Can Vitamin A Protect Against Cancer?
Vitamin A is a vitamin found in both animal products (like meats, milk, and eggs) and plant foods (like fruits and vegetables). It supports immune function, vision, and cell growth. Retinol is a specific type of vitamin A often used in skincare and cosmetics.
Most of the time, people get enough vitamin A through a balanced diet, and much of the research done so far focused on vitamin A from food, not supplements.
Key takeaways:
Some studies suggest that vitamin A may reduce the risk of breast cancer and other cancers, but the results are inconsistent and hard to draw conclusions from.
Research suggests that vitamin A may lower the risk of heart disease and other chronic illnesses.
The research on vitamin A
Research on vitamin A has mainly focused on diet — not supplements.
Breast cancer risk
Because of inconsistent results across studies, it’s hard to draw conclusions about vitamin A and breast cancer risk.
Some studies have suggested that low vitamin A intake and a low serum concentration of vitamin A (the amount of retinol in the blood) are risk factors for breast cancer, but the results have been mixed.
One meta-analysis found that dietary vitamin A, dietary vitamin E, and total vitamin E intake (from diet and supplements) reduced breast cancer risk. But when they looked at only cohort studies, meaning studies that had two groups — one that took the supplements and one that didn't — the results weren't significant.
Vitamin A and breast cancer treatment
Changes in vitamin A may also be a side effect of some breast cancer treatments. A study of 230 people with breast cancer found that serum levels of vitamin A dropped after radiation therapy. The study didn’t look at whether taking vitamin A supplements could address this deficiency. Instead, the researchers recommended “nutritional assistance” should be offered to people in treatment.
Skin cancer risk
Many people worry that retinol, a form of vitamin A used in topical anti-aging and acne products, may increase the risk of cancer. This may be because retinol speeds up our bodies’ skin cell turnover process and makes new skin more sensitive to sun exposure.
But research has shown that retinols do not increase the risk of skin cancer.
Whether or not you use topical retinol, avoiding prolonged sun exposure and wearing sunscreen significantly reduces your risk of skin cancer.
Other cancers and chronic diseases
Researchers have also looked at vitamin A’s effects on other chronic health conditions, including other types of cancers.
A meta-analysis found that eating foods rich in mixed carotenoids, which can be converted to vitamin A in the body, benefits cardiovascular and metabolic health.
Studies have also found that diets richer in micronutrients including vitamin A can improve immune functioning and outcomes in people with head and neck cancer and may reduce the risk of oral and pharyngeal cancers.
However, research has found that vitamin A supplements do not protect against non-small cell lung cancer or improve survival for melanoma patients and may actually increase the risk of prostate cancer.
More studies in people are needed, especially research focusing on people who take vitamin A supplements.
Safety, side effects, and drug interactions
A condition known as vitamin A toxicity (hypervitaminosis A) may occur with long-term intake of more than 9 mg daily, but there have been reports of toxicity with vitamin A doses as low as 6 mg daily, especially in people who regularly drink alcohol.
Symptoms of toxicity include nausea, vomiting, headache, blurred vision, muscular weakness, and elevated liver function tests.
Drug interactions
Warfarin: Large doses of vitamin A may increase the anticoagulant (blood thinning) effects of warfarin, which raises the risk of bleeding.
Orlistat: If you take the weight loss medication orlistat, it may reduce the amount of vitamin A your body can absorb.
Topical retinoids (tretinoin, acitretin, bexarotene): If you use topical retinoids, your doctor might recommend avoiding vitamin A supplements.
How to get more vitamin A in your diet
The best way to get this essential nutrient is to eat a balanced diet. Many animal- and plant-based foods contain vitamin A.
Animal sources of vitamin A include beef liver, cod liver oil, salmon, butter, and eggs.
Plant food sources of vitamin A include sweet potatoes, carrot, butternut squash, spinach, collard greens, cantaloupe, mango, and grapefruit.
Note: Ethanol (the active ingredient in alcoholic beverages) may affect how the liver breaks down vitamin A — if you drink alcohol, your body may not be absorbing vitamin A as well as it could. Alcohol also increases the risk of breast cancer.
