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New study: More vegetarians affected by stroke

- and there is focus on nutrient deficiencies

New study: More vegetarians affected by strokeThe whole climate debate has made it increasingly popular to become a vegetarian or a vegan. However, according to a new and comprehensive study from Oxford, this choice of lifestyle may have grave health consequences and can increase your risk of apoplexy, also known as stroke, cerebral hemorrhage or cerebral thrombosis. The study is published in British Medical Journal. Earlier studies also give rise to concern, as a plant-based diet often lacks protein, vitamin D, vitamin B12, iodine, selenium, iron, and omega-3 fatty acids, and that can increase the risk of thyroid disorders, neurological disorders, infections, chronic inflammation, impaired fertility, growth disturbances in children etc. Some of these deficiencies are insidious and difficult to link to the diet.

It is always a good idea to show consideration for the climate and animal welfare. Still, we must not forget that humans have consumed meat and fish for around two million years. Animal food sources, which have contributed to our relatively large brains and physical development, contain complete proteins and a number of vitamins, minerals, and fatty acids, and for a vegetarian or vegan it is difficult if not impossible to obtain sufficient quantities of all of these nutrients. It takes a great deal of knowledge and insight to know how to get the required amount of essential nutrients if you are vegetarian or vegan, and supplements may even be necessary.

Higher risk of stroke

The large Oxford study was initiated in 1993. The researchers followed 48,000 Brits for up to 18 years. They used data from the EPIC-Oxford study, where half the participants were carnivores, while the other half consisted of vegetarians, vegans or so-called pescetarians (vegetarians who eat fish).
The volunteers were interviewed about their diet habits at baseline and again in 2010. The scientists also made a note of social status, medical history, smoking habits, and physical activity level. The study found that vegans and vegetarians were up to 20 percent more likely to have a stroke. On the other hand, vegetarians and vegans had a 22 percent lower risk of cerebral thrombosis.

Fish is healthy but the study results warrant more research

The study also showed that the participants who ate fish instead of meat had a 13 percent lower risk of coronary thrombosis. Dr. Tammy Tong, the main author, told The Guardian that these results call for further studies. Although the vegetarian and vegan lifestyles have increased in popularity in recent years, science still does not know enough about the exact advantages and disadvantages associated with this way of living.
One of the things that explain the increased stroke risk is lack of some essential nutrients that are found in meat, fish, and other animal food sources. The scientists therefore wish to look closer at what it is that increases the risk of stroke in vegans and vegetarians. It is highly possible that the explanation lies in the lack of vitamin D and the two omega-3 fatty acids, EPA and DHA, which have several cardio-protective mechanisms. Another thing could be lack of selenium and zinc, two antioxidants that protect the cardiovascular system.

University of Copenhagen: Vegans lack essential nutrients

Researchers from the University of Copenhagen compared vegans aged 18-61 years with meat-eating peers. The study showed that vegans got far too little protein, vitamin D, iodine, and selenium. The vegan women also got too little vitamin A. Vegetarians also risk lacking these nutrients. Other studies show that vegetarians and vegans often lack vitamin B12. So, what does all of these mean in terms of health?

Protein and its many functions

Meat, fish, eggs, and dairy products contain complete proteins with all the essential amino acids that serve as building blocks for the proteins and have a number of physiological functions. Lack of protein and essential amino acids may result in unstable blood sugar, fatigue, neurological disorders, insomnia, overweight, impaired immunity, muscular weakness, and problems with skin, hair, and nails.

It is a disturbing thought that a person can eat a vegan diet for two to three years before any signs of a vitamin B12 deficiency show up

Vitamin B12 deficiency is insidious

There is vitamin B12 in meat, fish, eggs, and dairy products. Vitamin B12 is mainly known for its role in the formation of red blood cells, whereas vitamin B12’s role in the brain and nervous system is often overlooked. Lack of vitamin B12 can cause anemia, neurological disorders, impaired fertility, and permanent damage to the child’s growth and learning abilities.
Although bacteria in our colon are able to produce small quantities of vitamin B12, we are unable to absorb the nutrient. This requires the presence of intrinsic factor, a protein that enables absorption in the small intestine. Vegetarians and vegans are therefore advised to take a vitamin B12 supplement.

An estimated 12 million people worldwide are believed to lack vitamin B12

All cells need vitamin D

Vitamin D is primarily found in cod liver, cod roe, oily fish, eggs, and high-fat dairy products. Although our primary source of vitamin D is the sun during the summer period, vegan diets make it even more difficult to reach the desired level of the nutrient.
Lack of vitamin D increases the risk of infections, inflammation, osteoporosis, atherosclerosis, cancer, and multiple other symptoms because all cells in the body depend on this vitamin. It is possible to cover your need for vitamin D from sun exposure during the summer period, whereas all people living at this latitude are advised to take a high-dosed supplement in the winter.

Selenium for your metabolism, fertility, circulation, and cancer prevention

Selenium is mainly found in fish, shellfish, seaweed, offal, meat, eggs, and Brazil nuts. The natural selenium content in European farmland is low, which makes it rather difficult for vegans and vegetarians to get sufficient quantities of this essential trace element. Selenium supports a variety of selenium-containing proteins, enzymes and antioxidants and is important for the immune system, the metabolism, cardiovascular health, sperm cells, and cancer prevention, and it also functions as an antagonist that protects against mercury and other heavy metals.
Lack of selenium increases the risk of cardiovascular diseases, infertility, cancer, thyroid disorders, infections, and cataracts. When shopping for selenium supplements, it is best to choose selenium yeast with a variety of different selenium compounds, just like you get by eating a varied diet with many different selenium sources.

According to a review article published in StatPearls, around one billion people worldwide lack selenium, mainly as a result of selenium-depleted soil.

Iodine for metabolism, estrogen balance, detoxification, and pregnancy

Iodine is mainly found in fish, shellfish, and seaweed. There is not very much iodine in the soil. Iodine is important for child growth, metabolism, estrogen balance, and excretion of environmental toxins such as fluoride, chloride, and brome.
Iodine enrichment of table salt is mandatory, as it can help prevent goiter, but it remains unclear if the added amount is enough to meet the body’s requirements. Iodine deficiency may cause thyroid disorders and imbalances in the estrogen balance, and it may increase the risk of breast cancer. If a pregnant woman lacks iodine, it increases her risk of giving birth to a child with mental disabilities.

Sea salt does not provide enough iodine

Iron for blood formation and brain enzymes

We get iron from liver, meat, eggs, pumpkin seeds and other seeds, nettles, spinach, and red beet. Iron from animal sources (heme iron) has better absorption than iron from vegetable sources (non-heme iron). An iron deficiency typically causes paleness (due to anemia), fatigue, dizziness, heart palpitations, impaired immunity, changes to skin, hair and nails, stunted growth and learning difficulty in children. Women of childbearing age are at particular risk of iron deficiency because of the blood they lose during their menstrual period.

Omega-3 from fish is often utilized better

Vegetable sources such as linseed oil and walnuts contain the form of omega-3 called ALA. Helped by certain enzymes, ALA is converted into EPA and DHA, which have a number of physiological functions. The conversion from ALA to EPA and DHA is often limited, which means that most people benefit more from getting EPA and DHA directly from dietary sources such as oily fish and shellfish or from fish oil supplements. Sea algae supplements only contain limited amounts of EPA and DHA.
Lack of omega-3 fatty acids increases the risk of cardiovascular disease, impaired immune defense, inflammation, cramps, menstrual pain, skin problems, and depression.

Symptoms are often misdiagnosed

Many vegetarians and vegans focus enormously on their diet. In the case that both they and any of their children feel perfectly healthy for a long period, the diet would be the last thing they question. Because of this, many symptoms may be misdiagnosed or interpreted incorrectly. Therefore, it is a good idea to inform the doctor about the particular eating habits.

The Danish Veterinary and Food Administration recommends the following supplements for vegans:

  • 10 micrograms of vitamin D daily during the winter period – from October to April
  • 2 micrograms of vitamin B12 daily

Depending on your diet, the following vitamins and minerals may also be relevant:

Vegetarians may also need the listed supplements

Normally, you can get what you need by taking a good multivitamin tablet with bioavailable minerals.


Tammy Y N Tong. Risk of ischaemic heart disease and stroke in meat eaters, fish eaters, and vegetarians over 18 years of follow-up: results from the prospective EPIC-Oxford study. BMJ 2019

Nicola Davis. Being vegetarian lowers heart disease but increases chance of stroke. The Guardian September 2019

Dag Viljen Poleszynski. Skader kjøttspisning mennesker, klimaet og dyr? Helsemagasinet Vitenskap og Fornuft. 2019

Ebba Nexø. Vegetarer risikerer at få for lidt B12-vitamin. marts 2018

Ulla Gjeset Schølberg. Veganere mangler vitaminer og mineraler. 2016

Brigham and Women´s Hospital. Study: How vitamin D and fish oil affect risk of heart attack, stroke and cancer. November 2018

Aparna Shreenath. Selenium Deficiency. StatPearls. May 6, 2019

Nicolas V.C. Ralston, Laurs J. Raymund. Mercury’s neurotoxicity is characterized by its disruption of selenium biochemistry. Elsevier

Rychlik W. The need for iodine supplementation. OMS 12. 06. 2017

Frederick R. Stoddard et al. Iodine Alters Gene expression in the MCF7 Breast Cancer Cell Line: Evidence for an Anti-Estrogen Effect of Iodine. International Journal of Medical Sciences. 2008

Omega-3 Index better predicts risk for death than serum cholesterol, study shows. News Medical Life Sciences. March, 15, 2018

Sarawoti Khadge et al. Long-chain omega-3 polyunsaturated fatty acids decrease mammary tumor growth, multiorgan metastatis and enhance survival. November 2018

Yoon Moberg. Får du nok jern? Det Natur- og Biovidenskabelige Fakultet.

Else Molander. Anbefalinger vedr. vegansk kost. Fødevarestyrelsen. Januar 2019
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