring, mackerel and sardines), liver, mushrooms and egg yolks.
Some foods have vitamin D added to them. These include margarine and some low-fat milk and dairy products. All infant formula contains vitamin D.Vitamin D deficiencyChildren might be at risk of vitamin D deficiency if they: keep all their skin covered spend most of their time indoors and don’t get much or any sun have a condition affecting how the body controls vitamin D levels – for example, liver disease, kidney disease, problems with absorbing food (such as coeliac disease or cystic fibrosis and some medicines can affect vitamin D levels have been breastfed for a long time and have a mother whose vitamin D is low. Signs of vitamin D deficiency include rickets, delayed motor development, muscle weakness, aches and pains, and fractures.Treating vitamin D deficiencyTalk with your GP if you’re worried about your child’s vitamin D levels, or you’re pregnant and think you might have low vitamin D.Your GP can order a blood test, which is the best way to check vitamin D levels.
For mild deficiencies, your GP might say that your child needs to get a bit more sun.If you or your child has a severe vitamin D deficiency, your GP might say you or your child should take vitamin D supplements, as well as getting more sun.If you or your child can’t get more sun, the GP might say that taking vitamin D supplements is the best thing to do. You might take a vitamin D supplement in one large, single dose, or you might take a supplement for several weeks or months.You can also talk to a dietitian about vitamin D supplements.Solariums aren’t recommended as way to improve vitamin D levels or to treat vitamin D deficiency. Solariums can cause skin cancer.Vitamin D, pregnancy and breastfeedingA baby’s vitamin D stores go up during development in the womb and go down after birth until the baby starts getting vitamin D from sunlight along with diet.If a pregnant woman has low levels of vitamin D, she might not pass on enough vitamin D to her baby.Breastfeeding babies don’t get much vitamin D from breastmilk, because breastmilk doesn’t have much.
And if a breastfeeding mum has low vitamin D, it can be even harder for her baby to get enough vitamin D. It’s even trickier if the breastfeeding mum lives further south in Australia and it’s winter.If you have any concerns about whether your baby is getting enough vitamin D, you can talk with your GP about using a vitamin D supplement. Doctors often say a daily supplement of 400 micrograms (μg) is good for mothers who are breastfeeding babies at risk of vitamin D deficiency.It’s still OK for you to breastfeed your baby if you’re taking a vitamin D supplement.Infant formula has higher levels of vitamin D, so formula-fed babies don’t usually need a supplement.Most cases of rickets in Australia are in children who have dark skin. This is because women who have dark skin – particularly those who wear covered clothing – have been found to have a high risk of vitamin D deficiency and don’t pass on adequate amounts of vitamin D to their children. Feedback Tell us what you think