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Person wearing sunglasses and a winter hat soaking up the sun to get vitamin D in winter. An illustrated sun with rays is in the top left corner.

January 31, 2023 • read

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How to boost your vitamin D levels this winter

It’s natural for winter’s shorter days to leave you wanting to cocoon indoors. But this instinctive urge to hibernate comes with a glaring trade-off. Less time outdoors and fewer hours of sunlight mean a decrease in your body’s ability to produce vitamin D. Luckily, sunlight isn’t the only source of the so-called sunshine vitamin. Here’s how vitamin D affects your body and how to get enough of it during the winter.

What’s vitamin D and why’s it beneficial?

Vitamin D isn’t just one substance. It’s actually a group of nutrients that are essential for human health. One of its components, vitamin D2, comes from plant sources. This makes it cheaper to produce, making it the form you’re most likely to find in supplements and fortified foods.

Vitamin D3, in contrast, comes from animal sources. Fatty fish like sardines and salmon contain large amounts of it, as do egg yolks and red meat, though it’s also available in supplement form. While both forms are beneficial for humans, vitamin D3 may raise vitamin D blood levels more effectively than D2.

So, what does vitamin D do? Likely a whole bunch of things. A number of organs and tissues in your body have vitamin D receptors, suggesting it may play a part in many of your physiological processes. More research is needed, however, to give scientists a full picture of its role.

What’s clear is that vitamin D helps your body to absorb calcium and phosphorus. These minerals are crucial for maintaining healthy bones and teeth and enabling proper muscle movement. Beyond that, vitamin D contributes to heart and nerve function. As a result, a lack of it can be a factor in everything from heart failure to erectile dysfunction to depression.

If you’re worried that your vitamin D levels are off, Maple can help. Maple is a telehealth platform that connects you with Canadian-licensed doctors and specialists from your phone, tablet, or computer. With Maple, you can speak to a doctor about your vitamin D concerns from the comfort of your home at a time that’s convenient for you.

Does vitamin D help with mood?

Taking a vitamin D supplement may improve mood if you’re experiencing depression and have a vitamin D deficiency. But, not everyone experiencing depression is vitamin D-deficient. If your vitamin D levels are normal to begin with, you’re unlikely to see a boost in mood after taking it as a supplement.

How much vitamin D do I need per day?

The recommendations for Canadian vitamin D values vary depending on your age, pre-existing health conditions, and a variety of other factors. Generally, Osteoporosis Canada recommends that healthy adults between the ages of 19 and 50 supplement their diet with 400 to 1000IU of vitamin D a day.

Adults over 50, or younger individuals with health risks like osteoporosis, multiple fractures, or a condition affecting their ability to absorb vitamin D should aim for more — between 800 to 2000IU a day. The truth is, however, that more research is needed for science to fully understand the exact cause and effect of differing supplement dosing levels.

If you’re testing your blood serum levels, 75nmol/L (nanomoles per litre) is considered a healthy vitamin D level for almost everyone. The medical consensus is that this level of vitamin D is sufficient for preventing diseases like rickets and osteoporosis.

Some individuals may require higher doses — 10,000IU a day or more — due to specific health conditions. In these cases, however, treatment is supervised by an endocrinologist.

Is it normal to have lower levels of vitamin D in the winter?

It’s not only normal to have lower levels of vitamin D in the winter, it’s expected. Your body makes vitamin D in response to sunlight. Since the amount of sun exposure you get decreases in winter, your vitamin D production will naturally fall too.

This effect becomes more pronounced the further away from the equator you live. While individuals close to the equator are unlikely to experience vitamin D deficiency, dark winters in Canada leave vitamin D levels low for about 40% of Canadians.

What happens when vitamin D levels are too low?

Symptoms of vitamin D deficiency can vary widely, from the physical to the mental. They’re also on a spectrum, which means they can vary from mild to quite pronounced depending on the level of deficiency. Symptoms include:

  • Low energy and fatigue
  • Muscle weakness
  • Muscle aches
  • Hair loss
  • More frequent respiratory infections
  • Osteopenia (low bone density)
  • Osteoporosis
  • Weak tooth enamel
  • Increased risk of falls and fractures
  • Increased risk of seasonal affective disorder (SAD) and other forms of depression
  • Erectile dysfunction
  • Rickets

What can I do to boost my vitamin D levels during the winter?

It’s one thing to know about the benefits of vitamin D. It’s another to figure out how to get enough of it in your diet naturally. The flesh of fatty fish like salmon and sardines along with fish liver oils are some of the richest food sources of vitamin D — and they’re a great option to eat healthy — but they’re not for everyone. Luckily, you can still reap the immunity-boosting benefits of vitamin D as a vegetarian or vegan.

Vitamin D-rich food for vegetarians

If you’re looking for nutritional forms of vitamin D and eat eggs and dairy products, you’re in luck. Eggs are nutrient-rich with significant levels of vitamin D. After cooking, each egg yolk contains 32IU of vitamin D.

The caveat is that eggs are more likely to be high in nutrients when they come from chickens that receive regular exposure to sunlight. That means you’ll want to opt for farm-raised or free-range eggs if you’re looking for a vitamin D boost this winter.

Nutritional vitamin D sources for vegans

Sources of vitamin D may be fewer on a vegan diet, but you still have some great options. While many vegetables don’t have significant amounts of vitamin D, mushrooms are the exception. When exposed to UV light, mushrooms create vitamin D naturally, just like humans. This makes them a great dietary source for it.

While cow’s milk is off the table for anyone on a vegan diet, alternative milks are often fortified with vitamins. Though you’ll want to double-check the label, this usually makes most soy, oat, nut, and rice milks good sources of vitamin D.

Tofu’s another food that’s often vitamin D-fortified. Just 100g of fortified tofu can contain as much as 13% of your daily dose of the sunshine vitamin.

While orange juice doesn’t naturally contain vitamin D, most brands choose to fortify theirs with both vitamin D and calcium. Since vitamin D improves calcium absorption, this combination is especially beneficial.

How can I prevent vitamin D deficiency during winter?

Beyond looking at your diet, maintaining healthy vitamin D levels means exposing yourself to sunlight this winter. You’ll have to actually go outside for this, however. UVB rays don’t penetrate glass, so you can’t get vitamin D through a window. Instead, incorporate physical activity into your day with a sunny midday walk to keep you feeling healthy all winter long.

Keep in mind, however, that winter calls for layering up, which prevents full sun exposure to much of your skin. This, coupled with a lower UV index, may mean that your body can’t synthesize adequate vitamin D levels.

To help prevent deficiency, it’s a good idea to take a vitamin D supplement. This is especially important for young children who require it for proper growth and bone development.

A word to the wise, though. If you think you’re feeling the effects of its deficiency and are wondering, “How soon will I feel better after taking vitamin D?”, know that it can take a while. Oral supplementation may take a few months to bring your levels up to the recommended range, so it’s best to start even before winter rolls in.

When to take vitamin D

Worrying about when to take your vitamin D — e.g. morning or night — isn’t worth it. More important is what you take with your supplement.

Because it’s fat-soluble, your body absorbs vitamin D best when it’s paired with high-fat foods. If you want to know the exact amount, 11g of fat — the equivalent of about 18 almonds — is the sweet spot. You’re better off taking it with this amount of fat than worrying about timing your dose.

What happens if I take too much vitamin D?

It may seem like more is better, but you can take too much vitamin D. Beyond 4,000IU — the equivalent of 100mcg — vitamin D may be unsafe. Long-term, excessive vitamin D intake can result in a condition known as vitamin D toxicity (VDT). Under medical supervision, however, patients with certain medical conditions may receive more than that for limited periods.

VDT isn’t caused by excessive sunlight, and you’re unlikely to reach this level through diet alone. Taking too much vitamin D in supplement form is almost always the cause of VDT.

What are the symptoms of vitamin D toxicity?

VDT is a relatively rare, but serious condition. The major side-effect of too much vitamin D is hypercalcemia, or too much calcium in your blood. Given how necessary calcium is to bone and teeth health, this may sound like a good thing, but it’s not. Having excessive calcium levels actually weakens your bones.

Beyond that, symptoms of vitamin d overdose can include:

  • Confusion
  • Apathy
  • Nausea
  • Loss of appetite
  • Vomiting
  • Abdominal pain
  • Excessive urination
  • Excessive thirst
  • Dehydration
  • Heart arrhythmia (irregular heartbeat)
  • Bone pain
  • Kidney stones
  • Blood vessel damage
  • Kidney failure

When should I talk to a doctor about my vitamin D intake?

While sunny outings and a balanced diet go a long way toward achieving optimal winter vitamin D levels, they may not be sufficient. A variety of factors, including lifestyle, age, skin colour, body mass index, and preexisting health conditions, can all play a role in your daily vitamin D needs.

If you’re unsure whether you’re getting enough, seeing a doctor online is a great next step. The doctor can help you determine how much vitamin D is right for you, or if you need a supplement at all.

Alternatively, if you’re looking to get enough of the sunshine vitamin from your diet, speaking to a dietitian online might be in order. Not only can they demystify how to incorporate more vitamin D into your diet, but an online dietitian can also help you develop a customized nutrition plan, taking your unique circumstances into account.

Whatever you decide, however, don’t let the symptoms of too much or too little vitamin D be ignored. Your health is too important to be left up to chance.

This blog was developed by our team and reviewed by a medical professional.

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