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Information on the latest vitamin D news and research.

Find out more information on deficiency, supplementation, sun exposure, and how vitamin D relates to your health.

New randomized controlled trial finds that vitamin D influences blood pressure, even in healthy young adults

A new randomized controlled trial out of Spain has found that low dose vitamin D supplementation does not change lipid levels but does lower blood pressure in young healthy women.

Past research has shown that increased vitamin D levels is associated with better overall cardiovascular health. However, if there is a causal relationship, it is still unclear whether vitamin D benefits the heart through regulation of blood pressure, reducing lipids levels, preserving insulin secretion, some other way or by a combination of these.

Additionally, almost all studies examining vitamin D and cardiovascular health have looked at cardiovascular disease patients, not healthy populations. In the current study, researchers wanted to know what effect vitamin D supplementation might have in a healthy population.

They enrolled 165 young healthy women into their trial and divided them into three groups. Those that had low levels of iron were randomly assigned to receive vitamin D-fortified skim milk or to receive a placebo skim milk. Those that had healthy iron levels were assigned to a reference group. In total, 54 women were assigned to the vitamin D group, 55 to the placebo group, and 56 to the reference group.

The women in the vitamin D or placebo group were required to drink one 500 mL carton of skim milk per day. These cartons of milk contained 15 mg of iron per unit. The vitamin D group’s milk cartons contained 200 IU of vitamin D per carton in addition to the iron.

The women underwent this daily fortified milk consumption for 16 weeks. At the end of the trial, the researchers found:

  • The vitamin D group’s vitamin D levels increased from 24.9 ng/ml at baseline to 28.5 ng/ml, and the placebo group’s vitamin D levels stayed level, from 25.16 ng/ml at baseline to 25.28 ng/ml after 16 weeks.
  • Glucose and lipid levels did not change over time in either the vitamin D or the placebo group, and the researchers observed no difference between groups.
  • Over time, LDL cholesterol increased in the placebo group but slightly decreased in the vitamin D group. However, this was not quite statistically significant (p=0.07).
  • In the vitamin D group, systolic and diastolic blood pressure decreased significantly compared to the placebo group, which saw no change in blood pressure (p=0.017).

The researchers concluded,

“Consequently, the results of this randomized placebo-controlled trial show that consumption of a daily physiological dose of cholecalciferol (i.e., the Spanish RDA) in a fortified food was able to significantly decrease blood pressure, and support a direct effect of vitamin D metabolites on the renin-angiotensin-aldosterone system and blood pressure.”

The researchers pointed out that, although the use of healthy women was novel, it could be considered a limitation to the study. Other limitations include the use of only one level of fortification and that the effects of fortified food was not compared to other supplements.

A further limitation is the very small dose the researchers used. In their conclusion, they note that the dose of 200 IU is physiological, but it is not physiological by definition. A physiologic dose describes a dose that mimics the potency of what would occur naturally. Moderate full-body summer sun exposure induces production of 10,000-25,000 IU, and if this were a daily habit, sun exposure is equivalent to about 5,000 IU/day.

Still, it’s amazing that such a small dose and rise in 25(OH)D can still find statically significant results in blood pressure. There have been a few vitamin D and blood pressure randomized controlled trials now. It would be nice to see a meta-analysis of these randomized controlled trials to see what all of them combined have to say.

Source

Toxqui, L. et al. Changes in blood pressure and lipid levels in young women consuming a vitamin D-fortified skimmed milk: a randomized controlled trial. Nutrients, 2013.

  About: Jeff Nicklas

Jeff Nicklas was a staff member for the Vitamin D Council from October 2013 to January 2015. He is now pursuing his passion for public health through graduate studies.

4 Responses to New randomized controlled trial finds that vitamin D influences blood pressure, even in healthy young adults

  1. Ian says:

    I actually think that a meta analysis would be a bit premature because the study’s doses and co-factors have not be adequate. We need more studies giving higher doses, such as 4000iu to 5000iu daily for at least 6 months and some studies giving the key co-factors, magnesium, K2 and zinc.

  2. Michael says:

    Hello all,
    My autistic son developed extremely high blood pressure in his early twenties while off living on his own. It remained high despite all efforts, dietary / exercise / etc. until he began Vitamin D some four or five years ago (We can’t remember the year.) His blood pressure was always high despite the 3 meds and about 30 points higher than mine. After several years on 5000 iu daily, his blood pressure is almost always in the normal range with the same 3 meds.

    Michael

  3. Michael says:

    Hello all,

    Here is a little hint for you and the people you know: Horizontal chalk-white spots or splotches on the fingernails is a sign of zinc deficiency. Since zinc is mostly in the prostate, men need more zinc. The worse case I ever saw was a high school student with more than a hundred taking up half the area of his nails. When I mentioned he should eat ocean fish and brown rice, he bragged that he only ate steak and wasn’t interested in other food.

    Michael