Scientists discovered a group of molecules in plants that shields them from sun damage. 

Biochemical tests conducted showed that plants produce special molecules and send them to the outer layer of the leaf epidermis to protect themselves. These molecules, called sinapate esters (Sinapic acid or hydroxycinnamic acid), appear to block ultraviolet-B radiation at every wavelength across the UVB spectrum from penetrating deeper into leaves where it might otherwise disrupt a plant's normal development.

Metabolites are increasingly drawing attention due to their bioactivities which include antioxidant, anti-microbial, anti-inflammatory, anti-cancer, anti-anxiety and the aforementioned UV filtering activities.

Sinapic acid is present in fruits, vegetables, cereal grains, oilseed crops, and some spices and medicinal plants.

Oxidative stress is a physiological state linked to the development of many diseases, including cancer, cardiovascular diseases, stroke, and neurodegenerative disorders such as Alzheimer's and Parkinson's disease. It is generally accepted that the consumption of plant foods is associated with a lower risk of development of oxidative stress-related diseases.

Although isolated plant compounds have a high potential in protection of the skin, whole herbs extracts show better potential as radioprotective agents due to their complex composition. Many studies show that for example green and black tea (polyphenols) ameliorate adverse skin reactions following UV exposure.

Topical application as well as ingesting organic Aloe Vera gel accelerates wound healing and assist in new cell growth.

Spectrophotometer testing indicates that a concentrated extract of Krameria triandra (a plant species in the genus Krameria, in Peru - a slow-growing shrub that nurtures in semi-arid areas of the Andean region) absorbs 25 to 30% of the amount of UV radiation typically absorbed by octyl methoxycinnamate (AKA Octinoxate – the highly toxic chemical found in many sunscreens).

Sesame oil (made from Sesamum indicum, also called benne) resists 30% of UV rays, while coconut, peanut, olive, and cottonseed oils block out about 20% of UV radiation.

Conclusion: It is never good to ‘bake’ in the sun all day. However, natural vitamin D is regulating the absorption of calcium and phosphorus and facilitating normal immune system function. Getting enough vitamin D is important for normal growth and development of bones and teeth, as well as increased resistance against many diseases, including viral infections.

While the U.S. National Academy of Medicine considers 600–800 IU of daily vitamin D to be sufficient, the U.S. Endocrine Society recommends 1,500–2,000 IU per day. When your skin is exposed to sunlight, it makes vitamin D from cholesterol natural. The sun's ultraviolet B (UVB) rays hit cholesterol in the skin cells, providing the energy for vitamin D synthesis to occur.

To a certain extent, you can ‘eat your natural sunscreen’ by consuming your fruits (especially organic strawberries and grapes), seeds and vegetables or apply whole herbs extracts, In general, you should avoid all-day full sun exposure, as the radiation of the sun will cause oxidative damage to your skin.