Here at Proper, we 🤓 nerd 🤓 out over the science of sleep. Years of rigorous research went into developing our products to directly support aspects of the mind and body that impact sleep quality. Our PhD-led formulations team looked for ingredients backed by multiple human clinical studies that verified the efficacy of the ingredient itself AND its dosage—with no conflicting findings. All were double-blind and placebo-controlled.

We’ve taken this same vigor and applied it here, to our ingredient guides that evaluate what the science says (and doesn’t say) about various vitamins, minerals, and herbs/natural botanicals. Some are in our products, others aren’t. The goal? Equip you with the know-how to make the most informed decisions for your personal sleep journey.

Known as calciferol in science speak and “the sunshine vitamin” more casually, this fat-soluble vitamin is primarily known for helping the body absorb calcium, which is necessary for optimal bone health.

Several studies have found that vitamin D deficiency (also known as VDD) is a risk factor for poor sleep quality, short sleep duration, and daytime sleepiness. (1) There may also be a relationship between VDD and certain sleep disorders such as Restless Leg Syndrome and Obstructive Sleep Apnea. (2-3)

Researchers have indicated several potential reasons behind this relationship between vitamin D and sleep:

  • Location of vitamin D receptors
    These receptors and the enzymes controlling their activation are found in parts of the brain that happen to be related to sleep regulation, including the hypothalamus and prefrontal cortex. (4-6)

  • Relationship between vitamin D and melatonin
    Select studies point to the link between vitamin D and the production of melatonin, a natural hormone that affects our sleep-wake circle (circadian rhythm) (7)—although there are contradicting studies (see section below).

In addition to directly affecting sleep, vitamin D can also indirectly affect sleep by modulating chronic pain and inflammatory diseases.

  • Chronic pain
    One common symptom of VDD is chronic nonspecific pain, (8) which increases the risk of poor quality of sleep and short sleep duration. (9)

  • Inflammatory diseases
    Vitamin D has been found to impact our immune system by decreasing the release of inflammatory substances such as prostaglandin D2 cytokines, both of which indirectly impact sleep. (10-11)

Evidence-backed ingredients + dosages

Proper has multiple human clinical studies verifying the efficacy of each ingredient AND dosage in our supplements—with no conflicting findings.

Vitamin D has been extensively studied, but not all the clinical trials have yielded consistent results.

While some studies point to the beneficial relationship between vitamin D and melatonin, there has been one study (12) which found the opposite: those with higher levels of vitamin D had lower levels of melatonin—although this study was conducted exclusively on subjects with multiple sclerosis, so these results cannot be generalized to the healthy adult population.

Another potential red flag related to the effect of vitamin D on sleep is that one study (13) found no significant difference in the Pittsburgh Sleep Quality Index (PSQI) score between deficient group and non-deficient group. However, like the study above, this study was conducted on a niche patient population of women in the last trimester of their pregnancy.

  • Supports bone health (14-15)
    And prevents low bone mineral density, which is associated with an increased risk of osteoporotic fracture.

  • May affect risk of multiple sclerosis
    Early evidence (16) points to the correlation between the level of serum vitamin D and risk of multiple sclerosis, although further research needs to be done to confirm this hypothesis.

Symptoms of vitamin D deficiency include: (17)

  • Fatigue
  • Bone pain
  • Muscle aches, cramps, or general weakness
  • Mood changes
Supplements backed by years of rigorous research

Proper formulations directly support aspects of the mind + body that impact sleep quality.

However, in order to identify whether these symptoms are the result of low levels of vitamin D, your doctor will take a blood test. Some consider blood levels of 20 - 40 ng/mL to be normal while others recommend 30 - 50 ng/mL. (18)

Although you can get vitamin D from sun exposure (more on that below), it won’t supply enough to solve for vitamin D deficiency.

With supplementation, the recommended dietary allowances (RDAs) for vitamin D intake are as follows: (1)

  • Teens 14 - 18 years old: 15 mcg (600 IU)
  • Adults 19 - 70 years old: 15 mcg (600 IU)
  • Adults 71+ years old: 20 mcg (800 IU)

Note that it IS possible to get too much vitamin D (greater than 375 nmol/L or 150 ng/mL), which causes nausea, vomiting, muscle weakness, dehydration, and, in extreme circumstances, kidney stones. So it’s best to discuss with your healthcare provider before beginning a supplement regimen.

Roughly 40% of U.S. adults don’t get enough vitamin D, with the following groups at higher risk of a deficiency: (19-20)

  • Older adults
  • Those with darker skin (which blocks sun absorption)
  • Those who are overweight
  • Those who live in locations with limited sunlight
  • Those with cystic fibrosis, Crohn’s disease, or celiac disease

READ MORE: The FDA Regulates Supplement Facts Differently Than Nutrition Facts. Here's Why.

While sun exposure is the most common way to trigger vitamin D synthesis, it’s also possible to up your stores through supplementation and diet.

Vitamin D supplements (21)

While multivitamins contain varying levels of vitamin D, many also consume vitamin D in dietary supplement form. Typically, you’ll either find vitamin D alone or combined with other nutrients such as vitamin K2, magnesium, calcium, and/or fish oil. There are two types of vitamin D commonly found in supplements: vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). The latter raises your levels higher and for longer than the former.

Because vitamin D is fat soluble, it dissolves best in supplement form when taken alongside meals (especially ones with ample health fats). For this reason, many find that the best time of day to take their supplement is the morning alongside breakfast.

Vitamin D in food (22)

Unfortunately, there are few natural food sources of vitamin D. Fatty fish (specifically trout, salmon, tuna, and mackerel) is the best source, but you’ll also find small amounts in beef liver, egg yolks, cheese, and mushrooms (especially mushrooms that have been exposed to ultraviolet light).

There are also foods fortified to increase the vitamin D content, including milk (both as a dairy product and plant-based), breakfast cereals, and select brands of orange juice and yogurt. 

READ MORE: The 15 Best + Worst Foods For Your Sleep

While vitamin D deficiency has been identified as a risk factor for poor sleep, there is conflicting evidence on its relationship to melatonin. If you suspect that you’re deficient, schedule a blood test to confirm before proceeding with a supplement regimen—and be sure to talk to your healthcare provider about the correct dosage since it is possible to get too much vitamin D.

Interested in exploring alternative natural ingredients for sleep? We’ve got you covered:

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