Skip to content

Pregnancy is a time when one should try to eat as well as possible, especially for the health of the developing baby. Included in this is the baby's brain development and later intellectual functioning (neurocognitive development). A recent study found that a mother's vitamin D levels during pregnancy are associated with the IQ of the child - that is, higher levels of vitamin D during the second trimester  of pregnancy were associated with higher IQs at age 4 to 6 in the child.

Just keep in mind that it's an association - it does not mean that lower vitamin D levels cause lower IQ. Vitamin D levels go hand in hand with other things - for example, vitamin D levels are lower when a person has chronic inflammation or an underlying health condition. Other studies have had mixed results - some had similar findings of effects on intellectual development, but others did not. Black women are at higher risk of vitamin D deficiencies due to their skin melanin content (harder to get enough vitamin D from the sun).

However, these results do add support for trying to correct vitamin D deficiencies and keeping vitamin D levels higher during pregnancy - by taking supplements and getting sunlight. Note that it's very hard to get enough vitamin D through food. The researchers said that prenatal supplements typically contain 400–600 IU vitamin D, but this is probably insufficient to correct vitamin D deficiencies, in which case they recommend daily supplementation of 800 to 1000 IU vitamin D.

From Medical Xpress: Vitamin D levels during pregnancy linked with child IQ

Vitamin D is a critical nutrient and has many important functions in the body. A mother's vitamin D supply is passed to her baby in utero and helps regulate processes including brain development. A study published today in The Journal of Nutrition showed that mothers' vitamin D levels during pregnancy were associated with their children's IQ, suggesting that higher vitamin D levels in pregnancy may lead to greater childhood IQ scores. The study also identified significantly lower levels of vitamin D levels among Black pregnant women. ...continue reading "Vitamin D Levels During Pregnancy Associated With A Child’s IQ"

Several studies are now suggesting that low vitamin D levels are linked to increased risk of getting COVID-19. And if you get COVID-19, low vitamin D levels are linked to a higher risk of developing serious symptoms requiring admission to intensive care,  and also not surviving. These studies are observational and don't prove that vitamin D levels are the cause, but a number of studies from countries worldwide and several lines of research are suggesting the same thing.

The best source of vitamin D is sunlight, but if taking supplements - then take vitamin D3. Researchers, doctors, and medical organizations vary in their recommended dosages, but many (such as Mayo Clinic) suggest 1000 to 2000 IU per day. The minimum daily requirement is 600 IU.

Some studies also suggest that having adequate magnesium is needed for vitamin D to be metabolized well. Good food sources of magnesium are nuts, seeds (especially pumpkin seeds), peanut butter, whole grains, beans, leafy vegetables, some fatty fish (halibut, salmon, mackerel), milk, yogurt, dark chocolate, legumes (beans), quinoa, tofu, and bananas. Daily magnesium requirements are 420 mg for men, 320 mg for women. Food is generally considered a better source than supplements.

However, some researchers point out that having a disease (e.g. diabetes) or chronic inflammation results in lowering of vitamin D levels (and not that low vitamin D levels causes disease). We need good double-blind studies (people randomly assigned to groups, and no one knows who is getting what) to understand if it really is vitamin D that's causing beneficial health effects.

Excerpts from Medscape: Low Vitamin D in COVID-19 Predicts ICU Admission, Poor Survival

Having low serum vitamin D levels was an independent risk factor for having symptomatic COVID-19 with respiratory distress requiring admission to intensive care — as opposed to having mild COVID-19 — and for not surviving, in a new study from Italy. ...continue reading "Vitamin D and COVID-19"

A recent study found that giving daily vitamin D supplements to children with severe asthma and low vitamin D levels did not prevent severe asthma attacks, reduce the time to an asthmatic attack, or enable the children to reduce the maintenance dose of an inhaled corticosteroid. Very disappointing!

As of 2018, it is estimated that 5.5 million children in the US have asthma, and that asthma led to more than 546,000 emergency department visits and 80,000 hospitalizations. So the researchers started the study hoping that vitamin D3 supplements could help with asthma attacks.

The well-done year long study recruited children (6 to 16 years old) from 7 US medical centers. They were assigned randomly to different groups (vitamin D or placebo), and with no one knowing who got vitamin D and who didn't. The children took 4000 IU/day of vitamin D3 or a placebo for 48 weeks, and all were maintained with a low-dose of inhaled corticosteroid (fluticasone propionate).

The findings contrast with earlier observational studies (basically a snap-shot of  groups of people) that found a link with severe asthma and lower vitamin D levels. Meanwhile, other well-done studies (women assigned randomly to different groups, etc) have found no protective effect from vitamin D3 supplementation during pregnancy - that is, it did not protect children up to the age of 6 from asthma.

Excerpts from Science Daily: Compared to placebo, vitamin D has no benefit for severe asthma attacks, study finds

Contrary to earlier results, vitamin D supplements do not prevent severe asthma attacks in at-risk children, according to the first placebo-controlled clinical trial to test this relationship.  ...continue reading "Children With Severe Asthma Not Helped By Vitamin D Supplements"

2

Disappointing results from a large study of more than 18,000 adults that looked at whether daily vitamin D supplements for 5 years helps prevent depressionThe Harvard Medical School researchers found that vitamin D didn't prevent depression or improve mood.

The study was large (more than 18,000 adults over the age of 50), double-blind (no one knew who was getting what to prevent bias), had people assigned randomly to either getting vitamin D3 (2000 IU/d of cholecalciferol) or a placebo, and lasted 5 years. The researchers summary of findings: "These findings do not support the use of vitamin D3 in adults to prevent depression."

By the way, the results of this well-done study (which was designed to see cause and effect) are in contrast to observational studies that suggested that a person's vitamin D levels and vitamin D supplements are correlated with the risk of depression and depressive symptoms. Once again a well-done vitamin D study did not provide the health benefits that people were hoping for.

From Medical Xpress: Large study confirms vitamin D does not reduce risk of depression in adults

Vitamin D supplementation does not protect against depression in middle-age or older adulthood according results from one of the largest ever studies of its kind. This is a longstanding question that has likely encouraged some people to take the vitamin.  ...continue reading "Study Finds That Vitamin D Supplements Don’t Prevent Depression"

2

The past year has resulted in disappointments for the vitamin and mineral supplement industry as study after study didn't find health benefits from routinely ingesting them. Instead, study after study found health benefits from eating a good diet, specifically one that has as few as possible highly processed foods, but lots of whole foods, and rich in whole grains, fruits, vegetables, nuts, seeds, and legumes (beans). And in this way, also high in fiber. Think along the lines of a Mediterranean diet.

The following are some of the studies finding no benefits to various vitamin and mineral supplements. Many found the results of the vitamin D studies especially disappointing.

1) From Science Daily - Vast majority of dietary supplements don't improve heart health or put off death, study finds

In a massive new analysis of findings from 277 clinical trials using 24 different interventions, Johns Hopkins Medicine researchers say they have found that almost all vitamin, mineral and other nutrient supplements or diets cannot be linked to longer life or protection from heart disease.   ...continue reading "Four Vitamin Studies Have Disappointing Results"

For years researchers have been finding links between vitamin D and all sorts of health benefits, including lower incidence of cancer with higher vitamin D levels. A recent study by Michigan State physicians found that taking vitamin D supplements for at least 3 years resulted in cancer patients living longer, that is, "having significant reduction of cancer-related mortality" . However, it did not prevent cancer.

One issue with much of the vitamin D research that has been done is whether vitamin D is really  causing these health benefits or is it just an association? Perhaps people who take vitamin D are also different in some way from those who  don't, or something else is going on, and this may be confusing the results.What was nice about this  study is that it was a review of studies already done, but the researchers only included vitamin D studies  that used randomly controlled trials (RCT).

In the RCTs  included in the study, people were randomly assigned to different groups and either they were 1) given vitamin D supplements for 3 years or more, or 2) they did not take vitamin D supplements (the placebo group). Thus they evaluated 10 RCT studies with 79,055 persons who were followed for 4 years or more. Vitamin D was associated with significant reduction of cancer-related deaths (when compared with the placebo group). But there was no reduction in cancer incidence. Meaning the vitamin D did not prevent cancer (have a protective effect) in the studies they looked at.

The researchers did not say what they thought was an optimal vitamin D supplement dose or optimal levels in the blood. By the way, keep in mind that vitamin D can easily be gotten from exposure to sunshine. After all, it is called the sunshine vitamin.

From Science Daily: Vitamin D could help cancer patients live longer   ...continue reading "Vitamin D and Cancer"

For a few years I've been noticing that studies of vitamin D have had mixed results for a number of medical conditions. A number of times initial studies found an association with low levels of vitamin D and a number of medical conditions, but follow up well-designed studies are just not finding the same results with vitamin D supplementation - or results have been mixed. Also, in some studies, what initially looked like vitamin D being protective for some cancers and multiple sclerosis, now looks like it's sunlight that is giving the protective results. In some cases, vitamin D levels are a proxy for sunlight exposure (the more sunlight exposure, the higher the vitamin D levels in the person). The following 6 studies recently published highlight this same trend of mixed results.

While vitamin D levels increased from high dose vitamin D, there was no change in bone bone mineral density (BMD) in older adults during the 12 months of the study. No adverse effects form the vitamin D supplementation was reported [the older adults received 12,000 international units (IU), 24,000 IU, or 48,000 IU once a month]. From Science Daily: Vitamin D supplements are of no benefit to the over 70s

There is little benefit for those over 70 taking higher dose vitamin D supplements to improve their bone strength and reduce the risk of falls, new research has revealed.

High doses of vitamin D (4000 international units) appeared more beneficial than low dose vitamin D (400 international units) supplements in advanced colorectal cancer patients. From Medical Xpess: High-dose vitamin D shows benefit in patients with advanced colorectal cancer

...continue reading "Recent Vitamin D Studies Have Mixed Results"

The results of a recent study by Vanderbilt University may help explain why some people have difficulty raising their low vitamin D levels - it may be that their magnesium levels are low. It appears that magnesium may regulate vitamin D levels - when vitamin D levels are low, magnesium supplementation raises vitamin D levels, and when vitamin D levels are high, magnesium supplementation lowers them to a normal level.

What are good food sources of magnesium? Magnesium is found in many plant and animal foods and beverages. Good sources of magnesium include green leafy greens, legumes (beans), whole grains, nuts, dark chocolate, and fatty fish such as salmon. Foods containing dietary fiber generally provide magnesium. By the way, dietary surveys of people in the United States consistently show that intakes of magnesium are lower than recommended amounts. From Medical Xpress:

Study shows magnesium optimizes vitamin D status

A randomized trial by Vanderbilt-Ingram Cancer Center researchers indicates that magnesium optimizes vitamin D status, raising it in people with deficient levels and lowering it in people with high levels

...continue reading "Magnesium Regulates Vitamin D Levels In the Body?"

Long-awaited  vitamin D studies are finally appearing this year. A large international study found that higher levels of vitamin D in a person's blood is associated with a lower risk of colorectal cancer. Those with the highest vitamin D levels had a 21% lower risk (compared to the lowest group) of colorectal cancer after an average 5.5 years.

But the researchers generally do not recommend vitamin D supplements - saying that most people had adequate levels from foods and sunshine. However, they suggest that the risk for vitamin D deficiency is higher for those with very dark skin; for older adults (their skin may not be as efficient at synthesizing vitamin D); and for those who do not go outside at all - and that these groups may need supplementation (but not beyond 4000 IU per day - because higher levels have negative health effects). From Medical Xpress:

Large international study links blood vitamin D levels to colorectal cancer risk

new study authored by scientists from the American Cancer Society, the Harvard T.H. Chan School of Public Health, the U.S. National Cancer Institute, and more than 20 other medical centers and organizations finds that higher circulating vitamin D concentrations are significantly associated with lower colorectal cancer risk. This study strengthens the evidence, previously considered inconclusive, for a protective relationship. Optimal vitamin D concentrations for colorectal cancer prevention may be higher than the current National Academy of Medicine recommendations, which are based only on bone health ...continue reading "Vitamin D and Colorectal Cancer Risk"

Another study has found that the most common vitamin and mineral supplements (multivitamins, vitamin D, calcium, and vitamin C), don't offer hoped for health benefits, and may actually carry some risks. This latest study was a review of other studies, and examined whether specific vitamins or minerals would  lower the risk of cardiovascular disease (including heart attacks and strokes) and death from any cause (referred to as all cause mortality"). [Posts discussing other research finding problems with supplements.]

In general, the review of studies of popular supplements (multivitamins, vitamin D, calcium, and vitamin C) show no consistent benefit (no significant effect) for the prevention of cardiovascular disease, heart attacks, or stroke, nor any lowering of death (all cause mortality). On the other hand, folic acid and B-vitamins with folic acid, B6, and B12 reduced stroke (folic acid showed a 20% reduction in stroke), but niacin and antioxidants were associated with an increased risk of death from any cause (10% increase). But overall the effects in the studies were small. Vitamin D did not show any benefits in reducing death, but the researchers pointed out that many vitamin D studies are now under way, and the results of vitamin D studies so far are mixed (e.g. 16 showing positive effects from vitamin D, 17 showing a more favorable effect in the control group, and 10 neither).

On the other hand, the researchers stressed that eating a well balanced diet has lots of health benefits and is recommended by the U.S. Dietary Guidelines Advisory Committee. Three dietary patterns are frequently discussed as beneficial: 1) a healthy American diet (sometimes called a "prudent diet") low in saturated fat, trans fat, and red meat, but high in fruit and vegetables, 2) a Mediterranean diet, and 3) a vegetarian diet. All 3 of these diets are rich in fruits and vegetables (which means increased fiber), are relatively rich in vitamins and minerals, and meet Dietary Reference Intake guidelines.  ...continue reading "Study Finds No Benefit From Most Supplements"