The best Vitamin D supplement to take this winter - a leading nutritional doctor explains
Most of us know we should take Vitamin D in the darker months but there remains considerable confusion as to how much we need to take, which type, in what form or which combination is best.
Professor Robert Thomas
5th December 2024 at 11:32 AM GMT
This article looks at the evidence for capsules, sprays, gummies and examines whether combinations with probiotics, minerals and other vitamins such K2 are better or are just marketing ploys to get us to part with our hard-earned money.
Why we need to take extra vitamin D
As well as osteoporosis, low levels of vitamin D are linked with an increased risk of viral infections (including Covid), fatigue, seasonal affective disorders (SAD), demotivation and cognitive impairment. In the longer term it contributes to the developments of a whole host of medical conditions ranging from diabetes, heart disease, cancer, arthritis and dementia.
Vitamin D is present in small amounts in nuts, egg yolks, oily fish, fresh vegetables mushrooms, grains, and meat from grass-fed animals. Over 80 per cent of the body’s vitamin D, however, comes from the skin following exposure to sunlight. Without sun, even with a good diet, vitamin D levels drop by half every six weeks so, unless we take positive action, we will have less than a quarter of the optimal levels of Vitamin D in our bodies by January.
Investing in a winter holiday in the sun, budget allowing, while taking sensible precautions is an excellent way to top up levels.
For the rest of us, who don’t get the luxury of basking in the Bahamas over New Year, Vitamin D supplement remains the only reliable option. There are hundreds of different types available over the counter – here is an overview of the evidence to help you decide which one and how much to take:
How much vitamin D should we take?
The official recommended daily amount (RDA) for adults is 600iu (15 mcg) but this is based on the prevention of rickets. Doctors and nutritionists generally agree that that to achieve levels at the upper end of the normal range 1000iu would be needed, although this is an estimate as absorption varies considerably between individuals. Also, in order to correct a known deficiency it would be good to take 3000iu for a few months then drop down to 1000iu to maintain healthy levels.
Vitamin D2 or D3?
Both actually help raise blood levels, although D3 is generally considered slightly more active and longer-lasting. It is the form which is naturally produced can look for a product made from lichen or micro-algae.
Gummies, sprays or capsules?
Research from the University of Sheffield showed that taking vitamin D by oral spray is just as effective as taking a tablet so this may be a more attractive option for young children instead of swallowing a capsule. A study for North Carolina, USA found that the absorption of vitamin D from gummies was slightly better that a capsules.
Gummies are certainly a more attractive to children, and some adults, and may improve compliance. The negative effects of the sugar, sweeteners and colouring content is a concern and is also a risk that, as they look like sweets they can be overdosed.
What helps absorption and utilisation of vitamin D?
As a fat-soluble vitamin, it’s better to take with food, especially if it contains healthy fats such as those in olive oil, avocado, fish, nuts and seeds. Magnesium is essential for converting vitamin D into its active form in the body so it would sensible to eat foods high in magnesium including leafy greens (spinach, kale), pumpkin seeds, whole grains and beans. If you’re concerned you may not be getting enough magnesium a good quality mineral supplement would be useful.
Excess alcohol and poor gut health can both impair vitamin D absorption. Lifestyle measures to improve gut health include exercise, avoiding sugar and eating more healthy bacteria-rich foods such as kimchi.
Vitamin D and probiotics
On top of lifestyle measures, several robust clinical studies have shown that combining probiotics with vitamin D significantly increases absorption. Vitamin D is also a natural pre-biotic which enhances healthy bacterial colonisation in the gut. As a consequence, the scientific committee of the national Covid nutritional intervention study selected the Yourgutplus supplement which contains five lactobacillus strains with 1000iu of vitamin D3 and demonstrated clinically relevant rises in blood vitamin D levels as well as an improvement in symptoms.
This supplement then went on to be chosen for the International Prostate Cancer Intervention Study which demonstrated significant improvements in prostate-related symptoms and disease progression.
Vitamin D with K2
If you are taking a calcium supplement, studies are now suggesting that ensuring adequate vitamin K2 would be beneficial. K2 helps to direct calcium into the teeth and bones and away from soft tissues including the coronary arteries. In fact, a study in the BMJ suggested that calcium supplements were associated with an increased risk of heart disease. Another study in the BMJ showed they only have a minimal effect on bone density.
On the other hand, studies which combine calcium with vitamin K reduced cardiac risk and improved bone density. The data that Vitamin K2 is necessary with vitamin D is less robust but it would be sensible to ensure adequate intake of K2 containing foods such as seaweed, grass-fed animals and fermented foods such as natto, kimchi and sauerkraut.
Avoid taking too much
Reassuringly your body cannot get too much vitamin D from sunshine because your skin limits the amount it makes However, when it comes to supplements, it’s important to remember that for most minerals and vitamins, more is not better as excess levels can do harm. As vitamins go, vitamin D is one of the safer ones but blood levels greater than 375 nmol/L (150 ng/mL) can cause nausea, vomiting, muscle weakness, confusion, pain, loss of appetite, dehydration, excessive urination and thirst, and kidney stones. Many nutritional institutions advise not going over 3000iu per day.