According to Gram Research analysis, a 2026 cross-sectional study of over 12,700 American adults found that people with the highest vitamin C levels were 1.91 times more likely to have melanoma, and high vitamin D levels also increased melanoma risk, particularly in men and people with diabetes. The findings suggest that excessive vitamin supplementation may not protect against skin cancer and could potentially increase risk, contradicting the common assumption that more vitamins are always beneficial.
A new study of over 12,000 American adults found something surprising: people with higher levels of vitamin D and vitamin C in their blood had a greater risk of developing melanoma, a serious type of skin cancer. Researchers analyzed health data from two time periods (2003-2006 and 2017-2018) to understand this connection. The findings suggest that more of these vitamins isn’t always better, especially when it comes to skin cancer prevention. The study recommends personalized approaches to vitamin supplementation rather than assuming higher levels are always protective.
Key Statistics
A 2026 cross-sectional analysis of 12,743 American adults found that those with the highest vitamin C levels had a 1.91 times greater risk of melanoma compared to those with lower levels, according to research reviewed by Gram.
In a study of over 12,000 U.S. adults, men with high serum vitamin D levels showed a 3.55 times increased melanoma risk, with even stronger associations observed in diabetic patients who had an 18.81 times higher risk.
A 2026 NHANES data analysis demonstrated that a predictive model combining vitamin D and C levels with other risk factors achieved 0.863 accuracy (excellent performance) in identifying melanoma cases among 12,615 participants.
Research from 2026 revealed a non-linear dose-response relationship between serum vitamin C levels and melanoma risk, indicating that the relationship between vitamin levels and skin cancer is more complex than previously understood.
The Quick Take
- What they studied: Whether the amount of vitamin D and vitamin C in people’s blood affects their chances of getting melanoma (a dangerous skin cancer)
- Who participated: Over 12,700 American adults from two national health surveys conducted between 2003-2006 and 2017-2018. The study included people of different ages, races, and backgrounds
- Key finding: Adults with the highest vitamin C levels were nearly twice as likely to have melanoma compared to those with lower levels. High vitamin D levels also increased melanoma risk, especially in men and people with diabetes
- What it means for you: Taking large amounts of vitamin D or C supplements may not protect against skin cancer and could potentially increase risk. Talk to your doctor before taking high-dose vitamin supplements, and focus on sun protection through sunscreen and protective clothing instead
The Research Details
Researchers looked at health information collected from thousands of American adults during two different time periods. They measured the amount of vitamin D and vitamin C in people’s blood and checked whether those people had been diagnosed with melanoma. They also collected information about other factors that might affect skin cancer risk, like sun exposure, smoking, weight, and family history.
The researchers used special statistical methods to understand the relationship between vitamin levels and melanoma risk. They looked at whether the connection was straight-line (more vitamin = more risk) or curved (where the risk changes differently at different vitamin levels). They also created a prediction model to see how well vitamin levels could predict who might get melanoma.
This research approach is important because it uses real-world health data from a large, representative sample of Americans rather than a small lab study. Cross-sectional studies like this can identify patterns and associations that might warrant further investigation. By examining data from two different time periods, the researchers could see if their findings were consistent over time, making the results more reliable.
The study included a large sample size (over 12,000 participants), which makes the findings more statistically reliable. The researchers controlled for many other factors that could affect melanoma risk, such as sun exposure history, smoking, and weight. However, because this is a cross-sectional study, it shows associations but cannot prove that high vitamin levels directly cause melanoma. The study’s findings were confirmed through sensitivity analyses, which test whether results hold up under different statistical approaches.
What the Results Show
The study found that adults with the highest levels of vitamin C in their blood were 1.91 times more likely to have melanoma compared to those with lower levels. This means if melanoma affected 10 people in a low-vitamin C group, it would affect about 19 people in the high-vitamin C group. High vitamin D levels (75 nmol/L or higher) were also associated with increased melanoma risk.
When researchers looked at specific groups, the effect was even stronger in men and people with diabetes. Men with high vitamin D levels had 3.55 times the melanoma risk, and diabetic patients with high vitamin D had an extremely elevated risk (18.81 times higher). These findings suggest that the relationship between these vitamins and melanoma risk may depend on a person’s sex and health status.
The researchers also created a prediction model combining vitamin levels with other risk factors. This model was very good at identifying who might have melanoma, with an accuracy score of 0.863 (on a scale where 1.0 is perfect). The relationship between vitamin levels and melanoma wasn’t simple and straight-line; instead, it showed complex patterns where risk increased at certain vitamin levels.
The study revealed that the connection between vitamin levels and melanoma risk wasn’t linear—meaning the risk didn’t increase steadily with higher vitamin levels. Instead, there were specific ranges where risk jumped significantly. This suggests that moderate vitamin levels might be safer than very high levels. The predictive model worked well when combining vitamin measurements with other known risk factors like sun exposure history and smoking status.
Previous research has generally suggested that vitamin D protects against cancer, but this study contradicts that assumption for melanoma specifically. The finding that high vitamin C levels increase melanoma risk is particularly surprising, as vitamin C is often promoted as an antioxidant that should protect skin health. This research suggests the relationship between vitamins and skin cancer is more complex than previously thought and may depend on individual factors like genetics, sun exposure, and overall health status.
This study shows associations but cannot prove that high vitamin levels cause melanoma. People with high vitamin levels might have other characteristics that increase melanoma risk. The study couldn’t determine whether people were taking supplements or getting vitamins from food. Vitamin levels were measured at only one point in time, so researchers couldn’t track how changes in vitamin levels affected melanoma risk over time. The study included mostly data from specific time periods, so results may not apply to all Americans or other populations.
The Bottom Line
Avoid taking high-dose vitamin D and vitamin C supplements without medical guidance. Instead, focus on proven melanoma prevention strategies: use broad-spectrum sunscreen (SPF 30+) daily, wear protective clothing, and limit sun exposure during peak hours (10 AM-4 PM). If you’re considering vitamin supplementation, discuss it with your doctor first, especially if you’re male or have diabetes. Get vitamin D from moderate sun exposure and food sources rather than high-dose supplements.
This research is especially important for men and people with diabetes, who showed the strongest associations between high vitamin levels and melanoma risk. Anyone considering taking vitamin D or C supplements should pay attention to these findings. People with a family history of melanoma or those who spend significant time in the sun should be particularly cautious about supplement use. However, people with documented vitamin deficiencies should still follow their doctor’s recommendations.
Melanoma develops over years or decades, so the protective benefits of changing your vitamin supplementation habits won’t be immediate. However, starting sun protection practices now can reduce your melanoma risk over time. If you stop taking high-dose supplements, you won’t see immediate changes, but you’re reducing a potential risk factor for future skin cancer development.
Frequently Asked Questions
Does vitamin D supplementation increase melanoma risk?
A 2026 study of 12,743 adults found that high serum vitamin D levels (≥75 nmol/L) were associated with increased melanoma risk, especially in men and people with diabetes. However, this shows association, not direct causation. Consult your doctor before starting or stopping vitamin D supplements.
Is it safe to take high-dose vitamin C supplements?
A recent analysis found that people with the highest vitamin C levels had 1.91 times greater melanoma risk. While this doesn’t prove supplements cause cancer, it suggests excessive vitamin C intake may not be protective. Get vitamin C from food sources like citrus fruits and vegetables instead.
What’s the best way to prevent melanoma?
Research shows proven melanoma prevention includes daily broad-spectrum sunscreen (SPF 30+), protective clothing, limiting sun exposure during peak hours (10 AM-4 PM), and avoiding high-dose vitamin supplements without medical guidance. These strategies are more effective than relying on vitamin supplementation.
Why do men have higher melanoma risk with high vitamin D?
A 2026 study found men with high vitamin D had 3.55 times greater melanoma risk compared to women. The reason isn’t fully understood, but it may involve differences in sun exposure patterns, skin type, or how men’s bodies process these vitamins. More research is needed.
Should I stop taking my vitamin supplements?
Don’t stop supplements without talking to your doctor first, especially if you have a documented deficiency. However, if you’re taking high-dose vitamin D or C supplements for general health, discuss with your doctor whether you actually need them or could get these nutrients from food instead.
Want to Apply This Research?
- Track daily sun exposure time (in minutes), sunscreen application (yes/no with SPF level), and any vitamin supplements taken (type and dose). Monitor skin changes monthly by taking photos of any moles or spots and noting changes in size, color, or shape
- Set daily reminders to apply sunscreen 15 minutes before going outside, even on cloudy days. Log your sun exposure and protective measures each day. If you’re currently taking vitamin D or C supplements, use the app to track your intake and set a reminder to discuss supplement use with your doctor at your next appointment
- Create a monthly skin check routine using the app’s photo feature to document any moles or spots. Track seasonal changes in sun exposure and adjust protection strategies accordingly. Monitor supplement intake if you continue taking vitamins, and review your sun protection habits quarterly to ensure consistency
This research shows associations between vitamin levels and melanoma risk but does not prove that vitamins directly cause skin cancer. Individual risk factors vary greatly. Do not start, stop, or change any vitamin supplements without consulting your healthcare provider. If you have concerns about melanoma risk or skin changes, see a dermatologist. This article is for educational purposes and should not replace professional medical advice. People with documented vitamin deficiencies should continue following their doctor’s recommendations.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.