Seed Oils and Sunburn: What the Studies Actually Show

No human study has tested whether cutting seed oils makes you burn less. That is the honest answer to the search.

What exists is mouse work on dietary fat and UV damage, one human trial on a low-fat diet and sun-damaged skin, and several small human trials on vitamin E, vitamin C and aspirin. I stopped burning after I took PUFA out of my diet. Below is what backs that up and what does not.

Do seed oils cause sunburn?

The idea is simple. Seed oils are mostly linoleic acid, a polyunsaturated fat (PUFA). The fat you eat ends up in your skin. UV light makes free radicals, and polyunsaturated fats are the easiest fats for them to damage.

Here is what has been tested.

• Mice, UV and the type of fat. Hairless mice ate diets with 20% fat, made of sunflower oil and hydrogenated saturated fat in different ratios, while they got 10 weeks of UV. The more polyunsaturated fat in the mix, the worse the outcome: more tumours, more of them turning into carcinoma, and shorter survival. After a single strong UV exposure, immune suppression in the skin was 57% on the polyunsaturated diet and almost absent on the saturated one. (Reeve 1996)
• Mice, linoleic acid and redness. In another hairless mouse study, a diet rich in linoleic acid led to a higher UVB redness score and more prostaglandin E2 in the skin than a diet rich in alpha-linolenic acid, the omega-3 in flaxseed oil. (Takemura 2002)
• People, a low-fat diet and sun damage. 76 patients with a history of skin cancer were randomized to their usual diet, about 40% of calories from fat, or a diet with 20% fat. Over 24 months the usual-diet group developed 10 new actinic keratoses per patient. The low-fat group developed 3. (Black 1994)

Notice what is missing. The mouse studies measured tumours and immune reactions more than sunburn. The human trial cut all fat, not seed oils, and counted sun-damage spots, not burns.

Seed oils and inflammation

A sunburn is inflammation, so this search belongs here. In blood tests the case is weak. A meta-analysis of 30 randomized trials with 1,377 people found that eating more linoleic acid did not significantly change TNF, interleukin-6 or C-reactive protein. The authors add that in the trials with the largest increases in linoleic acid, CRP may have gone up. (Su 2017)

Blood markers are not skin. But the trials do not show that seed oils inflame you.

Vitamin E, vitamin C and aspirin before sun

This part has real human data, and it is mixed.

• Vitamin E plus C worked in a small trial. In a double-blind trial with 10 subjects, the vitamin group took 2 g of vitamin C with 1,000 IU of natural vitamin E for 8 days. The UV dose needed to cause redness rose from 80 to 96.5 mJ/cm2 on the vitamins and fell from 80 to 68.5 on placebo. (Eberlein-König 1998)
• A larger effect over 50 days. With 2 g of vitamin E and 3 g of vitamin C a day, the redness threshold rose from 103 to 183 mJ/cm2. Either vitamin alone did nothing significant. (Fuchs 1998)
• Vitamin E alone did little. In 45 volunteers, 1,200 IU a day for a week moved the threshold from 60 to 65 mJ/cm2. With vitamin C added it went from 50 to 70. (Mireles-Rocha 2002)
• Or nothing. 8 people took 400 IU a day for 8 weeks. Vitamin E in their skin went up and one marker of fat oxidation went down, but sensitivity to UV did not change. (McArdle 2004)
• On the skin. A solution of 15% vitamin C and 1% vitamin E, applied for 4 days, gave about 4-fold protection against redness and sunburn cells. That was pig skin, not human. (Lin 2003)
• Aspirin. In a double-blind crossover trial in healthy young women with fair skin, 250 mg of aspirin suppressed UVB and UVA redness. So did an antihistamine and indomethacin. (Grundmann 2001)

Those are the doses used in the studies. In my view even the best result is a fraction of what clothing or shade does.

Seed oils vs beef tallow

Nobody has run a sunburn trial of tallow against seed oil, in the kitchen or on the skin. The difference is in the fat itself. Beef tallow is about 2 to 3% linoleic acid. Sunflower and safflower oil are about 65 to 75%. The full table is in PUFA foods to avoid.

The mouse study above is the closest thing to a test, and its saturated fat was hydrogenated cottonseed oil, not tallow.

Why are seed oils bad for skin? The honest part

Here is the evidence against my position.

• Fish oil is PUFA, and it reduced sunburn. 42 healthy people took 4 g a day of EPA or oleic acid for 3 months. On EPA the redness threshold rose from 36 to 49 mJ/cm2. (Rhodes 2003) In 13 light-sensitive patients, 3 months of fish oil raised it from 19.8 to 33.8 mJ/cm2. (Rhodes 1995) The most unsaturated fats there are made skin harder to burn. That does not fit a simple story that more double bonds means more burning.
• Linoleic acid looked good for skin in a survey. Among 4,025 American women aged 40 to 74, higher linoleic acid intake was associated with less dry skin and less skin thinning. Higher total fat intake was associated with more wrinkles. This is an association from a single day of diet recall. (Cosgrove 2007)
• The studies in my favour are in mice, or they cut total fat, not seed oils.
• My own result is one person. I also changed the rest of my diet and my time in the sun in the same years, and skin adapts to regular sun.

So do not skip sun protection because of a diet. Shade, clothing, and sunscreen when you will be out longer than your skin can take, still apply. Do not let a child burn to test a theory.

What I do

I used to turn pink within an hour and I blamed my genes. Since I stopped eating PUFA I can spend hours outside without burning. That is my experience, not a study result.

• I do not eat seed oils. I cook with butter, coconut oil and tallow.
• I take a mixed-tocopherol vitamin E and I also put it on my skin.
• I sometimes take aspirin before a long day in the sun. Aspirin has real risks. Read aspirin benefits and risks first.
• I build up sun time slowly, and I get out of the sun before I burn.

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What Ray Peat wrote about unsaturated fat and the skin is in Ray Peat on PUFA. How I use vitamin E on skin is in vitamin E oil for skin.

Quick answers

Do seed oils cause sunburn?

It has not been tested in people. In hairless mice, diets higher in polyunsaturated fat gave worse UV damage, and in one human trial a low-fat diet reduced new sun-damage spots. No human trial has removed seed oils and measured sunburn.

Is there a link between seed oils and sunburn?

The link is a hypothesis built on mouse studies and on the fact that polyunsaturated fats oxidize easily. Human trials of fish oil, which is also polyunsaturated, found less sunburn, not more, so the picture is not simple.

Do seed oils cause inflammation?

A meta-analysis of 30 randomized trials found that eating more linoleic acid did not significantly change blood markers of inflammation such as TNF, interleukin-6 and CRP.

Is beef tallow better than seed oils for sunburn?

No trial has compared them. Beef tallow contains about 2 to 3% linoleic acid and sunflower oil about 65 to 75%, so tallow adds far less polyunsaturated fat to the diet.

Does vitamin E prevent sunburn?

Slightly, and mainly together with vitamin C. In small trials the combination raised the UV dose needed to cause redness, while vitamin E alone had little or no effect. It does not replace shade, clothing or sunscreen.

Does aspirin help with sunburn?

In one double-blind crossover trial in healthy young women, 250 mg of aspirin reduced UV-induced redness. Aspirin has bleeding and stomach risks and is not a sun protection product.