Being vegan and vitamin D-deficient affects your bone health

All the different awareness campaigns for sustainability and eating plant-based diets have inspired more and more people to become vegetarians or vegans. However, there are health aspects that need attention. Vegetarians and vegans in particular have lower intakes of protein, vitamin D, and many other essential nutrients, according to a new Spanish study that is published in Nutrients. It is therefore recommended that adult vegetarians and vegans take vitamin D supplements to counter their risk of osteoporosis and other diseases related to vitamin D deficiencies.

It has become increasingly popular to eat plant-based diets, especially among people in the industrialized countries, but we lack information about how this affects bone health. The new Spanish study therefore looked into this. The study included 301 participants (66% were women), of which 93 were omnivores (they eat everything), 96 were lacto-ovo-vegetarian (they include dairy and eggs in their diets), and 112 were vegan, which means they exclude any type of food that contains animal protein. The researchers looked at the following in the three groups of participants:

• Food intake and nutrient content of the diet
• Body composition (percentage and distribution of muscle, fat, etc.)
• Physical activity level
• Blood levels of vitamin D (25-hydroxycholecalciferol, 25 OHD) because one of vitamin D’s functions is to increase the uptake of calcium from the alimentary tract
• PTH (parathyroid hormone) that is released by the parathyroid gland and helps regulate blood levels of calcium
• BAP (bone alkaline phosphatase), a marker of the activity of the bone producing cells
• NTx (N-telopeptides type I collagen), a marker of the breakdown of old bone tissue

The study showed the following:

• Lacto-ovo-vegetarians and vegans in particular had lower intakes of protein, fat, calcium, phosphorous, vitamin D, retinol (pure vitamin A), iodine, and zinc. On the other hand, they had higher intakes of carbohydrates, fiber, carotenes, magnesium, and vitamin K compared with omnivores
• Participants in the three groups had similar body composition, at least those who were physically active on a regular basis
• Bone mass and muscle mass were positively related to BAP, physical activity, and vitamin D
• Insufficient vitamin D levels in the blood (below 75 nmol/L) were observed in 93 percent of the participants
• Severe vitamin D deficiency (less than 25 nmol/L) was significantly more common among vegans
• Lacto-ovo-vegetarians and vegans in particular had significantly higher levels of PTH and NTx compared with omnivores

Based on their observations, the scientists concluded that adult vegans can lower their risk of bone loss through proper diet planning and the use of vitamin D supplements. Most of the body’s cells have vitamin D receptors (VDR) that regulate around 10 percent of our genes. Vitamin D is needed to regulate our immune defense, inflammatory processes, insulin sensitivity, brain activity, cancer prevention, and a number of other functions. The study suggests that vegetarians and vegans in particular should also focus on getting enough protein, iodine, and zinc. The same goes for vitamin B12, iron, selenium, and omega-3 fatty acids. Lacking these things can have detrimental consequences for your health.

References:

Elena Garcia-Maldonado et al. Bone Remodelling, vitamin D Status, and Lifestyle Factors in Spanish Vegans, Lacto-Ovo Vegetarians and Omnivores. Nutrients 2024

Elizabeth Rosee Eveleigh et al. Systematic review and meta-analysis of iodine nutrition in modern vegan and vegetarian diets. British Journal of Nutrition 2024

Weikert C et al. Vitamin and Mineral Status in a Vegan Diet. Deutsches Aerzteblatt Online. November, 2020