Vegetable oils against UV rays from the sun, good or bad idea?

Whilst the sun is essential to our well-being due to its vital contribution of vitamin D, it is also known to cause several damages to the epidermis: skin conditions, sunburn, photoaging (sun spots, wrinkles, skin dryness...), skin cancer, etc. It has been demonstrated that the use of sunscreens significantly reduces the risk of many of these conditions. However, with the controversy surrounding sun filters, suggesting they could permeate into the body through the skin, their use raises many concerns.

To mitigate the risks associated with this absorption, vegetable oils have emerged as a viable alternative in the field of "natural" health due to their purported photoprotective benefits. They have been reported to contain UV filters and would thus contribute to protecting the skin from the sun. Indeed, certain vegetable oils have demonstrated their absorptive power within the UVA and UVB ranges, thereby indicating potential for use as broad-spectrum UV protectors.

Several studies have been conducted to assess the actual UV protection value provided by vegetable oils. However, opinions vary with different results. An initial study conducted in 2000 revealed that raspberry seed oil would have a sun protection factor for UVB (SPF) and for UVA (PFA) of 28 ± 50 and 6.75 ± 7.5, respectively. This broad-spectrum UV protection would even be comparable to that of a sunscreen containing titanium dioxide. It would thus protect the skin against damage induced both by UVA (320 ± 400 nm) and UVB (290 ± 320 nm) due to their diffusing and absorbing capabilities.

In 2016, another study demonstrated that the SPF values for other vegetable oils range between 2 and 8, determined by the UV spectrophotometric method in the 290 - 320 nm range. As a result, they obtain the following values:

According to MARTINIAKOVA, in a study conducted in 2021, the SPF values of vegetable oils would be even lower than those reported so far, even for raspberry oil. The protection index against UVA and UVB of 14 virgin vegetable oils alongside actual sunscreens for reference was measured, using conventional SPF tests in vitro and in vivo . The in vivo tests were carried out in the accredited laboratory of the National Institute of Public Health in Prague using the ISO 24444 method, an international standard for SPF testing.

Indeed, to assert that a skincare product provides protection from UV-related damage, European regulations require a guarantee of a minimum level of protection. The SPF must be measured using standardised methods that are internationally recognised. The majority of the tested vegetable oils would thus have values between 2.5 and 4.5 in vivo, and between 0.01 and 0.6 in vitro, with the exception of tamanu oil which has a value of around 11, likely due to its high proportion of calophyllolides.

Reminder : Based on regulated tests, an SPF 2 can allow approximately 50% of UVB rays to pass through, an SPF 15 allows 7%, an SPF 20 allows 5%, an SPF 30 allows 3%, an SPF 50 allows 2%, and an SPF 100 only allows 1% to pass through.

Vegetable Oils: Are they effective in protecting the skin from the sun?

Whilst these vegetable oils have indeed recorded an SPF, none appear to be high enough to provide adequate and useful protection against harmful UV rays on their own, making claims that vegetable oils can be used as sunscreen incorrect and harmful. The risk of burning is thus very high, especially when considering people's application habits.

However, the antioxidant and restorative effects of plant oils may play a role in supporting the skin's ability to reduce the harmful impacts of UV rays. Moreover, all these studies have evaluated the level of protection of different plant oils against UVB and not UVA rays, which penetrate deeper into the skin and are responsible for premature ageing and, more seriously, certain types of skin cancer, even though they account for 95% of the UV rays that reach the skin.

It is globally recommended to favour high SPF of 30 or more to help prevent cellular damage caused by the sun and reduce the risk of skin cancer in sensitive populations. Therefore, the only way to preserve one's sun capital is to apply a daily sun care product with higher protection combining mineral and organic filters, in addition to limiting sun exposure, seeking shade and wearing covering clothing.

Note : Thanks to its high content of antioxidant flavonoids, which make it a natural sun protector (an in vivo SPF of around 20, evaluated and proven by the Hélioscience Laboratory), we have incorporated karanja oil (INCI: Pongamia Glabra Seed Oil) into the composition of our face sun creams , in addition to conventional UV filters, to benefit from the photoprotective properties of both.