As most of you know, I am a passionate advocate of optimizing your vitamin D levels because of its many capabilities. In previous articles, I’ve discussed in detail how it helps boost immune function, manage blood sugar levels, and lower your risk of cancer.
The best way to produce vitamin D is through sensible sun exposure. However, with autumn now in full swing, the days are getting shorter. Thus, people who live in areas who don’t get enough sunlight won’t be able to produce the appropriate amount of vitamin D to support their health.
To spread awareness of this issue, I recently appeared on NTD News, offering viewers practical strategies to optimize their vitamin D levels during fall, as well as the upcoming winter. These points are also explored below.
Why Fall Makes Vitamin D Trickier to Optimize
Fall is a beloved season in the U.S., drawing many nature lovers to northern states and basking in the changing picturesque foliage.1 However, this presents certain health problems down the line:
• Changes in the Earth’s angle against the sun — Earth follows an elliptical orbit, which means that its distance between the sun varies throughout the year.2 Following this logic, the Earth’s axis and distance from sun during fall cause shorter days, a lower sunlight angle, and cooler temperatures. The result? Lower vitamin D levels.
• Factors affecting vitamin D production — Ultraviolet B (UVB), the type of sunlight that triggers vitamin D production on your skin, is affected by season, time of day, latitude, clouds, and your skin’s melanin concentration.
In many places during summer, incidental sun is enough to produce vitamin D, but not in late fall and winter. So, shifting your diet and taking supplements (as needed) are essential to maintaining optimal levels.3
How Much Sun Exposure Helps in Autumn?
There isn’t a one-size-fits-all approach when optimizing your vitamin D in fall. Here are some guidelines, according to the U.S. Environmental Protection Agency (EPA):4
• Check the daily UV Index (UVI) — This is a forecast provided by the National Weather Service, providing information on the current UV radiation readings throughout the day. Here’s a tip — the highest numbers occur during solar noon.5
• Consider your Fitzpatrick phototype — It’s a guide that describes how certain skin colors react when exposed to sunlight. Thus, it can be used to help you determine how much time you need to be exposed during the day. Here’s a chart from DermNet to help you:6
| Skin Type | Typical Features | Tanning Ability |
|---|---|---|
| I | Pale white skin, blue/green eyes, blonde/red hair | Always burns, does not tan |
| II | Fair skin, blue eyes | Burns easily, tans poorly |
| III | Darker white skin | Tans after initial burn |
| IV | Light brown skin | Burns minimally, tans easily |
| V | Brown skin | Rarely burns, tans darkly easily |
| VI | Dark brown or black skin | Never burns, always tans darkly |
Framing the information above within the context of my NTD News segment, if you live in higher latitudes and/or have deeper skin tones, you’ll generally synthesize less D from the sun, especially during fall.
What’s a good sign your body has produced enough for the day? In a previous article, I noted that the limit is when your skin begins to turn slightly pink. If that doesn’t even happen to you during fall, then you’ll need to compensate the remaining through your diet.
The Best Foods for Vitamin D in Fall
Continuing the point above, vitamin D is also found in various foods. The table below shows you well-known sources and how much you’ll get, depending on serving size:7
| Food | Serving Size | Vitamin D Amount (IU) |
|---|---|---|
| Rainbow trout, freshwater | 3 ounces | 645 |
| Salmon | 3 ounces | 383 to 570 |
| Herring | 3 ounces | 182 |
| Tilapia | 3 ounces | 127 |
| Yogurt, plain | 8 ounces | 116 |
| Kefir, plain | 1 cup | 100 |
| Cheese, American | 1.5 ounces | 85 |
| Mushrooms, raw | 1 cup | Between 0 to 1,110 |
Should You Take Vitamin D2 or D3, and How Much?
Aside from food, you can optimize your vitamin D levels through supplementation. However, there is some confusion between what is generally available to consumers — vitamin D2 and D3:
• Have yourself tested first — No matter which strategy you employ — sunlight exposure, food, and supplements — it’s always a good idea to have your vitamin D levels tested to know your baseline.
When visiting a lab, ask for a 25-hydroxy vitamin D test. This measures the current vitamin D levels circulating within your body. In America, most guidelines set the sufficiency cutoff at 40 nanograms per milliliter (ng/mL), or 100 nanomoles per liter (nmol/L) in Europe. However, I believe that isn’t enough — the real protective benefits of vitamin D occur when you reach a range between 60 and 80 ng/mL.
• Vitamin D2 versus D3 — As noted in my interview with NTD News, vitamin D2 comes from plants, while vitamin D3 comes from animals. If you’re going to pick one, I recommend vitamin D3, as it’s significantly more effective at raising blood vitamin D levels.
One more thing about vitamin D3 — it’s a fat-soluble nutrient. This means that in order to be fully absorbed, you need to take it with meals that include healthy fat, such as pasture-raised egg yolks, tallow, or grass fed butter.
• Supplement interactions — When taking vitamin D3 supplements, remember to increase your intake of magnesium and vitamin K2. These nutrients improve how your body processes vitamin D. For every 5,000 international units (IUs) of vitamin D you ingest, take around 180 micrograms (mcg) of vitamin K2 in MK-7 form, as well as 400 milligrams (mg) of magnesium.
• Medications affecting vitamin D function — Check with your doctor if you’re taking medications such as statins and steroids. According to the Office of Dietary Supplements, corticosteroid medications such as prednisone can impair vitamin D metabolism.8
• Rechecking interval — Have your blood tested every three to six months. This gives you enough time to see the effectiveness of your regimen at boosting vitamin D levels, and whether or not adjustments are needed.
Does Using Sunscreen in Fall Block Vitamin D Production?
Public messaging of sunlight exposure can be confusing. For example, dermatology organizations advise not seeking UV exposure for vitamin D because UV is a proven skin-cancer risk and even advise wearing sunscreen while outside.9 In short, they’re advocating that you avoid and fear sunlight.
• The link between sunlight and skin cancer — The fear of increased cancer risk perpetuated by dermatologists has some merit, but it’s important to understand the nuances. As I mentioned in the interview, making vitamin D through sunlight can increase your risk of squamous cell and basal cell carcinoma. But the good thing is that these are caught early and can be treated right away, making mortality risk very low.
Meanwhile, safe sun exposure lowers the risk of melanoma, which is the dangerous type of skin cancer you don’t want to get. Much of the reasons why melanoma risk increases is because many of us eat a diet high in linoleic acid (LA), which is perishable and becomes toxic when exposed to sunlight. It’s only that when you eliminate LA from your system that you can truly reap the benefits of sunlight safely — this process is explained below.
• Avoid excessive use of sunscreens — These products block vitamin D synthesis and even interfere with your endocrine health. In fact, a sunscreen with an SPF of just 30 blocks about 97.5% of UVB radiation, effectively shutting down your body’s ability to make vitamin D.
Rather, use sunscreen strategically, such as only applying it when you’re going to be out in the sun for prolonged periods of time. I recommend reading “Beyond Vitamin D Production — How Sensible Sun Exposure Supports Overall Health” for more information.
• Ditch vitamin D lamps — On a related note, devices that generate UV light, such as nail driers, can damage your DNA. In a previous article, I discussed published research showing how regular use of these products actually increase your risk of skin cancer.
A Simple Fall Checklist
Based on all the information I outlined above, monitoring and increasing your vitamin D levels can be burdensome. To help, here’s a handy checklist you can keep for reference. I recommend printing it out and hanging it somewhere visible:
• Daily base intake — The Office of Dietary Supplements recommends you aim for a daily intake of 600 to 800 IUs from all sources.10 However, this is a far too low a number.
As noted in my interview with NTD News, you can safely take 10,000 IUs a day without harming your health. That said, it’s important to check your levels, too. Vitamin D toxicity, while rare, is a real side effect.
• Shop smart — Keep fish such as wild-caught Alaskan salmon in your rotation. These are the safest choices as they’re generally low in mercury compared to farmed fish. Similarly, look for grass fed varieties of dairy products.
• Mind your medications — Consult with your doctor to rule out interactions on vitamin D synthesis if you’re currently taking medications for a disease.
• Develop your sun sense — Regularly review the UVI reports and be mindful of your Fitzpatrick phototype to make sure you don’t get sunburned.
• Test and retest — Take a 25-hydroxy vitamin D test and aim for a range between 60 to 80 ng/mL.
The Issue of Sunlight Exposure Without Fixing Your Diet
One important aspect I emphasized in my interview is linoleic acid (LA) becoming embedded in your skin. Purging it is crucial when it comes to optimizing vitamin D levels because sunlight exposure causes toxic metabolites to form, which will damage your cellular health. That said, it is paramount that you reduce your LA intake right away.
At the same time, I recommend increasing your intake of pentadecanoic acid, also known as C15:0. It is a rare, odd-chain saturated fat that displaces LA in your skin, allowing you to reap the benefits of regular sun exposure. For an in-depth explanation of how this process occurs, read “The Fast-Track Path to Clearing Vegetable Oils from Your Skin.” Once you’ve familiarized yourself with the benefits of C15:0, follow the protocol below:
1. Keep LA intake below 2% of your total daily calories — Remove all industrial vegetable oils from your diet, including soybean, corn, sunflower, safflower, cottonseed, canola, and grapeseed oils from your diet. LA is common in ultraprocessed foods, condiments, restaurant meals, and packaged snacks.
LA also accumulates in the fat of grain-fed livestock, especially chicken and pork, often reaching concentrations similar to those found in vegetable oils sold in groceries. To minimize exposure, choose pasture-raised or grass fed meat whenever possible.
2. Take 2 grams of C15:0 daily, split between meals — Use a high-quality pentadecanoic acid powder or a certified butter or ghee concentrate rich in C15:0. Divide the total dose across meals to promote consistent uptake into your tissues.
3. Check your progress every three months — Use a red blood cell test or dried blood spot test to confirm that your C15:0 levels are at least 0.4% and that LA remains under 5% of your total fat levels. These benchmarks indicate successful cellular remodeling.
If your results stop improving, look for unrecognized sources of LA or review your dosing for possible inconsistencies.
4. Encourage fat turnover through healthy lifestyle changes — Boost the clearance of stored LA with intermittent fasting, high-intensity training, and regular heat exposure via sauna sessions or hot baths.
Limit vigorous exercise to 75 minutes or less per week, as longer bouts can hinder recovery and longevity. When fasting, avoid chronic or extreme restriction, which can suppress thyroid function and metabolism. Sporadic, short fasts are safer and more sustainable.
5. Build up sun tolerance gradually, especially in your first two summers — While LA remains high in your body fat, the skin is more prone to UV-induced oxidative stress. During this period, avoid midday sunlight (11 a.m. to 3 p.m.) and go out during early morning or late afternoon instead.
Once LA levels decline and cell membranes stabilize, your skin’s resilience improves, allowing you to increase midday exposure slowly without burning.
Frequently Asked Questions (FAQs) About Optimizing Vitamin D Levels in Fall
Q: How much sun do I need for vitamin D in the fall?
A: There’s no one-size-fits-all answer, since your vitamin D production depends on factors like your skin tone, latitude, and the daily UV Index. As a rule of thumb, check your local UVI forecast each day.
If you have pale or fair skin, you’ll only need a short time of direct sunlight exposure. Those with deeper skin tones may need to take longer for similar vitamin D output. However, during late fall or for those living in northern regions, UVB levels often drop too low to make enough vitamin D, meaning sunlight alone may not be sufficient.
Q: What’s the best time of day to make vitamin D in autumn?
A: The best window is around solar noon — roughly between 11 a.m. and 2 p.m. — when the sun’s rays hit the Earth most directly. This is when UVB exposure is strongest, allowing your body to produce vitamin D more efficiently in less time.
In fall, the sun’s lower angle means UVB rays are weaker, so early morning or late afternoon exposure won’t trigger much vitamin D production. If you live in northern states, your skin may not generate any vitamin D during the later months of fall. In those cases, food and supplementation become helpful.
Q: Which foods are highest in vitamin D for fall meal planning?
A: When sunlight isn’t enough, you can boost your vitamin D by adding certain foods to your meals. Natural sources include fatty fish like wild-caught Alaskan salmon, rainbow trout, herring, and tilapia. Grass fed dairy products such as yogurt, kefir, and cheese also provide smaller amounts. For plant-based options, mushrooms exposed to sunlight or UV light are viable.
Q: Should I take vitamin D3 or D2 in fall?
A: If you’re planning to take a supplement, vitamin D3 (cholecalciferol) is the superior choice. D3 is the form your body naturally makes from sunlight and is far more effective than D2 (ergocalciferol), which comes from plants. Since it’s a fat-soluble vitamin, take D3 with a meal that includes healthy fats, such as grass fed butter, pasture-raised egg yolks, or tallow, so it can be absorbed properly.
For every 5,000 IUs of vitamin D3, pair it with about 180 mcg of vitamin K2 (MK-7 form) and 400 mg of magnesium to enhance absorption and balance calcium metabolism. Lastly, always test your levels before supplementing, especially if you’re taking medications.
Q: When should I test my vitamin D levels in fall?
A: It’s best to test early in the season (around late September or October) to establish your baseline and then retest every three to six months to track progress. Ask your health care provider for a 25-hydroxy vitamin D test for accurate results.
While many labs consider 40 ng/mL sufficient, optimal protection for immunity, metabolic health, and cancer prevention typically appear between 60 and 80 ng/mL. If your results are below this range, consider combining sun exposure with dietary and supplemental vitamin D3 throughout fall and winter.
Test Your Knowledge with Today’s Quiz!
Take today’s quiz to see how much you’ve learned from yesterday’s Mercola.com article.
How does structured laughter therapy affect anxiety and overall life satisfaction?
Nice blog here Also your site loads up very fast What host are you using Can I get your affiliate link to your host I wish my site loaded up as quickly as yours lol
Hello i think that i saw you visited my weblog so i came to Return the favore Im trying to find things to improve my web siteI suppose its ok to use some of your ideas