This took a little digging, but in a 1 teaspoon (6 grams) serving there is either no vitamin K, or it is so small it does not warrant mention. So you can eat a fair amount of it without concern, but I would still not recommend consuming an entire container to yourself in a single sitting unless you already do that regularly, and your INR has been relatively stable.
To those unaware, both vegemite and marmite are made with brewer’s yeast extract. Vegemite is Australian/New Zealand, while marmite is British/UK. Either is a spread you’d apply to toast. As I remember, either tastes like sadness but I digress…
Marmite/vegemite is an acquired taste for most, but it is incredibly healthy. Very low in saturated fat, cholesterol and calories (9 calories per serving). And a good source of protein, iron and selenium, and a very good source of thiamin, riboflavin, niacin, vitamin B6, folate, magnesium and potassium. The warning about sodium is outdated – there’s no relationship between sodium and heart disease.
Vegemite/marmite is also vegetarian, and vegan. However some of the key ingredients of vegemite/marmite are malt extract derived from barley and yeast extract, from yeast grown on barley and wheat. Therefore either is not gluten free.
Vegemite/marmite contains MSG, which is not the health risk myth that still persists. But if you have an allergy to yeast, or are prone to yeast infections (IE: thrush) – consuming vegemite/marmite is not a good idea. Allergic reactions to baker’s yeast may include a congested/runny nose and inflammation/itching of the skin.