Most people associate vitamin D3 with sun exposure; however, there is mixed information regarding how much time we should spend in the sun; and when there is no sun... how much D3 should we ingest from a supplement?
The current UK guidelines indicate that we should take 400 IU (International Units) per day, and no more than 1,000 IU per day. However, many believe this number is woefully insufficient.
In 2015, researchers at UC San Diego and Creighton University challenged the US recommendations for vitamin D intake, saying they underestimated the need by a factor of ten.
Given that the US RDA was higher than the UK (600 vs. 400), it underlines the need to seriously re-evaluate the guidelines.
Current UK Vitamin D Recommendations
Over in America, the upper limit for vitamin D supplementation is currently set at 4,000 IU per day. This is four times as much as the UK upper limit.
Strange when you consider that the accepted No Observed Adverse Effects Level (NOAEL) of vitamin D is actually 10,000 IU.
Indeed, Vitamin D Council Executive Director John Cannell, M.D., has suggested that it would be surprising to witness side effects in much higher dosages: “If there are any studies showing 20,000 IU/day is unsafe, I would like to see them.”
The question, however, is not whether 1,000 or 10,000 IU is dangerous: the NOAEL proves that it isn't. The question is whether 1,000 is enough to help a person achieve a healthy vitamin D status.
There is much evidence to suggest that the answer is no. In a Belgian study conducted in 2011, even comparatively large doses of vitamin D failed to raise respondents' level sufficiently.
Patients who initially demonstrated very low levels of vitamin D were given the equivalent of 4,200 IU/day, for example, and yet 62% failed to achieve a final 25(OH)D of at least 30 ng/ml.
The study clearly emphasised that 4,000 IU – which would be deemed very high strength by the UK authorities – is, in fact, not enough for some people. Indeed, 5,000 or 7,000 IU is not enough for some people.
That said, anyone who exceeds 5,000 IU per day would be wise to have a 25(OH)D test 2-3 months after starting their supplement protocol to determine their vitamin D status.
What Exactly is Vitamin D Anyway?
Vitamin D3 is a fat-soluble vitamin that that aids in bone health by regulating calcium homeostatic. It can be synthesised in the skin upon exposure to sunlight and then metabolised in the liver and kidneys.
Vitamin D3 is needed for the synthesis of calcium. Several cofactors are needed for the metabolism of vitamin D, including zinc, boron, vitamins A and E, and magnesium.
Most food sources are relatively low in vitamin D, but those with the best levels include oily fish such as salmon, mackerel and sardines, milk (vitamin D fortified) and eggs from hens that have been fed vitamin D.
UK guidelines recommend that people take vitamin D supplements during autumn and winter, when it's difficult to derive enough vitamin D from the sun. Some people, however, should take supplements year-round.
Diseases Associated with Vitamin D Deficiency
Research indicates that there is an inverse relationship between vitamin D deficiency and autoimmune diseases, including type 1 diabetes, MS, lupus and arthritis. Vitamin D deficiency has also been linked to cognitive deterioration.
Researchers in the UK have suggested that there is a higher risk of certain diseases, including dementia, in those living at northern latitude due to the inability to make adequate vitamin D from the limited sunlight exposure in those regions (2015).
Supplementation with vitamin D has been associated with an improvement in Crohn’s Disease, and may improve retardation and rickets in children.
Vitamin D and Cancer
There appears to be a direct correlation between vitamin D, cancer and immunity.
In a 2018 Japanese cohort study of 7,345 people, cancer risk was 22% lower among those with the highest vitamin D levels compared with those with the lowest levels.
This was after adjustments were made for several known cancer risk factors including age, weight (BMI), physical activity levels, smoking and alcohol intake.
Researchers also found a lower risk of liver cancer for people with a higher vitamin D intake.
Vitamin D and Candida
Recent studies published in the Journal of Infectious Diseases state that there is a positive relationship between vitamin D and Candida infections.
Candida is a fungal infection caused by an overgrowth of bacteria, which is often associated with eating a diet high in sugar. It can occur in the mouth, also known as thrush, or in the vagina in the form of a yeast infection.
Vitamin D produces an anti-microbial peptide called cathelicidin, which has been shown to fight off infections such as Candida.
Symptoms of Vitamin D Deficiency
You may be deficient in vitamin D if:
- You don’t get enough sunlight
- You don’t take supplements
- Your body requires more Vitamin D than normal, such as in the case of obesity and pregnancy
Symptoms of vitamin D deficiency include fatigue and general aches and pains. A simple blood test can tell if you are deficient, and this can be obtained through your doctor on the NHS.
People who may experience vitamin D deficiency are those with dark skin, people who spend a lot of time indoors during the day, those who cover up or wear sunscreen, people who live in the northern latitudes, older individuals, infants and pregnant women.
Obesity will also negatively impact your vitamin D levels.
Vitamin D and Skin Type
Knowing your skin type will help you understand how much vitamin D you are absorbing through the sun’s rays. Melatonin is a substance that dictates your skin colour; those with darker skin have higher levels of melatonin.
The following is a list of skin type and their characteristics:
- Type 1: White: very fair complexion, red or blonde hair, blue eyes and freckles; always burns, never tans.
- Type 2: White: fair complexion, red or blonde hair, blue, hazel or green eyes; usually burns, has difficulty tanning.
- Type 3: Cream white: fair complexion, any eye or hair colour, very common; gradually tans, sometimes burns.
- Type 4: Brown: typical Mediterranean Caucasian complexion; tans with ease, rarely burns.
- Type 5: Dark brown: Middle Eastern complexion; tans very easily.
- Type 6: Black: never burns.
Should You Increase Your Vitamin D Intake?
Some people consider vitamin D3 to be the most important vitamin, and it’s not hard to see why given the overwhelming amount of data highlighting the benefits. The truth, however, is that you need all of them.
That said, increasing your intake of vitamin D should be a top priority if you live in a country with low levels of sunlight in the winter or if you avoid the sun when it is out during summer.
You may also only obtain the desired healthy vitamin D levels if you supplement well above what is currently advised. That's if research carried out by The Vitamin D Council is anything to go by.
The Vitamin D Council recommends a daily vitamin D dosage of 5,000 IU for adults, although a 2017 study suggests 6,000 IU may be a more accurate figure.
Supplementing with vitamin D3 is inexpensive and will help to improves immunity.
Individuals with health issues should consider upping their vitamin D intake. Chronic diseases are caused by inflammation, which typically begins in the digestive tract.
Inflammation makes it difficult for many nutrients to be absorbed by the small intestine. Supplemental vitamin D, which has been shown to benefit gut and immune health, will give your body a greater chance of absorbing the nutrients it needs.
U.K. public health officials recommend increased public understanding of safe sun exposure. (2015, January 21).
Latitude may affect risk of developing dementia, new study reports. (2015, January 19).