A good part of the articles I write are based on questions and suggestions by CaL members, and Vitamin D is a fairly popular subject in the whole wellness spectrum. Given that it is estimated that over a billion people worldwide are deficient in Vitamin D , it really ought to be a subject of nutritional concern.
Add to that, it is estimated that between 70 to 100% of the Indian population is deficient in Vitamin D. This is attributed to the fact that our dairy products are rarely fortified and exposure to the sun is mostly shunned. Consequently, this deficiency has been observed across urban and rural settings, irrespective of geography and socioeconomic strata. 
To begin with, foods with significant amounts of naturally occurring Vitamin D are quite limited . Folks who eat non-vegetarian food shouldn’t have much of a problem getting their doses of Vitamin D, given that oily fish (e.g. Salmon) and certain fish based oils (e.g. cod liver oil) are rich in this nutrient . Vegetarians who only avoid animal flesh and include milk and/or eggs in their diet won’t have it easy, but will be able to manage. Those of us however who only eat plant based foods will likely face Vitamin D deficiencies. This article is primarily for those of us with entirely plant based diets.
Vitamin D – Basics
Sources: We can get our Vitamin D from three sources – sun exposure, food and supplements. a fat soluble vitamin (meaning we can’t pee out any excess, so overdosing is more possible than with water soluble vitamins)
How it helps: Vitamin D is helpful for the intestinal absorption of Calcium in addition to promoting bone health. When combined with Calcium, Vitamin D can be helpful against Osteoporosis. Vitamin D also plays roles in cell growth, immune function and in reduction of inflammation among others.
Deficiency & Overdose: Vitamin D deficiency causes Rickets in children, Osteomalacia in adults and is also associated with the onset of Osteoporosis and indicated in the growth of certain cancers. Conversely, Vitamin D toxicity (overdose) can cause symptoms such as anorexia, weight loss, polyuria, and heart arrhythmia.  Vitamin D deficiency may also contribute to the very high prevalence of conditions such as rickets, osteoporosis, cardiovascular diseases, diabetes, cancer and infections such as tuberculosis in India. 
Who is at risk of deficiency: Breast-fed infants whose mothers have low Vitamin D levels, those with lactose intolerance and/or milk allergies, older adults, people with limited sun exposure, dark skinned people, those with inflammatory bowel disease and other similar conditions (which impair absorption), the obese or those who have undergone gastric bypass surgery. Additionally, those following vegan (pure plant based foods) or ovo-vegetarian (eggs and plant based foods only, no dairy or meats) are also found to be at risk of Vitamin D deficiency. 
Drug Interactions: Corticosteroid medications can cause issues with Vitamin D metabolism. Some cholesterol lowering, weight loss and epilepsy medications also interfere with Vitamin D metabolism. 
Vitamin D, RDA/AI
Age Male Female Pregnancy Lactation
0 - 12 months* 400 IU
1 - 13 years 600 IU
14 - 18 years 600 IU
19 - 50 years 600 IU
51 - 70 years 600 IU
> 70 years 800 IU
Plant-based Sources of Vitamin D
I went through a list of over 2,000 foods containing Vitamin D and found virtually none that were plant based and contained significant quantities of Vitamin D. Of those that do, very few are available in India. The only plant food I could find, of which we wouldn’t have to eat a bucket full to get anywhere, is white mushrooms, exposed to ultraviolet light. Research has indicated that pulsed ultraviolet light massively increases levels of Vitamin D in mushrooms . I’m not sure if this practice is prevalent in India, but consumer pressure is likely to get mushroom farmers to begin doing so, most of whom are in the unorganised sector.
To give you an example, from my list (which may not be reflective of all plant based foods available in India), the only item I could find that contained any Vitamin D at all and was available in India, were white mushrooms, cooked by microwaving. These contain 0.3 micro-grams (mcg) of Vitamin D, per 100 grams of mushrooms. We need about 15 mcg per day, which amounts to eating about 5 kilos of mushrooms a day. I’m sure we can agree that may be a little too much for most of us.
The only plant based food with significant amounts of Vitamin D is to my mind, mushrooms treated with UV light. 
Vitamin D from the Sun
Our skin absorbs UV B radiation, which is then ultimately converted to vitamin D3. The sun must however be directly overhead, without which the amount of vitamin D3 produced will be very little if any. Your skin tone too affects D3 production; the fairer the skin the greater the UV absorption and the greater the production. Additionally, factors like air pollution, use of sunscreen, filters such as glass or plastic, season, age and time of day also effect this method of Vitamin D production. 
Vegetarian Friendly Vitamin D Fortification
Vegetarians who do not consume animal derived products including meat and dairy, and are unable to boost their vitamin D levels through diet or the sun could consider fortified products such as juices and cereals. Quite a few of these are fortified with added vitamins and minerals, vitamin D being one of them. For instance, Kellogg’s All Bran Original will get us 4.3 mcg of Vitamin D, per 100 grams of product consumed. Read the nutrition label carefully though to check how much of the product you’ll have to consume to get you daily required dose. 
Dairy Sources of Vitamin D
If you include dairy products in your diet, there are quite a few available options, though you’ll have to keep the caloric content in mind. The most effective dairy source of Vitamin D turns out to be Buttermilk, with every 100 grams delivering 1.3 mcg of Vitamin D, which compares favourably against its caloric content. There are more options, both fortified and regular though the regular ones don’t have as much as we’d like. Whole milk for instance delivers 0.1 mcg per 100 grams of product. On the other hand fortified whole milk has 1.3 mcg per 100 grams. Remember to read the nutrition label carefully. 
Animal Sources of Vitamin D
The first entry to be considered here is egg, based on our socio-dietary structures. A 100 grams of fresh, whole egg delivers 2 mcg of Vitamin D, which isn’t great, but the most effective so far. Chicken doesn’t have much, delivering about 0.2 mcg per 100 grams, pork spareribs gets us about 2.6 mcg / 100gm, which is the most for pork, beef liver 1.2 mcg / 100gm but fish, now that’s another story. Salmon will give you your entire quota of vitamin D in a single serving! If Salmon is unavailable, cod liver oil capsules are your next bet with 250 mcg / 100gm, of which we will consume tiny amounts in the form of individual capsules. In fact, cod liver oil capsules are likely the best bet for anyone wanting to maintain consistent levels of vitamin D and are alright with animal sources. 
- Vitamin D—Effects on Skeletal and Extraskeletal Health and the Need for Supplementation
- Vitamin D Fact Sheet for Health Professionals
- Vitamin D Deficiency in India: Prevalence, Causalities and Interventions
- Concentration of vitamin D2 in white button mushrooms (Agaricus bisporus) exposed to pulsed UV light
- USDA Nutritional Database, SR28
- Sunlight and Vitamin D – A global perspective for health