Sun Exposure and Vitamin D

Sun exposure is the most efficient way to get vitamin D₃, but few of us get enough sunlight or expose enough skin on a regular basis to get UVB rays to convert to active vitamin D.

In a study of Middle Eastern countries, 82% were vitamin D deficient⁴ and in the US, over 40% of the population is deficient, including 70% of Hispanics and 80% of blacks.³ Darker skin has more melanin, which is supposed to protect us from excess UVB absorption, but if we don’t get enough sunlight, it can prevent needed absorption. These number get worse in darker winter months!

In winter, when the sun is lower in the sky, UVB rays are blocked by the atmosphere, letting only skin cancer-causing UVA rays through. In winter, in any latitude north of Atlanta, the sun is too low to get any vitamin D-making UVB rays. To get UVB rays, the UV Index must be over 3.¹ To check your UV Index daily, use a free UV Index finder. There are many, like this one.

Getting enough vitamin D from the sun in the Northern Hemisphere winter is impossible, and it can be difficult in the summer, too. So how did people survive before vitamin D supplements? Traditional people sourced vitamin D from organ meats, such as liver and liver oil, the highest food sources of vitamin D.

Most Westerners don’t eat organ meats or fish livers anymore, making supplementation critical all year round. Other foods contain vitamin D, but not in quantities studies suggest will deliver the most benefit.

Vitamin D Content of Various Foods⁵

Food	Vitamin D content in International Units (IUs) per serving
Cod liver oil, 1 Tbsp	1360
Swordfish, cooked, 3 oz	566
Salmon (sockeye) cooked, 3 oz	447
Tuna, canned in water, drained, 3 oz	154
Orange juice fortified with vitamin D, 1 cup	137
Milk, vitamin-fortified, 1 cup	115-124
Yogurt, fortified with 20% daily value vitamin D, 6 oz	80
Sardines, canned in oil, drained, 2 sardines	46
Liver, beef, cooked, 3 oz	42
Egg yolk, 1 large	41
Cereal, fortified with 10% daily value vitamin D, 1 cup	40
Cheese, Swiss, 1 ounce	6

To get vitamin D from food, fish is a good option, but three ounces of cooked salmon only has roughly 450 international units (IU). This may be enough to meet FDA minimum standards, but more and more studies suggest we need much more than 400 IU a day.²

New studies suggest the optimal range for vitamin D₃ is 50-80 ng/mL on a blood test. The current normal range is 25-100 ng/mL. To keep your vitamin D₃ levels on the high end of normal, dosing is typically around 4-5,000 IU a day in winter.⁸ This is 3-4 Tbsp cod liver oil a day, which few would likely tolerate. (Instead, you can take 4-5 drops of sheep wool lanolin-based Liquid Sun Vitamin D.)

Benefits of Vitamin D

Better Blood Sugar

In a study published in the journal Menopause, 680 women were evaluated for a link between high blood sugar and vitamin D deficiency. The study concluded that vitamin D deficiency below 30 ng/mL is associated with 29% greater chance of fasting blood glucose levels above 100 mg/dL, aka being prediabetic. In this study, conducted in Brazil, 64% of participants were vitamin D deficient.⁶

Less Urinary Incontinence

In a 2010 study of more than 1,800 women, researchers evaluated the potential link between vitamin D deficiency (below 30 ng/mL) and female pelvic disorders, such as urinary incontinence. They concluded that likelihood of urinary incontinence was significantly reduced in women 50 and older with vitamin D 30 ng/mL or higher and that higher vitamin D levels are associated with decreased risk of pelvic floor disorders in women.⁷

Healthy Cell Division with High-Dose Vitamin D

In a 2019 study, a dose of 400 IU per day of vitamin D was compared with a high initial dose of 8,000 IU per day, reducing to 4,000 IU per day. The higher dose resulted in better outcomes related to immune support and healthy cell division.⁸ Vitamin D levels at the lower end of the normal range have been proven to prevent bone-related concerns, such as rickets, but keeping blood levels of vitamin D in the higher end of the normal range has been shown to have a global effect on health and wellbeing, including issues related to mood, cognitive function, heart, blood sugar, immunity, and more.⁹

Arterial Plasticity

In a 2017 study, 70 overweight men with vitamin D deficiencies men were split into four dose-specific vitamin D supplementation groups (placebo, 600 IU/day, 2,000 IU per day, and 4,000 IU per day) for 16 weeks. The 4,000 IU group resulted in significantly less arterial stiffness compared to the other groups, who received lower dosages or no vitamin D supplementation.¹⁰

Boosted Immunity

One report studied almost 19,000 subjects between 1988 and 1994, finding that individuals with deficient vitamin D (<30 ng/ml) were more likely to succumb to upper respiratory tract infection than those with sufficient levels. Another study of 800 military recruits in Finland found those with deficient vitamin D lost significantly more days from active duty secondary to upper respiratory infections than recruits with higher vitamin D levels.¹¹

Trying to find the best vitamin D supplement for you? My favorite is LifeSpa’s highly absorbable Liquid Sun Vitamin D. Try it and let us know what you find!

To get the support you need, read all my vitamin D articles here.