Vitamin D is one of the most critical vitamins for overall health and longevity, but how do you get it, and how much do you need?
what is Vitamin D?
Vitamin D is both a nutrient and a hormone our bodies make. It reduces cancer cell growth, boosts the immune system, improves cognitive function, strengthens our bones, and reduces inflammation, and scientists are actively investigating other possible functions.
Studies on vitamin D
Bone Fractures
Vitamin D helps maintain strong bones. Studies show increased bone fractures in older adults with low vitamin D.
A meta-analysis of 12 randomized controlled trials that included more than 42,000 people 65+ years of age, most women, looked at vitamin D supplementation and a placebo. Researchers found that higher intakes of vitamin D supplements—about 500-800 IU per day—reduced hip and non-spine fractures by about 20%. Lower intakes (400 IU or less) failed to offer fracture prevention.
Multiple Sclerosis
A person’s genetic background plus environmental factors, including inadequate vitamin D, have been identified to increase the risk of MS.
Studies of people with MS have found that higher vitamin D levels are associated with reduced disease activity and progression. They also found that MS is much higher far north (or far south) of the equator than in sunnier climates.
In a study among healthy young adults in the US, white men and women with the highest vitamin D levels had a 62% lower risk of developing MS than those with low vitamin D levels. Young adults from Sweden found a 61% lower risk of MS with higher vitamin D levels, and young Finnish women found that low serum vitamin D levels were associated with a 43% increased risk of MS.
While several clinical trials are underway to examine vitamin D as a treatment in persons with MS, there are no clinical trials aimed at preventing MS. This is likely because MS is a rare disease. The trial would need to be significant and long-lasting. However, if the studies are accurate, approximately 40% of cases may be prevented by correcting vitamin D insufficiency.
Flu, Common Cold, and COVID-19
The flu virus wreaks havoc in the winter and lessens in the summer because vitamin D levels are highest in summer.
Studies show that children with vitamin D deficiency are more likely to contract respiratory infections. In contrast, children exposed to sunlight have fewer respiratory infections, and adults with low vitamin D levels are likelier to report a recent cough, cold, or upper respiratory tract infection. Also, a large meta-analysis (a study of studies) has shown low vitamin D levels increase the risk of COVID-19.
A randomized controlled trial in Japanese school children tested whether taking daily vitamin D supplements would prevent seasonal flu. The trial followed 340 children for four months during the height of the winter flu season. Half of the study participants received pills that contained 1,200 IU of vitamin D; the other half received placebo pills. Researchers found that type A influenza rates in the vitamin D group were about 40% lower than in the placebo group; there was no significant difference in type B influenza rates.
Other Autoimmune Conditions (rheumatoid arthritis, psoriasis, Hashimoto’s, and more)
A randomized, double-blind, placebo-controlled trial following more than 25,000 men and women ages 50 and older found that taking vitamin D supplements (2,000 IU/day) for five years reduced the incidence of autoimmune diseases by about 22%, compared with a placebo. Autoimmune conditions observed included rheumatoid arthritis, psoriasis, polymyalgia rheumatica, and autoimmune thyroid diseases (Hashimoto’s thyroiditis, Graves’ disease).
Cognitive Decline
In an analysis of more than 427,000 White European participants, a 54% higher risk of dementia was seen among participants with low vitamin D blood levels of <25 nmol/L compared with those with adequate 50 nmol/L levels.
vitAMin d from food
Most people consume only about 140 IUs of vitamin D daily. This amount may be even lower for vegans or those who suffer from inflammatory bowel diseases, such as ulcerative colitis and Crohn’s disease, which can disrupt normal digestion. Additionally, individuals who have undergone gastric bypass surgery, which typically involves the removal of the upper part of the small intestine where vitamin D is absorbed, may also have reduced levels of this vital nutrient.
Only a few foods naturally contain vitamin D. Foods naturally rich in vitamin D3 are wild salmon, sardines, mackerel, tilapia, tuna fish, swordfish, trout with skin on, cod liver oil, and beef liver. Small amounts are found in egg yolks, milk, cereal, and orange juice fortified with vitamin D.
Certain mushrooms contain higher amounts of D2 because they are intentionally exposed to high doses of ultraviolet light. You can increase vitamin D levels in your mushrooms by letting them sit outside in the sun for 20-30 minutes.
Vitamin D from the sun
Most of our vitamin D comes from the sun, but the amount absorbed can vary widely. Just because you’re in the sun doesn’t mean you’re absorbing it. Remember that the body stores vitamin D from summer sun exposure, but it only lasts a few months. By late winter, many people are deficient.
The following decreases vitamin D absorption:
- Using sunscreen reduces vitamin D absorption by over 90%.
- Wearing full clothing
- Spending a lot of time indoors. Sitting by the window on a sunny day will not increase vitamin D. You must be outside to soak up the sun’s rays.
- People with darker skin are typically deficient in vitamin D due to having higher amounts of the pigment melanin, which acts as a natural sunscreen.
- Obese people tend to have lower vitamin D levels. Vitamin D accumulates in excess fat tissues but is not readily available for use by the body when needed.
- Seniors have lower vitamin D levels because it’s harder for their bodies to absorb vitamin D
- People who live in colder environments
Vitamin D Deficiency and Toxicity
Worldwide, an estimated 1 billion people have inadequate vitamin D levels due to lack of sun exposure, insufficient food rich in vitamin D, poor absorption, or a metabolic need for higher amounts. In the U.S., Vitamin D deficiency is widespread, affecting approximately 42% of the U.S. population. Most people with vitamin D deficiency don’t notice any symptoms. Others may notice vague symptoms such as:
- Muscle pain
- Fatigue or tiredness
- Increased sensitivity to pain
- Hair loss
- Mood changes: depression, anxiety, irritable
- A tingly, “pins-and-needles” sensation in the hands or feet
- Waddling while walking due to muscle weakness in the hips or legs
- A history of broken bones
- Getting sick more easily
- Muscle twitches or tremors
- Muscle spasms
- Rickets: A rare condition in infants and children of soft bones and skeletal deformities caused by failure of bone tissue to harden.
- Osteomalacia: A condition in adults of weak and softened bones that can be reversed with supplementation. This is different than osteoporosis, in which the bones are porous and brittle, and the condition is irreversible.
Too Much Vitamin D
Vitamin D toxicity, also called hypervitaminosis D, is extremely rare. Still, it is a severe condition when you have excessive amounts of vitamin D. Vitamin D toxicity is caused by large doses of vitamin D supplements, not by food or sun exposure. Symptoms include stomach pain, dizziness, and constipation.
Supplementing with vitamin D?
The Recommended Dietary Allowance for vitamin D for adults 19 years and older is 600 IU (15 mcg) daily for men and women, and for adults >70 years, it is 800 IU (20 mcg) daily.
Many functional medicine doctors argue this is well under what people need and recommend 4,000-5,000 IU (International Units) daily for adults and 500-1,000k IU per day for kids, or 35 IUs per pound of body weight.
For example, I weigh 120 lbs x 35 = 4,200 IUs daily (1 IU = 25 mcg)
Keep in mind the metric for vitamin D is changing. The FDA is moving from IU to mcg to make it more standardized (1000 IUs = 25 mcg).
If you want a good Vitamin D supplement, click HERE
The Difference Between Vitamin D3 and D2 Supplements
Vitamin D supplements are available in two forms: vitamin D2 (“ergocalciferol” or pre-vitamin D) and vitamin D3 (“cholecalciferol”). Both are also naturally occurring forms that are produced in the presence of the sun’s ultraviolet-B (UVB) rays. Vitamin D2 is made from plants and found in fortified foods and supplements, and vitamin D3 is naturally produced in the human body and is found in animal foods.
There is an ongoing debate about whether vitamin D3 is better than vitamin D2. Some experts cite vitamin D3 as the preferred form as it is naturally produced in the body and found in most foods that naturally contain it.
Whatever you decide, always take your Vitamin D the first part of the day with a big meal, Vitamin K, or a high-fat food to enhance absorption.
How To cheCK your Vitamin D Levels
In Western Medicine, the “normal” range for Vitamin D in blood work is 30-100 ng/mL (nanograms per milliliter). However, Functional medicine doctors recommend Vitamin D levels between 50 and 80 (ng/mL) because 30-100 is a wide range.
While evidence supports the benefits of consuming vitamin D, the U.S. Preventive Services Task Force (USPSTF) concluded that knowing one’s vitamin D level isn’t helpful for most people, so you must request to check your vitamin D level.
If you want to check your vitamin D levels, call your doctor or click HERE to order an at-home lab test that arrives promptly at our door. Ideally, you want to test your Vitamin D two times a year, in winter and summer.
If you’re looking for a good Vitamin D supplement, this is the one my whole family takes. Click Here
If you have a question or want me to speak at an event, email me at aftannfit@gmail.com or follow me on Instagram or Facebook.
