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Seasonal Wellness

Fall Is Vitamin D Season: An Ayurvedic and Naturopathic Guide

By Dr. Neha Kaushik Chillara, NMD · October 2026

As the days shorten across the Northeast, most of us quietly lose our main source of vitamin D: the sun. That makes fall the ideal time to check in on this essential nutrient. Here’s what it does, how to get enough through the darker months, and how Ayurveda and Naturopathic medicine work together to keep you balanced until spring.

What Vitamin D Does

Vitamin D behaves more like a hormone than a typical vitamin. The body converts it into an active form, calcitriol, which acts on receptors found in tissues throughout the body. Research connects healthy levels to several areas of health:

• Bones: Vitamin D helps the gut absorb calcium. This is its best-established role, and long-term deficiency softens and weakens bone.^[1]
• Immunity: A large analysis of 25 clinical trials found that vitamin D supplements modestly reduced respiratory infections. The benefit was greatest in people who started out deficient.^[2]
• Liver: The liver performs the first step in activating vitamin D. Low levels are also strongly associated with fatty liver disease.^[3]
• Natural detox pathways: Active vitamin D switches on CYP3A4, one of the main enzymes the body uses to break down medications and other compounds.^[4]
• Sleep: Deficiency is linked to a higher risk of sleep problems.^[5]
• Mood: Low levels are linked to depression. One analysis found a benefit for people already living with depression.^[6]

In short, vitamin D is essential, and correcting a deficiency matters. It works best as one part of a balanced approach to health, as an initial step.

Why Fall and Winter Matter

Our skin makes vitamin D only when it receives ultraviolet B (UVB) light. In fall and winter, the sun sits lower in the sky, so its rays travel through more atmosphere and most UVB is filtered out before it reaches us.

A classic study measured this directly in Boston, which sits at nearly the same latitude as Connecticut. From November through February, skin made essentially no vitamin D from sunlight, no matter how much time people spent outdoors.^[8] Researchers have since confirmed that above roughly 35 degrees north, skin production stops for several winter months.^[11]

This means the vitamin D you build up over summer has to carry you through winter. For many people it runs low by late winter, which is why fall is a good time to test your level and plan ahead.

The Best Time of Day for Sunlight

Midday is best. UVB is strongest when the sun is highest, roughly 10 a.m. to 3 p.m., with a peak near noon. Early-morning and late-afternoon light contains very little UVB, so skin makes almost no vitamin D at those times.^[11,12]

A simple check is the shadow rule: if your shadow is longer than you are tall, the sun is too low for much vitamin D production.

Short sessions work best. Researchers in the UK calculated that 10 to 15 minutes of midday summer sun on the arms and legs can be enough for a fair-skinned person.^[12] Longer exposure adds little vitamin D but raises the risk of sunburn and skin damage, so cover up or use sunscreen once you reach your limit.

A few factors change how much vitamin D you make:

• Skin tone: Darker skin contains more melanin, a natural sunscreen, so it needs more time in the sun to make the same amount.^[1,12]
• Age: Older skin makes far less. One study found adults over 70 produced about a quarter as much as young adults.^[13]
• Windows: Glass blocks UVB, so sitting in a sunny room or car does not help.
• Clouds and pollution: Both reduce the UVB that reaches the ground.

From spring through early fall, a few minutes of midday sun several times a week is a natural way to build your stores. Through the Northeast winter, food and supplements have to fill the gap.

Many people practice Surya Namaskar or take walks at sunrise, and morning light is wonderful for setting the body’s daily rhythm and supporting sleep. For vitamin D, though, the sun needs to be higher. If your goal is vitamin D, add a few minutes outdoors near midday on warmer, sunny days.

Foods That Provide Vitamin D

Few foods contain much vitamin D naturally, so choosing the right ones and sourcing them well matters. The amounts below come from the NIH Office of Dietary Supplements.^[9] For comparison, the recommended daily intake for most adults is 600 IU, rising to 800 IU after age 70.^[9]

• Cod liver oil (1 tbsp): 1,360 IU. Choose a purified, third-party-tested brand. It’s also very high in vitamin A, so avoid it during pregnancy unless your provider approves.
• Rainbow trout (3 oz, cooked): 645 IU.
• Sockeye salmon (3 oz, cooked): 570 IU. Wild salmon contains far more than farmed.
• UV-treated mushrooms (½ cup): 366 IU. Look for “UV-treated” or “high in vitamin D” on the label.
• Fortified plant milk (1 cup): 100–144 IU. Choose organic or Non-GMO Project Verified, and go easy on rice milk, which can contain arsenic.
• Fortified cow’s milk (1 cup): 120 IU. Organic milk comes from cows given non-GMO feed.
• Sardines (2): 46 IU.
• Egg (1 large): 44 IU. Hens raised on pasture in the sunlight lay eggs with more vitamin D.

Atlantic mackerel is another good low-mercury choice. King mackerel is on the FDA’s list of fish to avoid because of its high mercury content.^[14]

Even a careful diet rarely provides enough vitamin D on its own in winter. Food works best alongside sunlight in the warmer months and, when needed, a supplement in the colder ones. As winter turns to spring and Kapha builds, lighter preparations keep digestion balanced, such as baked fish with warming spices or mushrooms sautéed with ginger and black pepper.

The Ayurvedic Perspective

Ayurveda has long understood that our needs change with the seasons. Its seasonal routine, called ritucharya, is described in the classical texts Charaka Samhita and Ashtanga Hridaya.^[15,16] Late fall and early winter is Hemanta ritu, and the classical guidance for this season fits well with what we now know about vitamin D.

Agni and nourishing foods

Ayurveda teaches that digestive fire, or agni, is strong in early winter, so the body handles richer, heavier, and more unctuous foods well.^[16] This suits vitamin D, which dissolves in fat and is absorbed better alongside it.^[9] Taking a supplement with a meal containing ghee, sesame oil, or other healthy fats aligns with both traditions.

Abhyanga and bone health

Daily self-massage with warm sesame oil is a cornerstone of the winter routine for calming the cold, dry qualities of Vata. Ayurveda links weakened bones to depletion of asthi dhatu, the bone tissue, often alongside aggravated Vata. Supporting vitamin D and calcium status complements this traditional focus on nourishing bone through the cold season.

The Naturopathic Perspective

Naturopathic medicine focuses on identifying the root cause and supporting the body’s own ability to heal. With vitamin D, that means testing first, correcting what is actually low, and looking at the nutrients that work alongside it.

Take it with your largest meal

Because vitamin D is fat-soluble, food helps. In a Cleveland Clinic study, patients whose levels had not responded to supplements saw their levels rise by about 50% after switching to taking vitamin D with their biggest meal of the day.^[17] A later randomized trial found a smaller but still meaningful benefit of about 15% compared with taking it on an empty stomach.^[18]

Magnesium matters

The enzymes that convert vitamin D into its active form depend on magnesium.^[19] Many Americans fall short on magnesium, so leafy greens, pumpkin seeds, almonds, and legumes are worth adding to your winter plate.

Vitamin K2

Vitamin D increases calcium absorption, and vitamin K2 helps direct calcium into bone. Naturopathic practitioners often pair the two, although clinical evidence for the combination is still developing. Anyone taking warfarin or another blood thinner should not take vitamin K without medical supervision.

Watch for interactions

Vitamin D can interact with some common medications, including certain statins, thiazide diuretics, corticosteroids such as prednisone, and the weight-loss drug orlistat.^[9] Let your practitioner know everything you take.

Know Your Number

A simple blood test called 25-hydroxyvitamin D, or 25(OH)D, is the best way to know where you stand. If you have never been tested, or do not know your result, fall is an ideal time to find out.

Our practitioners generally aim for 65–85 ng/mL. Recommended ranges vary between organizations. The National Academy of Medicine considers 20 ng/mL adequate for most people and advises caution above 50–60 ng/mL.^[9] The Endocrine Society does not set a target level.^[10] Because guidance differs, we tailor each patient’s goal to their health history and recheck levels to make sure they stay in a safe range.

More is not always better. Vitamin D is stored in the body, so it can build up. Taking too much over time can raise blood calcium to harmful levels, causing nausea, weakness, confusion, and kidney stones.^[9] For adults, the upper limit is 4,000 IU per day unless a provider is supervising a higher dose.^[9] Testing first lets your practitioner choose a dose that fits your starting level.

Prepare for Winter With Us

At the Institute for Ayurvedic and Naturopathic Therapies, we combine modern testing with time-honored seasonal wisdom. A vitamin D consultation includes a review of your health history, guidance on testing, and a personalized plan for food, sunlight, and supplementation that fits your constitution and the season.

This article is for educational purposes only and is not medical advice. Please consult your healthcare provider before starting any supplement, especially if you are pregnant, take medications, or have a medical condition.

References

1. Holick MF. Vitamin D deficiency. N Engl J Med. 2007;357(3):266–281.
2. Martineau AR, et al. Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data. BMJ. 2017;356:i6583.
3. Barchetta I, et al. Strong association between non-alcoholic fatty liver disease (NAFLD) and low 25(OH) vitamin D levels in an adult population with normal serum liver enzymes. BMC Med. 2011;9:85.
4. Thummel KE, et al. Transcriptional control of intestinal cytochrome P-450 3A by 1α,25-dihydroxy vitamin D3. Mol Pharmacol. 2001;60(6):1399–1406.
5. Gao Q, et al. The association between vitamin D deficiency and sleep disorders: a systematic review and meta-analysis. Nutrients. 2018;10(10):1395.
6. Cheng YC, Huang YC, Huang WL. The effect of vitamin D supplement on negative emotions: a systematic review and meta-analysis. Depress Anxiety. 2020;37(6):549–564.
7. Okereke OI, et al. Effect of long-term vitamin D3 supplementation vs placebo on risk of depression or clinically relevant depressive symptoms. JAMA. 2020;324(5):471–480.
8. Webb AR, Kline L, Holick MF. Influence of season and latitude on the cutaneous synthesis of vitamin D3. J Clin Endocrinol Metab. 1988;67(2):373–378.
9. NIH Office of Dietary Supplements. Vitamin D: Fact Sheet for Health Professionals.
10. Demay MB, et al. Vitamin D for the prevention of disease: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab. 2024;109(8):1907–1947.
11. Alshahrani FM, et al. Light side and best time of sunshine in Riyadh, Saudi Arabia. Dermatoendocrinol. 2013;5(1):177–180.
12. Webb AR, Engelsen O. Calculated ultraviolet exposure levels for a healthy vitamin D status. Photochem Photobiol. 2006;82(6):1697–1703.
13. MacLaughlin J, Holick MF. Aging decreases the capacity of human skin to produce vitamin D3. J Clin Invest. 1985;76(4):1536–1538.
14. U.S. Food and Drug Administration. Advice about eating fish.
15. Charaka Samhita, Sutrasthana, Chapter 6 (Tasyashitiya Adhyaya), on seasonal regimen.
16. Ashtanga Hridaya, Sutrasthana, Chapter 3 (Ritucharya Adhyaya), on seasonal regimen.
17. Mulligan GB, Licata A. Taking vitamin D with the largest meal improves absorption and results in higher serum levels of 25-hydroxyvitamin D. J Bone Miner Res. 2010;25(4):928–930.
18. A prospective randomized open-label trial to evaluate the effect of food on vitamin D absorption. American College of Rheumatology meeting abstract.
19. Uwitonze AM, Razzaque MS. Role of magnesium in vitamin D activation and function. J Am Osteopath Assoc. 2018;118(3):181–189.