Vitamin D is arguably one of the most important vitamins you can take. And while it’s available in some animal-based foods, it’s hard to get enough through food only.
What’s staggering is that despite its importance, it’s estimated that over one billion people worldwide are either deficient or have insufficient levels of vitamin D 1, which is primarily the result of inadequate sun exposure, but also diets lacking in the vitamin.
And because vitamin D is a fat-soluble vitamin and many factors can influence its effectiveness, it takes a bit of special attention to ensure you’re getting enough.
So while the best multivitamin will always contain plenty of Vitamin D, you should take the time to learn about the role Vitamin D plays in the body and how to best maximize your intake.
We’re going to explore why taking vitamin D is essential for your health and when is the best time to take it to maximize its effect.
What is Vitamin D?
With more than 1000 target genes in the human body and most cells containing a vitamin D receptor (VDR) 2, vitamin D plays numerous roles in maintaining health and well-being, so we can agree that it’s pretty important.
Vitamin D is one of the four fat-soluble vitamins in the human body along with vitamins A, E, and K. Nicknamed the ‘sunshine vitamin’, it’s best known for being synthesized in the skin in response to UV rays emitted by the sun.
But supplement wise there are two forms of vitamin D you’ll find: ergocalciferol (D2) and cholecalciferol (D3). The former is found in plant foods, while the latter is found in animal-based and fortified foods. However, studies suggest that vitamin D3 is more effective at increasing serum levels of vitamin D than D2.
If you’re not familiar with why you need vitamin D, keep reading.
Why Vitamin D Is Essential For Good Health
Regardless of age, everyone requires vitamin D. Adequate levels of vitamin D are necessary for nearly every system and cell in your body, but despite this, it’s still one of the most common deficiencies around.
Vitamin D is involved in:
- Immune function—With insufficient levels of vitamin D, your immune system takes a big hit. That’s because vitamin D plays a role in both the innate and adaptive immune system 3, which is your immediate and long-term immune responses. Deficiency has been associated with an increased risk of autoimmune diseases like rheumatoid arthritis, MS, diabetes, and IBD, as well as an increased susceptibility to infection.
- Inflammation—Along with modulating the immune system, vitamin D also plays an essential role in the inflammatory response by regulating the production of inflammatory cytokines and inhibiting the proliferation of pro-inflammatory cells 4.
- Bone health—The importance of vitamin D can’t go unnoticed, especially for women, when it comes to bone health. Vitamin D plays important roles in the mineralization of the collagen matrix in bone to maintain bone health and strength 5. And because estrogen plays such a significant role in bone strength, declining estrogen levels during menopause spell trouble, as estrogen regulates bone-building osteoclasts’ activity. With insufficient vitamin D, the body triggers the release of hormones that mobilize calcium from bone to increase serum concentrations, which means bone strength suffers and the risk of fractures increases.
- Mood—Do you ever notice your mood takes a dip when you haven’t seen sunshine in a while? That’s vitamin D hard at work! Research shows that vitamin D may be a powerhouse for treating mood disorders because VDR receptors are present in areas of the brain responsible for regulating mood 6. Studies also show that people with low vitamin D are at a higher risk for depression, which may be because of vitamin D’s role in regulating the synthesis of serotonin, your happy hormone 7.
- Glucose regulation—A little-known fact about vitamin D is that it also plays a role in blood sugar. It’s involved in maintaining proper glucose levels but also reducing the risk of insulin resistance, decreasing triglyceride levels, and reducing weight gain. And research suggests that a vitamin D deficiency may negatively influence the production of insulin 8.
- Testosterone production—Men, you’ll want to load up on the sunshine vitamin. There’s a substantial presence of VDR’s and vitamin D metabolizing enzymes in the male reproductive tract, especially the Leydig cells of the testis 9, which means it’s a key player in testosterone production. It's no coincidence that the best multivitiamin for men will always provide a large dose of Vitamin D!
The Best Time To Take Vitamin D
Of course, the most effective way to raise your serum vitamin D levels is to get in that sunshine!
About 20 minutes of sun exposure once per day between the hours of 10 am - 2 pm is the most ideal, but for people who live in a country where sunshine isn’t available year-round, getting sufficient exposure becomes challenging.
If you’re not getting vitamin D through the sun, you have to be careful with your supplementation timing.
Because vitamin D is a fat-soluble vitamin, it doesn’t dissolve in water and is absorbed best when taken with a fat source, which means that taking vitamin D with food is always recommended.
To give you an idea of how vital a fat source is, one study found that participants who took vitamin D alongside a high-fat meal saw a 32% increase in serum vitamin D levels compared with participants who took it alongside a low-fat meal 10.
Things like avocados, healthy oils (coconut, olive, avocado), nuts, and seeds are all great options for healthy fat sources that maximize absorption and therefore maximize efficacy.
If you’re someone who struggles to remember to take their vitamin D supplement, lump it in with anything you take at breakfast!
Most people pop their supplements first thing in the morning, so adding in your vitamin D then is an easy way to remember. But if you’re opting for a pure D3 liquid, most will be emulsified in fat to ensure proper absorption.
However, be mindful that taking vitamin D later in the day may not be the best idea.
A small study suggests that vitamin D can interfere with melatonin production, thereby increasing the risk of sleep disturbances, poor sleep quality, and reduced sleep duration 11. If you forget to take it during the day, save it for the next morning!
Final Thoughts: When to take Vitamin D
When it comes to vitamin D, supplementation should really be non-negotiable. Because the risk of deficiency is so high and because it’s involved in so many essential functions, vitamin D should be a staple in either your multivitamin or as a pure vitamin D3 liquid supplement.
- O Sahota. Understanding vitamin D deficiency. Age Ageing. 2014;43(5):589-591.
- S Sirajudeen, I Shah, A Al Menhali. A Narrative Role of Vitamin D and Its Receptor: With Current Evidence on the Gastric Tissues. Int J Mol Sci. 2019; 20(15):3832.
- M Hewison. Vitamin D and Innate and Adaptive Immunity. Vitamins & Hormones. 2011; 86:23-62.
- K Yin, DK Agrawal. Vitamin D and inflammatory diseases. J Inflamm Res. 2014;7:69-87.
- C Aranow. Vitamin D and the immune system. J Investig Med. 2011; 59(6):881-886.
- DW Eyles, S Smith, R Kinobe, M Hewison, JJ McGrath. Distribution of the vitamin D receptor and 1 alpha-hydroxylase in human brain. J Chem Neuroanat. 2005;29(1):21-30.
- RP Patrick, BN Ames. Vitamin D and the omega-3 fatty acids control serotonin synthesis and action, part 2: relevance for ADHD, bipolar disorder, schizophrenia, and impulsive behavior. FASEB J. 2015;29(6):2207-2222. doi:10.1096/fj.14-268342
- KA Al-Shoumer, TM Al-Essa. Is there a relationship between vitamin D with insulin resistance and diabetes mellitus? World J Diabetes. 2015;6(8):1057-1064.
- S Pilz, S Frisch, H Koertke, J Kuhn, J Dreier, B Obermayer-Pietsch, E Wehr, A Zittermann. Effect of Vitamin D Supplementation on Testosterone Levels in Men. Horm Metab Res. 2010.
- B Dawson-Hughes, SS Harris, AH Lichtenstein, G Dolnikowski, NJ Palermo, H Rasmussen. Dietary fat increases vitamin D-3 absorption. J Acad Nutr Diet. 2015;115(2):225-230.
- D Golan, E Staun-Ram, L Glass-Marmor, et al. The influence of vitamin D supplementation on melatonin status in patients with multiple sclerosis. Brain Behav Immun. 2013;32:180-185.