Vitamin D & Absorption Rates + Sun Exposure

Vitamin D is an essential nutrient that helps to regulate and balance the phosphorus and calcium in our body. Our body naturally produces vitamin D if it is exposed to five to 30 minutes of direct sunlight. This is why those who live in the northern hemisphere or otherwise spend a lot of time indoors risk developing a deficiency. This can be very serious, as it can lead to osteoporosis and rickets. Furthermore, this vitamin is essential for a healthy immune system, helping to prevent autoimmune diseases and cancer. A number of foods do contain natural levels of vitamin D, but it is often required to take supplements. However, being able to get vitamin D in a natural way is always better.

We need this vitamin for our bone health and the best way to do that is through sun exposure. However, it is also vital to remember that too much sun exposure can also be damaging. If you have a deficiency, you may develop softer, weaker bones, potentially leading to deformities. Rickets is most common in children, and adults can develop osteomalacia. So, besides knowing how to get hold of vitamin D, you also need to know how to absorb it properly for maximum effect.

How Do We Get Vitamin D?

Most of the vitamin D in our body is created by our skin being exposed to the sun. It is best to have sun exposure between March and October, and between 11am and 3pm. We can also get the vitamin from oily fish, eggs and meats. Plus, it is added to all formula milk for infants, and most soya products, breakfast cereals, powdered milks, dairy products, and fat spreads. Often, however, these are just small amounts and there is only a legal requirement to add vitamin D to infant formula milk, so there is rarely a guarantee on any other product that the levels are high enough.

How Much Vitamin D Do You Need?

There are many reasons why you may feel you have a vitamin D deficiency. However, you should never aim to diagnose yourself, so do make an appointment with your physician for a 25 hydroxy-vitamin D blood test. This test is most suitable for people with dark skin (they need more sunlight exposure) and the elderly. After the test, your doctor may recommend that you supplement your diet to get to the right amount of International Units (IU). The recommended IUs for the average adult is 600.

A number of medical conditions can cause vitamin D deficiency as well. Some of these conditions include:

• Crohn’s disease
• Cystic fibrosis
• Celiac disease
• Kidney disease

If you suffer from any of these conditions, it is likely that you will already have been told to supplement.

How to Increase Levels of Vitamin D

There are a number of ways to help you increase your levels of vitamin D. While direct sun exposure is best, this is not always possible. Hence, try to focus on foods instead. Supplements are there solely to ‘supplement’ (add on to) your own efforts. Below are a few common foods and other items that you can add to your diet for increased levels of vitamin D.

Food/Drink Amount of Vitamin D
Fortified milk 1 cup gives you around 30% of the daily recommended value.
Oily fish 3 oz of mackerel or salmon will give you 100% of the daily recommended value.
Canned tuna 3 oz of canned tuna is the equivalent of 40% of your daily recommended value.
Fortified cereals, eggs, liver Each of these will give you around 10% of your daily recommended value.

Do make sure that, wherever possible, you eat organic food. This is because non-organic meats and produce may contain various pesticides, hormones and other chemicals that could potentially destroy the levels of vitamin D that naturally occur in the food.

It is recommended to buy fortified products, with many drinks and dairy products falling into that category. Choose milk, orange juice, cereals and yoghurt, for instance. Do check the label to make sure it actually is fortified.

Sun Exposure Is Better

As previously stated, however, the sun is your biggest friend when it comes to catching those important vitamins. Your body is a perfect little machine to convert the UVB rays into the vitamin. This is why people who live in sunny climates usually don’t need to supplement. However, remember that UVB radiation doesn’t go through glass, so you actually have to go outside. Additionally, the rays of the sun can be harmful as well. So, while an SPF 8 sun blocker cancels out 95% of the vitamin D you can create, you also shouldn’t spend all your time in the sun unprotected.

Try to stick to about 10 to 15 minutes of direct sun exposure a day, between 11am and 3pm, about three to four times per week. If you are dark skinned, you will need to spend a little bit more time in the sun. If you don’t live in a sunny climate, you will not be able to make vitamin D between October and March. There is insufficient UVB radiation in the sun’s rays for this. Hence, you should opt for food sources and supplementation between these months. However, it is not advisable to swap direct sunlight for sunbeds.

Recommendations for babies and children are slightly different. During the summer months, they should always be covered up with suitable clothing and they should spend time in the shade. An SPF 15 is also a minimum recommendation. Because of this, it is suggested that all children take vitamin D supplements.

Too Much of a Good Thing

There is such a thing as too much vitamin D. In fact, it can be toxic. What happens when you overdose on vitamin D is that your body’s calcium levels get too high. This won’t happen from being in the sun or eating foods that are fortified. However, it can happen if you take too many supplements. Signs and symptoms to look out for include:

• Nausea
• Constipation
• Feelings of confusion
• Kidney stones
• An abnormal heartbeat

Too much vitamin D can be particularly dangerous for people with histoplasmosis, sarcoidosis, lymphoma, and various kidney diseases.

Who Can Develop Vitamin D Deficiency?

There are a number of population groups in which vitamin D deficiency is particularly common. This is why these groups should always take supplements at the levels recommended by their physicians. These are:

• Women who are pregnant or nursing. This will ensure the mother has sufficient vitamin D, but that the baby is born with enough stores as well.
• Children and babies between 6 months and five years, unless they consume at least 500ml of infant milk formula each day.
• Those over the age of 65.
• Anyone who doesn’t get regular sun exposure, such as those who cover their skin, always work indoors or who are housebound.
• Darker skinned people, including African Caribbean, Africans and South Asians who live in this country.

Vitamin D Absorption – How to Give Your Body a Helping Hand

There are a number of things that you can do in order to make sure your body is able to absorb the right amounts of vitamin D. These include:

1. Choosing the right supplement. Vitamin D is either D2 (ergocalciferol) or D3 (cholecalciferol). D3 is the more potent and important supplement and is the one that naturally occurs in the human body.
2. Have your supplement with your biggest meal. It is fat soluble, which means some fat needs to be in your stomach in order for it to be properly absorbed. This is also true for vitamins A, E and K. Hence, take them during or right after your biggest meal, so your body can process it. The time of day that it is taken is irrelevant, however.
3. Check your meds. A number of meds counteract the workings of vitamin D. Others contain high levels of vitamin D (particularly D2), which means you may not need supplements. Medications that can stop proper absorption include water pills, verapamil, cytochrome substrates, tiazac, dilacor, Cardizem, lanoxin, dovonex and Lipitor. Always take supplements as recommended by your physician if you have been prescribed these medications.
4. Increase your food intake of natural vitamin D foods. It is known that a co-factor is magnesium. Hence, if you eat plenty of magnesium (or supplement it), your body will be better able to absorb the vitamin D as well.
5. Lose weight. Being obese is known to be a contributing factor to lower levels of vitamin D. If you eat a healthy diet and get plenty of exercise, your levels of vitamin D should also be higher.
6. Speak to your physician. You may have an underlying health condition that is causing your deficiency. If so, this needs to be addressed as well.

Resources and References:

Vitamin D Factsheet – General info on Vitamin D. (
How to Get the Necessary Vitamin D – How to obtain the Vitamin D that you need. (Vitamin D Council)
9 Things That Can Undermine Your Vitamin D Level – How your vitamin D is reduced. (