Thorne D-1,000 Review

The evidence on vitamin D for immune support is mixed. A 2019 pooled analysis of 25 trials with 11,321 people found vitamin D lowered the odds of a sudden respiratory infection by about 12 percent, with the biggest benefit in very deficient people taking daily or weekly doses ^[1]. A 2021 update found a much smaller benefit, about 3 percent lower risk and slightly shorter symptoms ^[2]. Several large placebo-controlled trials found no benefit. In 15,804 older adults, 2,000 international units daily for one year did not lower upper respiratory infections ^[3]. In 2,157 adults aged 70 or older, 2,000 international units daily for three years did not reduce infections ^[4]. Among 8,851 schoolchildren given weekly vitamin D for three years, tuberculosis and respiratory infections were not reduced ^[5]. In 408 adults with asthma, vitamin D did not reduce colds, and African American participants had more colds on it ^[6]. One capsule of this product gives 25 micrograms, below the 2,000 international unit daily amount used in several of these trials; the record lists 75 micrograms a day as the intake. Animal and cell studies are never counted.

Vitamin D is the main ingredient here, and all ten panelists spoke about it, with most recommending it or taking it themselves. They use it for immune support, brain and mood, bone health, muscle, and general health or longevity, and several say to get blood levels tested, with targets that range from 40 up to 100 nanograms per milliliter. Four of them take vitamin D3, often 5,000 IU in the morning, one suggests at least 10,000 IU daily in winter, and another takes it in fall and winter when sun is limited. Because it is fat soluble, one panelist says to take it with dietary fat, and three pair it with vitamin K2 or magnesium. One notes there is little point in supplementing unless you are deficient, and no one said they stopped; vitamin E, a smaller ingredient in this product, got only brief mentions.

The rules read 19 of 52 human studies showing improvement as 96 percent of people improving, but 21 studies found no effect and several large placebo-controlled trials found no benefit, so the evidence is mixed rather than a clear improvement. So it is graded Tier 4, lower than the rules alone gave.

Combine with: For blood sugar support, pair vitamin D3 with ingredients that have more direct evidence: berberine (often 500 mg two to three times daily with meals) for glucose and lipid metabolism, magnesium glycinate or citrate (200-400 mg) to support insulin sensitivity, chromium picolinate (200-600 mcg) for glucose handling, and alpha-lipoic acid (300-600 mg) for insulin sensitivity and oxidative stress. Omega-3 fish oil (EPA/DHA) can support cardiovascular and triglyceride health. For vitamin D itself, take it with a fat-containing meal and consider adding vitamin K2 (MK-7, 90-180 mcg) to help direct calcium to bone and away from soft tissues, plus magnesium as a cofactor for vitamin D activation. Check 25-hydroxyvitamin D levels to confirm the dose, and consult a healthcare provider before combining supplements with meds, since additive glucose-lowering effects can occur.