Vitamin D: More Than a Vitamin — A Hormone for Every Stage of Life 🌞

Vitamin D is often grouped with vitamins like C or B12, but it’s actually quite different. Vitamin D functions like a hormone, meaning it sends messages throughout the body and affects many systems at once — not just bones.

When sunlight hits your skin, your body makes vitamin D. It is then activated by the liver and kidneys into its hormone form, which helps regulate calcium, muscle strength, immune function, and even how certain genes are switched on and off.¹²

Because vitamin D works in so many areas of the body, having enough matters at every age.

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Why Vitamin D Is Important at Every Stage of Life

Babies and Children 👶

Vitamin D is essential for growing strong bones. Without enough, children can develop soft or weak bones (a condition called rickets).

Studies show that giving vitamin D supplements to infants and children prevents rickets and supports healthy growth.³

Most experts recommend:

400 IU per day for babies

600 IU per day for children and teens⁴

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Adults 🧑‍🦱

In adults, vitamin D helps:

Keep bones strong

Support muscle function

Help the body absorb calcium properly

Low vitamin D levels can lead to bone thinning and increase fracture risk over time. Large studies show that supplementation is most helpful for people who start out with low levels.⁵⁶

For most adults, the general recommendation is:

600 IU per day⁴

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Older Adults 👵

As we age, our skin becomes less efficient at making vitamin D from sunlight, and we often spend more time indoors. This increases the risk of deficiency.

Research shows that vitamin D (especially when combined with calcium) can:

Lower the risk of fractures

Improve muscle strength

Reduce fall risk in older adults⁷⁸

Recommended intake after age 70:

800 IU per day⁴

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Vitamin D and Muscle Strength 💪

Vitamin D doesn’t just help bones — it also plays a role in muscle health. Studies in postmenopausal women show that vitamin D supplementation can improve muscle strength, which is important for balance and independence as we age.⁹

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Vitamin D During Midlife and Menopause 🌸

Why Vitamin D Matters More in Midlife

During perimenopause and menopause, estrogen levels decline. This can speed up bone loss and increase fracture risk. Vitamin D becomes especially important during this time to:

Improve calcium absorption

Support bone density

Reduce overactivity of parathyroid hormone, which can weaken bones¹⁰¹¹

Low vitamin D levels are very common in midlife women, particularly in northern climates.

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Menopause Society Guidance

The Menopause Society (formerly the North American Menopause Society) recognizes that standard vitamin D recommendations may not be enough for many women in midlife.

They suggest that most perimenopausal and postmenopausal women benefit from:

1,000–2,000 IU of vitamin D daily

This range is considered safe and effective for maintaining healthy vitamin D levels and protecting bone health.¹²

Many experts aim for blood levels of vitamin D of at least 30 ng/mL, especially in women at risk of bone loss.¹³

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How Much Vitamin D Do You Need?

Life Stage Typical Daily Recommendation

Babies (0–12 months) 400 IU³

Children & Teens 600 IU⁴

Adults (19–70 years) 600 IU⁴

Adults 70+ 800 IU⁴

Midlife & Menopausal Women 1,000–2,000 IU¹²

Upper Safe Limit (Adults) 4,000 IU/day¹

> Vitamin D is fat-soluble, so more is not always better. Very high doses should only be taken under medical guidance.

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Beyond Bones: Other Benefits

Research suggests that vitamin D may also:

Support immune health

Reduce the risk of respiratory infections in people with low levels⁶

Be linked to lower overall mortality in older adults⁸

Not all studies show benefits in people who already have adequate vitamin D levels — which is why individualized advice matters.

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Getting Vitamin D Naturally ☀️

Vitamin D comes from:

Sun exposure (10–30 minutes a few times per week, depending on skin type and location)

Foods like fatty fish, eggs, fortified milk, and plant milks

Supplements when sun and diet aren’t enough

In northern regions, vitamin D deficiency is especially common during fall and winter.

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Final Thoughts

Vitamin D is much more than a vitamin — it’s a hormone that supports bones, muscles, immune health, and healthy aging. In countries like Canada and many parts of the Northern Hemisphere, long winters, limited sunlight, indoor lifestyles, and sunscreen use mean that vitamin D deficiency is extremely common across all ages. Because of this, regular vitamin D supplementation is essential for almost everyone, not just those with known risk factors. Ensuring adequate intake is a simple, safe, and effective way to support lifelong health — especially during fall and winter months.

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References

1. Holick MF. N Engl J Med. 2007;357(3):266–281.

2. Bouillon R et al. Endocr Rev. 2008;29(6):726–776.

3. Munns CF et al. J Clin Endocrinol Metab. 2016;101(2):394–415.

4. Institute of Medicine. Dietary Reference Intakes for Calcium and Vitamin D. 2011.

5. Lips P et al. Endocr Rev. 2001;22(4):477–501.

6. Martineau AR et al. BMJ. 2017;356:i6583.

7. Bischoff-Ferrari HA et al. JAMA. 2004;291(16):1999–2006.

8. Bolland MJ et al. Lancet Diabetes Endocrinol. 2018;6(11):847–858.

9. Beaudart C et al. J Clin Endocrinol Metab. 2022;107(7):e2672–e2685.

10. Gallagher JC. J Clin Endocrinol Metab. 2013;98(11):4331–4338.

11. Reid IR et al. Lancet. 2014;383(9912):146–155.

12. The Menopause Society. Menopause. 2022;29(11):1281–1283.

13. Pludowski P et al. Nutrients. 2023;15(2):277.