Vitamin D Science and the Top 12 Foods You Need Now

Vitamin D Science and the Top 12 Foods You Need Now

In This Article

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

FoodVitamin 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.

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Dr. John



6 thoughts on “Vitamin D Science and the Top 12 Foods You Need Now”

  1. Thank you for this.
    Another recent article of yours on vitamin D encouraged me to increase my intake this winter. Since pre and post menopause I’ve experience severe SAD. I believe increasing my vitamin D has helped because I don’t feel depressed this year by the grey winter skies we here in Ontario, Canada live with.

  2. Having recently seen an Ayurvedic doctor I was surprised to have her take me off of my Vit D supplement. I’ve been taking about 4,000mg of Vit D each day as I live in Ireland and the sun is not that present. She told me that Vit D stays in our bodies for 6 months. Since I’ve been taking high doses for a long time, I shouldn’t need to start supplementing until next autumn. I’ve never heard this about Vit D nor can I find any supportive information online. Is this true? I’d love to know more about this as it certainly isn’t something discussed in all the information about the importance of Vit D.

    • Hi Tamara,

      I have seen Dr. John write that we do carry vitamin D for some months, specifically into the winter months, but I have not seen studies confirming how long it stays in the body.

      The best way to know for sure about your vitamin D levels is to have them checked. Dr. John suggests having levels tested around September and March so you can see the high at the end of summer and the low at the end of winter, so you can best know how to customize your supplementation.

      LifeSpa Staff

  3. Dr. Douillard, I don’t think you realize you linked Coppertone’s UV Index! I found it a little strange (and misaligned) when reading their recommendation to avoid the sun and wear sunscreen over a UV index of 3.


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