Can You Get Vitamin D On A Cloudy Day?

Overview

A daily dose of at least 1,500 IU (international unit) of vitamin D is required to maintain our body functions.¹ Among all the ways we can get vitamin D, the sun remains our main source. A study by Anticancer Research showed that approximately 30 minutes of direct sunlight gave you an equivalent of between 10,000-20,000 IU of vitamin D.² 

Can you get vitamin D on a cloudy day?

If the question “Can I get vitamin D on a cloudy day?” lingers in your mind, the good news is that the answer is yes: you can still get vitamin D when it’s cloudy out. Even though you cannot see the sun through the grey clouds, it is still shining, and the ultraviolet (UV) rays needed to produce vitamin D in your body gets to the earth’s surface. When the sun shines, the sunlight emits UV rays that can not be seen with the naked eye because, compared to light, they have shorter wavelengths. Although the eyes do not see it, the skin definitely feels it. 

The sun releases two types of UV rays: UVA rays that cause premature skin ageing and UVB rays that cause visible burning of the skin (sunburn). Although UVA and UVB rays affect the skin in different ways and timelines, they both cause harm to the skin. To protect your skin from UV rays from the sun, using sunscreen with a sun protection factor (SPF) of at least 15 is highly recommended. Unprotected sun exposure leads to damage in the DNA of skin cells, causing changes or defects, which can lead to premature ageing and skin cancer. 

The two most common types of skin cancer are squamous cell cancer and basal cell cancer. These types of skin cancers typically occur on the face, head, neck, hands and arms because these body parts are the most exposed to UV rays.³ Most cases of melanoma, the deadliest kind of skin cancer, are caused by exposure to UV radiation. UV rays also cause damage to the eye, and hence we are advised not to look directly at the sun and to wear, on sunny days, sunshades that block out both UVA and UVB rays to prevent conditions such as eye cancer and cataracts.

The UV index is an indication of the intensity of the UV rays released when the sun shines. It can be found in newspapers, radio and other forms of media in many countries.⁴ UV index is usually higher between 10 a.m. and 4 p.m. because this is when the earth is fully exposed to the sun the most. UV rays are also more intense during the summertime, resulting in sunburns or sunspots on our skin.⁵ WHO published a guide on when it is safe to be out in the sun. For effective sun protection, sunscreen, hats, glasses and clothing are highly recommended.⁴

• A UV index of 0 to 2 means it is safe to enjoy the outdoors.
• A UV index of 3 to 7 during midday hours means it is safe to be outside with sun protection like sunscreen and a hat.
• For a UV index of 8 and above, sun protection is a must. You should use sunscreen on all exposed parts of your body.

Cancer Research UK recommend the ‘shadow rule’ to figure out when the sun is strong.⁵ It is quite simple and works anywhere in the world. To do this, look at the length of your shadow, if it is shorter than your height, it means that the UV rays from the sun are strong, and this is when you’re more likely to get sunburn and need to protect your skin, especially if you get easily sunburned or have fairer skin. Even though clouds may block out some UV light, more than 90% of UV radiation still passes through and causes sunburn. Even on a cloudy day, you should not skip the sunscreen and do not forget to reapply regularly.

Benefits of vitamin D

Vitamin D, also called the sunshine vitamin, is one of the most important nutrients our body needs. It helps our body better absorb calcium in the intestine. Calcium is required to maintain bone health, facilitate blood clotting and regulate our heartbeat. Vitamin D also helps to maintain sufficient calcium and phosphate levels in the blood to enable normal bone hardening and to prevent hypocalcemic tetany (involuntary spasms and cramps from muscle shrinkage). It is also needed by osteoblasts (bone formation) and osteoclasts (bone removal) for bone growth and bone repair. ⁶

Vitamin D helps to prevent rickets in children or osteomalacia in adults, a condition where the bones become soft and deformed. With the help of calcium, vitamin D also works to protect menopausal women and older adults from osteoporosis.⁷ Sufficient vitamin D levels in your body can decrease the risk of some autoimmune diseases, including multiple sclerosis (MS), type 1 diabetes, lupus and psoriasis.⁸

Having adequate levels of vitamin D is beneficial to people with MS. A relationship has been established between low levels of vitamin D and MS.⁹ When someone has MS, their immune system attacks myelin. This coating protects the nerve cells. Research suggests that the positive effects vitamin D has on the immune system can help improve the effects of MS, such as improving quality of life, lessening the severity and frequency of their symptoms, and lengthening the time to progress from relapsing-remitting MS to the secondary progressive phase. But the evidence is not conclusive. Although more research is needed to prove this, people with MS can take vitamin D supplements at the recommended dosage, but high doses can cause instability in calcium levels.¹⁰

Seasonal affective disorder 

Seasonal affective disorder (SAD), also known as winter depression,¹¹ is a type of depression that happens with seasons. The symptoms start in late fall and early winter time but go away during spring and summer. People who live away from the equator and those with a history of depression are at a higher risk of getting SAD. Younger people, as well as women, are more likely to develop SAD than older people and men.

SAD has been noticed in people with low levels of vitamin D due to little to no sun exposure and low oral intake of vitamin D through food or supplements. It is, however, unclear if vitamin D supplementation can help to relieve the symptoms of SAD.¹² The types of treatment for SAD that have been studied include light therapy, dietary supplements like vitamin D, antidepressants and talking therapy.

How much vitamin D do you need?

The Recommended Dietary Allowance (RDA) of vitamin D is 400-800 IU or 10 mg.¹³ You have sufficient vitamin D when your vitamin D level is 30 to 32 ng/mL. To maintain a 30 to 32 ng/mL level, you need approximately 2,200 to 3,000 IU/d of vitamin D from all sources, including ultraviolet light exposure, food and supplements.⁹ 

Potential risks from vitamin D

Vitamin D levels above 100 ng/mL can lead to a buildup of calcium in the blood caused by vitamin D toxicity. This toxicity primarily occurs with supplements and not with sun exposure.⁹ The journal¹⁴ lists the symptoms as weakness, anorexia, dry mucus membrane, frequent urination, nausea, vomiting and in severe cases, stupor and coma. If not treated by discontinuing supplements, vitamin D toxicity may cause bone pain or affect kidney functions due to the formation of calcium stones or kidney failure.

Vitamin D may also interact negatively with some medications such as steroids, orlistat (a weight loss drug) and thiazide diuretics.⁶ People who are taking these and any other type of medication should discuss their health status with their healthcare provider for safe vitamin D intake.

Vitamin D supplements

The amount of vitamin D you require is determined by your age, risk factors and how low your vitamin D levels are.¹⁵ Your healthcare provider may prescribe oral vitamin D supplements in the form of vitamin D₃ or vitamin D₂.¹⁶ There is a wide range of options for vitamin D supplements available in drug stores which include liquids, drops, chewable tablets and capsules. Most vitamin D supplements contain approximately 400 IU of vitamin D; however, some multivitamins boast of between 800-1000 IU. In rare cases, vitamin D may be given through the skin via injections, like in people with liver disease, gastrectomy or whose intestines are not able to absorb vitamin D.

You may also supplement with some vitamin D-rich foods such as fish and shellfish, mushroom, cheese, sardines, beef liver, salmon, herring, tuna, egg yolk, vitamin D-fortified low-fat milk, yoghurt, some orange juices, and certain oatmeals and cereals which provide between 20-100 IU in a serving. Cod liver oil, being a good source of vitamin D, contains 450 IU of vitamin D as well as vitamin A and omega-3 fatty acids (in a teaspoonful). Caution should be taken when supplementing with cod liver oil because it may cause vitamin A toxicity in large doses.¹⁷ People who have a higher risk of vitamin D deficiency, including pregnant and breastfeeding women, are recommended to make sure they get their daily dose of vitamin D.

Summary

Even on a cloudy day when the clouds are grey, and the sun is not shining as intensely as you think it should for you to get your daily dose of vitamin D, you can still get as much vitamin D as you need. Care should be taken to wear sun protection even on cloudy days because even when we do not see the sun shining, the UV rays from the sun can cause damage to our skin while giving out vitamin D.