Fatty fish such as swordfish or salmon have the highest concentration of IUs per serving, with six ounces of either cooked swordfish or salmon providing one’s required daily dose. However, these fish are often prohibitively expensive, and may be tainted with mercury or other contaminants.
A large egg would contain 41 IU of vitamin D, meaning that an individual would need to consume 40 eggs in order to get their recommended daily dose.
An individual would need to consume 57 ounces of cooked beef liver daily to receive the 800 IU required dosage of Vitamin D. To put it in perspective, an average serving of beef liver is just 3 ounces.
Store-bought pasteurised milk, often enriched with Vitamin D, contains 114-115 IU per serving, meaning 800 IU is equivalent to 8 glasses a day. Yogurt, margarine, and cheese have even smaller IU concentrations, meaning that increasingly unrealistic servings would be needed to meet the daily dosage.
Ready-to-eat Cereal is often fortified with Vitamin D. However, at just 40 IU per cup, the dosages is extremely small. To get the 800 IU, a person would have to consume 20 cups of cereal daily.
Supplements on the market often run above or below the recommended daily dosage. Forti-D meets the exact recommended daily amount of 800 IU.
Individuals with darker skin-tones often have more melanin in their skin. This natural pigment acts as a “sunscreen,” slowing down the natural production of Vitamin D. The naturally tanned complexion of Filipinos has been pinpointed as a potential cause for the high levels of Vitamin D deficiency in the country.
Individuals who wear clothing that often covers most of the body, or else avoid the sun frequently, do not get enough of sunlight, one of the few reliable natural sources for Vitamin D.
By explicitly blocking UV rays, sunscreen actively prevents the production of Vitamin D. However, the non-use of sunscreen is considered an active cause of skin cancer.
Exposure to the sun is one of the few most effective and natural ways of absorbing Vitamin D. However, as it comes with attendant risks (sunburn, skin cancer), few people opt to walk out in the sun. The rise of indoor lifestyles is a definite contributing factor to the prevalence of Vitamin D deficiency.
Similar to sunscreen, umbrellas and parasols — particularly the UV-repellant kind — block out the sunlight necessary for the body to naturally produce Vitamin D. While they do prevent sunburn, they cut-off a natural source of the vitamin, helping contribute to Vitamin D deficiency.
Many modern cosmetic products come with UV protection, acting as a form of sunscreen. While these are highly recommended in order to prevent sun damage and skin aging, they create a similar effect to sunblock agents: they prevent the body from producing Vitamin D.
The haze of “smog” over many urban areas acts, in its own way, as artificial cloud cover, preventing the helpful UV rays from penetrating to the ground below. This means that individuals who live in metropolitan areas may be more at risk of Vitamin D deficiency, even if they do walk around in the sun.
As the body ages, natural vitamin production slows and decreases owing to the deterioration of the cells involved. Older individuals would do well to start adding Vitamin D supplements to their roster of vitamins, since bone disease also increases in prevalence among the aging population.