Gluten-free diets not only do not deprive you of various vitamins, but they also offer many health benefits, including a gluten-free & vitamin D boost. Vitamin D plays various roles in the body and is essential for maintaining overall health. In this article, we will explore the effects of vitamin D on different parts of the body, as well as how to measure it and the best ways to consume it, including gluten-free options to ensure you get the most out of this vital nutrient.”
How Does the Body Obtain Vitamin D?
Cholesterol is naturally present in our skin. When we’re exposed to direct sunlight, specifically to UVB rays, this cholesterol undergoes a transformation to become vitamin D (cholecalciferol). Vitamin D is also found in dietary sources like dairy, fish, egg yolks, poultry, and red meat, where it is absorbed through the intestines. Additionally, another form of vitamin D, present in supplements and edible mushrooms, can be absorbed through the intestines.
Regardless of its source—whether from the skin, food, or supplements—vitamin D enters the bloodstream and travels to the liver. There, it converts to 25-hydroxyvitamin D. This form then travels to the kidneys, where it transforms into 1,25-dihydroxyvitamin D, the active form of vitamin D. To ensure adequate vitamin D levels, in addition to sunlight exposure and a diet rich in vitamin D, we need a healthy fat absorption system, sufficient cholesterol, and healthy skin, liver, and kidneys.
What Role Does Vitamin D Play in the Body?
Vitamin D, along with hormonal systems, helps the body absorb and maintain optimal calcium and phosphate levels in the blood. This is essential for bone structure, muscle contraction, and nervous system health. A deficiency in vitamin D can lead to bone deformities and fragility.
Vitamin D also has anti-inflammatory effects and supports cell growth control, neuromuscular function, immune system health, and glucose regulation.
Vitamin D’s Impact on Health:
- Bone Health: Vitamin D enhances calcium absorption, helping to maintain bone density and prevent osteoporosis, especially in middle-aged and older adults. It also supports proper muscle contraction, essential for healthy muscle fibers. A combined intake of calcium and vitamin D supports skeletal and muscular health.
- Cancer Prevention: Vitamin D has anti-inflammatory properties and regulates immune responses, potentially inhibiting cancer cell growth. Low vitamin D levels have been associated with various types of cancer, with evidence suggesting that every 8 ng/mL increase in vitamin D may reduce cancer risk by 7% and cancer mortality by 2%. However, more research is needed to confirm these findings.
- Cardiovascular Health: Vitamin D regulates hormone systems related to blood pressure, helping to maintain healthy blood pressure levels, reduce inflammation, and prevent vascular fibrosis. Higher vitamin D levels are linked to lower risks of heart disease, including heart attacks and heart failure, with every 10 ng/dL increase potentially reducing heart disease risk by 10%.
- Mental Health: Vitamin D plays a role in neurological processes, with its receptors found on nerve cells related to mood regulation. While the effect of vitamin D on depression remains debated, more studies are required to confirm this.
- Multiple Sclerosis (MS): MS is an autoimmune disorder that attacks the protective layer (myelin) around nerves in the brain and spinal cord, leading to symptoms like movement disorders, blindness, tremors, and imbalance. Studies show that low vitamin D levels, especially under 30 nmol/L, may increase MS risk by over 40%.
- Glucose Metabolism: Vitamin D affects glucose metabolism by activating receptors on pancreatic beta cells, prompting insulin release and lowering blood sugar. While there may be concerns about vitamin D increasing insulin resistance, studies show that it does not. Research on 2,423 participants showed that vitamin D supplements had no additional effect in those with normal vitamin D levels but reduced type 2 diabetes risk by 62% in those with vitamin D deficiency.
- Weight Loss: Although the exact mechanism is unclear, vitamin D has been linked to weight loss. Exercise and calorie restriction have been associated with increased vitamin D levels in the blood, even without supplementation. Additionally, vitamin D and calcium supplementation can lead to slight weight loss, especially when combined with diet and exercise.
Blood Tests for Vitamin D Levels
To determine if you are getting sufficient vitamin D, a doctor may request a 25-hydroxyvitamin D blood test. Results fall into one of several categories to assess your vitamin D status.
| Interpretation | Vitamin D Level (ng/mL) | Vitamin D Level (nmol/L) |
| Deficiency causing rickets/osteomalacia | Less than 12 | Less than 30 |
| Insufficient level, often asymptomatic but not optimal for full health | 12 to 20 | 30 to 50 |
| Adequate level for a healthy individual | 20 or more | 50 or more |
| Toxicity level | More than 50 | More than 125 |
Recommended Daily Intake of Vitamin D
Everyone over the age of one needs 600 IU (15 micrograms) of vitamin D daily. For individuals over 70, this amount increases to 800 IU (20 micrograms) per day. However, recommendations vary: for example, Public Health England advises everyone over age 4 to take 400 IU per day, while the Endocrine Society recommends at least 1,500 to 2,000 IU (37.5 to 50 micrograms) daily for adults. Vitamin D needs can depend on factors such as diet, location, lifestyle, race, age, and baseline vitamin D levels.
Dietary Sources of Vitamin D
The best dietary sources of vitamin D are fatty fish like salmon, trout, and tuna, as well as cod liver oil. Liver, meats, egg yolks, cheese, and mushrooms also contain small amounts of vitamin D.
Sunlight
Sun exposure allows UVB rays to convert cholesterol in the skin into vitamin D. However, this process is less effective in people with darker skin and those of older age. Since UVB rays do not pass through glass, sunlight filtered through windows does not help produce vitamin D. Depending on sunlight intensity and individual factors, 20 to 30 minutes of direct sunlight exposure at least twice a week between 10 a.m. and 4 p.m. is recommended, exposing the face, arms, hands, and legs. However, UV rays are a leading cause of skin cancers, so wearing sunscreen with SPF 15 or higher is advisable. Sunscreen with SPF over 8 significantly blocks vitamin D synthesis, but as many people apply it unevenly or infrequently, a little vitamin D can still be synthesized.
Vitamin D Supplements
Due to the limited dietary sources of vitamin D, supplements are often needed. Testing your vitamin D levels is recommended to determine an appropriate dose. If a deficiency is confirmed, higher doses under medical supervision may be required. A common regimen involves taking one 50,000 IU capsule weekly for 8 weeks, then switching to a regular maintenance dose. For those with normal levels, 500 to 2,000 IU daily is advised. Vitamin D supplements come in various dosages, with many available as 50,000 IU capsules. For individuals with normal levels, one 50,000 IU capsule per month is typically recommended.
There are also high-dose 300,000 IU vitamin D injections, equivalent to six 50,000 IU capsules, which are usually unnecessary and may cause toxicity if not medically warranted. Please avoid using high-dose vitamin D injections without medical advice, especially as they may interact with medications such as Orlistat, steroids, statins, and thiazide diuretics. Consult a healthcare provider to adjust your vitamin D intake if you are taking these medications.
Vitamin D Deficiency
Vitamin D deficiency can result from inadequate intake of food or supplements (especially among those who avoid dairy or follow a vegan diet), or from an inability to activate the vitamin due to liver or kidney disorders. Other risk factors include older age, low sunlight exposure, darker skin, fat absorption issues, obesity, and gastric bypass surgery. In children, deficiency can lead to rickets, while in adults it can cause osteomalacia, weak bones, bone pain, muscle cramps, dental issues, seizures, and weakened immunity.
Vitamin D Toxicity
While vitamin D has many benefits, excessive intake can be dangerous. Being fat-soluble, it accumulates in the body and is not easily eliminated. Toxicity may occur when the average daily intake exceeds 4,000 IU, though symptoms typically appear at intakes above 10,000 IU. Overuse may result in cardiovascular disease, certain cancers (such as pancreatic cancer), and bone fractures, similar to deficiency effects.
Vitamin D toxicity leads to elevated blood calcium levels (hypercalcemia) and excessive calcium in the urine (hypercalciuria), causing symptoms like nausea, vomiting, muscle weakness, mental confusion, loss of appetite, dehydration, excessive urination, intense thirst, and kidney stones. If blood levels are exceedingly high, calcium may deposit in soft tissues like the heart and arteries, leading to kidney failure, abnormal heart rhythms, and possibly death.
The primary cause of vitamin D toxicity is excessive supplement use. Sun exposure cannot cause vitamin D toxicity, no matter how intense, and dietary sources are limited. Be cautious with supplements, and check for any additional vitamin D in multivitamins or other products to avoid overconsumption.