Nutritionist Henrietta Norton explains how you can boost your levels.
One in five of us in the UK is estimated to have insufficient blood levels of vitamin D for good health – we simply can’t produce enough from sunshine alone and this is especially true for those of us in Northern Europe. The half-life of vitamin D is three to six weeks so evengathered stores over the summer rapidly decline by the time we get to the deeper winter.
Additionally, sunscreens, longer office working hours, medications such as statins and our age can affect our levels further. Our dietary habits have changed somewhat too and eating vitamin D-rich foods such as oily fish and whole-fat dairy as part of our daily diets has fallen
out of favour.
For some time the Department of Health has recommended an increased vitamin D intake for ‘at risk’ groups such as the elderly, children under five and pregnant and breastfeeding women. More recently, however, the Scientific Advisory Committee of Nutrition (SACN) has recommended that the UK population has an intake of 10 pg per day. This is the amount needed for the majority of the population to maintain a concentration of 25 nmol/l of vitamin D in the blood when UVB sunshine exposure is minimal. For many, 25nmol/l may not even be enough to maintain optimum health, with some requiring up to 100nmol/l for optimum health.
Virtually every cell in the body has a vitamin D receptor which, when bound to vitamin D, can influence the expression of more than 200 genes. Previous concerns about vitamin D deficiency have been associated with poor bone health, most notably the development of rickets, a condition which is again on the increase according to national statistics. However the observations from the most recent large cohort studies have unravelled other key physiological roles of vitamin D and a causative relationship between vitamin D deficiency and an increased risk of cancers, pre-eclampsia, diabetes, heart disease, autoimmune diseases, autism and the flu.
As we’ve already established, sunshine is arguably not a reliable source of vitamin D since sufficient solar radiation depends on the season and there are also associated risks of skin ageing and cancer. Notably, all of Europe gets insufficient UVB intensity from November to the end of March, resulting in minimal skin production of vitamin D during the winter season, independent of age.
For this reason, many people look at boosting their levels of vitamin D either through supplements or their diet. When looking at supplements, choose wisely and opt for high
quality, easily absorbed forms of the vitamin. More natural food forms provide both the active and stored forms of vitamin D ready for your body to use easily. A study conducted showed that food-grown vitamin D includes both the ‘stored’ (25-hydroxy) and biologically ‘active’ (1-25 hydroxy) forms of vitamin D3. The body will always need to convert any ‘stored’ form of vitamin D3 into the ‘active’ form for it to do its various jobs like supporting calcium absorption. This makes supplementing in the ‘active’ form preferential. A highly absorbable and biologically active form may also minimise the need for ‘mega dosing’.
Boosting your vitamin D levels with food is an excellent idea, especially if your skin has not been exposed to sunshine. Here are the top five vitamin D rich foods…
Seafood is the highest source of vitamin D so aim to have two to three portions per week. Choose trout, halibut, sardines, herring, salmon, mackerel and oysters.
2 Whole milk
Organic full fat milk contains much more vitamin D than semi-skimmed and has not had anything added or removed. An even better option would be unpasteurised milk from a farm shop, if you have one in your area. Unfortunately the most popular form of milk is semi-skimmed, which contains significantly lower amounts of fat soluble vitamins including vitamin D.
3 Chicken and duck eggs
Eggs are a good source of vitamin D and are so versatile and easy to make. Ensure you eat the yolk as this is where you’ll find the vitamin D.
Some mushrooms have the ability to produce vitamin D when exposed to sunlight. The normal button mushrooms you find in the supermarket will contain very little vitamin D, so opt for a selection of portabello, maitake, morel, chanterelle and oyster mushrooms for a higher content.
5 Beef liver
Beef liver contains a nice amount of vitamin D per serving along with a host of other beneficial nutrients.
Avoid foods that have been artificially fortified with vitamin D and instead opt for food that contains vitamin D naturally from the list above.
As with many nutrients, vitamin D follows a U-shaped curve, meaning that high levels can be just as problematic for health as low levels. Excess intake is associated with increased risk of cardiovascular disease, kidney stones and low bone density. The latter is especially important to recognize as many will self-treat with high strength vitamin D supplements to reduce osteoporosis risk but may in fact be encouraging the ‘leaching’ of important nutrients for bone density out of the bone matrix. To understand your individual need, consider getting the guidance of a well trained nutritional therapist or functional medicine practitioner or requesting a vitamin D blood test with your GP.