A new review of research shows that vitamin D deficiency is a major health problem in Portugal, affecting a large portion of the population. Vitamin D is crucial for strong bones and overall health, but many Portuguese people aren’t getting enough of it from sunlight or food. The study looked at multiple research projects to understand how common this problem is and what might help. While eating more vitamin D-rich foods and spending time outdoors can help, researchers suggest that adding vitamin D to common foods (like milk and bread) might be the most effective solution for the whole population.

The Quick Take

  • What they studied: How common vitamin D deficiency is in Portugal and what strategies might help fix this public health problem
  • Who participated: This was a review that looked at multiple previous studies conducted in Portugal. The individual studies used different groups of Portuguese people, ranging from local communities to national surveys
  • Key finding: Vitamin D deficiency is very common in Portugal, with some people having severe deficiency. Simply telling people to take supplements or eat more vitamin D-rich foods hasn’t worked well enough to solve the problem
  • What it means for you: If you live in Portugal or a similar climate, you may be at risk for low vitamin D. The research suggests that adding vitamin D to everyday foods like bread and milk might be more helpful than individual supplements for the whole population, though personal supplementation may still help certain people

The Research Details

This was a narrative review, which means researchers looked at and summarized findings from multiple previous studies about vitamin D deficiency in Portugal. Rather than conducting one new study, the authors gathered information from various cross-sectional studies (studies that look at a population at one point in time) that had been done at different locations and times across Portugal. These previous studies measured vitamin D levels in blood samples and documented how many people had low levels. The review approach allowed the researchers to see the big picture of vitamin D deficiency across the country and identify common patterns and causes.

Using a review approach is important because it shows the overall scope of a health problem rather than just looking at one small group. By combining results from many studies, researchers can see if vitamin D deficiency is truly widespread and understand it as a public health issue affecting many people, not just a few individuals. This type of evidence is crucial for making decisions about national health policies

This is a narrative review, which means it summarizes existing research but doesn’t use the most rigorous statistical methods. The strength of the findings depends on the quality of the individual studies reviewed. The authors acknowledge that vitamin D definitions aren’t standardized across all studies, which can make comparisons tricky. However, the consistent finding of high vitamin D deficiency across multiple independent studies strengthens the conclusion that this is a real and significant problem in Portugal

What the Results Show

The review confirms that vitamin D deficiency is extremely common in Portugal, affecting a substantial portion of the population. Many people have severe deficiency, meaning their vitamin D levels are dangerously low. This is consistent with patterns seen across Europe and worldwide. The research shows that Portugal has a particularly serious problem with vitamin D deficiency compared to some other countries. The main causes identified include: not enough vitamin D in typical Portuguese diets, limited sun exposure for some people, and insufficient time spent outdoors. Additionally, Portugal has high rates of sedentary lifestyles (people not moving enough) and obesity, which make the problem worse.

The review also examined why current solutions haven’t fully worked. When doctors recommend vitamin D supplements to people who are deficient, it helps those individuals but doesn’t significantly reduce the overall problem in the population. This suggests that relying only on supplements for people who know they’re deficient isn’t enough to solve a widespread public health issue. The research points out that lifestyle changes like exercising outdoors and eating more vitamin D-rich foods are helpful but may not be sufficient given how sedentary and overweight many Portuguese people are

This finding aligns with research from other European countries showing high rates of vitamin D deficiency. However, Portugal appears to have a particularly severe problem, especially with cases of severe deficiency. The review builds on previous individual studies by confirming that this isn’t just a local issue in one city or region—it’s a widespread national problem. The conclusion that food fortification might work better than individual supplements is a newer recommendation that differs from older approaches that focused mainly on supplements

This review has several important limitations. First, it summarizes existing studies rather than collecting new data, so the quality depends on those previous studies. Second, different studies used different definitions of what counts as vitamin D deficiency, making it hard to compare results exactly. Third, the review doesn’t provide a precise number for how many Portuguese people are affected because the individual studies used different populations and methods. Finally, while the review suggests food fortification might be effective, there isn’t yet strong evidence from large studies showing exactly how well it would work in Portugal

The Bottom Line

Based on this research, here are evidence-based steps: (1) Spend 10-30 minutes outdoors several times per week when possible to boost natural vitamin D production—moderate confidence; (2) Eat more vitamin D-rich foods like fatty fish, egg yolks, and mushrooms—moderate confidence; (3) If you’re at risk (older adults, people with limited sun exposure, or those with digestive issues), ask your doctor about vitamin D supplements—moderate to high confidence; (4) Support policies that add vitamin D to common foods like milk and bread, as this may be the most effective population-wide solution—moderate confidence based on this review

Everyone in Portugal should be aware of this issue, but especially: older adults (who have weaker bones and need more vitamin D), people who spend most of their time indoors, people with digestive disorders that affect nutrient absorption, people with darker skin (which makes vitamin D production from sun harder), and anyone with bone health concerns. People living in other northern European countries or areas with limited sunlight should also pay attention. This is less critical for people who already get regular sun exposure and eat plenty of vitamin D-rich foods, though they may still benefit from awareness

If you start taking vitamin D supplements or eating more vitamin D-rich foods, you won’t notice immediate changes. Vitamin D works slowly in your body. It typically takes 2-3 months of consistent vitamin D intake to significantly raise blood levels. Benefits for bone health and overall wellness may take 6-12 months to become noticeable. If you’re severely deficient, your doctor may recommend higher doses, and improvements might be seen in 1-2 months

Want to Apply This Research?

  • Track daily outdoor time in minutes and vitamin D-rich foods consumed (servings of fatty fish, fortified milk, egg yolks, mushrooms). Set a weekly goal of at least 150 minutes outdoors and 3-4 servings of vitamin D foods
  • Use the app to set reminders for outdoor activity at specific times (morning or midday sun exposure is most effective). Log meals that contain vitamin D sources and track supplement intake if taking them. Create a weekly outdoor activity plan (walks, exercise, gardening) and monitor completion
  • Track trends over 3-month periods rather than daily fluctuations. Monitor energy levels, mood, and bone/muscle health alongside vitamin D behaviors. If using supplements, note any changes in how you feel. Consider sharing data with your doctor to inform discussions about vitamin D testing and supplementation needs

This review summarizes research about vitamin D deficiency in Portugal but is not medical advice. Vitamin D levels vary by individual, and what’s right for one person may not be right for another. If you’re concerned about your vitamin D levels, have bone health issues, or are considering supplements, consult with your doctor or healthcare provider. They can test your vitamin D levels and recommend an appropriate plan for your specific situation. This information is especially important if you’re pregnant, nursing, have digestive disorders, or take medications that affect nutrient absorption. Do not start or stop supplements without medical guidance.