By Franziska Spritzler
Vitamin D is an extremely important vitamin that has powerful effects on several systems throughout the body (1).
Unlike most vitamins, vitamin D actually functions like a hormone and every single cell in your body has a receptor for it.
Your body makes it from cholesterol when your skin is exposed to sunlight.
It's also found in certain foods such as fatty fish and fortified dairy products, although it's very difficult to get enough from diet alone.
The recommended daily intake is usually around 400-800 IU, but many experts say you should get even more than that.
Vitamin D deficiency is very common. It's estimated that about 1 billion people worldwide have low levels of the vitamin in their blood (2).
According to a 2011 study, 41.6 percent of adults in the U.S. are deficient. This number goes up to 69.2 percent in Hispanics and 82.1 percent in African-Americans (3).
These are common risk factors for vitamin D deficiency:
- Having dark skin.
- Being elderly.
- Being overweight or obese.
- Not eating much fish or milk.
- Living far from the equator where there is little sun year-round.
- Always using sunscreen when going out.
- Staying indoors.
People who live near the equator and get frequent sun exposure are less likely to be deficient, because their skin produces enough vitamin D to satisfy the body's needs.
Most people don't realize that they are deficient, because the symptoms are generally subtle. You may not notice them easily, even if they are having a significant negative effect on your quality of life.
Here are eight signs and symptoms of vitamin D deficiency.
1. Getting Sick or Infected Often
One of vitamin D's most important roles is keeping your immune system strong so you're able to fight off the viruses and bacteria that cause illness.
It directly interacts with the cells that are responsible for fighting infection (4).
If you become sick often, especially with colds or the flu, low vitamin D levels may be a contributing factor.
Several large observational studies have shown a link between a deficiency and respiratory tract infections like colds, bronchitis and pneumonia (5, 6).
A number of studies have found that taking vitamin D supplements at dosages of up to 4,000 IU daily may reduce the risk of respiratory tract infections (7, 8, 9).
In one study of people with the chronic lung disorder COPD, only those who were severely deficient in vitamin D experienced a significant benefit after taking a high-dose supplement for one year (10).
Bottom Line: Vitamin D plays important roles in immune function. One of the most common symptoms of deficiency is an increased risk of illness or infections.
2. Fatigue and Tiredness
Feeling tired can have many causes and vitamin D deficiency may be one of them.
Unfortunately, it's often overlooked as a potential cause.
Case studies have shown that very low blood levels can cause fatigue that has a severe negative effect on quality of life (11, 12).
In one case, a woman who complained of chronic daytime fatigue and headaches was found to have a blood level of only 5.9 ng/ml. This is extremely low, as anything under 20 ng/ml is considered to be deficient.
When the woman took a vitamin D supplement, her level increased to 39 ng/ml and her symptoms resolved (12).
However, even blood levels that aren't extremely low may have a negative impact on energy levels.
A large observational study looked at the relationship between vitamin D and fatigue in young women.
The study found that women with blood levels under 20 ng/ml or 21–29 ng/ml were more likely to complain of fatigue than those with blood levels over 30 ng/ml (13).
Another observational study of female nurses found a strong connection between low vitamin D levels and self-reported fatigue.
What's more, the researchers found that 89 percent of the nurses were deficient (14).
Bottom Line: Excessive fatigue and tiredness may be a sign of vitamin D deficiency. Taking supplements may help improve energy levels.
3. Bone and Back Pain
Vitamin D is involved in maintaining bone health through a number of mechanisms.
For one, it improves your body's absorption of calcium.
Bone pain and lower back pain may be signs of inadequate vitamin D levels in the blood.
Large observational studies have found a relationship between a deficiency and chronic lower back pain (15, 16, 17).
One study examined the association between vitamin D levels and back pain in more than 9,000 older women.
The researchers found that those with a deficiency were more likely to have back pain, including severe back pain that limited their daily activities (17).
In one controlled study, people with vitamin D deficiency were nearly twice as likely to experience bone pain in their legs, ribs or joints compared to those with blood levels in the normal range (18).
Bottom Line: Low blood levels of the vitamin may be a cause or contributing factor to bone pain and lower back pain.
4. Depression
A depressed mood may also be a sign of deficiency.
In review studies, researchers have linked vitamin D deficiency to depression, particularly in older adults (19, 20).
In one analysis, 65 percent of the observational studies found a relationship between low blood levels and depression.
On the other hand, most of the controlled trials, which carry more scientific weight than observational studies, didn't show a link between the two (19).
However, the researchers who analyzed the studies noted that the dosages of vitamin D in controlled studies were often very low.
In addition, they noted that some of the studies may not have lasted long enough to see the effect of taking supplements on mood.
Some controlled studies have shown that giving vitamin D to people who are deficient helps improve depression, including seasonal depression that occurs during the colder months (21, 22).
Bottom Line: Depression is associated with low vitamin D levels and some studies have found that supplementing improves mood.
5. Impaired Wound Healing
Slow healing of wounds after surgery or injury may be a sign that vitamin D levels are too low.
Results from a test-tube study suggest that the vitamin increases production of compounds that are crucial for forming new skin as part of the wound-healing process (23).
One study on patients who had dental surgery found that certain aspects of healing were compromised by vitamin D deficiency (24).
It's also been suggested that vitamin D's role in controlling inflammation and fighting infection is important for proper healing.
One analysis looked at patients with diabetic foot infections.
It found that those with severe vitamin D deficiency were more likely to have higher levels of inflammatory markers that can jeopardize healing (25).
Unfortunately, at this point there is very little research about the effects of vitamin D supplements on wound healing in people with deficiency.
However, one study found that when vitamin D deficient patients with leg ulcers were treated with the vitamin, ulcer size reduced by 28 percent, on average (26).
Bottom Line: Inadequate vitamin D levels may lead to poor wound healing following surgery, injury or infection.
6. Bone Loss
Vitamin D plays a crucial role in calcium absorption and bone metabolism.
Many older women who are diagnosed with bone loss believe they need to take more calcium. However, they may be deficient in vitamin D as well.
Low bone mineral density is an indication that calcium and other minerals have been lost from bone. This places older people, especially women, at an increased risk of fractures.
In a large observational study of more than 1,100 middle-aged women in menopause or postmenopause, researchers found a strong link between low vitamin D levels and low bone mineral density (27).
However, a controlled study found that women who were vitamin D deficient experienced no improvement in bone mineral density when they took high-dose supplements, even if their blood levels improved (28).
Regardless of these findings, adequate vitamin D intake and maintaining blood levels within the optimal range may be a good strategy for protecting bone mass and reducing fracture risk.
Bottom Line: A diagnosis of low bone mineral density may be a sign of vitamin D deficiency. Getting enough of this vitamin is important for preserving bone mass as you get older.
7. Hair Loss
Hair loss is often attributed to stress, which is certainly a common cause.
However, when hair loss is severe, it may be the result of a disease or nutrient deficiency.
Hair loss in women has been linked to low vitamin D levels, although there is very little research on this so far (29).
Alopecia areata is an autoimmune disease characterized by severe hair loss from the head and other parts of the body. It's associated with rickets, which is a disease that causes soft bones in children due to vitamin D deficiency (30).
Low vitamin D levels are linked to alopecia areata and may be a risk factor for developing the disease (31, 32, 33).
One study in people with alopecia areata showed that lower blood levels tended to be associated with a more severe hair loss (33).
In a case study, topical application of a synthetic form of the vitamin was found to successfully treat hair loss in a young boy with a defect in the vitamin D receptor (34).
Bottom Line: Hair loss may be a sign of vitamin D deficiency in female-pattern hair loss or the autoimmune condition alopecia areata.
8. Muscle Pain
The causes of muscle pain are often difficult to pinpoint.
There is some evidence that vitamin D deficiency may be a potential cause of muscle pain in children and adults (35, 36, 37).
In one study, 71 percent of people with chronic pain were found to be deficient (37).
The vitamin D receptor is present in nerve cells called nociceptors, which sense pain.
One study in rats showed that a deficiency led to pain and sensitivity due to stimulation of nociceptors in muscles (38).
A few studies have found that taking high-dose vitamin D supplements may reduce various types of pain in people who are deficient (39, 40).
One study in 120 children with vitamin D deficiency who had growing pains found that a single dose of the vitamin reduced pain scores by an average of 57 percent (40).
Bottom Line: There is a link between chronic pain and low blood levels of the vitamin, which may be due to the interaction between the vitamin and pain-sensing nerve cells.
Correcting a Vitamin D Deficiency is Simple
Vitamin D deficiency is incredibly common and most people are unaware of it.
That's because the symptoms are often subtle and non-specific, meaning that it's hard to know if they're caused by low vitamin D levels or something else.
If you think you may have a deficiency, then it's important that you speak to your doctor and get your blood levels measured.
Fortunately, a vitamin D deficiency is usually easy to fix. You can either increase your sun exposure, eat more vitamin D rich foods or simply take a supplement.
Fixing your deficiency is simple, easy and can have big benefits for your health.
Reposted with permission from our media associate Authority Nutrition.
By Hrefna Palsdottir
Biotin is a water-soluble B-vitamin that helps your body convert food into energy.
It is especially important during pregnancy and breastfeeding.
In addition, biotin is important for the health of your hair, skin and nails.
This article explains everything you need to know about biotin, including its seven main health benefits.
What Is Biotin?
Biotin is one of the B-vitamins, also known as vitamin B7.
It was once called coenzyme R and vitamin H. The H stands for Haar und Haut, which is German for hair and skin.
Biotin is water-soluble, which means the body doesn't store it. It has many important functions in the body.
It's necessary for the function of several enzymes known as carboxylases. These biotin-containing enzymes participate in important metabolic pathways, such as the production of glucose and fatty acids (1).
A commonly recommended intake is 5 mcg (micrograms) per day in infants and 30 mcg in adults. This goes up to 35 mcg per day in breastfeeding women.
Biotin deficiency is fairly rare. However, some groups—such as pregnant women—may experience it in mild forms (2).
Eating raw eggs may also cause a deficiency, but you would need to eat a lot of eggs for a very long time. Raw egg whites contain a protein called avidin, which binds to biotin and prevents its absorption. Avidin is inactivated during cooking.
Summary: Biotin is a water-soluble B-vitamin that's important for energy metabolism. Deficiency is quite rare, although it has been associated with the long-term consumption of raw eggs.
1. Plays a Key Role in Macronutrient Metabolism
Biotin is important for energy production. For example, several enzymes need it to function properly (1).
These enzymes are involved in carb, fat and protein metabolism. They initiate critical steps in the metabolic processes of these nutrients.
Biotin plays a role in:
- Gluconeogenesis: This metabolic pathway enables glucose production from sources other than carbs, such as amino acids. Biotin-containing enzymes help initiate this process (3).
- Fatty acid synthesis: Biotin assists enzymes that activate reactions important for the production of fatty acids (4).
- The breakdown of amino acids: Biotin-containing enzymes are involved in the metabolism of several important amino acids, including leucine (5).
Summary: Biotin assists in energy production. It supports a number of enzymes involved in the metabolism of carbs, fats and protein.
2. May Help Brittle Nails
Brittle nails are weak and easily become chipped, split or cracked.
It's a common condition, estimated to affect around 20 percent of the world's population (6).
Biotin may benefit brittle nails (7).
In one study, 8 people with brittle nails were given 2.5 mg of biotin per day for 6 to 15 months. Nail thickness improved by 25 percent in all 8 participants. Nail splitting was also reduced (8).
Another study of 35 people with brittle nails found 2.5 mg of biotin per day for 1.5 to 7 months improved symptoms in 67 percent of participants (9).
However, these studies were small and more research is needed.
Summary: Brittle nails are fragile and easily become split or cracked. Biotin supplements may help strengthen the nails.
3. Good for Your Hair
Biotin is often associated with increased hair growth and healthier, stronger hair.
Surprisingly, there is very little evidence to support this.
However, a deficiency in biotin may lead to hair loss, which indicates that the vitamin is important for hair (2, 10).
While it is often marketed as an alternative treatment for hair loss, only people with an actual biotin deficiency get significant benefit from supplementing (11).
Whether it improves hair growth in healthy people has yet to be determined.
Summary: Biotin is claimed to promote hair growth and healthy hair, but the evidence is weak. However, deficiency has been linked to hair loss and those who are actually deficient may benefit from supplementing.
4. Plays a Role During Pregnancy and Breastfeeding
Biotin is important during pregnancy and breastfeeding. These life stages have been associated with an increased requirement for this vitamin (12, 13).
In fact, it has been estimated that up to 50 percent of pregnant women may develop a mild biotin deficiency. This means that it may start to affect their well-being slightly, but isn't severe enough to cause noticeable symptoms (14, 15, 16).
Deficiencies are thought to occur due to the faster biotin breakdown within the body during pregnancy (17).
Additionally, a major cause for concern is that animal studies have found that a biotin deficiency during pregnancy may cause birth defects (18, 19, 20).
Nevertheless, remember to always consult your doctor or dietitian/nutritionist before taking supplements during pregnancy and while breastfeeding.
Summary: If you're pregnant or breastfeeding, your biotin requirements may go up. Up to 50 percent of women may get less of this vitamin than they need during pregnancy.
5. May Lower Blood Sugar Levels in Diabetics
Type 2 diabetes is a metabolic disease. It's characterized by high blood sugar levels and impaired insulin function.
Researchers have studied how biotin supplements affect blood sugar levels in type 2 diabetics.
Some evidence shows biotin concentrations in blood may be lower in people with diabetes, compared to healthy individuals (21).
Studies in diabetics given biotin alone have provided mixed results (21, 22).
However, several controlled studies indicate that biotin supplements, combined with the mineral chromium, may lower blood sugar levels in some people with type 2 diabetes (23, 24, 25, 26).
Summary: When combined with chromium, biotin may help lower blood sugar levels in people with type 2 diabetes.
6. May Benefit the Skin
Biotin's role in skin health isn't well understood. However, it is known that you may get red, scaly skin rashes if you're deficient (27, 28).
Some studies also suggest that biotin deficiency may sometimes cause a skin disorder called seborrheic dermatitis, also known as cradle cap (29, 30).
Biotin's role in skin health may be related to its effect on fat metabolism, which is important for the skin and may be impaired when biotin is lacking (27).
There is no evidence showing that biotin improves skin health in people who aren't deficient in the vitamin.
Summary: People with a biotin deficiency may experience skin problems. However, there is no evidence that the vitamin has benefits for skin in people who aren't deficient.
7. Affects Multiple Sclerosis
Multiple sclerosis (MS) is an autoimmune disease. In MS, the protective covering of nerve fibers in the brain, spinal cord and eyes is damaged or destroyed (31).
This protective sheath is called myelin and biotin is thought to be an important factor in producing it (32).
A pilot study in 23 people with progressive MS tested the use of high doses of biotin. More than 90 percent of participants had some degree of clinical improvement (33).
While this finding needs much more study, at least two randomized controlled trials have been carried out in people with progressive MS. The final results have not been published, but the preliminary results are promising (34, 35, 36).
Summary: High biotin doses hold promise for treating multiple sclerosis, a serious disease that affects the central nervous system.
Which Foods Contain Biotin?
Biotin is found in a wide variety of foods, so an actual deficiency is rare.
Foods that are particularly good sources include:
- Organ meats, such as liver and kidney
- Yeast
- Egg yolks
- Cheese
- Legumes, such as soybeans and peanuts
- Leafy greens
- Cauliflower
- Mushrooms
- Nuts and nut butters
In addition, your gut bacteria produce some amount of biotin. It's also available as a supplement, either on its own or as a component of mixed vitamin supplements.
Summary: Many foods contain significant amounts of biotin and it is also available as a supplement. Your gut bacteria can also produce it.
Safety and Side Effects
Biotin is considered very safe. Even mega doses of up to 300 milligrams daily to treat multiple sclerosis have not led to adverse side effects (33).
To put this in perspective, 300 milligrams is 10,000 times the commonly recommended 30 microgram dose for adults.
Because it's a water-soluble vitamin, excess amounts are excreted in urine.
However, there have been some reports of high-dose biotin causing strange results on thyroid tests, so check with a doctor before using if you are currently taking thyroid medication (37).
Summary: Biotin appears very safe, even at extremely high doses. There are no known side effects of supplementing with biotin.
The Bottom Line
Biotin is a B-vitamin that plays a crucial role in carb, fat and protein metabolism.
Many of its potential health benefits are based on weak evidence. Nonetheless, it may be important for your skin, hair and nails.
Additionally, pregnant or breastfeeding women may require more biotin. High doses are also being investigated as a potential treatment for multiple sclerosis.
You can find biotin in a wide variety of foods, so actual deficiency is very rare.
For this reason, supplements probably have no significant benefits for healthy people who eat a balanced diet based on real food.
Reposted with permission from our media associate Authority Nutrition.