Older vs. younger — who is more at risk of low vitamin D?

As we age our body becomes less efficient at producing vitamin D. Combined with changing lifestyle habits, you would expect to get more deficient in the essential nutrient as you get older. 

But Medichecks’ analysis of over 30,000 customers had a surprising result—young adults had lower vitamin D levels. 

Why has this happened? And what can be done about it?

In this article we’ll answer:

• Why does the production of vitamin D decline with age?
• Why are young adults at higher risk of low vitamin D levels?
• The consequences of vitamin D deficiency in young adults
• What can young people do to improve their vitamin D levels?

Why does the production of vitamin D decline with age?

 

Have you ever wondered how we get vitamin D from sunlight? 

We have certain molecules (7-dehydrocholesterol, or 7DHC) in our skin. When sunshine hits our skin, the 7DHC molecules absorb the sunlight and become energised. They need to rearrange themselves to suit their new energy, and the first thing they rearrange into is pre-vitamin D3. 

The heat from our bodies transforms pre-vitamin D3 into vitamin D3, a form which can leave the skin and enter the bloodstream. There, it circulates to the liver and kidneys, where it is metabolised into usable forms. 

1. Skin concentration

The levels of 7DHC in our skin are thought to decrease by up to 50% as we age [1]. Similarly, studies have shown that half as much vitamin D is produced in elderly skin vs. younger skin.

2. Metabolic changes

Metabolic changes within the body reduce the capacity to process vitamin D and calcium, including changes in the liver and kidneys. 

3. Lifestyle

Changes in lifestyle that occur due to ageing also affect vitamin D intake or production such as:

• Reduced appetite due to medication or illness: people are less likely to get enough vitamin D from food 

• Reduced mobility due to weaker muscles: beyond the fact that outdoor exercise increases sun exposure, indirect positive effects of exercise include improved vitamin D metabolism and optimised bone health

• Becoming housebound or living in residential care: older adults can’t easily go outside in the sun when they want to, increasing the risk of deficiency

Why are young adults at higher risk of low vitamin D levels?

 

Our yearly data analysis revealed that 23.8% of 18-30 year-olds had low vitamin D levels. In contrast, 10.2% of adults over 60 years old were deficient. This means younger adults were more than twice as likely as older adults to have low vitamin D — opposite to what you might expect.

And when we dug a little deeper we saw this was not an anomaly. Our data over the last six years shows young adults consistently report lower vitamin D levels than the elderly. 

Many people already know why we need vitamin D, so, what is happening here?

Modern lifestyle and urban living are, unsurprisingly, the two main reasons the younger generation has lower vitamin D levels. These include:

1. An indoor lifestyle
2. Poor dietary choices
3. Geographical factors
4. Lack of awareness

1. An indoor lifestyle

One survey found less than a quarter of UK-based 17- to 23-year-olds had enjoyed time outdoors in a green space [2]. 

That’s over 75% of young people who are spending more time indoors than outside in nature. This may not necessarily be by choice. For example, if you work in an office, restaurant, café, or shop, you may struggle to get out into the daylight. 

Students also spend most of their day inside studying. But even if you study by a window, the glass blocks beneficial UVB rays.

And unless you’re working remotely (which is also probably indoors), you need to commute to work. For many people, this means a couple of hours a day spent sitting in a car or on public transport further reducing opportunities for skin exposure.

Most of us are guilty of spending too much time on our phones, and the rise of screens likely plays a part in how much time we spend inside. Many young adults choose gaming or streaming over outdoor activities. 

Technology is more prominent than ever, with TV shows and games becoming increasingly stimulating and addictive. 

2. Dietary options

You can get a small amount of vitamin D from your diet, by eating nutrient-rich foods such as:

• Fatty fish (e.g. sardines, tuna, herring, and mackerel)

• Egg yolks

• Mushrooms (especially those grown in natural light)

• Fortified milk and cereals

4. Low budget

Students have a bit of a reputation for eating badly (chips and kebab after a night out, anyone?), and a diet of fast food or highly processed food can contribute to low vitamin D levels. This in part, is due to having a low budget, but a lack of cookery skills is also a factor in preventing young people from eating nutritious meals.

5. Poverty

Around 8.1 million UK working-age adults are living in poverty, and the need for food banks to supply emergency food has risen steadily over recent years [3,4]. 

Food banks are a vital resource, and volunteers and donors do their best to ensure families receive balanced nutrition. But fresh eggs, fish and mushrooms are not suitable for donating, and fortified milk and cereals tend to be more expensive, meaning they may not be considered by donors.

6. Avoiding meat products

Although plant-based diets are usually healthy in many ways, most sources of vitamin D come from animal products. While mushrooms produce vitamin D in a similar way to humans, many mushrooms grown in supermarkets are grown indoors. 

Wild mushrooms are the best source but never pick or eat wild mushrooms unless you are certain they are edible. 

7. Geographical factors

The UK isn’t exactly renowned for its sunny weather.

So how does British weather affect your vitamin D levels?

Well, continuous cloud cover blocks UVB rays. Air pollution in cities can also block UVB rays, preventing vitamin D synthesis in the skin. People living in northern latitudes will struggle too, where the weaker UV rays mean you are also more likely to experience low vitamin D levels.

8. Lack of awareness

While the elderly may be advised by health professionals to keep an eye on their vitamin D levels or take a supplement, young people may not even realise they are at risk until they start seeing symptoms of deficiencies. 

 

The consequences of vitamin D deficiency in young adults

 

People of all ages need vitamin D, but having low levels early on in life can affect you in the long term. 

Weakened immune system

Having levels of vitamin D below 75 nmol/L can compromise the immune system, making you prone to seasonal colds and viruses. From illnesses to infections, a weakened immune system disrupts daily life and wellbeing.

 While Medichecks found 23.8% of 18-30 year-old customers were deficient in vitamin D, 58% of young adult customers had suboptimal levels of vitamin D. 

Weaker bones

Calcium absorption and vitamin D are critically interlinked—without enough vitamin D, your body can’t absorb calcium properly. 

Until you turn 30, your bones are still growing and strengthening, and a deficiency could lead to reduced bone density. 

Vitamin D is so critical to good bone development that babies and young children are advised by the NHS to take a supplement. Vitamin D deficiency as a youth could cause a higher risk of osteoporosis and fractures in later life. 

Poor mental health

There is growing evidence that vitamin D is closely linked to mental health, particularly depression [5,6]. While most studies conclude with more research being needed, the effect that getting outside into fresh air or nature has on improving the mood is unquestionable. 

 

What can young people do to improve their vitamin D levels?

 

Everyone can benefit from vitamin D. Here are four simple ideas for ways to increase your vitamin D levels that anyone can try.

1. Spend more time outdoors

Even on a cloudy day, you can still get a small amount of UVB rays. Just fifteen minutes in the sun without sunscreen is enough to up your vitamin D levels (just make sure you use sunscreen afterwards if you’re outside for longer periods to reduce your risk of skin cancer). Some ideas for ways to get outside:

• Go for a quick lunchtime walk

• Get off your train or bus one stop early and walk the rest of the way

• Play sports outside e.g. running, cycling, football

• Take a coffee break outside instead of at your desk

• Check your emails in the sun

• Download an app blocker on your phone — perhaps with one less distraction it will be easier to get outside

The most important thing is to make sure you have some skin showing for maximum sunshine absorption — roll up your sleeves or trouser legs if it’s not warm enough for shorts and t-shirts.

Aiming to be outside when the sun is highest in the sky will ensure maximum UVB absorption, but remember your sun cream once you’ve soaked up those rays! 

2. Eat more vitamin D-rich foods

Some low-budget, vitamin D-friendly meals include:

• Tuna mayo sandwich – include a side salad or cucumber sticks for extra vitamins, and sprinkle grated cheese for a calcium bonus

• Scrambled eggs with mushrooms

• Tinned sardines on toast – use wholemeal bread as it’s more nutrient-rich than white bread (some wholemeal breads are even fortified with vitamin D)

3. Take a supplement

Government advice is that everyone should take a daily vitamin D supplement in autumn and winter [7]. Choosing vitamin D3 supplements over vitamin D2 or vitamin D is preferable.

4. Raise awareness and educate 

By taking an active interest in our health, or convincing others to think about theirs, we can spread awareness and promote proactive healthcare. 

• Teaching your kids how to make nutritious meals is information they can carry for life

• By getting outdoors more yourself, you can create good habits and inspire others to do the same

• If you know someone who is at risk of being deficient you can invite them on walks in the sun, share this article, or advise them to look into their vitamin D levels

• Regular health checks can be useful, including blood tests, to measure vitamin D levels and identify deficiencies early

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References

1. Giustina A, Bouillon R, Dawson-Hughes B, Ebeling PR, Lazaretti-Castro M, Lips P, et al. Vitamin D in the older population: a consensus statement. Endocrine. 2023;79: 31–44. doi:10.1007/s12020-022-03208-3
2. Part 2: Sleep, loneliness, activities and health behaviours. In: NHS England Digital [Internet]. 20 Dec 2024 [cited 20 Dec 2024]. Available: https://digital.nhs.uk/data-and-information/publications/statistical/mental-health-of-children-and-young-people-in-england/2023-wave-4-follow-up/part-2-sleep-loneliness-activities-and-health-behaviours
3. Francis-Devine B, Roberts N, Malik X. Food poverty: Households, food banks and free school meals. 2024 [cited 20 Dec 2024]. Available: https://commonslibrary.parliament.uk/research-briefings/cbp-9209/
4. UK Poverty 2024: The essential guide to understanding poverty in the UK | Joseph Rowntree Foundation. 23 Jan 2024 [cited 20 Dec 2024]. Available: https://www.jrf.org.uk/uk-poverty-2024-the-essential-guide-to-understanding-poverty-in-the-uk
5. Li G, Mbuagbaw L, Samaan Z, Falavigna M, Zhang S, Adachi JD, et al. Efficacy of Vitamin D Supplementation in Depression in Adults: A Systematic Review. J Clin Endocrinol Metab. 2014;99: 757–767. doi:10.1210/jc.2013-3450
6. Parker GB, Brotchie H, Graham RK. Vitamin D and depression. J Affect Disord. 2017;208: 56–61. doi:10.1016/j.jad.2016.08.082
7. Vitamin D. In: nhs.uk [Internet]. 23 Oct 2017 [cited 20 Dec 2024]. Available: https://www.nhs.uk/conditions/vitamins-and-minerals/vitamin-d/