Gram Research analysis shows that adult-onset vitamin A deficiency reshapes gut bacteria differently in males and females, with female rats developing deficiency twice as fast as males and showing unique bacterial changes. Both sexes experienced weakened gut barriers and anxiety-like behavior, but the specific bacterial alterations were sex-specific, suggesting that vitamin A deficiency affects men and women differently at the microbial level.
A new study shows that when adults don’t get enough vitamin A, it changes the bacteria living in their gut and affects their body in different ways depending on whether they’re male or female. Researchers fed adult rats either normal diets with vitamin A or diets without it for 20 weeks. They found that females developed vitamin A deficiency faster than males, and their gut bacteria changed more dramatically. Both sexes showed signs of anxiety and weakened gut barriers, but the bacterial changes were unique to each sex. This research helps us understand how vitamin A deficiency affects adults differently than children.
Key Statistics
A 2026 research article published in The Journal of Nutrition found that female rats developed vitamin A deficiency in 12 weeks with serum levels dropping from 1.1 to 0.5 micromoles per liter, while males took 16 weeks to reach the same deficiency threshold.
In the same 24-rat study, female rats showed a significant increase in the Bacillota to Bacteroidota bacterial ratio (from 4.18 to 7.0) when vitamin A deficient, while males did not show this change, indicating sex-specific gut microbiome responses.
Both male and female rats in the vitamin A deficiency group developed weakened gut barriers and increased immune gene expression after 20 weeks, demonstrating shared systemic effects despite sex-specific bacterial changes.
Female rats displayed anxiety-like behavior by week 12 of vitamin A deficiency, while male rats did not show these behavioral changes, suggesting sex-specific effects on the nervous system.
The Quick Take
- What they studied: Whether vitamin A deficiency in adult rats causes different changes in gut bacteria and body functions between males and females
- Who participated: 24 adult Wistar rats (a common laboratory rat breed), split equally between males and females, aged 9 to 10 weeks at the start. Half received normal vitamin A in their food, and half received none for 20 weeks.
- Key finding: Female rats developed vitamin A deficiency twice as fast as males, and their gut bacteria changed more noticeably. Both sexes showed anxiety-like behavior and weakened gut barriers, but the specific bacterial changes differed between males and females.
- What it means for you: This research suggests that vitamin A deficiency affects men and women differently, particularly in how it reshapes gut bacteria. While the findings are from rats, they hint that adults of different sexes may need to pay attention to vitamin A intake for gut health and mental wellbeing. More human studies are needed before making dietary changes.
The Research Details
Researchers took 24 adult rats and divided them into four groups: males eating normal food with vitamin A, males eating food without vitamin A, females eating normal food with vitamin A, and females eating food without vitamin A. Each group had 6 rats. For 20 weeks, the researchers monitored vitamin A levels in the rats’ blood every 4 weeks. At weeks 12 and 18, they tested the rats’ behavior, looking for signs of anxiety. After 20 weeks, they collected samples from the rats’ blood, gut, liver, brain, and fat tissue to measure vitamin A levels, examine the bacteria living in their guts, and look for changes in how their bodies were working.
The researchers used standard statistical tests to compare the groups, making sure to account for the possibility of false findings when testing many different measurements. This approach allowed them to see not just whether vitamin A deficiency happened, but how it affected different body systems and whether those effects differed between males and females.
Most previous research on vitamin A deficiency focused on children and young animals during their growth and development. This study is important because it specifically looks at what happens when adults develop vitamin A deficiency, which is less well understood. By studying both males and females separately, the researchers could identify sex-specific differences that might be missed if they only looked at one sex. Understanding these differences is crucial for developing better health recommendations for men and women.
This study was published in The Journal of Nutrition, a respected peer-reviewed scientific journal. The researchers used a controlled experimental design where they carefully controlled diet and monitored outcomes over a long period (20 weeks). They collected multiple types of samples and measured many different outcomes, giving a comprehensive picture. However, this was an animal study using rats, so the findings may not directly apply to humans. The sample size was relatively small (24 rats total), which is typical for laboratory studies but means results should be confirmed in larger studies.
What the Results Show
Female rats reached vitamin A deficiency much faster than males. At week 12, female rats had vitamin A levels drop to half of normal (from 1.1 to 0.5 micromoles per liter), while male rats didn’t reach deficiency until week 16. Interestingly, the female rats didn’t lose weight or eat less food despite this rapid deficiency, suggesting their bodies were depleting vitamin A stores quickly.
The gut bacteria changed differently in males and females. In female rats, a key ratio of bacteria called Bacillota to Bacteroidota increased significantly (from 4.18 to 7.0), but this change didn’t happen in males. However, both sexes showed changes in their viruses (tiny organisms that infect bacteria), though the patterns were different. These bacterial changes are important because gut bacteria influence digestion, immunity, and even mood.
Behavior and anxiety showed sex-specific patterns. By week 12, female rats displayed anxiety-like behaviors in tests, but male rats didn’t show these signs until much later, if at all. This suggests that vitamin A deficiency may affect the nervous system differently in females. Both sexes, however, showed shared problems: their gut barriers weakened (meaning the lining of their intestines became more permeable), their immune systems became more active, and their fat cells grew larger.
The researchers found that vitamin A deficiency triggered increased expression of immune genes in both sexes, meaning the body was mounting an immune response. Fat tissue also showed changes, with fat cells becoming enlarged in both males and females. These systemic (whole-body) responses suggest that vitamin A deficiency affects multiple body systems beyond just the gut bacteria. The weakening of the gut barrier is particularly significant because a compromised gut barrier can allow harmful substances to enter the bloodstream, potentially triggering inflammation and other health problems.
Previous research has shown that vitamin A is essential for maintaining a healthy gut barrier and supporting the immune system, but most studies focused on young animals during development. This study extends that knowledge by showing that adult-onset vitamin A deficiency also damages the gut barrier and triggers immune responses. The finding that females develop deficiency faster than males is novel and suggests that sex hormones may influence how quickly the body depletes vitamin A stores. The sex-specific changes in gut bacteria add to growing evidence that males and females respond differently to nutritional deficiencies.
This study used laboratory rats, not humans, so the findings may not directly translate to human health. The sample size was small (only 6 rats per group), which limits how confident we can be in the results. The study lasted 20 weeks, which is a significant portion of a rat’s lifespan but may not reflect what happens over years in humans. The researchers didn’t measure all possible vitamin A metabolites or examine all aspects of immune function, so some effects may have been missed. Additionally, this was a controlled laboratory setting where rats ate only the assigned diet, which doesn’t reflect real-world eating patterns where people consume varied foods.
The Bottom Line
Based on this research, adults should ensure adequate vitamin A intake through diet or supplementation, particularly if they have risk factors for deficiency. Good sources include liver, sweet potatoes, carrots, spinach, and kale. However, this study was conducted in rats, so these findings should not yet be considered definitive for humans. Anyone concerned about vitamin A deficiency should consult a healthcare provider. The research suggests that males and females may respond differently to deficiency, so personalized approaches may be beneficial.
This research is most relevant to people at risk for vitamin A deficiency, including those with malabsorption disorders, severe dietary restrictions, or limited access to nutrient-rich foods. It may also interest healthcare providers treating patients with anxiety, gut problems, or immune issues. Women may want to pay particular attention given the faster development of deficiency in female rats. However, this is preliminary animal research, so it should inform further investigation rather than immediate behavior change in humans.
In the rat study, vitamin A deficiency developed over 12 to 16 weeks, with behavioral changes appearing by week 12 in females. In humans, the timeline would likely be different depending on initial vitamin A stores, diet, and individual factors. Improvements from correcting a deficiency typically take weeks to months, depending on severity and how the deficiency is addressed.
Frequently Asked Questions
Does vitamin A deficiency affect men and women differently?
According to a 2026 rat study, yes. Female rats developed vitamin A deficiency twice as fast as males and showed unique changes in gut bacteria. Both sexes experienced anxiety and weakened gut barriers, but the bacterial shifts were sex-specific, suggesting biological differences in how deficiency develops.
What happens to your gut bacteria when you don’t get enough vitamin A?
Research shows vitamin A deficiency changes the balance of gut bacteria, though the specific changes differ between sexes. In female rats, the ratio of Bacillota to Bacteroidota bacteria increased significantly. These bacterial changes can affect digestion, immunity, and potentially mood and behavior.
Can vitamin A deficiency cause anxiety?
In this rat study, female rats developed anxiety-like behavior within 12 weeks of vitamin A deficiency, while males did not. This suggests vitamin A may play a role in nervous system function, though human studies are needed to confirm whether deficiency causes anxiety in people.
How long does it take to develop vitamin A deficiency as an adult?
In the rat study, deficiency developed in 12 to 16 weeks depending on sex. In humans, the timeline would vary based on initial vitamin A stores, diet quality, and individual absorption. Most people have stored vitamin A in their liver that can last months.
What are the best food sources of vitamin A?
Liver, sweet potatoes, carrots, spinach, kale, and other orange and dark green vegetables are excellent sources. Animal sources like liver provide retinol, the most readily absorbed form. Plant sources provide carotenoids, which the body converts to vitamin A.
Want to Apply This Research?
- Track daily vitamin A intake in micrograms (target 700 micrograms for adult women, 900 for adult men) alongside mood and digestive symptoms. Note any anxiety, bloating, or digestive changes to identify patterns.
- Add one vitamin A-rich food to your daily diet: a small serving of sweet potato, carrots, spinach, or liver. Log it in the app with your mood and energy level to track correlations over time.
- Over 8 to 12 weeks, monitor vitamin A intake, anxiety levels, and digestive health. If symptoms improve, maintain the habit. If not, consider consulting a healthcare provider about potential absorption issues or other causes.
This article summarizes research conducted in laboratory rats and should not be interpreted as medical advice for humans. Vitamin A deficiency is a serious condition that requires professional diagnosis and treatment. If you suspect you have a vitamin A deficiency or are experiencing anxiety, digestive issues, or other health concerns, consult a qualified healthcare provider. Do not attempt to self-diagnose or self-treat based on this research. Vitamin A supplements can be toxic in high doses, so any supplementation should be done under medical supervision. This research is preliminary and findings from animal studies do not always apply directly to humans.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.