Sunny Podcast #5 – Jen Aliano from GrassRootsHealth.net on Vitamin D, Pregnancy, and Lifelong Women’s Health

Pregnancy is a different biological state

One of the most important reframes in maternal health is understanding that pregnancy is not simply a time when women need more nutrients. It is a period when physiology itself changes.

As Jen explains, “Vitamin D is the sunshine vitamin. Most of the vitamin D we get is obtained from UVB exposure from sunlight. And on top of that, vitamin D is actually used in our body as a hormone, a cell signalling molecule, and it’s a regulator of our genes.”

Vitamin D is converted through multiple steps in the body, from vitamin D₃ to 25(OH)D and finally to its active hormonal form, calcitriol. Outside of pregnancy, this conversion is tightly regulated to protect calcium balance, but pregnancy is the exception.

“By the time a woman has reached the end of her first trimester of pregnancy, her level of calcitriol would be toxic or potentially fatal to a non-pregnant individual,” she explains, adding that this is not pathology but biology responding to increased developmental demands. “That is an indication that something is going on during pregnancy that is really needing that extra source of vitamin D.”

Moving research into real life: the GrassrootsHealth approach

GrassrootsHealth was founded precisely because vitamin D research was not being translated into public health practice. As Jen recounts,

“Grassroots Health became the organisation to move research into practice… to disseminate the information that these researchers had been finding on vitamin D and cancer, vitamin D and prenatal outcomes.”

From the beginning, the organisation emphasised two core principles agreed upon by dozens of international vitamin D researchers:

1. The accurate measurement of vitamin D status is not the intake. It is the vitamin D serum level measured as the 25 OHD level in the blood,
2. 40 to 60 nanograms per millilitre… was the optimal target range for general health.

This approach led to the now well-known principle: test, not guess. Human response to vitamin D intake varies dramatically, as Jen illustrates, “The wife only needs to take 2000 IU of vitamin D a day. But her husband… needs to take 10,000 IU a day to be within that range.” Digestion, genetics, medications, body composition, and lifestyle all influence response, which is why, as she emphasises, “That’s why it’s so important to measure your vitamin D level and then dose based on what your level currently is.”

Why do most women enter pregnancy deficient

Despite growing awareness, vitamin D deficiency remains a widespread issue, affecting pregnant women in particular. “About 90% of the US population is below that recommended level of 40 to 60,” Jen notes.

The reasons are structural rather than individual failure. Guidelines remain focused narrowly on bone health, “based on bone health alone, not based on all the other benefits that vitamin D can provide,” while sun avoidance, indoor living, sunscreen use, latitude-related vitamin D winters, and low-dose prenatal vitamins compound the problem. “Our prenatal vitamins don’t have enough vitamin D,” she states.

Insight also comes from ancestral comparisons, as studies of East African populations living traditional outdoor lifestyles show naturally higher vitamin D levels, with pregnant women exhibiting the highest levels in their communities. Pregnancy itself appears to raise vitamin D needs when supply allows.

Preterm birth and other pregnancy outcomes

One of the strongest findings discussed in the interview comes from work at the Medical University of South Carolina. “Getting vitamin D levels to 40 or higher during pregnancy reduced the risk of preterm birth by 62%,” Jen explains.

Preterm birth is not the only outcome influenced. Adequate vitamin D levels affect multiple pregnancy outcomes, including preeclampsia, postpartum haemorrhage, gestational diabetes, and postpartum depression, and they influence infant outcomes ranging from low birth weight and respiratory infections to asthma and even IQ later in childhood. Vitamin D also plays a role before pregnancy, supporting fertility, reducing miscarriage risk, and improving outcomes in conditions such as PCOS (Polycystic Ovary Syndrome).

As Jen summarises, vitamin D “acts directly on the genes, is a regulator of our immune system,” helping protect pregnancy and support fetal development.

Looking beyond trials: the totality of evidence

Some listeners may be surprised by links between prenatal vitamin D and disease risk later in life. Jen addresses this directly, explaining that randomised controlled trials spanning decades are often impossible, and instead, we must look at the totality of evidence. “You’re looking at the basic science… the clinical experiences, the observational studies and the meta-analyses,” alongside seasonal and geographic patterns described by the fetal origins hypothesis.

Importantly, achieved vitamin D levels matter more than assigned doses. “When we reanalysed the data based on achieved vitamin D serum level, that’s when you see the 60% decreased risk,” she explains.

Omega-3s, brain development, and maternal mental health

Vitamin D does not act alone. Omega-3 fatty acids, particularly DHA and EPA, are essential for brain development and are linked to reduced preterm birth risk and lower rates of postpartum depression. “Our brains are made of these healthy fats,” Jen notes, adding that omega-3s and vitamin D together support both physical and mental health.

Historically, this combination was delivered through foods such as cod liver oil, which naturally contains both nutrients.

Breastfeeding and supporting the mother

Breastfeeding is often framed as inadequate for vitamin D, yet the issue lies upstream. “If we as mothers are not getting enough… how are we supposed to pass it along to our babies?” Jen asks.

In the Hollis and Wagner trials, researchers compared giving 400 IU of vitamin D to both mother and infant versus giving 6,400 IU to the mother alone. The result was clear: “That second amount given to the mom was then providing the baby with its needed 400 IU… through the breast milk.”

Daily intake matters because vitamin D₃ has a short half-life, meaning consistent maternal intake is required to provide a steady supply to the infant.

Supporting the mother supports the baby, biologically and effectively.

Vitamin D beyond pregnancy: breast cancer and lifelong health

Vitamin D’s importance extends well beyond pregnancy. GrassrootsHealth research shows decreased risk in several cancers, especially breast and colon cancer, with greater reductions observed at higher vitamin D levels. “We’ve found an even greater decreased risk of breast cancer when you get vitamin D levels into the 60 to 80 range,” Jen explains.

Crucially, this begins before pregnancy, improving fertility, reducing miscarriage risk, and potentially eliminating preeclampsia risk when women enter pregnancy with adequate vitamin D levels.

The missed opportunity: acting without measuring

Perhaps the most important message from the entire conversation concerns action. “The biggest missed opportunity is what do you do with that information?” Jen says. Blind supplementation is not prevention. “You cannot assume… You have to measure.”

GrassrootsHealth’s protocol is simple: assess risk, test baseline levels, dose individually, retest, and adjust. “You can’t just guess.”

Safety, responsibility, and generational impact

Safety concerns often deter women from adequate vitamin D intake, yet Jen is clear. “There’s been zero evidence of any harm or toxicity at those intakes during pregnancy,” even at daily intakes of 4,400 to 6,000 IU in trials. Toxicity does not occur until far higher serum levels. “Vitamin D is a very safe nutrient to take,” she emphasises.

The deeper message is responsibility, not fear. “It’s our job to make choices for our body… and those choices can affect the entire lifespan of our baby.”