I use considerably more of most vites than Soylent, but not Vitamin A. The LEF multivamin mix I use has 5000 IU, which is the same as the FDA’s basis for DV (Daily Value) in food labeling, which is the same that Soylent uses.
You’re right that this is higher than the RDA, but it is still within safe limits.
The National Institutes of Health specifies 10,000 IU as the tolerable upper intake level for adults (UL):
That’s not how science works. If there’s one study suggesting something might help or might hurt, you have no basis for any conclusions. It’s when several studies corroborate each other that science has learned something. The studies on Vitamin A and bone health are mixed and inconclusive. Even if you wish to show an abundance of caution, keeping the limit at 5,000 IU instead of 10,000 IU does that:
Results of some studies indicate that vitamin A intake is not associated with detrimental effects on bone mineral density (BMD) or fracture risk (39-41). However, results of some prospective studies suggest that long-term intakes of preformed vitamin A in excess of 1,500 mcg/day (5,000 IU/day) are associated with increased risk of osteoporotic fracture and decreased BMD in older men and women (42-44). Although this level of intake is greater than the RDA of 700-900 mcg/day (2,300-3,000 IU/day), it is substantially lower than the UL of 3,000 mcg/day (10,000 IU/day). Only excess intakes of preformed vitamin A (retinol), not beta-carotene, were associated with adverse effects on bone health.
For what it’s worth, the LEF supplement uses Beta Carotene, not Vitamin A Palmitate. (Soylent uses Vitamin A Palmitate, i.e., “preformed vitamin A.”)
And if you’re interested in the studies cited above, here they are:
.39. Rejnmark L, Vestergaard P, Charles P, et al. No effect of vitamin A intake on bone mineral density and fracture risk in perimenopausal women. Osteoporos Int. 2004;15(11):872-880. (PubMed)
.40. Sowers MF, Wallace RB. Retinol, supplemental vitamin A and bone status. J Clin Epidemiol. 1990;43(7):693-699. (PubMed)
.41. Ballew C, Galuska D, Gillespie C. High serum retinyl esters are not associated with reduced bone mineral density in the Third National Health And Nutrition Examination Survey, 1988-1994. J Bone Miner Res. 2001;16(12):2306-2312. (PubMed)
.42. Michaelsson K, Lithell H, Vessby B, Melhus H. Serum retinol levels and the risk of fracture. N Engl J Med. 2003;348(4):287-294. (PubMed)
.43. Promislow JH, Goodman-Gruen D, Slymen DJ, Barrett-Connor E. Retinol intake and bone mineral density in the elderly: the Rancho Bernardo Study. J Bone Miner Res. 2002;17(8):1349-1358. (PubMed)
.44. Feskanich D, Singh V, Willett WC, Colditz GA. Vitamin A intake and hip fractures among postmenopausal women. JAMA. 2002;287(1):47-54. (PubMed)