Strong Bones, Protection Against Long COVID

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In this issue

  • Building strong bones: the impact of vitamin K
  • Can you protect yourself against long COVID?
  • Recipe: Salsa and cheese fish bake

Osteoporosis, a disorder characterized by weakened and fragile bones is one of the most common bone-related health conditions. To maintain strong, fracture resistant bones and prevent osteoporosis we are encouraged to consume calcium rich foods and/or take calcium supplements. However, the story of bone health is much more intricate and the maintenance of healthy bones involves not only calcium but also a complex interplay of many other nutrients.

This issue focuses on the role of vitamin K, and its interaction with vitamin D and calcium in the prevention of osteoporosis.

Building strong bones – more than just calcium

Calcium is one of the most abundant minerals in all tissues of the human body. It plays an essential role in various bodily processes, including muscle contraction, blood clotting, and nerve function. In bones calcium provides structural support, making up to 30-35% of total bone weight.

Bones also act as a reservoir for minerals like calcium and magnesium. If our diets are short of calcium, there will be insufficient calcium in the bloodstream. When that happens, we draw calcium from our bones to meet our physiological needs. Over time, this can lead to a decrease in bone density, which will increase the risk of fractures. So, for decades we have been cautioned to optimize our intake of calcium to prevent osteoporosis, and many women have been encouraged to take high dose calcium supplements, regardless of how much calcium is in their diets.

The absorption of calcium depends on adequate circulating levels of vitamin D, so is compromised if we are vitamin D deficient – a common problem in northerly countries like Canada. [1] More recent clinical trials seeking evidence for osteoporosis prevention therefore used various combinations of calcium and vitamin D. [2]

The calcium paradox

Although insufficient intake of either calcium or vitamin D is detrimental not only to bone health, but also to health in general, too much calcium may also be a bad thing. Studies have shown that excessive calcium intake, particularly in the form of high-dose supplements, may not provide the bone health benefits we’ve come to assume, and could cause unwanted side effects, including an increased risk of cardiovascular disease. Some studies have shown a higher risk of heart attacks in those taking calcium supplements compared to those who don’t. [3]

One reason calcium supplements might increase heart disease risk is that excess calcium can end up as hard deposits attached to blood vessel walls. [4] This is called calcification. Calcification causes blood vessels to become stiff, making it harder for them to expand and contract as needed. And so the heart has to work harder to pump blood, and blood pressure becomes difficult to control.

Calcification can also occur in other tissues, and interfere with their function. In kidneys this may lead to kidney stones. In joints, calcification contributes to the pain of osteoarthritis. Calcification in the brain may even increase the risk of developing Alzheimer’s Disease. [5]

Vitamin K – the calcium traffic cop

Enter vitamin K. Vitamin K is actually a group of fat-soluble vitamins that play an essential role in various bodily functions, primarily blood clotting and bone metabolism. The two main forms are vitamin K1 (phylloquinone), found in leafy greens and other plant-based foods, and vitamin K2 (menaquinone) mainly found in animal foods. K2 is also synthesized by bacteria in our gut and found in fermented foods like cheese, yogurt and kefir.

While both K1 and K2 are needed to regulate blood clotting, vitamin K2 is a star when it comes to bone health, as it is needed for the production of a protein called osteocalcin. Osteocalcin ensures that calcium binds to bones. K2 is also needed for the production of another protein – matrix Gla-protein (MGP) – which helps prevent calcium from building up in blood vessels and other tissues, keeping the arteries clear and flexible.

Here’s how vitamin K2 helps to prevent osteoporosis: [6]

  1. Enhances Calcium Utilization: Vitamin K2 activates osteocalcin, which helps calcium bind to the bone matrix, making bones denser and stronger.
  2. Reduces Calcium Buildup in Arteries: As well as ensuring that calcium is directed to the bones, vitamin K2 blocks calcium buildup in arteries, reducing the risk of calcification.
  3. Stimulates Bone Formation: Vitamin K2 also plays a role in stimulating bone-forming cells, ensuring a balance between bone formation and breakdown.

Sources of vitamin K

To obtain vitamin K1 from diet load up on leafy greens – spinach, kale, broccoli, and Brussels sprouts are all good sources. Vitamin K2, on the other hand is present mainly in animal products. Chicken, egg yolks, liver and other organ meats are all good sources. Fermented soy products and sauerkraut are appropriate sources for vegetarians. Dairy products like hard cheeses are also good sources, as are fermented dairy foods like kefir and yogurt. But beware! Vitamin K is a fat-soluble vitamin. While full fat Greek yogurt is a good source of K2, zero fat yogurt contains, well, zero!

One welcome innovation in the supplement industry is that many vitamin supplements now also include vitamin K2. I always recommend taking vitamin D capsules that include vitamin K2. Usually, you will find that for every 1000 IU of vitamin D3 there are 120 mcgs of K2.

Vitamin K2 and warfarin

Warfarin, also known as Coumadin, is a blood thinner that works by inhibiting the action of vitamin K, which is crucial for blood clotting. If you take warfarin you may need to avoid taking additional vitamin K2 as it might interfere with warfarin’s effectiveness, and make it harder for your doctor to manage your drug dose effectively.

Newer generation blood thinners, like rivaroxaban (Xarelto), Apixaban (Eliquis) or dabigatran (Pradaxa) work differently from warfarin, and don’t directly interfere with vitamin K metabolism, according to current research.[6]

Vitamin K2 – how much is too much?

The tolerable upper limit of a nutrient is the maximum amount considered to be unlikely to pose a risk of adverse health effects in humans. For vitamin K, no tolerable upper limit has been set because no adverse effects have been shown, even at high intakes. Toxicity is rare and unlikely to result from eating foods containing vitamin K.

While in Canada there are no recommendations for vitamin K supplements to prevent osteoporosis, in Japan, where most of the studies that demonstrated the benefits of vitamin K for bone health were carried out, supplementing with vitamin K is routinely recommended. Daily doses of up to 45mg (45,000 mcg) have been given to elderly patients at risk of osteoporosis without adverse effects [7].

Natto, a popular dish in Japan made from fermented soybeans, is rich in vitamin K2. In my opinion it is an acquired taste, and not everyone is a fan. But if you like it and can get it, one serving (100g) of natto contains approximately 1mg (1000 mcg) of vitamin K2 [8].

But, as always, if you have specific concerns about your vitamin K intake and any interactions it may have with your medications, consult with your doctor.

Can you protect yourself against long COVID?

It might be a smart move to routinely start wearing a mask again, especially in crowded spaces as the cold and ‘flu season approaches and COVID infection rates increase. Hospitals across the country are seeing a surge in test positivity and admissions. No doubt the disease is milder since vaccination. However, even those with mild cases can be susceptible to what has become known as ‘long COVID.’

Also known as post-acute sequelae of SARS-CoV-2 infection (PASC), long COVID refers to persistent symptoms that linger for weeks or months after acute COVID-19 infection. Most people recover from COVID-19 within a few weeks. However, some individuals experience lingering symptoms that can significantly impact their daily lives. These symptoms can vary widely, and may include fatigue, shortness of breath, chest pain, joint pain, brain fog, difficulty concentrating, and more. One prediction suggested that, worldwide, up to ten percent of those who have had COVID will suffer from this debilitating condition.

Is there any way to predict who will get long COVID?

Predicting who will develop long COVID is challenging, since it affects such a diverse range of individuals, including those whose original infection was mild or even asymptomatic. But we do know that certain risk factors may increase the likelihood of experiencing long-term symptoms. Research suggests that individuals with severe initial infections, older adults, and those with pre-existing health conditions, especially obesity and diabetes, may be at a higher risk of developing the condition.

A recent study from the UK conducted on women in the Nurses’ Health Study 2 found that a healthy lifestyle before COVID-19 infection was linked to a significantly lower risk of long COVID. The healthy lifestyle factors included [9]

  • Normal body weight (BMI)
  • Never smoking
  • A high-quality diet
  • Moderate alcohol intake
  • Regular exercise
  • Adequate sleep

The study suggests that women with all these healthy life style factors had a 49% lower risk of long COVID compared to those without any, and that 36.0% of long COVID cases could have been avoided if all participants had 5 or 6 healthy lifestyle factors. Healthy BMI and adequate sleep were independently associated with a lower risk of long COVID.

  • Adequate exercise was defined as at least 150 minutes per week of moderate to vigorous physical activity
  • Moderate alcohol intake was defined as 5 to 15 g per day (one drink contains about 10 g of alcohol)
  • A high-quality diet was defined as the upper 40% of the Alternate Healthy Eating Index-2010 score.

The Alternative Healthy Eating Index (AHEI) was developed by Harvard researchers, and rates foods and nutrients according to whether they can help prevent chronic diseases [ ]. Basing your diet on a combination of foods now known for their health promoting qualities has been shown to lower your risk for cancer, diabetes, heart disease and dementia. The highest scores come from higher intakes of fruits and vegetables, nuts, legumes, fish, healthy fats like olive oil, and whole grains.

Salsa and cheese fish bake

This quick and easy fish recipe is a handy middle of the week dish which uses only 3 ingredients, all of which can be stock items in your fridge or freezer. The combination of a mild flavoured fish like plaice and the tasty salsa and cheese topping make it acceptable to children (or adults) who are reluctant fish eaters!

Any white fish can be used as long as the pieces are not too thick. Use a mild or hot salsa depending on everyone’s tolerance for spiciness. A well-flavoured cheddar cheese makes a good topping. No measuring is involved – just scale up the recipe depending on the number of people you are feeding.


  1. Frozen plaice fillets
  2. Salsa
  3. Grated cheddar cheese


  1. Preheat your oven to 375°F (190°C).
  2. Place the frozen plaice fillets in a single layer in an oiled baking dish.
  3. Spread a generous layer of salsa over each plaice fillet, ensuring even total coverage.
  4. Sprinkle a generous amount of grated cheese on top of each fish fillet.
  5. Bake in the preheated oven for about 15-20 minutes or until the fish is cooked through and the cheese is melted and bubbly.
  6. For a golden finish, you can broil the dish for an additional 2-3 minutes, keeping a close eye to prevent burning.
    Serve with a side of fresh salad or broccoli or other vegetables for a delicious, low-carb meal!



1. Addressing vitamin D deficiency in Canada: a public health innovation whose time has come. Schwalfenberg GK, Genuis SJ, Hiltz MN. Public Health. 2010 Jun;124(6):350-9

2. Jin J. Vitamin D and Calcium Supplements for Preventing Fractures. JAMA. 2018;319(15):1630. doi:10.1001/jama.2018.3892

3. Associations of dietary calcium intake and calcium supplementation with myocardial infarction and stroke risk and overall cardiovascular mortality in the Heidelberg cohort of the European Prospective Investigation into Cancer and Nutrition study (EPIC-Heidelberg). Li K, Kaaks R, Linseisen J, Rohrmann S. Heart. 2012 Jun;98(12):920-5.

4. Calcium supplements: Good for the bone, bad for the heart? A systematic updated appraisal. Morelli MB, Santulli G, Gambardella J. Atherosclerosis. 2020 Mar;296:68-73.

5. Arterial calcification and cerebral disease : stroke and dementia. Jashari F, Wester P, Henein M. In: Cardiovascular calcification [Internet]. 1st ed. Cham: Springer; 2022. p. 237–58

6. Molecular Pathways and Roles for Vitamin K2-7 as a Health-Beneficial Nutraceutical: Challenges and Opportunities. Jadhav N et al. Front Pharmacol. 2022 Jun 14;13:89692

7. Vitamin K administration to elderly patients with osteoporosis induces no hemostatic activation, even in those with suspected vitamin K deficiency. Asakura H et al. Osteoporos Int. 2001 Dec;12(12):996-1000.

8. Vitamin K fact sheet. National Institutes of Health.

9. Lifestyle risk factors, inflammatory mechanisms, and COVID-19 hospitalization: A community-based cohort study of 387,109 adults in UK. Hamer M, Kivimäki M, Gale CR, Batty GD. Brain Behav Immun. 2020 Jul;87:184-187

10. Alternative dietary indices both strongly predict risk of chronic disease. Chiuve SE, Fung TT, Rimm EB, Hu FB, McCullough ML, Wang M, Stampfer MJ, Willett WC. J Nutr. 2012 Jun;142(6):1009-18

Note: Articles or commentary in this newsletter are not intended as medical advice. Please check with your doctor if you have a concern about your health.
©2011 Aileen Buford-Mason. All rights reserved.